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ACTA CARSOLOGICA

ISSN 0583-6050

© ZNANSTVENORAZISKOVALNI CENTER SAZU

Uredniški odbor / Editorial Board

Franco Cucchi, University of Trieste, Italy

Jože Čar, University of Ljubljana, Slovenia

Franci Gabrovšek, Karst Research Institute ZRC SAZU, Slovenia

Ivan Gams, University of Ljubljana, Slovenia

Matija Gogala, Slovenian Academy of Sciences and Arts, Slovenia

Andrej Kranjc, Karst Research Institute ZRC SAZU, Slovenia

Marcel Lalkovič, Te Slovak Muesum of Nature Protection and Speleology

Jean Nicod, Emeritus Professor, Geographical Institute, Aix en Provence, France

Mario Pleničar, University of Ljubljana, Slovenia

Trevor R. Shaw, Karst Research Institute ZRC SAZU, Slovenia

Tadej Slabe, Karst Research Institute ZRC SAZU, Slovenia

Glavni in odgovorni urednik / Editor-in-Chief

Andrej Kranjc

Pomočnik urednika / Co-Editor

Franci Gabrovšek

Znanstveni svet / Advisory Board

Ahmad Afrasibian, Philippe Audra, Ilona Bárány – Kevei, Pavel Bosák, Arrigo A. Cigna, David Drew, Wolfgang Dreybrodt, Derek Ford, Helen Goldie, Laszlo Kiraly, Alexander Klimchouk, Stein-Erik Lauritzen, Bogdan Onac, Armstrong Osborne, Arthur Palmer, Ugo Sauro, Boris Sket, Kazuko Urushibara-Yoshino.

Naslov uredništva / Editor’s address:

Inštitut za raziskovanje krasa ZRC SAZU - Karst Research Institute ZRC SAZU

SI - 6230 Postojna, Titov trg 2, Slovenija

Fax: +386 (0)5 700 19 99, e-mail: kranjc@zrc-sazu.si

Spletni naslov / Web address: http://carsologica.zrc-sazu.si

Distribucija in prodaja / Ordering address:

Založba ZRC/ZRC Publishing

Novi trg 2, P.O.Box 306, SI-1001 Ljubljana, Slovenia

Fax: +386 (0)1 425 77 94, e-mail: zalozba@zrc-sazu.si, http://zalozba.zrc-sazu.si

Sprejeto na seji uredniškega odbora 25. januarja 2007.

Cover photo: Cover montage by Will Pearce. Images courtesy of Horton H. Hobbs III, John Mylroie, Arthur N. Palmer, and Ira D. Sasowsky..

Cena / Price

Posamezni izvod / Single Issue Individual / Posameznik: 15 € Institutional / Institucija: 25 €

Letna naročnina / Annual Subscription Individual / Posameznik: 25 € Institutional / Institucija: 40 €

ACTA CARSOLOGICA

36/1 2007

SLOVENSKA AKADEMIJA ZNANOSTI IN UMETNOSTI

ACADEMIA SCIENTIARUM ET ARTIUM SLOVENICA

Razred za naravoslovne vede – Classis IV: Historia naturalis

ZNANSTVENORAZISKOVALNI CENTER SAZU Inštitut za raziskovanje krasa – Institutum carsologicum

LJUBLJANA 2007

LET / yEARS

Inštitut za raziskovanje Krasa ZRC SAZU Karst Research Institute at ZRC SAZU

ACTA CARSOLOGICA je vključena v / is included into: Current Geographical Contents / Ulrich's Periodicals Directory / COS GeoRef / BIOSIS Zoological Record.

ACTA CARSOLOGICA izhaja s fnančno pomočjo / is published with the fnancial support of:

Agencije za raziskovalno dejavnost RS / Slovenian Research Agency, Slovenske nacionalne komisije za UNESCO /

Slovenian National Commission for UNESCO in / and Postojnska jama turizem d.d.

CONTENTS

VSEBINA

PAPERS ČLANKI

Franci GAbROvšEK 7 ON DENUDATION RATES IN KARST O hItROStI dENUdACIjE NA KRASU

Arthur N. PALmER 15 VARIATION IN RATES OF KARST PROCESSES

SPREmENLjIvOSt hItROStI KRAšKIh PROCESOv

Wolfgang dREybROdt & douchko ROmANOv 25 TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS By MIxING CORROSION IN THE SALTwATER-FRESHwATER TRANSITION ZONE.

ČASOvNO mERILO RAzvOjA POROzNOStI zARAdI KOROzIjE mEšANICE v mEjNEm ObmOČjU SLAdKOvOdNIh LEČ v mEdzRNSKO POROzNEm KARbONAtNEm ObALNEm vOdONOSNIKU

Andrej mIhEvC 35 THE AGE OF KARST RELIEF IN wEST SLOVENIA

StAROSt KRAšKEGA RELIEFA v zAhOdNI SLOvENIjI

William b. WhItE 45 EVOLUTION AND AGE RELATIONS OF KARST LANDSCAPES RAzvOj IN StAROStNI OdNOSI KRAšKIh POKRAjIN

Philippe AUdRA, Alfredo bINI, Franci GAbROvšEK, Philipp häUSELmANN, Fabien hObLéA, Pierre-yves jEANNIN, jurij KUNAvER, michel mONbARON, France šUštERšIČ, Paola tOGNINI, hubert tRImmEL & Andres WILdbERGER 53 CAVE AND KARST EVOLUTION IN THE ALPS AND THEIR RELATION TO PALEOCLIMATE AND PALEOTOPOGRAPHy RAzvOj jAm IN KRASA v ALPAh v LUČI PALEOKLImE IN PALEOtOPOGRAFIjE

Leonardo LAtELLA & Ugo SAURO 69 ASPECTS OF THE EVOLUTION OF AN IMPORTANT GEO-ECOSySTEM IN THE LESSINIAN MOUNTAIN (VENETIAN PREALPS, ITALy) POGLEdI NA RAzvOj POmEmbNEGA GEO-EKOSIStEmA v GORAh LESSINI (bENEšKE PREdALPE, ItALIjA)

Oana teodora mOLdOvAN & Géza RAjKA 77 HISTORICAL BIOGEOGRAPHy OF SUBTERRANEAN BEETLES – “PLATO’S CAVE” OR SCIENTIFIC EVIDENCE? zGOdOvINSKA bIOGEOGRAFIjA POdzEmELjSKIh hROšČEv – »PLAtONOvA jAmA« ALI zNANStvENI dOKAz?

david C. CULvER & tanja PIPAN 87 wHAT DOES THE DISTRIBUTION OF STyGOBIOTIC COPEPODA (CRUSTACEA) TELL US ABOUT THEIR AGE? KAj NAm POvE RAzšIRjENOSt StIGObIONtSKIh CEPONOŽNIh RAKOv (CRUStACEA: COPEPOdA) O NjIhOvI StAROStI?

Philipp häUSELmANN 93 HOw TO DATE NOTHING wITH COSMOGENIC NUCLIDES KAKO dAtIRAtI PRAzNINE S KOzmOGENImI NUKLIdI

bojan OtONIČAR 101 UPPER CRETACEOUS TO PALEOGENE FORBULGE UNCONFORMITy ASSOCIATED wITH FORELAND BASIN EVOLUTION (KRAS, MATARSKO PODOLJE AND ISTRIA; Sw SLOVENIA AND Nw CROATIA) zAKRASELA PERIFERNA IzbOKLINA POvEzANA z RAzvOjEm zGORNjEKREdNO-PALEOGENSKEGA PREdGORSKEGA bAzENA; KRAS, mAtARSKO POdOLjE IN IStRA (jz SLOvENIjA IN Sz hRvAšKA)

Robert G. LOUCKS 121 A REVIEw OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS AND ASSOCIATED SUPRASTRATAL DEFORMATION

mEdSEbOjNO zdRUŽENI PORUšENI PALEOKRAšKI jAmSKI SIStEmI IN dEFORmACIjE NAd NjImI LEŽEČIh PLAStI – PREGLEd

R. Armstrong L. OSbORNE 133 THE wORLD’S OLDEST CAVES: - HOw DID THEy SURVIVE AND wHAT CAN THEy TELL US? NAjStAREjšE jAmE NA SvEtU: KAKO SO SE OhRANILE IN KAj NAm LAhKO POvEdO?

Ira d. SASOWSKy 143 CLASTIC SEDIMENTS IN CAVES – IMPERFECT RECORDERS OF PROCESSES IN KARST KLAStIČNI SEdImENtI v jAmAh – NEPOPOLNI zAPIS KRAšKIh PROCESOv

Ognjen bONACCI 151 ANALySIS OF LONG-TERM (1878-2004) MEAN ANNUAL DISCHARGES OF THE KARST SPRING FONTAINE DE VAUCLUSE (FRANCE)

ANALIzA dOLGOČASOvNEGA (1878-2004) POvPREČNEGA LEtNEGA PREtOKA KRAšKEGA IzvIRA FONtAINE dE vAUCLUSE (FRANCIjA)

Fred G. LUISzER 157 TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

ČASOvNO USKLAjEvANjE RAzvOjA jAmSKIh PROStOROv IN SEdImENtACIjA v jAmI CAvE OF thE WINdS, mANItOU SPRINGS, COLORAdO, zdA

megan L. PORtER, Katharina dIttmAR & marcos PéREz-LOSAdA 173 HOw LONG DOES EVOLUTION OF THE TROGLOMORPHIC FORM TAKE? ESTIMATING DIVERGENCE TIMES IN ASTyANAx MExICANUS

KAKO dOLGO tRAjA EvOLUCIjA tROGLOmORFNIh ObLIK? OCENjEvANjE dIvERGENČNIh ČASOv PRI AStyANAX mEXICANUS

Peter tRONtELj, špela GORIČKI, Slavko POLAK, Rudi vEROvNIK, valerija zAKšEK & boris SKEt 183 AGE ESTIMATES FOR SOME SUBTERRANEAN TAxA AND LINEAGES IN THE DINARIC KARST

OCENE StAROStI zA NEKAtERE POdzEmELjSKE tAKSONE IN ŽIvALSKE LINIjE NA dINARSKEm KRASU

Eleonora tRAjANO 191 THE CHALLENGE OF ESTIMATING THE AGE OF SUBTERRANEAN LINEAGES: ExAMPLES FROM BRAZIL IzzIv OCENjEvANjA StAROStI POdzEmELjSKIh ŽIvALSKIh LINIj: PRImERI Iz bRAzILIjE

Andreas WESSEL, Petra ERbE & hannelore hOCh 199 PATTERN AND PROCESS: EVOLUTION OF TROGLOMORPHy IN THE CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I – PRELIMINARy OBSERVATIONS (INSECTA: HEMIPTERA: FULGOROMORPHA: CIxIIDAE) vzOREC IN PROCES: EvOLUCIjA tROGLOmORFNOStI PRI jAmSKIh mREŽEKRILNIh šKRŽAtKIh Iz AvStRALIjE IN hAvAjEv – PRELImINARNE UGOtOvItvE (INSECtA: hEmIPtERA: FULGOROmORPhA: CIXIIdAE)

207

ABSTRACTS

FOREwORD

Time occupies a curious place in science. In most of science, including karst science, “how” questions predominate. How are caves formed? How are caves eroded? How do animals survive in caves? How do animals come to lose their eyes and pigment in caves? But “when” questions have probably been asked from the very beginning of karst studies. Some of the fascination with time comes from the parent disciplines of biology and geology. Te diference between “catastrophism” and “uniformitarian-ism” in geology is also a question of diferences in time— rapid catastrophes versus slow, small changes. In biology, particularly in the late 19th and early 20th centuries, great controversies raged between the slow pace of evolution envisioned by Darwinians and the fast pace of evolution envisioned by neo-Lamarckians.

questions of time have been especially fascinating in the karst sciences, probably because our senses tell us that caves (and cave animals) are very ancient. Caves are afer all the dwelling place in mythology of ancient creatures—dragons especially. Of course our senses (and our mythology) can be deceiving, and perhaps caves and cave animals are not as old as they seem to be. wide difer-ences of opinion have persisted about the ages of both caves and cave animals—estimates at present that range between less than a million years to up to 100 million years! Te time is ripe to examine time in karst.

Te set of papers and abstracts in this volume is the result of a meeting, time in Karst, of karst scientists in Postojna, Slovenia, in March 2007. Jointly sponsored by the Karst Research Institute ZRCSAZU of Slovenia and the Karst waters Institute of the U.S.A., an international

group of scientists came together to learn about and discuss time processes in karst from six perspectives:

• Te age of karst landscapes, including caves and other karst landforms

• Te biogeographic history of cave animals, especially as it relates to the present and past distributions of cave animals

• methods of determining the age of caves, especially geophysical ones

• Paleokarst and what it can tell us about age

• Te sediment record

• Te age of lineages of cave animals, especially using molecular clock techniques

Both the Karst Research Institue ZRCSAZU and the Karst waters Institute have a history of promoting both international and interdisciplinary cooperation, and they are pleased to form a partnership in this international, interdisciplinary endeavour.

Te participation of many researchers in early stages of their careers was made possible by project SMARTKARST of the Karst Research Institute, ZRC SAZU, funded by the Marie Curie programme, sponsored by the European Commission. Many members of the Karst Research Institute ZRCSAZU and the Karst waters Institute worked hard to make this meeting possible, including Drs. Daniel Fong, Franci Gabrovšek, Andrej Kranjc, Tanja Pipan, and Ira Sasowsky.

tadej Slabe david C. Culver

TIME in KARST, POSTOJNA 2007, 5

COBISS: 1.01

ON DENUDATION RATES IN KARST O HITROSTI DENUDACIJE NA KRASU

Franci GABROVŠEK1

Abstract                                           UDC 551.331.24:551.44

Franci Gabrovšek: On denudation rates in Karst

Paper presents a simple mathematical model, which enables study of denudation rates in karst. A vertical fow of water which is uniformly infltrated at the surface is assumed. Denudation rate is calculated from the time needed to remove certain thickness of rock. Tis is done concretely on a limestone block dissected by a vertical array of fractures. It is shown that denudation rate increases with the thickness of removed layer and approaches an upper limit which is defned by the maximum denudation equations, which are based on assumption that all dissolution potential is projected into a surface lowering. Keywords: karst, denudation rate, limestone dissolution, mathematical model.

Izvleček                                            UDK 551.331.24:551.44

Franci Gabrovšek: O hitrosti denudacije na Krasu

V prispevku predstavim enostaven matematični model s katerim raziskujem dinamiko zniževanja kraškega površja. Predpostavim enakomerno napajanje s površja in vertikalno pronicanje vode. Denudacijsko stopnjo izračunam iz časa, ki je potreben za odstranitev določene debeline kamninskega sloja. Konkretno to naredim na primeru apnenca v katerem se voda pretaka v sistemu vertikalnih razpok. Hitrost denudacije narašča z debelino odstranjene plasti in doseže zgornjo mejo, ki je določena z enačbami, ki temeljijo na predpostavki, da se celoten korozivni potencial vode manifestira v zniževanju površja. Ključne besede: kras, denudacijska stopnja, raztapljanje apnenca, matematični model.

INTRODUCTION

Uniform lowering or surface denudation is a dominant karstifcation process (Dreybrodt, 1988; Ford & williams, 1989; white, 1988). Te denudation rate is defned as the rate (LT-1) of lowering of a karst surface due to the dissolution of bedrock. A common approach used to estimate the denudation rate is based on the presumed equilibrium concentration (or hardness) and the amount of water which infltrates into the subsurface. It is summarized in the famous Corbel’s equation (Corbel, 1959):

Dc (m/Ma) =

(P-E)H 1000-p

/

Te infltrated water in mm/y is the diference between precipitation P and evapotranspiration E. H is the equilib-

rium concentration (Hardness) in mg/L of dissolved rock, ρ is the density of limestone in g/cm3, f denotes the portion of soluble mineral in the rock, which will be 1 in this paper. Te factor 1000 corrects for the mixture of units used in the equation.

Tere are more general equations of this kind like that of white (1984, this issue). For a Limestone terrain in a temperate climate all these equations give denudation rate of the order of several tens of meters per million years. Similar results are obtained from fow and concentration measurements in rivers which drain a known catchment area. From the measured data the total rock volume removed from the area in a given time period can be calculated. Dividing the removed volume by the surface of the area and the time interval gives the denudation rate.

1 Karst Research Institute ZRC SAZU, Postojna, Slovenia, e-mail: gabrovsek@zrc-sazu.si Received/Prejeto: 01.02.2007

TIME in KARST, POSTOJNA 2007, 7–13

1

FRANCI GABROVŠEK

Eq.1 implies that all dissolution capacity of water is used in the rock column, i.e. the solution at the exit of rock block is close to saturation. Among the many assumptions behind such estimations of the denudation rate I will address two of which at least one must be valid:

1.  Most of the dissolution occurs close to the surface, i.e. within epikarst.

2.  In the long term, the dissolution at depth is integrated into a surface denudation.

It is the intention of this paper to theoretically validate “maximum denudation” approach.

SURFACE LOwERING AND THE VOLUME OF DISSOLVED ROCK

Dissolution of any rock is not instantaneous, but proceeds at some fnite rates. In conditions of difuse infltration through the karst surface and prevailing vertical fow, the concentration of dissolved rock in the infltrating water will normally increase with the depth as schematically shown by color intensity in Fig.1.

Fig. 1. Section of a terrain with a uniform surface infltration of aggressive solution and prevailing vertical fow. Color intensity denotes that the concentration of dissolved rock increases with depth.

Fig. 2 presents point at some depth z below the surface. Te volume ΔV of rock dissolved per unit surface area S in time Δt between the surface and the point is given by

AV/S = c(z)-q-&t /p                           2

where c(z) is the concentration of dissolved rock [M/L3] at the depth z, q is the infltration rate at the surface [L3/ (L2T)] and ρ is the density of the rock [M/L3].

Due to the surface lowering, the depth of the point is decreasing according to z(t) = z0 - D·t, where z0 is the

Fig. 2: Idealized profle through the rock column at time t = 0 (lef) and t > 0 (right). Te depth of the point which is at z0 decreases in time due to the surface lowering.

depth at t = 0 and D is the denudation rate (Fig. 2). Te volume of dissolved rock per surface area in time T above the point is then given by:

T                                       T

AV/S (T) = ^ fc(z(t)) dt = - fc(z0 - D • t) dt           3

Po                 Po

Introducing a new variable z=z0 - D·t into the right hand integral in Eq. 3 gives:

AV

W=w / c<z)dz

D-p. J

TIME in KARST – 2007

4

8

ON DENUDATION RATES IN KARST

Te complete volume of rock initially above z0 is z0·S. To remove this volume a time TD is needed, where z0 = D·TD. Using all this in Eq. 4, we obtain:

plete layer and D an avarege denudation rate. It is easy to see that if the solution quickly attains equilibrium Eq. 6 gives maximum denudation rates:

Sfc(z)dz

q-TD z0-p

fc(z)dz

zoPo            P

D,

D

VPo

fc(z)dz

As given, D is an average denudation rate, calculated from the time TD needed to remove a layer of thickness z0 from the rock column with initial a uniform porosity distribution in vertical direction. If a rock layer has a fnite thickness, z0 can be taken as the layer thickness, TD the time needed to remove the com-

If this is not the case D will be below Dc, since integral with ceq is maximal. In this case we rewrite Eq. 6 as:

D = ^-lfc(z)dz = fcJDc

C          7-J                                    P.

with increasing layer thickness an average concentration within the layer increases and average denudation rates approach maximal.

CALCULATION OF THE CONCENTRATION PROFILE

Te results given so far are valid for any “natural” c(z). To obtain some quantitative results we revert to a special case where the calcite aggressive water is infltrating into a vertical fracture network. Terefore we need to couple the rate equation for limestone and fow of laminar flm down a vertical fracture wall.

ature, the presence of the foreign ions and the nature of the system where dissolution proceeds (open, closed, intermediate) (Appelo & Postma, 1993; Dreybrodt, 1988). Te calcium equilibrium concentration normally takes values between 0.5 mmol/l – 3 mmol/l, which in terms of dissolved calcite means 50—300 mg/l .

LIMESTONE DISSOLUTION RATES Recently Kaufmann & Dreybrodt (2007) published the corrected rate equation with two linear regions and a non-linear region of dissolution kinetics:

«iC0-3^-^ c<03ceq R = ' a2(ceq -c) 0.3ceq<c< 0.9ceq           9

ßic^-c)" c>0.9c

," v eg         J                             eq

LAMINAR FLOw DOwN A SMOOTH VERTICAL wALL Only rough assumptions can be made about the fow regime of infltrated water. we assume a laminar flm fow down the walls of vertical fractures. Te velocity of such flm is given by (Bird et al., 2002):

3v

10

Te kinetic constants and rate orders are derived from theoretical and experimental results (Buhmann & Dreybrodt, 1985; Dreybrodt, 1988; Eisenlohr et al., 1999; Kaufmann & Dreybrodt, 2007). Values depend on the temperature, pCO2 and laminar layer thickness and are given in Kaufmann & Dreybrodt (2007). we will use α1 = 3·10-4 cm/s and α2 = 8·10-6 cm/s, values which are valid at 10°C for the open system dissolution (Kaufmann & Drey-brodt, 2007). Nonlinear kinetics will not be discussed here. It is valid close to equilibrium and does not change the results substantially. ceq depends on the pCO2, temper-

where δ is the flm thickness, g gravitational acceleration and υ the kinematic viscosity. More suitable master variable is a fow density along the fracture walls qf (cm2/s). Applying qf = vö we get:

T -'-""K)

11

TIME in KARST – 2007

5

7

6

8

9

FRANCI GABROVŠEK

THE COUPLING OF FLOw AND DISSOLUTION To get the evolution of a concentration in a falling flm, the mass balance for dissolved calcite must be coupled to the rate laws given in Eq. 9. In a small volume of water flm with thickness δ, width b, length dz and concentration c, the mass balance requires:

Aax(c -c)dt=Vdc=Aödc;c<03ceq Aa^- c)dt=Vdc=A8dc; 0.3 cn< c < 0.9^

12

where A is the surface of the water rock contact (b·dz). Integration of Eq. 12 gives the evolution of concentration in time as the flm fows down the fracture wall:

c(t)

0.3ceq(l-e-,^);c<0.3ceq

c_(l-0.7e-^);0.3c <c<0.9ca

13

where xi = bla{ . Note that τ1 is more than an order of magnitude smaller than τ2. The time domain can easily be converted into the space domain using z = v ■ t and qf =v-ö

Fig.3: Concentration profle in a flm fowing down a smooth vertical fracture and dissolving limestone walls. values of λ2 are calculated from the fracture fow density obtained if the fracture spacing is 1 m and infltration intensity is 0.114 mm/h, 10 mm/h, 20 mm/h, 30 mm/h and 40 mm/h for curves 1-5 respectively.

c(z)

0.3Ceq(l-e-^);c<0.3Ceq [ceq(l-0.7e-^);0.3ceq<c<0.9cK

14

where Xä =qf/<Xj . Fig. 3 presents the evolution of saturation ratio c(z)/c for diferent λ2. For most reasonable

eq

scenarios, the frst linear kinetics is active only close to the surface. Terefore, it will be integrated directly into the surface lowering (i.e. c(z= 0) = 0.3 c ).

SATURATION LENGTH λ AND THE FRACTURE FLOw DENSITy

Saturation length λ2 controls the vertical evolution of concentration profle. It depends on the kinetic constant and the fracture fow density. To estimate the latter we assume that the rain falling to the surface with an intensity q is evenly infltrated into a regular grid of fractures as shown on Fig. 4. Te fow density in each fracture is proportional to the ratio between the surface of the infl-tration area and the total breadth of the fractures draining the area. In a regular grid of fractures with fracture spacing d we obtain:

q,

= N-

15

Fig. 4: Rain falling with intensity q [Lt-1] is uniformly distributed into the fractures with fow density qf [Lt-1] according to Eq.15.

10

TIME in KARST – 2007

ON DENUDATION RATES IN KARST

where N depends on the geometry of fracture grid (e.g. ½ for a series of parallel fractures and ¼ for a square grid). For thin flms (δ < 0.005 cm) the rates are controlled by conversion of CO2 into H+ and HCO3- and therefore increase linearly with flm thickness. Infltration intensity below 3 mm/h into a series of fractures with d = 100 cm produces flm thicknesses below 0.005 cm. Extremely low infltration intensities (< 1 mm/h) and fracture spacing in the range of few centimeters result in flm thicknesses in the order of 0.001 cm. Tis reduces the kinetic con-

stant α approximately by a factor of 5. For thin flms, the flm thickness and α decrease with qf1/3. Consequently λ2 is proportional to the qf2/3. Tis has limited consequences for the dissolved volume and denudation rate discussed in the next section.

In the early stages, the fracture fow is not expected to be in the form of a free surface flm, but full fracture fow instead. Te saturation lengths in that case would be smaller than those derived here. Te evolution of such fractures is given in Dreybrodt et al. (2005).

RESULTS AND DISCUSSION

Inserting the concentration profle from Eq. 14 (second linear region only) into Eq. 7 gives:

D = ^^f(l-0.7e-z'^) dz P Jo

P                P Jo

16

z„

Although it is a matter of a defnition, the average denudation rate given in Eqs. 8 and 16 are not exactly what we are afer. what we look for is the actual lowering of karst surface, which is given by dzg I dTD. we will not go into mathematical details of derivation, but instead discuss its consequences on a plot of z0(TD). Note that the z0(TD) has no explicit form, but its inverse function does:

TD(z0) =

Dc-0.7■T>c-y^{\-s-1^1)

17

we will demonstrate the results on a characteristic data for a moderate climate with I=1000 mm/y and relatively bare karst area with ceq= 1mmol/l or H = 100 mg/L. For ρ = 2.5 g/cm3. DC for this case is 40 m/Ma. we assume that the rain infltrates into a parallel set of fractures with spacing d = 1 m.

Fig. 5a shows z0(TD) for four different saturation lengths arising from different infiltration intensities. yearly infiltration is 1000 mm/y for all curves. Therefore, the time period of dissolution is inversely proportional to the infiltration intensity. Dashed line shows the uniform lowering by D . we wee that all lines become practically parallel to maximum denudation line for zg > 2A2.The actual denudation rate becomes “maximal” when the removed thickness is larger than 2λ2. This is about the depth where the concentration reaches 90% of saturation. The slope of the dotted lines presents the averaged denudation rates for curve with λ2 = 70 m.

Fig. 5b shows the averaged rate for the same scenarios as Fig. 5a. Red dashed red curve clearly shows the fast approach of the actual rate to maximal for λ2 = 52.5 m.

Another interesting conclusion can be made from Fig. 5a. Diferent saturation lengths λ can also arise from diferent fracture spacing (see Eq. 15 for qf) . If we imagine a region with high fracture density within a region of low fracture density, the frst will initially be denuded faster, but latter on both actual rates will become the same. Terefore the diference made at the onset will stay projected in the surface. Tis is shown by the double arrow between lines 3 and 4.

TIME in KARST – 2007

11

FRANCI GABROVŠEK

Fig. 5: a) Te time dependence of removed thickness for several infltration intensities. I=1000 mm/y, h = 100 mg/L, ρ = 2.5 g/cm3, d = 100 cm, N = 2. dashed line show the “maximum denudation” rate which is 40 m/ma. dotted lines present the time averaged denudation rates (Eq.16). double arrow demonstrates the diference between the denuded thicknesses which is kept in time due to the initial rate diferences.

b) dependence of average denudation rates on the removed thickness for the same scenarios as in Fig. 5a. dashed line presents the actual surface lowering for λ2 = 52.5 m.

12 TIME in KARST – 2007

ON DENUDATION RATES IN KARST

CONCLUSION

Denudation rate in a block with initially uniform porosity increases as the denudation proceeds and becomes maximum denudation (Eq.1), when the thickness of removed layer is about twice the typical saturation length. Initial diferences arising from diferent saturation lengths remain imprinted in the surface.

If a soluble layer has a fnite thickness, the average denudation rate increases with the thickness, i.e. denudation is more efective on thick rock layers.

Te presented results are based on many assumptions which might not be valid. Nevertheless, it gives some theoretical validation of maximum denudation formulae and suggest some mechanisms that can cause irregularities in karst surface.

REFERENCES

Appelo, C. A. J. & D. Postma, 1993: Geochemistry, ground-water and pollution. A.A. Balkema, xvi, 536 pp, Rotterdam; Brookfeld, VT.

Bird, R. B., Stewart, w. E. & E.N. Lightfoot, 2002: transport phenomena. John wiley & Sons, Inc., xii, 895 p. pp, New york, Chichester.

Buhmann, D. & w. Dreybrodt, 1985: Te kinetics of cal-cite dissolution and precipitation in geologically relevant situations of karst areas.1. Open system.-Chemical geology, 48, 189-211.

Corbel, J., 1959: Vitesse de l’erosion.- Zeitschrif fur Geomorphologie, 3, 1-2.

Dreybrodt, w. , Gabrovšek, F. & D. Romanov, 2005: Processes of speleogenesis: A modeling approach. Vol. 4, Carsologica, Založba ZRC, 375 pp, Ljubljana.

Dreybrodt, w. , 1988: Processes in karst systems: physics, chemistry, and geology. Springer-Verlag, xii, 288 p. pp, Berlin; New york.

Eisenlohr, L., Meteva, K., Gabrovšek, F. & w. Dreybrodt, 1999: Te inhibiting action of intrinsic impurities in natural calcium carbonate minerals to their dissolution kinetics in aqueous H2O-CO2 solutions.- Geo-chimica Et Cosmochimica Acta, 63, 989-1001.

Ford, D.C. & P. williams, 1989: Karst geomorphology and hydrology. Unwin Hyman, 601 pp, London.

Kaufmann, G. & w. Dreybrodt, 2007: Calcite dissolutio n kinetics in the system CaCO3-H2O-CaCO3 at high undersaturation.- Geochimica Et Cosmochimica Acta, In Press.

white, w.B., 1984: Rate processes: chemical kinetics and karst landform development. In: La Fleur (Ed.): Groundwater as a geomorphic agent. Allen and Un-win, 227-248.

white, w. B., 1988: Geomorphology and hydrology of karst terrains. Oxford University Press, ix, 464 pp, New york.

TIME in KARST – 2007

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COBISS: 1.01

VARIATION IN RATES OF KARST PROCESSES SPREMENLJIVOST HITROSTI KRAŠKIH PROCESOV

Arthur N. PALMER1

Abstract                                                           UDC 551.44

Arthur N. Palmer: Variation in rates of Karst processes

Te development of karst is not a linear process but instead takes place at irregular rates that typically include episodes of stagnation and even retrograde processes in which the evolution toward maturity is reversed. Te magnitude and nature of these irregularities difers with the length of time considered. Contemporary measurements in caves show fuctuations in dissolution rate with changes in season, discharge, and soil conditions. Dissolution is sometimes interrupted by intervals of mineral deposition. Observed dissolution rates can be extrapolated to obtain estimates of long-term growth of a solution feature. But this approach is fawed, because as the time scale increases, the rates are disrupted by climate changes, and by variations that are inherent within the evolutionary history of the karst feature (e.g., increased CO2 loss from caves as entrances develop). At time scales of 105-106 years, karst evolution can be interrupted or accelerated by widespread fuctuations in base level and surface river patterns. An example is the relation between karst and the development of the Ohio River valley in east-central U.S.A. At a scale of 106-108 years, tectonic and stratigraphic events cause long-term changes in the mechanism and style of karst development. For example, much of the karst in the Rocky Mountains of North America has experienced two phases of pre-burial Carboniferous karst, mineral accretion during deep burial from Permian to Cretaceous, extensive cave development during Paleocene-Eocene uplif, and stagnation and partial mineral deposition caused by late Tertiary aggradation. At such large time scales, it is difcult to determine rates of karst development precisely, if at all. Instead it is appropriate to divide the evolutionary history into discrete episodes that correlate with regional tectonic and stratigraphic events. Key words: Karst evolution, dissolution rates, retrograde processes, paleokarst.

Izvleček                                                            UDK 551.44

Arthur N. Palmer: Spremenljivost hitrosti kraških procesov

Razvoj krasa ni lineareni proces, pač pa poteka s spremenljivo hitrostjo, značilna so tudi obdobja stagnacije in obdobja, ko je razvoj obrnjen v smeri manj zrele faze. Velikost in narava sprememb sta odvisni tudi od časovnega merila v katerem jih opazujemo. Današnja merjenja v jamah kažejo, da je hitrost raztapljanja odvisna od letnega časa, pretoka in pogojev v prsti. Raztapljanje je občasno prekinjeno z obdobjem izločanja. Izmerjene hitrosti raztapljanja lahko ekstrapoliramo v času in na osnovi tega sklepamo o rasti določene korozijske oblike. Vendar bomo pri tem storili napako, saj merjenja ne vsebujejo dolgočasovnih sprememb. Te so lahko posledica različnih dejavnikov, kot so klimatske spremembe in spremembe, ki nastanejo zaradi samega razvoja krasa (npr. uhajanje CO2 zaradi odpiranja jamskih vhodov). V časovnem merilu 105-106 let razvoj krasa prekinjajo ali pospešujejo spremembe erozijske baze in spremembe površinskih vodotokov. Tak primer je povezava med razvojem krasa in doline reke Ohio v vzhodnem delu centralnih ZDA. V časovnem merilu 106-108 let tektonski in strati-grafski dogodki povzročajo dolgočasovne spremembe v razvoju krasu. Tak primer je kras v Skalnem gorovju v Severni Ameriki. Dvem fazam zakrasevanja v karbonu je sledil pokop in mineralna zapolnitev med permom in kredo. Temu je sledil obširen razvoj jam med paleocensko-eocenskim dvigom ter stagnacija in delna mineralna zapolnitev v poznoterciarni agradaciji. V tako velikem časovnem merilu je težko določiti hitrost razvoja krasa, če sploh. Primerneje je, da razvojno zgodovino razdelimo v obdobja, ki ustrezajo pomembnejšim regionalnim tektonskim in stratigrafskim dogajanjem.

Ključne besede: razvoj krasa, hitrost raztapljanja, procesi nazadovanja, paleokras.

1 Department of Earth Sciences, State University of New york, Oneonta, Ny 13820-4015, U.S.A. e-mail: palmeran@oneonta.edu

Received/Prejeto: 27.11.2006

TIME in KARST, POSTOJNA 2007, 15–24

ARTHUR N. PALMER

INTRODUCTION

In any discussion of the age of karst, one must consider the rates of the genetic processes and how they vary with time. Tese are infuenced by the length of time over which they have operated. Karst development undergoes large variations in rate and is commonly interrupted by periods of stagnation or even retrograde processes in

One approach to interpreting karst history is to measure current rates of bedrock dissolution, for example by applying the mass balance, or by measuring rates of bedrock retreat with micrometers or standardized bedrock tablets. In the two following studies, empirical kinetic equations are applied. On the basis of prior dissolution experiments, feld measurements of water chemistry are used to estimate dissolution or accretion rates at specifc locations and times.

Field example: eastern New York State

Chemical measurements were made during 1985-1996 in streams of McFail’s Cave, New york (Fig. 1; Palmer, 1996). Suitable data-loggers were not available for use in this food-prone cave, so measurements were made randomly at every opportunity. Although statistically shaky

Fig. 1: map of mcFail’s Cave, New york, showing location of sampling sites.

which mass is accumulated instead of removed. Tis paper focuses on several feld examples that illustrate these processes and the difculty of quantifying them. Tese studies are still in progress and are used here only as points for discussion.

compared to continuous or short-interval sampling, this approach allowed full chemical analyses.

Te cave, in Silurian-Devonian limestones, consists of stream passages fed by dolines and ponors. Local soil PCO2 is 0.02-0.04 atm, but in this well-aerated cave the mean PCO2 of streams is only ~0.003 atm. Most measurements were made in the main passage and were correlated with discharge, but this location was not accessible during high fow. To provide broader coverage, additional measurements were made in similar passages with year-round accessibility. Chemical variations between sampling sites were negligible compared to variations with time. To allow extrapolation, the measurements were combined in a probability plot (Fig. 2), in which SI = log (IAP/K), IAP = (Ca2+)(CO32-), and K = calcite solubility product.

Fig. 2: Probability plot of calcite saturation index in mcFail’s Cave for the period 1985-1996, where SI = log(IAP/K). data points are triangles; X = example of probability interval used in table 1.

Although the passages involved are active canyons, the water is conspicuously supersaturated except during the highest 20-30% of fow. At low fow the calcite SI ofen exceeds +0.4 (~138% saturation). Calcite can precipitate

SHORT-TERM VARIATIONS IN DISSOLUTION RATE

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VARIATION IN RATES OF KARST PROCESSES

at approximately SI > +0.2, so why does it not precipitate in the cave at those times?

During a particularly dry summer (1995), a conspicuous calcite layer did accumulate on the canyon foors. Tis coating averaged 0.3 mm thick with inclusions of clay and quartz silt (Figs. 3 & 4). It was limited to surfaces that remained water-covered during lowest fow and formed a continuous layer in areas of steep gradient (supercritical fow) but only discontinuous patches in ponded water.

Fig. 3: main stream of mcFail’s Cave during the summer of 1995, with calcite coating on foor of canyon.

In mid-January, 1996, heavy rain fell on rapidly melting snow and produced a food with a return period of ~50 years. Te main cave entrance was covered by 5 m of water, and smaller inputs contained roaring waterfalls. Te calcite SI of the water entering the cave averaged -1.9 (cf. Fig. 2). Tis sample is not included in the statistics, as it was not random, but obtained purposely at the food peak, and it is not in the same class as the in-cave samples. However, it illustrates the high dissolutional capacity of extreme foodwater.

Te rate of limestone removal can be estimated by

S = 31.56 k (1 - C/Cs)n / ρ cm/yr

(Palmer, 1991), where S = rate of bedrock retreat, k = rate constant (mg-cm/L-sec), n = reaction order (di-

mensionless), Cs = calcite saturation concentration, C = actual concentration of dissolved calcite, and ρ = rock density (g/cm3). C/Cs is the saturation ratio, where 1.0 represents calcite saturation. From computer analysis, C/Cs ~ (IAP/K)0.35. For the cave conditions (mean PCO2 = 0.003 atm and T = 8°C), laboratory measurements by Plummer et al. (1978) show that k ~0.01 and n ~2.2 at C/Cs < 0.6, and k ~0.05 and n ~4 at C/Cs > 0.6 in open-system turbulent fow. Bedrock density is ~2.7 g/cm3 in this low-porosity rock.

From chemical measurements during the winter and spring of 1996, it was predicted that the entire calcite coating of 1995 should have been removed by the time the cave became accessible in May. In fact, all but a few sheltered remnants of the calcite had been removed by then. Although mechanical abrasion may have aided the removal in places, the agreement between prediction and result is mild support for the validity of this approach.

Fig. 2 includes a best-ft regression line through the chemical data. where this line extends below saturation, the probability scale was divided into 5% increments. From the mean SI in each increment, a net dissolution rate of 1.3 x 10-3 cm/yr was calculated for the period of study (Table 1). At that rate, the main cave stream would have deepened about 18 cm since the last glacial retreat in the region about 14,000 years ago. Tis is compatible with the presence of varved clays no more than a few centimeters above the lowest bedrock foors. Te clay was deposited when retreating glaciers blocked the local surface river, fooding the valley and neighboring caves.

Probability range

Mean

C/Cs

Mean S (cm/yr)

Net annual entrenchment (cm)

<0.05

~0.52

~0.017

~8.5 x 10 4

0.05 - 0.10

0.65

0.0064

3.2 x 10 4

0.10 - 0.15

0.74

0.0019

9.5 x 105

0.15 - 0.20

0.88

8.8 x 105

4.4 x 106

0.20 - 0.25

0.89

7.4 x 105

3.7 x 106

0.25 - 0.30

0.95

2.1 x 106

1.1 x 107

TOTAL:

1.3 x 10-3 cm/yr 13 mm/1000 yrs

tab. 1: Net dissolution rate in mcFail’s Cave canyons, 1985-1996,where the best-ft line in Fig. 2 falls below SI = 0. Entrenchment rates are calculated from the regression line, rather than from specifc data points, and provide only a rough approximation.

At the estimated entrenchment rate, the 10 m depth of the main McFail’s canyon would have required more than 700,000 years to form. Tis rate seems low for an active canyon with a gradient of 1.2 degrees, but it is

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ARTHUR N. PALMER

Fig. 4: Tin-section photomicrograph showing calcite crust on a limestone pebble from mcFail’s Cave (September, 1995).

compatible with U/T speleothem dates. Related caves at the same elevation as McFail’s contain speleothems dated up to 277 ka (Dumont, 1995; Lauritzen & Mylroie, 2000; Mylroie & Mylroie, 2004). Some speleothems were located near the cave foors, so the passages themselves are far older. But the entrenchment rate during this period must have varied because of climate changes and burial beneath glacial ice for several tens of thousands of years. (Te only known glaciation in the area was wisconsin-an.) Te coarse bedload in parts of the cave also suggests mechanical abrasion during high fow.

Te entrenchment rate has probably decreased with time. when entrances were blocked by glacial sediment, or had not yet enlarged enough to form open holes, escape of CO2 to the surface must have been severely lim-

ited and the mean aggressiveness would have been higher than it is today. Also, calcareous glacial deposits cause low-fow inputs to be saturated with calcite before they even reach the cave.

Te main canyon of the cave has an entirely vadose origin because it extends exactly down the local dip of the strata, except where it is defected by joints (Fig. 1). Terefore the canyon originated afer surface rivers had entrenched below its level (currently about 300 m above sea level). Although the age of the landscape is difcult to determine from the surface, data from the cave can provide helpful information.

Mammoth Cave, Kentucky

Meiman & Groves (1997), Anthony & Groves (1997), and Groves & Meiman (2005) conducted a similar study in the main river passage of Mammoth Cave, Kentucky. Tey made a high-frequency record of water levels in monitor wells, combined with periodic measurements of water chemistry. To calculate dissolution rates, they used the kinetic equation described above. Because of thick sediment, cave enlargement rates could not be estimated precisely. However, the authors determined that during the highest 5% of fow, 38% of the mass was removed (vs. about 65% in McFail’s). Te diference is probably due, at least partly, to the lack of entrances near the sampling sites in Mammoth Cave through which CO2 is lost, the higher carbonate content of soils in the New york karst, and the dominance of sinking-stream inputs to McFail’s Cave during severe foods.

VARIATION IN KARST PROCESSES AT TIME SCALES OF 105–106 yEARS

Te low-relief karst plateaus of Kentucky and Indiana, U.S.A., are developed on early Carboniferous carbonates and include extensive doline felds bordered by sinking streams. Tese include the Pennyroyal Plateau in Kentucky and the Mitchell Plain in Indiana. Tey are dissected to a maximum of 50-65 m by river valleys. Near rivers, inter-doline divides and residual fat areas lie 175-190 m above sea level, and up to a few tens of meters higher elsewhere. Although resistant beds form local fat areas, the overall surface is discordant to the strata. Te surface is mantled in many places by residual, colluvial, and alluvial sediment up to 30 m thick, the surface of which is concordant with the erosion surface on nearby bedrock. In the Mitchell Plain the deposits are attributed to a widespread Tertiary rise in base level (Palmer & Palmer, 1975). On the Pennyroyal, Ray (1996) calls this relatively fat surface the Green River Strath and attributes it to fu-vial processes.

18 TIME in KARST – 2007

Caves are common in the karst plains and in adjacent sandstone-capped uplands. Mammoth Cave, Kentucky, is the best-known upland example. Its highest passages correlate with nearby low-relief areas of the Pennyroyal (Fig. 5), and passage patterns and gradients show that the Pennyroyal was the source of the cave water (Palmer, 1981). Tese passages are mostly large canyons flled partly or completely with stream sediment (Fig. 6). Dating of these sediments by cosmogenic radionuclides gives ages up to 4 Ma (Granger et al., 2001), but in areas bordering the Green River (the outlet for Mammoth Cave water), most samples date to ~2.2 Ma (see also Anthony & Granger, 2004, 2006). Tese passages record a history of slow Tertiary entrenchment interspersed with aggradation, and with a widespread rise in base level of more than 20 m at ~2.2 Ma. Te fragmentary sediment surfaces at the same elevation in the Pennyroyal must be correlative. Te cause of the widespread aggradation at

VARIATION IN RATES OF KARST PROCESSES

Fig.5: Location of mammoth Cave and surrounding landscapes. m = mitchell Plain, P = Pennyroyal Plateau, U = sandstone-capped uplands. X = pre-Pleistocene head of Ohio River. 1, 2, 3 = sequence of drainage from Appalachian mountains. 1 is probable but entirely hypothetical. 2 = late tertiary “teays River,” which is well known by its former valley, now flled with glacial sediment. 3 = course of the Ohio River since the early Pleistocene. Afer Palmer (1981); see also Granger et al., ( 2001) for explanation.

Fig. 7: typical upper-level passage in mammoth Cave with detrital sediment fll. Tis is a former tourist trail that is no longer open to the public. Sediment once flled the passage almost half-way but later subsided into an underlying passage. Note banks of remaining sediment on the lef.

Fig. 6: Simplifed cross section through the Pennyroyal Plateau and mammoth Cave, Kentucky (afer Palmer, 1981).

2.2 Ma is uncertain. It correlates roughly with the onset of widespread continental glaciation at higher latitudes, but it may relate more directly to a drying climate during the late Pliocene, which would have favored the accumulation of sediments in lowlands.

Pleistocene continental glaciers extended southward as far as northern Kentucky and caused much rearrangement of surface drainage. Initial entrenchment below the uppermost passages in Mammoth Cave may have been triggered by the establishment of drainage from the Appalachian Mountains westward to the Mississippi River, to form the so-called “Teays River” (Fig. 7; see Granger et al., 2001). Later, the previously tiny Ohio River became one of the largest rivers on the continent when the Teays was diverted into it (Fig. 7). Tese shifs en-

hanced the rate of river entrenchment into the sediment-mantled plains of carbonate rock. Subsurface karst drainage developed and the surfaces became “sinkhole plains.” Pleistocene cave passages formed at various levels as much as 60-70 m below the Tertiary passages. Again, caves provide clues to the interpretation of surface landscapes that cannot be discerned from surface observations alone.

Could the karst plateaus have retained vestiges of their original fat surface for 2 Ma without signifcant lowering? Although dolines extend deeply into them, nearly fat remnants of the sediment-covered and resistant bedrock surfaces remain at approximately the same elevations as the sediment in the upper-level passages of Mammoth Cave, which suggests that parts of the original surface have survived with little or no lowering.

what is the current karst denudation rate? Much of the Mammoth Cave area is drained by the Turnhole Spring basin, which has an area of 220 km2 (quinlan et al., 1983). In this basin, Hess (1974) measured a mean-annual Ca content of ~60 mg/L and Mg of ~7.5 mg/L (see also Hess & white, 1993). Tese measurements represent a mean dissolved load of ~0.044 cm3/L calcite and ~0.020 cm3/L dolomite (with the simplifying assumption that

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ARTHUR N. PALMER

dolomite = Mg and calcite = Ca – Mg, in moles/L). Te annual precipitation is 1.26 m/yr, and about 2/3 of it lost to evapotranspiration, so a 220 km2 basin would have a mean runof of roughly 9 x 107 m3/yr. Te loss of carbonate rock is therefore about 6000 m3/yr. Roughly half of the basin consists of exposed carbonates, so the denudation rate on that half is about 5.5 cm/1000 years. Tis fg-ure corresponds to some of the lowest measured rates of carbonate denudation elsewhere (Ford & williams, 1989, p. 112–117). Transport of solids is neglected, as is subsurface dissolution. Te Mammoth Cave System represents a maximum porosity of about than 4%, even in areas of maximum passage density (Palmer, 1995).

when the denudation rate is extrapolated to 2 million years, it indicates an overall lowering of the solu-

ble Pennyroyal surface of roughly 100 m. Tis is impossible, because it exceeds the total relief between the original surface and the Green River. Tere is no doubt that most of the surface has been lowered (Fig. 6), but there were evidently long periods of stagnation, especially at the beginning, when large parts of the surface were mantled with thick sediment. Most of the denudation is in the form of doline growth. Gams (1965) points out that corrosion accelerates in dolines as they grow, because of enhanced CO2 production in their thickening soils. Apparently the rate of karst denudation is higher today than during the early Pleistocene.

KARST DEVELOPMENT AT TIME SCALES OF 107–108 yEARS

Karst that evolves throughout entire geologic periods borne et al. (2006) describe a similarly complex history or eras tends to do so in discontinuous steps in which in the Jenolan Caves of Australia.

lengthy episodes of stagnation exceed those of active karst processes. For example, certain karst areas of the Rocky Mountains and Black Hills (western U.S.A.) have undergone at least 7 diferent stages over the past 350 my but were actively forming only about 20% of that time. Jewel and wind Caves in South Dakota are good examples (Fig. 8). with mapped lengths of 218 and 196 km, they are among the most complex caves in both pattern and diversity of geologic history. Each successive set of features was superposed on the previous ones, because each provided favorable sites for those that followed. Os-

Fig. 8: Geologic setting of Wind Cave, South dakota. L = madison Limestone (early Carboniferous) underlain by thin Cambrian sandstone, S = late Carboniferous sandstone, Sh = mainly shale, K = Cretaceous sandstone, OS = Oligocene sediment (mainly siltstone, widely eroded). Te upper surface of the madison is irregular paleokarst. Wt = water table in lowest passage of Wind Cave. Te cave extends only a few meters below the water table. Arrows show dominant fow pattern of today.

20 TIME in KARST – 2007

Te major stages of karst development in the Black Hills are outlined below (Palmer & Palmer, 1989, 1995):

1. Early Carboniferous carbonates of the Madison Formation were deposited on a low-gradient continental shelf. Interbedded sulfates were included in the middle and upper Madison.

2. Brecciation and early voids formed by dissolution and reduction of sulfates, plus production of sulfuric acid (Fig. 9). Sulfate rocks were almost completely removed.

3.  A mid-Carboniferous karst formed throughout much of western North America (Sando, 1988). Surface

features included fssures and dolines up to 30 m deep. Caves concentrated at 20-50 m below the surface along former sulfate zones and intersect earlier breccias and caves (Fig. 10). Comparison with modern caves suggests some freshwater-saltwater mixing dissolution.

4. Te karst was buried by late Carboniferous detrital sediment, and most caves were completely flled. Te sedimentary burial continued through the Cretaceous to a depth of

VARIATION IN RATES OF KARST PROCESSES

Fig. 9: Early solution voids and brecciation related to early Carboniferous sulfate-carbonate interactions in jewel Cave, South dakota. Tese are exposed by collapse of wall of a later cave. height of photo is about 2 m.

at least 2 km. Buried caves and vugs, as well as voids in the Carboniferous sediment, were lined by white scale-nohedral calcite about 1-2 cm thick (Fig. 11). Pre-burial

Fig. 10: mid-Carboniferous paleokarst, bighorn mountains, Wyoming. Caves in clif were once flled with late Carboniferous sediment, but much of it has been removed by weathering and stream erosion.

Fig. 11: top: Scalenohedral calcite coating of mesozoic age on walls of Carboniferous vug, Wind Cave (crystal length ~1.5 cm). bottom: Rhombohedral calcite coating of late tertiary age on weathered walls of an early tertiary passage, jewel Cave (maximum thickness of calcite = 15 cm).

voids can be recognized by this distinctive coating. Along faults, surfaces were coated by euhedral quartz up to a 5 mm thick.

6.  Te Black Hills and Rocky Mountains were uplifed by the Laramide orogeny (latest Cretaceous through Eocene; Fig. 8). Te climate was more humid than today’s, and the present topography above the caves was formed by the end of the Eocene. Enhanced groundwater fow enlarged earlier caves to their present form (Fig. 12). Teir layout shows evidence for mixing between shallow and deep water (Palmer and Palmer, 1989), although Bakalowicz et al. (1997) suggest a purely thermal origin.

7. Te caves drained and were exposed to subaerial weathering, which produced thick carbonate deposits in many passages.

8.  Most of the Eocene landscape was buried by Oligocene sediments during a drying of the climate. Although much of this sediment has been removed by later

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ARTHUR N. PALMER

Karst processes operate at rates that vary considerably with time, and the magnitude of that variation is generally greater as the developmental time span increases. At every time scale, the developmental history of karst (at least in the examples described here) includes episodes of stagnation and of retrograde development when material is deposited instead of removed.

Modern measurements of the rates of karst processes can be extrapolated into the past, but this extrapolation becomes more suspect as the time span increases. Over the entire growth history of major cave systems (usually 106-107 years), many disruptions in rate are caused by changes in climate, base level, and river patterns. At time scales of 107-108 years, interpretation of evolutionary rates becomes difcult, and the history of karst is usually subdivided into discrete episodes, in the same manner as tectonic and sedimentary events.

erosion, the Eocene landscape on the resistant Paleozoic-Mesozoic rocks has survived almost intact, as have the underlying caves, thanks to the present semi-arid climate.

9. Partial blockage of springs by Oligocene sediments caused a second phase of calcite coating (mainly rhombohedral) averaging 15 cm thick in Jewel Cave (Fig. 11) but thinner in wind Cave. Te earlier scalenohedral coating is still visible in pockets and vugs that were isolated from the cave development and exposed by later breakdown.

In this sequence there is little information about developmental rates. Instead, the karst history is portrayed as a series of discrete episodes, which span a wide range of processes, groundwater conditions, tectonic relationships, and levels of diagenetic maturity of the host strata. All efects have overlapped, and in some caves it is possible to stand in a single spot and distinguish every phase of their history.

Fig. 12: typical cave passage of Eocene age in Wind Cave, showing remnants of earlier breccia (b) and paleo-fll (P).height of photo is about 2 m.

As a karst feature develops toward maturity, it tends to undergo inherent changes in developmental rate. For example, a cave may decrease in enlargement rate as entrances open and enlarge, allowing greater rates of CO2 loss. Rates of karst development may increase with time as dolines develop and enlarge, owing to greater exposure of soluble rock and accumulation of high-CO2 soils in depressions.

It is impossible to interpret caves and karst without a solid understanding of their surrounding geology and physiography. But, despite uncertainties about their rates of development, karst features can provide more information about the surrounding landscape than vice versa.

CONCLUSIONS

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REFERENCES

Anthony, D.M. & D.E. Granger, 2004: A Late Tertiary origin for multilevel caves along the western escarpment of the Cumberland Plateau, Tennessee and Kentucky, established by cosmogenic 26Al and 10Be.

- Journal of Cave and Karst Studies, 66, 2, 46-55. Anthony, D.M. & D.E. Granger, 2006: Five million years

of Appalachian landscape evolution preserved in cave sediments. - In R.S. Harmon and C.M. wicks (eds.): Perspectives on karst geomorphology, hydrology, and geochemistry – A tribute volume to derek C. Ford and William b. White: Geological Society of America, Special Paper 404, 39-50.

Anthony, D.M. & C.G. Groves, 1997: Preliminary investigations of seasonal changes in the geochemical evolution of the Logdson River, Mammoth Cave, Kentucky. - Proceedings of 6th Science Conference, 15-23, Mammoth Cave, Kentucky.

Bakalowicz, M.J., D.C. Ford, T.E. Miller, A.N. Palmer & M.V. Palmer, 1987: Termal genesis of dissolution caves in the Black Hills, South Dakota. - Geological Society of America Bulletin, 99, 729-738.

Dumont, K.A., 1995: Karst hydrology and geomorphology of the barrack zourie Cave System, Schoharie County, New york. - M.S. thesis, Mississippi State University, p. 71, Mississippi State, Mississippi.

Gams, I., 1965: Types of accelerated corrosion. - In O. Štelcl (ed.): Problems of the speleological research.

-  International Congress of Speleology, 133–139, Brno, Czech.

Granger, D.E., D. Fabel & A.N. Palmer, 2001: Pliocene-Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic 26Al and 10Be in Mammoth Cave sediments. - Geological Society of America Bulletin, 113, 7, 825-836.

Granger, D.E., J.w. Kirchner, & R.C. Finkel, 1997: quaternary downcutting rate of the New River, Virginia, measured from diferential decay of cosmogenic 26Al and 10Be in cave-deposited alluvium. - Geology, 25, 107–110.

Groves, C. & J. Meiman, 2005: weathering, geomorphic work, and karst landscape evolution in the Cave City groundwater basin, Mammoth Cave, Kentucky.

- Geomorphology, 67, 115-126. Hess, J.w., 1974: hydrochemical investigations of the central Kentucky karst aquifer system. - Ph.D. dissertation, Pennsylvania State University, p. 218, University Park, Pennsylvania.

Hess, J.w. & w.B. white, 1993: Groundwater geochemistry of the carbonate aquifer, south-central Kentucky, U.S.A. - Applied Geochemistry, 8, 189-204.

Lauritzen, S.-E. & J.E. Mylroie, 2000: Results of a speleo-them U/T dating reconnaissance from the Helderberg Plateau, New york. - Journal of Cave and Karst Studies, 62, 1, 20-26, Huntsville, Alabama.

Meiman, J. & C. Groves, 1997: Magnitude/frequency analysis of cave passage development in the Central Kentucky Karst. - Proceedings of 6th Science Conference, 11-13, Mammoth Cave National Park, Kentucky.

Mylroie, J.E. & J.R. Mylroie, 2004: Glaciated karst: How the Helderberg Plateau revised the geologic perception. - Northeastern Geology and Environmental Sciences, 26, 1-2, 82-92, Troy, New york.

Osborne, R.A.L., H. Zwingmann, R.E. Pogson & D.M. Colchester, 2006: Carboniferous clay deposits from Jenolan Caves, New South wales: Implications for timing of speleogenesis and regional geology. - Australian Journal of Earth Science, 53, 377-406.

Palmer, A.N., 1981: A geological guide to Mammoth Cave National Park. – Zephyrus Press, p. 210, Tean-eck, New Jersey.

Palmer, A.N., 1991: Origin and morphology of limestone caves. - Geological Society of America Bulletin, 103, 1-21.

Palmer, A.N.,1995: Geochemical models for the origin of macroscopic solution porosity in carbonate rocks. - In Budd, D.A., P.M. Harris, & A. Saller (eds.): Unconformities in carbonate strata: Teir recognition and the signifcance of associated porosity. - American Association of Petroleum Geologists, Memoir 63, 77–101.

Palmer, A.N., 1996: Rates of limestone dissolution and calcite precipitation in cave streams of east-central New york State. - Abstracts of Northeastern Section meeting, Geological Society of America, 28, 3, 89.

Palmer, A.N. & M.V. Palmer, 1989: Geologic history of the Black Hills caves, South Dakota. - National Speleological Society Bulletin, 51, 2, 72-99.

Palmer, A.N. & M.V. Palmer, 1995: Te Kaskaskia paleo-karst of the Northern Rocky Mountains and Black Hills, northwestern U.S.A. - Carbonates and Evapo-rites, 10, 2, 148-160, Troy, New york.

Palmer, M.V. & A.N. Palmer, 1975: Landform development in the Mitchell Plain of southern Indiana: Origin of a partially karsted plain. - Zeitschrif für Geomorphologie, 19, 1-39.

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ARTHUR N. PALMER

Plummer, L.N., T.M.L. wigley, T.M.L. & D.L. Parkhurst, 1978: Te kinetics of calcite dissolution in CO2-wa-ter systems at 5° to 60° C and 0.0 to 1.0 atm CO2. - American Journal of Science, 278, 179-216.

quinlan, J.F., R.O. Ewers, J.A. Ray, R.L. Powell & N.C. Krothe, 1983: Ground-water hydrology and geo-morphology of the Mammoth Cave Region, Kentucky, and of the Mitchell Plain, Indiana. - Indiana Geological Survey, Field trips in Midwestern geology, 2, 1-85, Bloomington, Indiana.

Ray, J.A., 1996: Fluvial features of the karst-plain erosion surface in the Mammoth Cave region. - Proceedings of 5th Science Conference, 137-156, Mammoth Cave, Kentucky.

Sando, w.J., 1988: Madison Limestone (Mississippian) paleokarst: A geologic synthesis. - In N.P. James and P. w. Choquette (eds.): Paleokarst: Springer-Verlag, 256-277, New york.

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COBISS: 1.01

TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS By MIxING CORROSION IN THE SALTwATER-FRESHwATER TRANSITION ZONE.

ČASOVNO MERILO RAZVOJA POROZNOSTI ZARADI KOROZIJE MEŠANICE V MEJNEM OBMOČJU SLADKOVODNIH LEČ V MEDZRNSKO POROZNEM KARBONATNEM OBALNEM

VODONOSNIKU

wolfgang DREyBRODT1 & Douchko ROMANOV2

Abstract                                       UDC 556.3:552.54:539.217

Wolfgang Dreybrodt and Douchko Romanov: Time scales in the evolution of solution porosity in porous coastal carbonate aquifers by mixing corrosion in the saltwater-freshwater transition zone.

Dissolution of calcium carbonate in the saltwater-freshwater mixing zone of coastal carbonate aquifers up to now has been treated by coupling geochemical equilibrium codes to a reactive-transport model. Te result is a complex nonlinear coupled set of diferential transport-advection equations, which need high computational eforts. However, if dissolution rates of calcite are sufciently fast, such that one can assume the solution to be in equilibrium with respect to calcite a highly simplifed modelling approach can be used. To calculate initial changes of porosity in the rock matrix one only needs to solve the advection-transport equation for salinity s in the freshwater lens and its transition zone below the island. Current codes on density driven fow such as SEAwAT can be used. To obtain the dissolution capacity of the mixed saltwater-freshwater solutions the calcium equilibrium concentration ceq(s) is obtained as a function of salinity by PHREEqC-2. Initial porosity changes can then be calculated by a simple analytical expression of the gradient of the spatial distribution s(x, y) of salinity, the distribution of fow fuxes q(x,y) and the second derivative of the calcium equilibrium concentration ceq(s) with respect to salinity s.

Tis modelling approach is employed to porosity evolution in homogeneous and heterogeneous carbonate islands and coastal aquifers. Te geometrical patterns of porosity changes and the reasons of their origin will be discussed in detail. Te results reveal initial changes of porosity in the order of several 10-6 per year. Tis places the time scale of cavern evolution to orders from several tens of thousands to a hundred thousand years. Keywords: Calcite dissolution, mixing corrosion, saltwater-freshwater, mixing zone, coastal aquifer, evolution of porosity.

Izvleček                                        UDK 556.3:552.54:539.217

Wolfgang Dreybrodt and Douchko Romanov: Časovno merilo razvoja poroznosti zaradi korozije mešanice v mejnem območju sladkovodnih leč v medzrnsko poroznem karbonatnem obalnem vodonosniku

Dosedanji modeli raztapljanja kalcijevega karbonata v območju mešanja sladke in slane vode temeljijo na združitvi geokemičnih ravnotežnih in reakcijsko transportnih modelov. Dobljeni sistem nelinearnih enačb zahteva veliko računske moči. Če je hitrost raztapljanja dovolj visoka in lahko predpostavimo, da je raztopina ves čas v ravnotežju glede na kalcit, rešimo problem z poenostavljenim modelskim pristopom. Začetno spreminjanje poroznosti v kamninski matriki določa advekcijsko tranportna enačbo, ki opisuje slanost v sladkovodni leči in prehodnem območju pod njo. Pri reševanju porabimo dostopne programske kode. Tokove nastale zaradi razlik v gostoti modeliramo s programom SEAwAT, topnost kalcita v mešanici sladke in slane vode v odvisnosti od slanosti pa izračunamo s programom PHREEqC-2. Začetno spreminjanje poroznosti lahko nato izračunamo z enostavnim analitičnim izrazom gradienta prostorske razporeditve slanosti s(x,y), razporeditve gostot toka q(x,y) in drugega odvoda ravnotežne koncentracije kalcija po slanosti.

Tak modelski pristop uporabimo pri računanju razvoja poroznosti v homogenih in heterogenih karbonatnih otokih in obalnih vodonosnikih. Podrobno so prikazani vzroki in geometrijski vzorci spreminjanja poroznosti. Rezultati kažejo, da je začetna hitrost spremembe poroznosti reda velikosti 10-6 na leto. To postavi časovno merilo razvoja jam v območje nekaj deset tisoč do sto tisoč let.

Ključne besede: Raztapljanje kalcita, korozija mešanice, območje mešanja sladke in slane vode, obalni vodonosnik, razvoj poroznosti.

1 Universitaet Bremen, FB1, Karst Processes Research Group, Bremen, Germany, e-mail: dreybrodt@ifp.uni-bremen.de

2 Freie Universitaet Berlin, Fachbereich Geowissenschafen, Berlin, Germany, e-mail: dromanov@zedat.fu-berlin.de

Received/Prejeto: 21.12.2006

TIME in KARST, POSTOJNA 2007, 25–34

wOLFGANG DREyBRODT & DOUCHKO ROMANOV

INTRODUCTION

Carbonate islands consisting of porous rocks show typical karst features characterized by large dissolution chambers close to the coast, which have been created by mixing corrosion in the fresh-saltwater transition zone (Mylroie and Carew, 2000). Figure1 represents the basic concept. Due to meteoric precipitation a freshwater lens

Fig. 1: Conceptual representation of a carbonate island from mylroie and Carew (2000).

the chlorine concentration s, termed as chlorinity further on, of the mixture undersaturation or supersaturation may result. Figure 3 gives an example. It depicts the diference

Fig. 3: Ace9(s) = ceg(s)-cmi[(j) as a function of chlorine concentration. Te curve extends from pure freshwater (right) to pure seawater (lef).

builds up, foating on the denser saltwater (Vacher, 1988) Te transition from freshwater to seawater is not sharp. Depending on many factors, such as tidal pumping, periodicity of annual recharge, and the heterogeneity of the rock’s properties in the aquifer it exhibits a transition zone. Tis zone can range from a few meters to half the depth of the lens. In this zone mixing between saltwater and freshwater activates mixing corrosion, which creates large chambers. Tese are called fank-margin caves. Figure 2 shows such a cave with its typical solutional features on its ceiling.

Fig. 2: Flank-margin cave.

when seawater mixes with a solution of H2O-CO2-CaCO3 saturated with respect to CaCO3 the mixture is no longer in equilibrium with respect to calcite. Depending on

hceq(s) = ceq(s)-cmix(s) of the calcium concentration c ix (s) of the mixture and that of its corresponding equilibrium concentration c (s) as a function of s. Tis is the amount of calcium, which can be dissolved or precipitated, when the mixed solution is in contact with carbonate rock. Te HO-CaCO-CO solution used to calculate this data is in

2                          32

equilibrium with a partial pressure of CO2 of 0.01 atm at a temperature of 20°C. Te seawater also is at 20°C. Te data in Fig. 3 were obtained by use of the code PHREEqC-2 (Parkhurst and Apello, 1999 ).

From Figure 3 it is evident that mixtures with low content of seawater, chlorinity s ≤ 0.3 mol/^, can dissolve calcite, whereas mixtures with higher chlorinity may precipitate calcite. Renewed aggressivity due to mixing therefore occurs only at the freshwater side of the mixing zone where chlorinity is low. If one assumes that dissolution of calcite proceeds sufciently fast the solution there will be saturated with respect to calcite.

Dissolution of minerals under such conditions is termed a gradient reaction (Phillips, 1991). Here we use this as a novel instrument to explain the evolution of porosity in carbonate islands. Dissolution rates of limestone are sufciently fast, such that afer mixing between saltwater and freshwater we assume saturation with respect to calcite in the entire lens.

Afer attaining equilibrium the local distribution of calcium concentration c (s(x,z)) becomes stationary and exhibits gradients. Necessarily advection and difusion must transport the dissolved limestone to the outfow of the aquifer.

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TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS ...

DISSOLUTION IN THE MIxING ZONE

Te advection term:

In Figure 4 we consider a volume element dxdydz at position (x,y,z), into which fow, with components qx and qz, enters perpendicular to dydz or dxdy. Te fux q is defned by the volume of fuid per time unit entering through a unit of surface area and is given in [cm3/(cm2s) = cms-1].

^fi-esh

+ (c«

»)■

(5)

Ac«? is the increase of equilibrium concentration as given in Figure 3, s is chlorinity of seawater.

sea

Te difusion term:

Our mass balance so far, however, is incomplete because gradients of ceq cause transport by difusion. Te rate qD of mass transport by difu-sion is given by

QD=-0-DV\cmbc+Ac )

(6)

Fig. 4: mass balance for the advection term.

Te component qx transports solution from the neighbouring elementary cell at position (x-dx, y,z) via the area dydz into the cell dxdydz. Tis solution has already attained equilibrium ceq(s(x-dx,y,z)) at position x-dx. when it enters into the volume element dxdydz it must dissolve or precipitate limestone to adjust its calcium concentration to equilibrium ceq(s(x,y,z)) at position x. On the other hand solution from the element dxdydz fows out into the neighbouring cell with fux qx(x,y,z). Mass conservation requires that the amount of limestone dissolved per time unit in the element dxdydz must be equal to the diference of mass transported into the cell and that transported out of it. From this one fnds

(qx(x, z) ■ Ceq(x, z) - qx(x -dx,z)- Ceq(x - dx, z))dydz

fit (1)

dxdydz

An analogue equation exists for qz the amount of limestone dissolved by the fux component q entering via the surfaces (dx,dy).

(q2 (x, z) • Ceq(x, z) - qz (x, z - dz) ■ Ceq(x, z - dz))dxdy

dxdydz

Qz (2)

Terefore

Qadv =Qx+Qz=Q' gfodipeq (S(.X>Z)) + Ceq (S(X> Z) ' ^tvq          (3)

Because the fux q follows the Darcy law of incompressible fuids, div(q) =0.

Qato-q-gradtfimu+te»,)

(4)

whereby we have replaced c^ = cmlx + Ace? ■ cmlx is the calcium concentration resulting from the mixing of sea-water and freshwater and is a linear function of Cl-con-centration s.

where D = qd/Φ + D is the

m

coefcient of dispersion. Φ is the porosity of the rock and d its grain size. (Phillips, 1991). Dm is the constant of molecular diffusion (10-5cm s-1).

Te total rate:

Te total dissolution rate q is then given by qD+q d.

Qui =Qgrad(cmi,)~ ^V2(cmjJ)+ qgrad(Aceq) - 0Z)V2(Ace?) (7)

Due to the linearity of c with salinity s (eqn. 5)

mix

one fnds grad(c i) proportional to grad(s).

Te distribution of salinity is governed by the ad-vection-difusion equation

ds/dt = qgrads - <M>(V)2.s = 0,

(8)

because the distribution s is stationary. From the linearity

of s with cmix we have

dc^,/dt=qgradcmlx-0D(V)2c^= 0,

(9)

Te total dissolution rate qtot is given by the master equation

ßto(=?grarf(ACJ-0i5V2(ACe?)

(10)

Since Δceq(s(x,z)) is a function of local distribution s(x,z) by diferentiating and using the chain rule, one fnds using equation 8

ßto,=-0(qd/0+Dm)-(Vs(x,z))2

ds2

(11)

Tis master equation relates the amount of dissolved material per unit volume of the rock matrix [mol cm-3 s-1]

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wOLFGANG DREyBRODT & DOUCHKO ROMANOV

to the gradient of salinity s, to the second derivative of ceq(s) = cmjx(s)+Aceq(s), and the fux q. d^c^/ds1 can be obtained by diferentiating twice the data set of Figure 3. Tis data set was obtained by using the program PHRE-EqC2 and calculating about 50 closely spaced points to avoid numerical errors, when diferentiating twice. Te result is shown in Figure 5.

Fig. 5: Second derivative

To obtain the initial distributions of fux q and chlorinity s in the lens of a carbonate island we have used SEAwAT by USGS (Guo and Langevin, 2002). Te modeling domain is shown in Figure 6. Te island is a strip of 1 km

Fig. 6: modeling domain of a carbonate island.

width. Porosity 0 and the hydraulic conductivity K are uniform (0=O.3O,K = l0m/day). Te transversal disper-sivity is aT = d = 0.01 cm, the longitudinal dispersivity is

Te function |Aä(3c)| and the fow distribution |?(x)| can be obtained by the numerical hydrologic model SEA-wAT, as will be shown in the next sections. To calculate the initial change of porosity it is sufcient to obtain the fux and salinity distribution of an island without considering calcite dissolution, because the time to establish a stationary state of the lens is in the order of 100 years. It is a good approximation to assume that during this time the change of porosity is insignifcant.

Equation. 11 can be written in terms of the change of porosity as

— = —Qtat=-0D(ys(x,z))2-----ip— (1/s)           (12)

dt p                                     ds p

M = 100 g/mol is the molecular weight at CaCO3, r=2.7 g/cm3 is the density of compact CaCO3. q the mass of CaCO3 dissolved per time from a unit volume of the rock matrix is given in mol s-1 cm3. 90/dt is the amount of volume dissolved per time from a unit volume of the rock matrix (cm3s-1/cm3). By use of equation 12 it is now possible to construct a conceptual frame for the evolution of porosity. Tests of this approach on simple benchmark models have shown its reliability and have found agreement to experimental data (Romanov and Dreybrodt, 2006).

al = 0.1 cm. Infltration is 3 . 10-3m/day =1.11m/year. Tis way the maximal depth of the lens is about 50 m below sea level. Te lower border of the domain reaches down to 70 m. At that boundary an impermeable layer imposes no-fow conditions. Te grid size in the domain is 1 m x 1 m in the part below sea level. In the part above sea level (2 m) the grid size is 0.2 m by 1 m. In its initial state when the island emerges out from the sea the entire aquifer is flled with seawater. when the island receives recharge from meteoric freshwater the lens builds up. A stable stationary lens is obtained afer about 30 years. Fig.7 shows the results of the model run.

Figure 7a shows the freshwater lens (white), the transition zone and its distribution of Cl-concentration by a color code. From this distribution of chlorinity one can extract the scalar value Vs(jc) and d2ceq(s(x))/d s1. Figure 7b shows the chlorinity in units normalized to its maximum value along several horizontal sections as depicted in Figure 7a. Te lowest section at -68 m is entirely in saltwater with maximum Cl-concentration. Te section at -55 m extends through the almost horizontal base of

INITIAL CHANGES OF POROSITy IN A HOMOGENEOUS ISLAND.

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TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS ...

Fig. 7: homogeneous island. a) Local distribution of chlorinity s(x). Te white region designates the freshwater lens. b) chlorinity along horizontal sections as indicated in a).

the lens and shows a wide zone where the concentration raises to that of seawater. Te upper sections cut through the mixing zone and there the rise in concentration from freshwater to seawater becomes steeper.

Te square of the gradient \Vs\ is shown by Figures 8a,b also normalized to its maximum value in Figure 8b. Figure 8a illustrates its local distribution, which exhibits large values only in the region of the transition zone. Te horizontal distribution along horizontal sections is depicted in Figure 8b.

Te second derivative d2c (,s(x))/3 s2 obtained from the Cl-concentration in Figure 7a is given in Figure 9a. Its distribution is limited to that part of the transition zone with 0 < s < 0.03 mole/^. See Figure 5. Tis corresponds to a narrow fringe at the freshwater side of the transition zone with seawater content from zero up to about 4%. In any case creation of porosity is possible only in this restricted region. Figure 9b for completeness depicts some distributions of 32c (s(3c))/3 s2 along horizontal sections.

To calculate the initial rate of change in porosity (conf. eqn 12) the Darcy fuxes q must be known. Tey are also obtained from the model run and shown in Fig 10. Te fux is low in the center of the island q^\ m/year), but increases by orders of magnitude when the fuid

Fig. 8: homogeneous island. a) Local distribution of the square of gradients |Vs(x)| , b) square of gradients along horizontal sections as indicated in a).

moves coastward, where it becomes about 0.2 m/day at the outfow.

Te dispersion coefcient D = qd/Ø + Dm (conf. eqn. 11) depends on the fux q, but also on the coef-cient of molecular difusion Dm=10-5 cm2/s. For low fux q<10-4 cms-1 and particle diameters d≤10-2 cm dispersion is dominated by molecular difusion. In the following scenarios we have used d=10-2 cm, a realistic value in porous limestone. Terefore in the range of fux, which can be read from Figure 10b the dispersion coefcient in the center of the island is D=10-5 cm2s-1. It increases by about 60% of this value at the coast.

From the data given in Figures 7a, 8a, and 9a the initial porosity is obtained by use of eqn. 12. Figure 11 illustrates these results. Changes in porosity are restricted to a small fringe in the transition zone and are fairly even along it. Tey are in the order of 10-6 year-1. Tis is sufcient to create substantial porosity within 100,000 years. At the outfow fank margin caves can develop in 10,000 years. One has to keep in mind, however, that the approximation as a homogeneous island is a high idealization. Any disturbances, which increase the width of the transition zone, will reduce the gradients of chlorinity and therefore on more realistic settings the initial porosity changes accordingly.

TIME in KARST – 2007

29

wOLFGANG DREyBRODT & DOUCHKO ROMANOV

Fig. 9: homogeneous island. Local distribution of the second

derivative P, b) second derivative along horizontal sections

ds2 as indicated in a).

As we have stated already, the second derivative is restricted to narrow regions in the freshwater side of the transition zone. It exhibits signifcant values only at locations where the water contains between zero and 4% saltwater (see Figure 5). On the other hand the gradient in salinity is maximal at mixtures of about 50% seawater, because it arises from a difusive process. In the region of maximal gradients, however, the second derivative is small. Vice versa in the region of high values of the second derivative, the gradients of salinity are low. Tis is illustrated in Figure 12. Tis fgure is an overlay of the horizontal distributions (grads)2 in Figure 8b (red curves), the second derivative in Figure 9b (green curves), and the initial porosity change in Figure 11b (black curves). All curves are normalized to their individual maximum values. Terefore their values are not comparable in this fgure. what can be compared, are the locations. Evidently the curves for gradients and second derivative are well separated. Te curves of porosity change are proportional to the product of the square of the gradient and the second derivative. Porosity change displays high values

Fig. 10: homogeneous island. a) Local distribution of fux b) fux along horizontal sections as indicated in a).

in between their maxima but close to the region of high values of the second derivative.

Figure 13 further illustrates this qualitatively. Te red region depicts the locations of the modeling domain where (grads)2 exhibits values val a 10"2 val^ valma is the maximal value. Te green region shows these locations for the second derivative and fnally the black region shows the locations of signifcant changes of porosity. Tese fndings agree with those of Sanford and Konikow (1989) who also found that changes in porosity are restricted to regions where waters contain between 0.5% and 3% of seawater.

It should be noted here that any mechanism, which changes the sigmoid shape of the salinity distribution to a linear profle would enhance evolution of porosity dramatically. In this case salinity gradients become constant in the entire mixing zone and their value is at least one order of magnitude higher at the maximal value of the second derivative. One could speculate that tidal pumping and fuctuations of the water table due to seasonal changes of infltration could cause such linear mixing zones. Present observations in boreholes give some evidence for such transition zones.

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TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS ...

Fig. 11: homogeneous island. a) Local distribution of initial change of porosity dip/dt. b) d<j>/ dt along horizontal sections as indicated in a).

Fig. 12: homogeneous island. (grads)2 (red),

ds2

(green), and)

dtp/ dt (black) along horizontal sections of the island. Numbers on the sets of curves give the depth of the section.

Fig. 13: homogeneous island. Regions of (grads)2 (red), of (green), and change of porosity (black).

INITIAL CHANGES OF POROSITy IN A HETEROGENEOUS ISLAND

A more realistic approach to nature can be taken by employing a geo-statistical distribution of hydraulic conductivities. Figure 14 shows such a distribution generated with the sofware of Chiang and Kinzelbach (1998). It covers conductivities of two orders of magnitude from about 380 m/day (red) down to 2 m/day (dark blue). Most of the aquifer is occupied by values between 10-200 m/day. Otherwise all previous boundary conditions are unchanged. Te fow feld is illustrated in Figure 15. Flux is unevenly distributed, because the heterogeneous distribution of conductivities distorts the pathways of fuid elements in comparison to the regular ones in a homogeneous island. Consequently the freshwater lens in Figure 16 shows a wide transition zone (compare to Figure 7a).

Fig. 14: heterogeneous island. Statistical distribution of hydraulic conductivity in the modeling domain.

TIME in KARST – 2007 31

wOLFGANG DREyBRODT & DOUCHKO ROMANOV

Fig. 15: heterogeneous island. Local distribution of fux q.

Fig. 16: heterogeneous island. Local distribution of chlorinity s(x). Te white region designates the freshwater lens.

Fig. 17: heterogeneous island. Local distribution of |Vs(x)| .

Te square of the gradient is limited to the seawa-ter side of the transition zone, as can be visualized from Figure 17. Te region of 0-4% mixtures extends far into

Fig. 18: heterogeneous island. Local distribution of derivatives

as2

Fig. 19: heterogeneous island. Local distribution of initial porosity change d<j>l dt.

Fig. 20: heterogeneous island. Regions of high values of (grads)2

o2 Ac (red), -----P (green), and change of porosity (black) in the

modeling domain.

the freshwater lens. Tis can be also visualized from the second derivatives as shown in Figure 18.

Figure 19 illustrates the initial change of porosity, which exhibits high values of 3 . 10-6 year1 (red) at only a few locations close to the freshwater side of the transition

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TIME SCALES IN THE EVOLUTION OF SOLUTION POROSITy IN POROUS COASTAL CARBONATE AqUIFERS ...

zone. At some favorable locations (red and yellow) caves ure 21 depicts (grads)2 (red), d2c /ds2 (green), and d(p/dt may evolve there in several 10,000 to 100,000 years.              (black) along selected horizontal sections.

Tis is further illustrated by Figure 20, which shows              In both fgures we fnd that the regions of (grads)2

the regions of high values for (grads)2 (red), d2c /ds2 (red), d2ceq /ds2 (green) are well separated and porosity (green), and 90/dt (black) in the modeling domain. Fig- develops in between. Due to the heterogeneity, however,

the patterns become complex.

Fig. 21: a) heterogeneous island. distributions of (grads)2 (red), ----^ (green), and porosity change (black) along selected horizontal

sections. Number on the sets of curves give the depth of the section.

INITIAL CHANGES OF POROSITy IN SALTwATER TONGUES.

when impermeable strata underlay an island sufciently close to its surface the freshwater lens cannot extend below this layer and a saltwater tongue intrudes from the coastland inward until it reaches the impermeable layer. From thereon the freshwater lens is truncated by this layer. In this situation mixing of waters is restricted to the transition zone of the tongue and one expects high dissolution rates in this region.

Fig. 22 shows the local distribution of chlorinity and the initial change of porosity using the statistical distribution in Figure 14 for the upper permeable part. Te mixing zone exhibits a structure similar to that of the heterogeneous island at the corresponding locations. Porosity changes at the outfow are low, but we fnd values up to 10-6 1/year land inward at various lo-

Fig. 22: Coastal aquifer with heterogeneous conductivity down to 29 m as used in Fig. 14. Te strata below 29 m are impermeable (grey). Local distribution of Cl-concentration s(x) and initial porosity change d<p/dt .

cations and also at the contact of the tongue with the impermeable rock.

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wOLFGANG DREyBRODT & DOUCHKO ROMANOV

CONCLUSION

we have taken substantial steps in modeling the initial porosity changes in fresh water - saltwater mixing zones under various geological settings. we have demonstrated that the knowledge of the distribution of salinity and the amount of the fow velocity is sufcient to calculate the initial distribution of porosity changes. Tese are the frst modeling results, which do not need scaling parameters for calibration as the models of Sanford and Konikow (1989), or more complex non-linearly coupled sets of diferential transport- advection equations (Saaltink et al., 2004). we now understand that in a stationary island high porosity can develop only if high salinity gradients exist in the region of low saltwater content to up to 3%. For the highly idealized scenarios of islands with homogenous hydraulic conductivity we fnd clear rules about the geometric distribution of porosity. Tese, however, are destroyed for islands with a statistical distribution of hydraulic conductivity. Each realization of a statistical distribution then will give diferent results, and a general standard scenario cannot be used as a tool. In heterogeneous settings porosity could occur at any place below the island and at favorable

Chiang, w. H., Kinzelbach, w. , 1998: Processing Mod-fow. A simulation system for modeling groundwa-ter fow and pollution

Guo, w. , Langevin, C. D., 2002: User’s guide to SEAwAT: a computer program for simulation of three-dimensional variable-density ground-water fow. U. S. Geological Survey Techniques of water-resources Investigations Book 6, USA.

Mylroye, J. E., and Carew, J., L., 2000: Speleogenesis in coastal and oceanic settings. In: Klimchouk, A., Ford, D. C., Palmer, A. and Dreybrodt, w. (Editors), Speleogenesis: Evolution of karst aquifers. National Speleological Society, Huntsville, 226-233.

Parkhurst, D. L., Apello, C. A. J., 1999 (Version 2): User’s Guide to PHREEqC – a Computer Program for Speciation, Reaction-path, 1D-transport, and Inverse Geochemical Calculations, Technical Report 99-4259. U. S. Geological Survey, USA.

settings also fank-margin caves will arise. Tis explains why presence of these caves is not the rule, as it should be in homogeneous settings, where porosity develops only at the base and the outfow of the lens. In view of the restricted knowledge about the hydraulic properties and the initial porosity of the rock, which one necessarily has in carbonate platforms, detailed applied modeling at present, and most likely in the next decades will not be available.

On the other hand our fndings give a frm basis for understanding the evolution of porosity on time scales of several ten to several hundred thousand years. Using an iterative procedure to implement changes of porosity and hydraulic conductivity in each time step will reveal the basic properties of processes involved in creating macro-porosity such as caves and conduits. Feed back mechanisms, which enhance dissolution in the regions of increased porosity and hydraulic conductivity could accelerate the evolution of porosity. Terefore time scales derived from the initial change in porosity represent upper limits only.

Further work into this direction is needed.

Phillips O. M., 1991: Flow and reactions in the permeable rocks. Cambridge University Press. Cambridge, New york, Port Chester, Melbourne, Sydney. 1991.

Romanov D. and Dreybrodt w., 2006: Evolution of porosity in the saltwater-freshwater mixing zone of coastal carbonate aquifers: An alternative modeling approach. Journal of Hydrology 329, 661-673 Saaltink, M.w., Batlle, F., Ayora, C., Carrera, J., Olivella, S., 2004: RETRASO, a code for modeling reactive transport in saturated and unsaturated porous media. Geologica Acta 2 (3), 235–251

Sanford w. E., Konikow L. F., 1989: Simulation of Cal-cite Dissolution and Porosity Changes in Saltwater Mixing Zones in Coastal Aquifers. water Resources Research, v. 25, No. 4, p. 655-667. 1989.

Vacher H. L., 1988: Dupuit-Ghyben-Herzberg analysis of strip-island lenses. Geological Society of America Bulletin, v. 100 p 580-591. 1988.

ACKNOwLEDGEMENT we thank TOTAL S.A. for supporting this work.

REFERENCES

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THE AGE OF KARST RELIEF IN wEST SLOVENIA STAROST KRAŠKEGA RELIEFA V ZAHODNI SLOVENIJI

Andrej MIHEVC1

Abstract                                    UDC 551.435.8 (497.4 Kras)

Andrej Mihevc: Te age of Karst relief in west Slovenia

Te age of a karst can be defned as the time when the karst rocks were uplifed out of the sea. Te other view of the age of karst is to defne the age of certain karst features or assemblages of karst features. On the Kras plateau there is a variety of forms that were formed at quite diferent times, but due to karst evolution, they coexist in today’s relief. On the plateau, that is slowly rising, the hydrological zones in karst surface are moving downwards. Streams from the side ceased to fow on the karst and former leveled surface that was formed in conditions of high ground water is dissected by numerous dolines. Blind valleys are incised at the side and some of them show the infuence of recent tectonics. Te lowering of relief by corrosion exposes caves that have formed deep beneath the surface and creates unroofed caves that become a part of the surface topography. From the morphological comparison of the unroofed caves, blind valleys and levelled surfaces and by dating of the sediment and considering the age of tectonic phases we can reconstruct the evolution and estimate the age of the karst landscape. Key words: karst, morphology, age, Kras, Slovenia.

Izvleček                                UDK 551.435.8 (497.4 Kras)

Andrej Mihevc: Starost kraškega reliefa v zahodni Sloveniji

Starost krasa lahko določimo s trenutkom, ko so bile kraške kamnine dvignjene iz morja. Drugi način opredelitve starosti krasa je z datiranjem reliefnih oblik ali skupin reliefnih oblik. Planoto Kras sestavlja vrsta zelo različnih reliefnih oblik, ki so nastale v različnem času, vendar so se zaradi posebnosti razvoja krasa ohranile in sobivajo v sedanjem reliefu. Na planoti, ki se počasi dviguje se hidrološke cone in kraško površje pomikajo navzdol. Vodotoki s strani so prenehali dotekati na kras in nekdanje v višini talne vode nastalo uravnano površje so razčlenile številne vrtače. Na robu krasa so vrezane slepe doline, nekatere od njih kažejo sledove tudi recentnih tektonskih premikov. Zniževanje reliefa zaradi korozije je razgalilo jame, ki so se oblikovale globoko pod površjem in ustvarilo brezstrope jame, ki so postale del današnje topografje površja. Z morfološko primerjavo brezstropih jam, slepih dolin in uravnav in datiran-jem sedimentov ter upoštevanjem starosti tektonskih faz lahko rekonstruiramo razvoj reliefa in ocenimo starost kraške pokrajine. Ključne besede: kras, morfologija, starost, Kras, Slovenija.

INTRODUCTION

Te question about time, like velocity of processes or age of karst surfaces and caves is a very important issue in karst studies. Te age and evolution of karst is also important when we study karst as a specifc ecosystem. It can tell us when karst and especially the caves start to form in a given area and how the landscape is changing.

The first explanation of geomorphic evolution and the age of the karst in w Slovenia were made by geologists. To estimate the age they used geologic data – the age of last marine sedimentation and the tectonic evolution of Dinaric mountains and the Alps (Grund 1914).

1 Karst Research Institute, ZRC SAZU, Titov trg 2, Sl – 6230 Postojna, Fax: +386 5 7001999, Andrej.Mihevc@guest.arnes.si Received/Prejeto: 01.02.2007

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Fig. 1: Te location of the Kras plateau and the study areas.

At frst karstologists were focused on understanding karst processes and the evolution of karst features like dolines, poljes and corrosion plains. Tey were much infuenced by the ideas of a geographic cycle promoted by Cvijić (1924). Karst evolution was divided into similar steps in the cycle but they also added a pre-karst phase of relief evolution with which they explained some morphological elements in karst.

Te cyclic explanation of the karst evolution was later modifed with climatic geomorphology (Roglič 1957, Radinja 1972). It emphasised the importance of climate on the morphological processes. Tis meant that some forms of relief, like conical hills and levelled surfaces were explained as a relicts from tropical climate. Because such a climate was present at the end of the Tertiary, these forms were determining the age of that relief features.

Another important climatic signal in the morphology of the Kras they estimate were the cold Pleistocene climates with periglacial processes in lower positions. Scree slopes, collapses in caves, fuvial deposits in contact karst areas and some fner sediment were explained as extremes of climate control and not normal karst phenomena. Tey were also used for determination of the age of features (Melik 1955, Gospodarič 1985).

Geomorphologists have abandoned the cyclic model of relief and are now paying more attention to structural elements in karst morphology like recent tectonic (Habič, 1982), feld measurements and observations on karst denudation (Gams 1963), comparative studies of diferent karst features or types of karst, like contact karst (Gams 1962, Mihevc 1994), the study of dolines and collapsed dolines (Mihevc 2001) and new geomorphologic features like unroofed caves (Mihevc 1996, 2001, Slabe 1997) as an important remnants of former landscapes and a source of sediments. Flowstones in the caves were dated (Hajna 1991, Mihevc 2001) and paleomagnetic methods were used in cave and karst sediments (Bosak & al. 1999, 2004).

Very important data were provided by latest research on the plate tectonics. Te tectonic evolution of the area is characterized since late Tertiary frst by northward motion of Adria micro plate which caused contraction deformations. Te contraction was exhausted at about 6 Ma ago and was followed by rotation accompanied with uplifs, folding and strike-slip basins formation. Tese events take place in two distinct phases (Vrabec & al. 2006, Fodor & al. 1998).

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GEOMORPHIC EVIDENCES ON THE AGE OF KRAS

Kras is a low Nw – SE trending longitudinal plateau along Trieste Bay (Adriatic Sea) between fysch Brkini hills on SE, Vipava Valley in NE, and the Soča River lowlands in Nw. Te plateau is about 45 km long and 14 km wide. Te surface of the plateau is slightly tilted from 500 m a.s.l on SE towards NE where it ends at about 100 m above the Soča river.

Te central part of Kras is built from highly permeable Cretaceous carbonate platform shallow marine limestone and less permeable dolomite. Eocene fysch that acts as an important impermeable barrier surrounds the carbonate massif.

Te age of the karst of Kras plateau can be defned as the time when the karst rocks were uplifed out of the sea. For the most of Dinaric karst in Slovenia this occurred afer the Eocene, since afer that there is there is no evidence of younger marine sediments. As soon as the carbonate rocks were exposed, we can expect that the karst was formed, but there are no remnants of karst features from that time. Most likely denudation has destroyed them.

Te other view on the age of karst is to defne the age of those karst features for which we know how and when they were formed and which evolution was stopped long time ago. Such features are levelled surfaces, which evolve at the level of the karst water and blind valleys that were formed by alogenic rivers. we can compare them with evolution of fuvial relief and unroofed caves, which are caves exposed to surface by denudation.

On the Kras plateau there is a variety of forms that were formed at quite diferent conditions and time but due to peculiarities of karst evolution they coexist in today’s relief. Tis can make the determination of the one age of a karst landscape difcult or impossible, but it tells us about the genesis of the landscape trough diferent phases.

Here we present the study of the part of the Kras, Divaški kras and Matarsko podolje and the edge of Podgorski kras from which there are some evidences about the evolution and age of Kras.

THE UNROOFED CAVES OF DIVAŠKI KRAS

Te Divaški kras is tilted slightly towards Nw at elevations between 450 and 400 m a.s.l, on the SE part of the Kras plateau. It is built up mostly by Cretaceous and Paleogene limestone. Te karst features here are exceptional; there are the sinking of the Reka river into Škocjanske jame cave via large collapse dolines with and hundreds of dolines. Te largest caves of the area are the 12,500 m long and 275 m deep Kačna jama and the 5800 m long and 250 m deep Škocjanske jame. Te caves were formed by the Reka river which can be reached at a depth of 195 m in Škocjanske jame and 156 m a.s.l. in Kačna jama.

Te main morphologic features of the area are collapsed dolines and dolines which together cover about 12% of the area. Te collapsed dolines are connected with active water caves. Te solution dolines cover less than 4% of the area. Te rest of the surface (88%) is level. Tese points out the prevailing surface leveling process in the present conditions

In this levelled surface there are several large unroofed caves (Mihevc 1996). As such caves appear on the surface due to denudation, and we may call their remains denuded caves. A cave ceiling will be the frst to be removed by denudation, which is why they are also called unroofed caves. Tey were frst found and

described in the Divača Karst. Te unroofed caves share on the surface is small, only about 0.16% of the entire surface.

Tree important unroofed caves have been found. Te frst is a 350 m long unroofed cave near Povir village at 400 m above the sea level. Tere is a remnant of a cave passage that was 6 m wide and over 5 m high. Te entire volume of the passage has been flled by allochtonous fuvial sediments of clay, silicate sands and gravel with pebbles up to 25 cm in diameter.

Te second is an unroofed cave near Divača on the slopes of doline Radvanj at the altitude of 390 - 415 m above sea level. It is exposed on the slope that dissects large cave passage, which is entirely flled with sediments. Similar sediments can be seen in the Divaška jama cave. Tis is a 600 m long cave, whose continuation towards 250 m distant unroofed cave is completely flled. Te cave was also flled, but the sediment was later washed from it by the seepage water. Here we can see that a part of the unroofed cave that still exists as an underground cave.

Te longest roofess cave is 1.800 m long remnant of caves whose passages were about 20 m large, and therein few a great underground river. Te cave was flled with fuvial sediments and massive fowstone. It is located

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Fig. 2: Te map of the divača karst. On the levelled surface the large collapse dolines are dominating features, solution dolines are frequent, but they represent only small proportion of the surface. Te outlines of the main caves and the main unroofed caves are marked. On the map made of dEm with 12.5 m grid the road cuts or causeways are also seen.

Legend: 1. Outline of the active river caves, 2. divaška jama cave, 3. Unroofed cave, 4. Unroofed caves mentioned in the text: A: Unroofed cave near Povir, b: Unroofed cave in doline Radvanj, continuation of divaška jama, C: Unroofed cave above škocjanske jame, 5. height of the surface, 6. height of the water level in caves, 7. Reka river and ponors, 8. Te supposed direction of water fow, 9. Outline of the town divača.

partly above the Škocjanske jame, where the actual river bed in the cave is 230 m below the unroofed cave.

On the basis of the shape of walls and sediments we may reconstruct some evolution of the caves and later the surface. Te caves are remnants of larger cave sys-

tems, which conducted waters from diferent sinking streams. Growth of speleo-thems in them was frequently interrupted by phases of erosion or backfll. Te caves were aferwards flled up with fuvial sediments. Te large pebbles in the caves testify the great gradient of the surface streams. Later all caves were flled with fner sediment, which could mean the lowering of the gradient in karst and aplanation. Later, the surface was tilted and up-lifed which caused lowering of the karst water level.

Te age of the unroofed caves can be established by comparative methods according the denudation rate of the surface. If we presume, that it is about 50 m/ Ma (Gams 1962) and there was some 100 m - 200 m of rock removed from above the caves that they are at least 2 – 4 Ma old, and probably older (Mihevc 1996, 2001).

Similar time frames 1.6 – 1.8 Ma or/and 3.8 to 5 Ma were given also by paleomag-netic datation of clastic sediments (Bosak & al. 1998) and by the timing with tectonic phase that started at 6 Ma (Vrabec & al. 2006). Te age of the roofess cave can also be illustrated by

the time, in which the water table in Kras lowered for 240

m, from about 400 m to 160 m a.s.l.

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Fig. 3: Formation of the unroofed cave. Te idealised drawing is representing actual cases of unroofed or partly denuded caves from the divača karst, where probably more than hundred meters of the rock above unroofed caves were removed. Te transformation of cave to the unroofed cave is here presented in three stages: a: Epiphreatic cave passage was formed deep below the surface, some fowstone was deposited afer the cave became inactive; b: Surface approached the cave. At one side the slope cut the cave and made the entrance into the passage; from the horizontal surface former vadose shafs transformed into vertical entrance. trough both entrances piles of boulders and scree deposited. c: Great deal of the ceiling dissolved, some collapsed and formed relief oblong depression of the unroofed cave ending in front of the entrance to the cave.

Fig. 4: Formation of the unroofed cave. Te idealised drawings are representing the actual cases of unroofed or partly unroofed caves from the divača karst which were completely flled with allogenic fuvial sediment.

Te transformation is here presented in three stages: a: Cave passage was formed deep below the surface. Tere was alternation of the sedimentation of fowstone and allogenic sediments of the underground river. towards the top of the profle sediments became fner. b: Surface approached the cave. At the side the slope cuts passage and exposed the cave sediments on the surface. c: Afer disintegration of the ceiling from the top oblong depression formed. In it there are alochtonous sediments and few blocks of limestone and some fowstone. Te unroofed cave ends with steep limestone wall or slope from where the karst surface continues.

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THE BLIND VALLEyS OF THE MATARSKO PODOLJE CONTACT KARST

Alogene rivers fowing to karst enhance the karstifcation process and form particular relief features. Phenomena and forms that develop at the contact of fuvial and karst relief are the result of the interaction of both morphological systems.

Te Matarsko Podolje is a 25 km long and 2-5 km wide tilted karst surface. In longitudinal section it gently raises from about 490 m on Nw to 650 m on SE side. Te karst surface continues towards SE but from the highest point there is an abrupt change and relief lowers over the distance of 2 km for 200 m to Brgudsko podolje karst surface.

Fig. 5: blind valleys brezovica (br) and Odolina (O) on the NW part of the matarsko podolje karst. blind valleys cut for about 50 m into the edge of the levelled karst surface where dolines and larger collapse dolines prevail. Tere are no traces of dry valleys or dry blind valleys.

Legend: 1. Sinking streams, 2. boundary fysch – limestone.

From the fysch Brkini hills that are NE of podolje there are 17 sinking streams that formed a row of large blind valleys in the edge of the Matarsko Podolje. Te bottoms of these valleys are situated between 490 to 510 m. As the valleys are incised in the border of the karst,

uplifed towards SE, the blind valleys lying more to the south are deeper. Te most Nw lying, Brezovica and Od-olina blind valley are cut for about 50 m only while the deepest is the last one, Brdanska dana on SE, deepened into limestone for 250 m.

Te blind valleys started to cut into the corrosion plain with small transverse and longitudinal gradient as in the other case the fuvial valleys should develop in them. Tey should be preserved on karst as dry valleys. Te corrosion plains along the ponors were controlled by the piezometric level this is why they are all at same altitude.

In the SE part where the uplif was stronger, the blind valleys show the disturbances caused by fast tectonic uplif and are preserved on the karst surface. Above the Račiška Dana blind valley there is a fossil one, on the bottom of which are some old sediment from fysch. Tis is now higher than the fysch hills where the sediment came from. Te other case is the most SE blind valley Brdan-ska Dana. It developed in the SE edge of the Matarsko Po-dolje. Te tectonic structure along which the Matarsko Podolje ends caused also the asymmetric development of the blind valley. Te w side of the blind valley was up-lifed and developed two fossil higher levels in the side of the blind valley.

Te Brkini series of blind valleys ofer enough data to follow the sequence of the morphological events and dominant factors which were decisive for the formation of the actual relief forms. Te former shape along the ponors on the border of impermeable hills was karst corrosion plain. Te water fow-ing on it had a modest gradient in karst and was capable of the aplanation of the surface only. Te lowering of the piezometric level in the karst enabled the development of the relief depressions along the ponors. Te deepen-

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ing and the contemporaneous widening of the valleys followed the lowering of the karst water to the altitudes about 500 m.

Te incision of blind valleys into the leveled surface probably started and continued trough the last tectonic phase that is 6 Ma before present. Tis is also accordance with the age of the cave sediments from Račiška pečina which were dated by paleomagnetic method and correlated with palaeonto-logic data to 3.5 Ma (Pruner & al. 2003).

Fig. 6: blind valleys Račiška dana (R) and brdanska dana (b) with fossil blind valleys (f1, f2). Tese valleys developed in SE part of matarsko podolje during the tectonic uplif. Uplif deformed older corrosion plain and created height diference between matarsko and brgudsko podolje. Further SE there is another blind valley (š) which developed at the edge of brgudsko podolje that was not uplifed. Račiška pečina cave that was once formed by sinking streams is at elevation about 600 m high above the recent ponors.

Legend: 1. Sinking streams, 2. boundary fysch – limestone, 3. Cave Račiška pečina.

THE UNROOFED CAVES OF THE EDGE OF THE PODGORSKI KRAS

Podgora karst is small 5 km wide and long karst plateau, Sw continuation of the Kras. Its surface is located at 500 to 450 m a.s.l. Te plateau surface is leveled and dismembered only by numerous dolines. Tere is a sharp edge of the plateau and towards w in less than 1 km relief drops for 400 m. At the foot of the plateau there are recent karst springs of the rivers Rižana and Osapska reka at altitudes of about 50 m a.s.l.

In the Črnotiče quarry, that is located on the edge of the plateau, several caves were opened. Shafs with stalagmites and stalactites on the walls were flled by gravel as well as numerous bones of large Pleistocene mammals felt down to shafs.

Tere are also large remnants of horizontal caves. Te largest, 150 m long partly unroofed passage with the diameter of more than 10 m was opened in the western part of the quarry. Te passage was entirely flled by massive fowstones deposited over the fuvial sediments, layers of gravel and conglomerate mixed up with sand and clay layers. Sedimentary fll was 17 m thick at least.

In the cave calcareous tubes a serpulids were found both in sediments and still attached to the scalloped wall. Tey match the morphology of extant serpulid tubes of marifugia cavatica (Mihevc 2000; Mihevc et al., 2001a). Marifugia cavatica Absolon and Hrabe, 1930 is the only fresh-water species of the Serpulidae family and the only

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ANDREJ MIHEVC

Fig. 7: dEm of the Podgorski kras. Levelled karst surface of Paleocene limestone and some intercalated fysch is in sharp contrast with fuvial relief that developed on Eocene fysch. At the foot of the karst there are the major karst springs where marifugia cavatica still lives today. Te fossil tubes were found in the large cave exposed in the Črnotiče quarry.

Legend: 1. Unroofed cave, 2: Flysch, 3: Limestone.

known tube worm inhabiting continental caves. Stable isotope analysis (Mihevc et al., 2002) of fossil tubes from Črnotiče quarry site is comparable with stable isotope compositions of recent fresh-water species and greatly difers from those of marine serpulids. marifugia cava-

tica is flter feeder with free-swimming larvae (Matjašič & Sket 1966). It is widely distributed within the Dinaric Karst and lives in springs of rivers Rižana and Osapska reka which are only few km and 370 m apart from the quarry.

Two profles were analysed within the cave and dated back to 1.76 Ma (Črnotiče I) and 2.5–3.6 Ma (Črnotiče II site) (Bosak & al. 1999, Bo-sak & al. 2004).

Geomorphologic evolution of the plateau shows similarities to those of Kras and Matarsko podolje. Epi-phreatic caves of the sinking rivers were flled with sediments; the surface was levelled and uplifed to present altitude. In the quarry there are several unroofed caves or remains old caves. Te evolution of vertical shafs with dominance of later autochthonous fll resulted from younger vadose speleogenesis and Pleistocene sedimentation.

Fig. 8: Te view of the unroofed cave in a quarry face. Lower part of the cave passage was flled with mostly laminated yellowish brown fuvial sediments. Upper part is flled with fowstone. Te karst denudation already unroofed the cave, so that the fowstone is exposed to the surface. tubes of marifugia cavatica are on the scalloped walls in the lower part of the cave profle, which were protected by fne fuvial sediments.

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CONCLUSIONS

Tree diferent relief settings on the Kras, Matarsko podolje and Podgorski kras plateau show quite similar evolution. Tere are old caves present everywhere, which are now exposed by denudation. Tey were epiphreatic caves that were formed by sinking rivers, bringing allo-genic sediments to caves. At the end of the morphogenet-ic phase all these caves were completely flled with fuvial sediments. Tis indicates the diminishing of the gradient in the whole area. Afer the caves were flled the three areas were levelled. Planation occurred in the similar conditions, most likely close to the level of the karst water.

Diminishing of the gradient which ended with pla-nation could mean the same tectonic phase which ended at about 6 Ma ago. Afer that a new tectonic phase started. Tree areas faced uplif and tilting for several hundreds meters. Te uplif was stronger in the SE part of the area. Karst denudation was evenly lowering the surface, so the surface remained well preserved, dissected on central parts of karst with dolines, which represent few percent of total area only. Te even denudation exposed former caves to the surface. Some of them are flled with sediments, from some sediments were washed away or were never flled.

On the edges of Matarsko podolje there were several sinking streams shaping blind valleys. Teir incision was controlled by the piezometric level of the water in karst or the Matarsko podolje and by the tectonic uplif, they are getting deeper towards SE. Tilt of planation surface, diferent depth and asymmetric or fossil blind valleys are clear indicators of the recent tectonics.

Ages of sediments in the unroofed caves and the morphological datations are in accordance with the ages of main tectonic phases. From these data we can conclude that the oldest elements of the relief are the unroofed caves. Te blind valleys are of same age even if they difer by the dimensions. Te main process on the surface is even denudation and formation of dolines that form only small proportion of the surface.

Te remains of tubes of marifugia cavatica preserved in a quarry, high above the recent water caves indicate that the karst environment suitable for cave animals has been present for at least 6 Ma and that there was no interruption from the time of the formation of the caves in the Črnotiče quarry and drop of water table and/or tectonic uplif for at least 370 m.

REFERENCES

Absolon, K. & S. Hrabe, 1930: Über einen neuen Süss-wasser-Polychaten aus den Höhlengewässern der Herzegowina. - Zool. Anz., 88, 9-10, 259-264.

Aguilar, J. P. , Crochet J.y., Krivic K., Marandat B., J. Mi-chaux J., Mihevc A., Šebela S. & B. Sige, 1998: Pleistocene small mammals from karstic fllings of Slovenia. - Acta carsologica, 27/2, 141-150, Ljubljana.

Bosak P. , Pruner P., & N. Zupan Hajna 1998: Palaeomag-netic research of cave sediments in Sw Slovenia. -Acta carsologica, 1998, let. 27, št. 2, str. 151-179.

Bosak P. , Mihevc A., Pruner P., Melka K., Venhodová D. & A. Langrová, 1999: Cave fll in the Črnotiče quarry, Sw Slovenia: Palaeomagnetic, mineralogi-cal and geochemical study. - Acta carsologica, 28/2, 2, 15-39, Ljubljana.

Bosák, P. , Mihevc A. & P. Pruner 2004: Geomorphologi-cal evolution of the Podgorski Karst, Sw Slovenia: contribution of magnetostratigraphic research of the Črnotiče II site with Marifugia sp. - Acta carso-logica, 2004, letn. 33, št. 1, str. 175-204, Ljubljana.

Cvijić, J., 1924: Geomorfologija I, 324, Beograd.

Fodor L. Jelen B., Marton E., Skaberne D., Čar J. & M. Vrabec, 1998: Miocene –Pliocene tectonic evolution of the Slovenian Periadriatic fault: Implications for Alpine-Carpatian extrusion models. - Tectonics, vol. 17, 5, 690-709.

Gams, I., 1962: Meritve korozijske intenzitete v Sloveniji in njihov pomen za geomorfologijo, Geografski vestnik 34/1962, 3-20, Ljubljana.

Gospodarič R., 1985: On the spelogenesis of Divaška jama and Trhlovca Cave. - Acta carsologica, xIII: 5-32, Ljubljana.

Gospodarič R., 1988: Paleoclimatic record of cave sediments from Postojna Karts. - Ann. Soc. geol. Belg., 111, 91-95.

Grund A., 1914: Der geographishes zyclus um Karst. -Zeitsch. d. Gesell f. Erdkunde, S. 621-640, Berlin

Habič P.,1982: Kraški relief in tektonika. Acta carsologi-ca, 4, 23-43, Ljubljana.

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ANDREJ MIHEVC

Knez M. & T. Slabe, 2005: Unroofed caves are an important feature of karst surfaces: examples from the classical karst. - Z. Geomorphol., 46, št. 2, str. 181-191

Kratochvil, J., 1939: Marifugia cavatica edini sladkovodni serpulid, ostanek starodavnega živalstva na jugo-slovenskem krasu. - Proteus, 6, 92-96, Ljubljana.

Matjašič, J. & B. Sket, 1996: Developpement larvaire du Serpulien cavernicole Marifugia cavatica Absolon et Hrabe. - Int. J. Speleol., 25B, 1, 9-16, L´Aquilla.

Melik, A., 1955: Kraška polja Slovenije v pleistocenu. - Dela Inštituta za geografjo SAZU, 3, 1-163, Ljubljana.

Mihevc, A., 1993: Contact karst of Brkini Hills. - Acta carsologica, 23, 100-109, Ljubljana

Mihevc, A., 1996: Brezstropa jama pri Povirju. - Naše jame 38, 92-101, Ljubljana.

Mihevc, A. & N. Zupan Hajna, 1996: Clastic sediments from dolines and caves found during the construction of the motorway bear Divača, on the Classical Karst. - Acta carsologica, 25, 169-191, Ljubljana.

Mihevc, A. Slabe T. & S. Šebela, 1998: Denuded caves-an inherited element in the karst morphology; the case from Kras. - Acta carsologica, 27/1, 165-174, Ljubljana.

Mihevc, A., 1999: Te caves and the karst surface-case study from Kras, Slovenia. - Etudes de géographie physique, suppl. xxVIII, Colloque européen-Karst 99, 141-144.

Mihevc, A., 2000: Fosilne cevke iz brezstrope jame – verjetno najstarejši ostanki jamskega cevkarja Marifu-gia (Annelida: Polychaeta). - Acta carsologica, 29/2, 261-270, Ljubljana.

Mihevc, A., 2001: Speleogeneza Divaškega krasa. - Zbirka ZRC, 27: 1-180. Ljubljana.

Mihevc, A. Sket B., Pruner P. & P. Bosák, 2001: Fossil remains of a cave tube worm (Polychaeta: Serpulidae) in an ancient cave in Slovenia. - Proc., 13th International Speleological Congress, 4th Speleological Congress of Latin America and the Carribean, 26th Brazilian Congress of Speleology, Brasilia, July 15-22, 2001, 20-24, Brasilia.

Mihevc, A., Bosak P. Pruner P. & B. Vokal 2002: Fossil remains of the cave animal Marifugia cavatica in the unroofed cave in the Černotiče quarry, w Slovenia. Geologija, 45, 2, str. 471-474, Ljubljana.

Pruner, P., Bosák P. Mihevc A. Kadlec J. Man O. & P. Schnabl, 2003: Preliminary report on palaeomag-netic research on Račiška pečina Cave, Sw Slovenia. – 11th International Karstological School „Classical Karst“. Karst Terminology. Guide booklet of the excursions and abstracts of lectures or poster presentations, Postojna, July 2003: 35-37. Postojna.

Radinja, D., 1972: Zakrasevanje v Sloveniji v luči celotnega morfogenetskega razvoja. Geografski zbornik, 13, SAZU, Ljubljana.

Roglič, J., 1957: Zaravni u vapnencima. Geografski glasnik 19, 103-134, Zagreb.

Sket, B., 1970: Über Struktur und Herkunf der unterirdischen Fauna Jugoslawiens. – Biol. Vestn., 18, 69-78, Ljubljana.

Slabe, T., 1997: Karst features discovered during motorway construction in Slovenia. - Environ. geol. (Berl.), 1997, letn. 32, št. 3, str. 186-190.

Vrabec, M., & L. Fodor, 2006: Late Cenozoic tectonics of Slovenia: structural styles at the Northeastern corner of the Adriatic microplate. Te Adria micro-plate: GPS geodesy, tectonics and hazards, - NATO Science Series, I V, Earth and Environmental Sciences, vol. 61). Dordrecht: Springer, 151-168.

Zupan Hajna, N., 1991: Flowstone datations in Slovenia. - Acta carsologica, 1991, let. 20, str. 187-204.

44

TIME in KARST – 2007

COBISS: 1.01

EVOLUTION AND AGE RELATIONS OF KARST

LANDSCAPES

RAZVOJ IN STAROSTNI ODNOSI KRAŠKIH POKRAJIN

william B. wHITE1

Abstract                                                           UDC 551.44

William B. White: Evolution and age relations of karst landscapes

Any karst landscape is a work in progress. Te observed evolution of the landscape is dictated by competing rate processes of surface denudation, stream downcutting, cave development, and tectonic uplif. quantitative data on these processes, applied to two physiographic provinces of the Appalachian Mountains of eastern United States gives ages and time scales that are in agreement with previous geomorphic interpretation. Te results are anchored, very loosely, by the few dates that have been established for cave sediments. Unfortunately, the measured rates vary over an order of magnitude as a result of local circumstances making regional interpretation a rough approximation at best. Key words: fuviokarst, karst denudation, landscape evolution.

Izvleček                                                            UDK 551.44

William B. White: Razvoj in starostni odnosi kraških pokrajin

Vsaka kraška pokrajina je delo, ki napreduje. Razvoj pokrajine, ki ga je mogoče opazovati, je odvisen od medsebojno tekmujočih procesov površinske denudacije, vrezovanja površinskih tokov, razvoja jam in tektonskega dvigovanja. Številčni podatki o teh procesih, zbrani za dve fziografski enoti v gorovju Apalači na vzhodu ZDA kažejo, da se starost in časovna skala ujemata s prejšnjimi geomorfnimi razlagami. Izsledke bolj ohlapno potrjuje nekaj podatkov, dobljenih za jamske sedimente. Žal pa so spremembe razmerja hitrosti zaradi lokalnih posebnosti v velikosti cele magnitude in je torej regionalna interpretacija v najboljšem primeru le grob približek. Ključne besede: kraška denudacija, razvoj pokrajine.

INTRODUCTION: wHAT DO wE MEAN By THE “AGE” OF A KARST LANDSCAPE?

By “landscape”, we usually mean some defned area of the earth’s surface as it exists at a single moment of time. Although most of the landforms remain constant on a human time scale, they are actually in the process of continuous evolution. In at least a microscopic way, today’s landscape is not quite the same as yesterday’s landscape. If the time scale is extended to thousands or millions of years, very large changes will have occurred to the landscape. Caves will have come and gone. A karst landscape, such as a doline plain, might superfcially look the same but they wouldn’t be the same dolines. Te land surface is continuously lowered by dissolution. Old dolines disappear and new dolines are formed.

Tus when we speak of the “age” of a karst landscape we must carefully specify both spatial scales and time scales. At the largest scales we can talk about global chemical erosion over geologic time (Gibbs et al., 1999). we can talk about the general lowering of a karst landscape, the phenomenon generally called “karst denudation”. we can talk about the diferential dissolution that produces surface karst landforms. we can talk about subsurface dissolution that produces caves. we can talk about the relative rates of landscape evolution on karstic and non-karstic rocks. we can talk about rates of tectonic uplif that provide the gravitational gradients that drive all of the processes. Te observed landscape in any geo-

1 Materials Research Institute and Department of Geosciences,Te Pennsylvania State University,University Park, PA 16802 USA; e-mail: wbw2@psu.edu

Received/Prejeto: 20.12.2006

TIME in KARST, POSTOJNA 2007, 45–52

wILLIAM B. wHITE

exposed rock surfaces using embedded reference pins and a precision micro and Hanna, 1970). The micrometer works best on bare rock surfaces. Mos dissolution takes place under a soil mantle. A technique to measure dissolu

soil

logic setting is the result of the interaction of all of thaensde competing rate processes. As a result, “age” becomes a very slippery concept.

Te objective of the present paper is to determbiyn ea what constraints on the time evolution of karst lacnodn-scapes can be extracted from known rates of the lagnidv-e scape processes. Te discussion will be limited to fuvio-karst. Tis means that consideration much be given to mass transport by surface streams on both carbonate and non-carbonate rocks as well as subsurface mass transport

by d thissol ution. Illustrat ive exam ples are taken from the Appalachian Mountains of eastern United States. In the Appalachians ar e di splayr e e d twa o in geologic se, t t itin i g s s: (1) i T ble limestl o ane v c a a llleys of the fs o ilde d h A e p v p o a lulachi ans w w a h ter e the k rarst s urf f daci e s is exposea d rb across wide van ll e e dy i f noors so that th e disolutional dissection of the karst is primarily vertical and distributed across the surface. (2) Te Appalachian Plateaus where the carbonate rocks are protected by clastic caprock and whe( r t e ) the diss o lutional attack i s primarily by valley incision around the perimeter.

UNIFORM LANDSCAPE L more com I NG: a K rb A on R a S teT o D ckEs N , U is D t A heTIe O n N sit

Setting aside the necessity for also removing insoluble 10e -12 fs o tr the units given. Because the ma i s n s balanc ( e i . e e q . ua-

residue, the evolution of a carbonate rock landscape coans be considered to be a purely chemical process. Te rBocekca mass is taken into solution and carried away by the choanr-d tinuous fux of water that moves through the system. Any measure of the rate of carbonate removal can be reca lcu-lated as an average lowering of the karst surface, a queapni-k tity known as the karst denudation rate.                     princ

Various methods have been devised for the direct measurement of denudation rate (summarized by white, 2000). Te rate of surface lowering can be measured directly on exposed rock surfaces using embedded reference pins and a precision micrometer (High and Hanna, 1970).

Te micrometer works best on bare rock surfaces. Most

In th limestone dissolution takes place under a soil mantle. A

calci technique to measure dissolution rates in soil is to bury

rock carefully weighed plaques of limestone for a known time,

react then re-excavate and weigh them again (Gams, 1981).

evap On the scale of the entire drainage basin, it is possible to estimate denudation rate by a mass balance calculation using the volume of water leaving the basin and

analy the concentration of dissolved carbonates contained in

Figu the water. Te denudation rate is then given by

D,

1 K

NL A ptR

ft Q(t)H(t)dt             [1 a]

In this equation, Dn is the denudation rate in m3km2yr1 (numerically equivalent to the more common unit of mm/ka), A is the basin area in km2, NL is the fraction of the basin underlain by carbonate rocks, ρ is the density of carbonate rock in gcm3, tR is the period of record in years, q(t) is the instantaneous discharge in m3s-1 (i.e. the hydrograph) and H(t) is the instantaneous (Ca + Mg) hardness in gcm3 (i.e. the chemograph). Te constant, K, contains unit conversions and has the value

t,ioKn, rceoqnutiarienss c uonittincuoonuvserseicoonrsd sanodf bhoatsh thdeis vchalaureg e1 a0n-1d2 for the units g eh tahrednmesasssw bhaiclahn acree e nqoutatoifonen reaqvuailraebslec,o an tvinaruioetuys orfe caopr-ds of both disc ps rwoxhiimcha taioren sn hoat voef tbeenena vpariolapbolse,d a. variety of approximations have be

If the reaction between infltrating water and car-Ibfo tnhaet er eraoctki oant t bhe tbwaese no fi nthfeil terpaitkinargs tw isa atessru amnded c taor breoancaht e e iqsu ailsisburmiuemd, toh er edaecnhudeqatuiiolnib raiutem c,a tnh eb ed ecanlucdualattieodn frraotme c fesr s(tW prhinitcei,p 1le9s8 (4w).hite, 1984).

rock at the b an be calcula

D

M

cal

P344

K

KK

1 CO2

1

3

K,

Ca 2

r2.

1 3 CO2

PC O3 (P-E) [2]

In thi s eq uatio n, Dn i s the denudatio n ra t e in a a m ll c m i te/ ka. Mea l is t t h e -d3 e m m olx ecu lar wm e igl h e t of ca l wcite e g (or a w ei ghted mi i tx of the m mo lecula r w eigh ts o f calci te and dolom ite) ans d ir is th e r ock den sity in g cm3. n mm K’s a re th e usual equilibrium constants for carbonate reactions and the γ’s are the activity coef e a cients. P-E (precipitation minus evapo tra nspiration) k i s the ar n e n mual runo s e in s m t d m e/yr

Many of the ear pl ier measur) e . ments e o cf k ea r st denue-dation rates were reviewed and analyzed by Smith and Atkis n cson (1976). A se lt e hctio n of m e , re recb en let de a sta ar e disp lay ed in Figure th . in e r c i h do sen examples i e n rnclude d ar ta from each of the three measurement methods described above and t hese give comparable results. e v a e regid o inal environmen ts representu e ted in Figure 1 include arid, al m -pine, northern, and temperate. Denudation rates vary by a factor of 5-10 within each group but the groups are almost completely overlapping. Local conditions at the sampling site, including soil cover, available water, and rock lithology, all contribute so that local site variation masks regional scale variations. Tere is also the question of how denudation rates have changed in response to climatic fuctuations of the Pleistocene. For the regional scale landscape evolution of interest in this paper,

molecular

dolomite

s for carb

on minus

rates were re recent data ar three measur The regional e perate. Denu almost compl soil cover, av asks regional

46 TIME in KARST – 2007

EVOLUTION AND AGE RELATIONS OF KARST LANDSCAPES

about the best that can be said is that exposed karst surfaces in the Appalachian Mountains would be lowered by dissolution at a rate of 20-30 mm/ka.

Fig. 1: measured denudation rates. All data have been converted to units of mm/ ka. KR – mt. Kräuterin, Austria (buried tablets) (zhang et al., 1995). LG – Logatec doline, Slovenia (buried tablets) (Gams, 1981).

hS – hochschwab massif, Austrian Alps (buried tablets) (Plan, 2005). C-y – Cooleman Plain and yarrangobilly Caves area, New South Wales, Australia (microerosion meter) (Smith et al., 1995). AK – southeastern Alaska (microerosion meter) (Allred, 2004). S-S – Saltfellet-Svartisen area, northern Norway (mass balance) (Lauritzen, 1984).

RATES OF VALLEy DEEPENING

Regional rivers draining through areas of fuviokarst cut normal valleys in the clastic rocks that overlie, underlie, or border the karstic rocks and may appear as surface streams in valleys cut into the karstic rocks. Measurements of the downcutting rates of larger rivers are difcult because many of them, in their lower reaches, are at grade with a sediment load balanced against the discharge. Lowering of the bedrock channel can be very slow. A few data are given in Table 1. Lowering rates in the tectonically stable Appalachians fall in the same 20-30 mm/ka range as is found for denudation of karst surfaces. Only one example, the Bighorn Basin in western United States is a factor of ten higher and may represent a higher rate of tectonic uplif.

tab. 1. downcutting Rate of Some moderate-Size Rivers

Small tributary streams that fow from surrounding non-karstic lands onto the karst and then sink at the contact with the soluble rocks seem to have a much higher rate of channel lowering. Some direct micrometer measurements in the beds of sinking streams are given in Table 2. Sinking stream waters are generally highly un-saturated so that sinking streams downcut rapidly into the carbonate rock at their sink points. Similar measurements at spring outlets produce much smaller numbers. Te highest values yet reported were for a muskeg-draining stream in Alaska (Allred, 2004) where there is an implication that organic acids may also play a role.

Name and Location

Rate (mm/ka)

Reference

Bighorn River, Wyoming

East Fork, Obey River, Tennessee

Green River at Mammoth Cave, Kentucky Juniata River, Newport, Pennsylvania New River at Pearisburg, Virginia

350 30

30 27 27

Stock et al. (2006)

Sasowsky et al. (1995) Anthony & Granger (2004)

Granger et al. (2001)

Sevon (1989)

Granger et al. (1997)

TIME in KARST – 2007 47

wILLIAM B. wHITE

tab. 2. downcutting Rate in Small Karst Streams

Name and Location

Cataract Cave, southeast Alaska County Clare, Ireland

Muskeg Infow Cave, southeast Alaska

Slate Cave, southeast Alaska Yarrangobilly, NSW, Australia

Rate (mm/ka)

Reference

137

Allred (2004)

500

High and Hanna (1970)

400

1670

Allred (2004))

1080

180

Allred (2004)

200

Smith et al. (1995)

CAVE DEVELOPMENT IN FLUVIOKARST

Caves – here considered to be master trunk caves related to surface base-level streams – have a three-stage development. (1) Te initiation phase is the evolution of an initial mechanical fracture to a critical-size protoconduit about one centimeter in aperture. (2) Te enlargement phase takes the protoconduit up to the meters to tens of meters diameter of a typical cave passage. (3) Te stagnation and decay phase is that period afer the cave passage has been drained and abandoned by lowering base levels. As the stagnation phase progresses, entrances are developed and process of collapse, speleothem growth, and sediment in-

48

INITIATION .STAGE

Q

_i

8 l

3 O

4 .

0

flling choke of the once continuous conduit. Deepening of surface valleys breaks the cave into fragments.

Te initiation phase is almost purely chemical. Nearly saturated water percolates along alternative paths in the carbonate rock, slowly enlarging them. Te initiation phase ends when one pathway becomes sufciently large to permit critically undersaturated water to pass completely through the aquifer. As a result, the fnal layout of the conduit system is largely determined during the initiation phase. Te initiation phase is particularly amenable to geochemical modeling and some very elegant models have been constructed (Dreybrodt et al., 2005). Te time scale for the initiation depends on assumed initial conditions but appears to be in the range of 10,000 to 20,000 years.

Te enlargement phase is largely independent of outside factors. T Te rate l o af retreat of pae s s iage wae l l l ys can ba e s descria b lel d s by th e Palr m ib eer-Dreybrodt equation (Palmer, 1991).

co, -

03 atm

10 20 30 Time (k-year)

31.56k

C

C

S J

Pr

[3]

S is tha e ll rate of wa ll rety r rea t in cm/yr. So 2 m . e calc ulations for pa, s k sa , ge

Fig. 2:Enlarge d m e p e e n n t phao s e n f or it y pical c a o t n e o^ea r p g eaZZZZZa v en on the

TIME in KARST – 2007

The relationship between hydraulic gradient, radius, R, is given by a form of the Darcy-Weisbach

hf

n

S

The enlargement phase is largely independent of outside factors. The rate of retreat of passage walls can be described by the Palmer-Dreybrodt equation (Palmer, 1991).

C

n

EVOLUTION AND AGE RELATIONS OF KARST LANDSCAPES

m

enlargement are plotted in Fig. 2. TCe rate constant, k, was taken from Palmer (1991). The rock density, ρR was set equal to 2.65 g/cm3. Te reaction order, n = 1, in the fast disso lut ioh n e rea g teim o e f . w T ale o renly en vir onmer n . t aS ll oy sensia - l tive paramo e tter i is t hF e i sa t2 u .ration ca o ten c centratiot n , of c w a alciua m ke carbonate whic h e d t epends o n the carbon dioxi k ,e parti al pressure. Figure 2 shv o ir w o ns the nassa ge es n itlargema e rant re a t t e e rs expected for n a a re asoh n icable range of n Oe 2 pressur es. Al-though the d ageta ils are sitm e e-sp ecit f e c s, even c r teougf h o c a lculao-tions suggest that 50,000 to 100,000 y e ars a r e suffic ient to allow a ma s ster cac v ie to develop.

Ta e relationship between hydraulic gradient, hf/L, discharge, q, and passage radius, R, is given by a form of the Dar rcy-d w ius e ,i sba c i h s equation

al p

h

fQ2

47T2gR5

[4]

SoSmoem mea mximaxuimu gmradgireandtise tnhtast t chant cbaen s ubpep sourptepdo brtye a given Fsiizgeu croen 3d ufoitr aar es epleoctteiodn ino fF idgiusrceh 3a rfgoer sa. s election of discharges.

Because ofB tehcea uloswe ohfy dthrea ulloicw r hesyidstranucleic o rfe sciosntadnucite of systemsd, itfhfe reelenvcaetiboent wdiefeenre tnhcee hbeeatdwweeante trhse a hneda dthwea tdeorws and thep drowvindsetrseuafmfi creieancht ehse aodf stuor dfarciev es ttrheeam cas vcea-nf oprrmo-i vide sufcacvieenst dhevaedl otop d breivnee aththe csauvrefa-fcoer mvainllge ypsr o(coers sm. Borye this protchees sf loofw au ftroopmir atchye, scuavrfeasc dee svterleoapm b.e nSeuacth scuarvfeacs eg valleys (voarl mleyorse t ohfate nth ieny t huen vdaelrledyra wina.lls) and drain of the fow from the surface stream. Such caves generally have fatter gradientsU thnalnik teh ke avrasltl esyusr tfhaacte tsh oery suunrdfaecrder vaianll.eys

Unrleikmea kina rasst fsiuxrefdacelse voar tsiounrfamcea rvkaelrlse yasn dw hariceh t haer eo continuwouhsilcyh etvhoel vaigneg ,i sc alovceks erdemina.in C asv efsx meda ye lreivdaet iuonp markersr eamnda ianr efi txheed oansl yth fe asturfeasc oef ltahned kscaarspte l afnaldlsc arpoeu for whipch atshee iang teh eis claovcke’esd hiins.t oCrayv aesn dm iasy t hreid pe huapswe ainrd with tecotnocneic-c uopnltifn,u obust coothnedruwiti sies rferamgamine nftxeedd a sa st hteh es

10 or lm

n = , i th

hf/

equ

4

* 2 L

[3]

n k

re = 0.5 nrp/ssc

\ s t

5 5 h

ge = n i

m3/sec

= 0.0: en                    are plotted in

0 i__l yst e eleva 1.00 1,50 surface streams can (m\ ppppppppppppppppppppppppppppppppp J

ten in the valley walls) and drain off

Fig. 3: Supportable hydraulic hea s a function of conduit erraadliluys hfoarv vea rfiloautst edri sgchrardgieesn. Tts et hdaanr ctyh-We eisbach friction factor, f = 100. Te gravitational acceleration, g = 9.8 msec-1.

itciohn a arned c doenctianyu pohuassley inev tohlev cianvge,’ sc haivsetosr y and is the phase ifne awthuircehs eonf ttrhaen ckeasr astr el adnedvsecloaped f oanr d the once-continu-do uws ictho ntedcutiot nisicf ruapglmifet,n bteudt aosththerew suisreface lowers and val-tlehyesm d.e eTpheins. iIsn ttheerm stsa ogfn iamtipoonr taanndced eacs abyio logical habitat, cth ee nftnraln csteasg ae ries dvevrye liomppeodr atanndt.t hUenfortunately, the de-atcaeil sl owf tehres caonndd vuaitl ldeeycsa yd eoefp thene .coInd uit depends on local csitracguem ist avnecreys idmopeos rntaont tl.en d itself to numerical analysis.

surface tlearnmdsc oafp eim faplolsr taarnocuen das t hbeiomlo. gTiciasl ihs atbhiet astt,a tghnea -

Unfortunately, the details of the conduit decay of the conduit depends on local circumstances does not lend itself to numerical analysis.

AGE RELATIONSHIPS IN THE PLATEAU FLUVIOKARST SETTING

Te Cumberland Plateau is the southern-most extension of the great Appalachian plateaus that extend from New york State into Alabama. Te Cumberland Plateau in Tennessee and Alabama is an upland of low-dip Mis-sissippian rocks. Te plateau is capped with a highly resistant quartzite which provides a reference elevation at about 550 to 600 meters. Te denudation of the resistant quartzite is very slow, 3-5 mm/ka, according to Anthony and Granger (2004). Te plateau is bounded by a pronounced escarpment into which deep valleys (known locally as “coves”) have been incised. At the base of the

western escarpment is a karst surface known as the Highland Rim. Te doline surface of the Highland Rim extends into many of the deeper coves. Mississippian limestones underlie the valley walls of the coves and much of the Highland Rim (Fig. 4).

Te downcutting rate of one incised valley, that of the East Fork of the Obey River in north-central Tennessee was frst calculated from magnetic reversals in the sediments of one of the caves in the valley wall (Sasowsky et al., 1995). Tis number was revised when cosmogenic isotope dating of the same cave showed that

TIME in KARST – 2007 49

L

wILLIAM B. wHITE

Fig. 4: Schematic cross-section through the western escarpment of the Cumberland Plateau. Ticknesses of individual beds are nominal values; bed thicknesses vary considerably over short distances (milici et al., 1979).

the paleomagnetic measurements referred to an earlier Cumberland River reversal (Anthony and Ganger, 2004). Te revised value Highland Rim.

of 30 mm/ka (Table 1) is similar the downcutting rate of other moderate size rivers and also very similar to the expected denudation rate.

Te Highland Rim surface at the base of the western escarpment has nearly eroded to the bottom of the carbonate sequence. It all about 150 meters of limestone have been removed. If the Highland Rim is raised according to the 30 mm/ka denudation rate, approximately 5 million years ago, the erosion surface was at the top of the limestone. Te sediments in Big Bone Cave were dated at 5.7 Ma (Anthony and Granger, 2004) and it was claimed that this date represents a time when the was fowing at the elevation of the

AGE RELATIONSHIPS IN APPALACHIAN VALLEy FLUVIOKARST SETTING

Te karst surfaces of the Great Valley and Valley and Ridge Provinces of the folded Appalachians are breached

anticlines. Deep erosion along the anticlines has exposed the Ordovician and Cambrian limestones and dolomites which now form the valley foors. Te more resistant quartzites on the fanks of the anticlines remain as long nearly-parallel ridges bounding the valleys (Fig. 5). Contemporary surface streams have downcut 50 to 75 meters into the valley surface. Tere must have been a time when the anticlines were frst breached to expose the carbonate rocks to denudation. Figure 6 shows the sequence of events (without time scale) and includes the recognized erosion surfaces identifed in central Pennsylvania.

Te Nittany Valley near State College, Pennsylvania is an interfuve area. Here are found residual soils

Fig. 5: Sketch showing topographic relations in central Pennsylvania. Ridges are supported by resistant quartzite; most of the valley foors are underlain by Cambrian and Ordovician carbonate rocks. Afer deike (1961).

50 TIME in KARST – 2007

EVOLUTION AND AGE RELATIONS OF KARST LANDSCAPES

Fig. 6: Te evolution of the Nittany valley in central Pennsylvania showing traditional erosion surfaces. Afer Gardner (1980).

with thicknesses averaging 50 meters. On the assumption that these are let-down soils consisting of the insoluble residues from the dissolution of the carbonate

Although doline plains give the impression of stable erosion surfaces, denudation measurements suggest the rate of lowering is comparable to the rate of downcutting of surface valleys. Te horizontal surface is maintained because of the internal drainage through the dolines. It is, therefore, problematic to attempt to assign and age to karst surfaces.

Cave development is very rapid compared with the evolution of the surface landscape. Caves in tectonically

rocks, a calculation based on insoluble residue content and bulk density suggests that more than 425 meters of carbonate rock were removed to accumulate this thickness of soil (white and white, 1991). On the (quite possibly unreasonable) assumption that the denudation rate has been 30 mm/ka, the removal of 425 meters of carbonates would require on the order of 14 million years, placing the beginning of what has been a uniform denudation process in mid-Miocene time. Te present relief between the valley foor and the ridge tops is about 250 meters. Te carbonate surface at the beginning of the denudation process would be 175 meters above the present-day ridge tops. However, the estimated denudation would not include the entire carbonate section so it does not represent the breaching of the anticline which must have taken place earlier.

Te accordant ridge-lines of the folded Appalachians are ofen taken to represent the Schooley Peneplain. If these quartzite-topped ridges erode as slowly as similar rocks on the Cumberland Plateau, the limestone would have flled the valley to the level of the ridge tops only 8 – 9 Ma ago. Te age of the Schooley Peneplain would be much less than many ages that have been assigned to it, some setting the age as far back as the Jurassic.

Te valley foors which represent the Harrisburg Survey have been dissected by present day streams to produce an internal relief of about 60 meters. Te caves of the Valley and Ridge Province are found within this interval. Some are inlet caves with high gradients due to the rapid downcutting of sinking streams. Others are fragments of base-level conduits. Given the observed rates of stream downcutting, the time span available for the development of these caves is 2 – 3 million years.

stable areas serve as better markers of temporarily stable pauses in base level lowering than do either surface streams or the elevations of karst “erosion surfaces”. Tis conclusion has been suspected at least since the work of Davies (1960) but was given much stronger support by recent cosmogenic isotope dating (Granger et al., 1963; Anthony and Granger, 1964). It is also supported by the present geochemical calculations and mass balance arguments.

CONCLUSIONS

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51

wILLIAM B. wHITE

REFERENCES

Allred, K., 2004: Some carbonate erosion rates of southeast Alaska – journal of Cave and Karst Studies 66, 89-97.

Anthony, D.M. & D.E. Granger, 2004: A late Tertiary origin for multilevel caves along the western escarpment of the Cumberland Plateau, Tennessee and Kentucky, established by cosmogenic 26Al and 10Be – journal of Cave and Karst Studies 66, 46-55.

Davies, w.E., 1960: Origin of caves in folded limestone – National Speleological Society bulletin 22, 5-18.

Deike, R.G., 1961: Karst development in Brush Valley, PA – Nittany Grotto Newsletter 9, 121-128.

Dreybrodt, w., F. Gabrovšek & D. Romanov, 2005: Processes of speleogenesis: A modeling approach – Car-sologica, No. 4, 375 p.

Gams, I., 1981: Comparative research of limestone solution by means of standard tablets – 8th International Congress of Speleology Proceedings, Bowling Green, Kentucky, USA, p. 273-275.

Gardner, T., 1980: Geomorphology of Nittany Valley – Chapter 5 in Soils and Geology of Nittany valley, E.J. Ciolkosz, R.R. Parizek, G. w. Petersen, R.L. Cunningham, T.w. Gardner, J.w. Hatch, & R.D. Shipman, Eds., Te Pennsylvania State University Agronomy Series No. 64, p. 52-75, University Park, PA.

Gibbs, M.T., G.J.S. Bluth, P.J. Fawcett, & L.R. Kump, 1999: Global chemical erosion over the last 250 My: Variations due to changes in paleogeography, paleocli-mate, and paleogeology – American journal of Science 299, 811-51.

Granger, D.E., D. Fabel & A.N. Palmer, 2001: Pliocene – Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic 26Al and 10Be in Mammoth Cave Sediments – Geological Society of America bulletin 113, 825-836.

Granger, D.E., J.w. Kirchner & R.C. Finkel, 1997: quaternary downcutting rate of the New River, Virginia, measured from diferential dcay of cosmogenic 26Al and 10Be in cave-deposited alluvium – Geology 25, 107-110.

High, D. & F.K. Hanna, 1970:A method for the direct measurement of erosion on rock surfaces – british Geomorpological Research Group technical bulletin No. 5, p. 24.

Lauritzen, S.-E., 1984: Some estimates of denudation rates in karstic areas of the Saltfellet – Svartisen Region, North Norway – Catena 11, 97-104.

Milici, R.C., G. Briggs, L.M. Knox, P.D. Sitterly & A.T. Statler, 1979: Te Mississippian and Pennsylvanian (Carboniferous) Systems in the United States – Tennessee – U.S. Geological Survey Professional Paper 1110-G, 38 p.

Palmer, A.N., 1991: Origin and morphology of limestone caves – Geological Society of America bulletin 103, 1-21.

Plan, L., 2005: Factors controlling carbonate dissolution rates quantifed in a feld test in the Austrian Alps – Geomorphology 68, 201-212.

Sasowsky, I.D., w.B. white & V.A. Schmidt, 1995: Determination of stream-incision rate in the Appalachian plateaus by using cave-sediment magnetostratigra-phy – Geology 23, 415-418.

Sevon, w.D., 1989: Erosion in the Juniata River drainage basin, Pennsylvania – Geomorphology 2, 303-318.

Smith, D.I. & T.C. Atkinson, 1976: Process, landforms and climate in limestone regions – Chapter 13 in Geomor-phology and Climate, E. Derbyshire, Ed., John wiley, p. 367-409, London.

Smith, D.I., M.A. Greenaway, C. Moses, & A.P. Spate, 1995: Limestone weathering in eastern Australia. Part I. Erosion rates – Earth Surface Processes and Landforms 20, 451-463.

Stock, G.M., C.A. Riihimaki, & R.S. Anderson, 2006: Age constraints on cave development and landscape evolution in the Bighorn Basin of wyoming, USA – journal of Cave and Karst Studies 68, 76-84.

white, w.B., 1984: Rate processes: chemical kinetics and karst landform development – in Groundwater as a Geomorphic Agent, R.G. LaFleur, Ed., Allen & Un-win, p. 227-248, London.

white, w.B., 2000: dissolution of limestone from feld observations – in Speleogenesis, A. Klimchouk, D.C. Ford, A.N. Palmer & w. Dreybrodt, Eds., National Speleological Society, p. 149-155, Huntsville, AL.

white, w.B. and E.L. white, 1991: Karst erosion surface in the Appalachian highlands – in Appalachian Karst, E.H. Kastning and K.M. Kastning, Eds. National Speleological Society, p. 1-10, Huntsville, AL.

Zhang, D., H. Fischer, B. Bauer, R. Pavuza & K. Mais, 1995: Field tests of limestone dissolution rates in karstic Mt. Kräuterin, Austria – Cave and Karst Science 21, 101-104.

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COBISS: 1.01

CAVE AND KARST EVOLUTION IN THE ALPS AND THEIR RELATION TO PALEOCLIMATE AND PALEOTOPOGRAPHy

RAZVOJ JAM IN KRASA V ALPAH V LUČI PALEOKLIME

IN PALEOTOPOGRAFIJE

Philippe AUDRA1, Alfredo BINI2, Franci GABROVŠEK3, Philipp HäUSELMANN4,

Fabien HOBLéA5, Pierre-yves JEANNIN6, Jurij KUNAVER7, Michel MONBARON8,

France ŠUŠTERŠIČ9, Paola TOGNINI10, Hubert TRIMMEL11 & Andres wILDBERGER12

Abstract                                           UDC 551.435.84(234.3)

Philippe Audra, Alfredo Bini, Franci Gabrovšek, Philipp Häuselmann, Fabien Hobléa, Pierre-Yves Jeannin, Jurij Ku-naver, Michel Monbaron, France Šušteršič, Paola Tognini, Hubert Trimmel & Andres Wildberger: Cave and Karst evolution in the Alps and their relation to paleoclimate and paleo-topography

Progress in the understanding of cave genesis processes, as well as the intensive research carried out in the Alps during the last decades, permit to summarize the latest knowledge about Alpine caves. Te phreatic parts of cave systems develop close to the karst water table, which depends on the spring position, which in turn is generally related to the valley bottom. Tus, caves are directly linked with the geomorphic evolution of the surface and refect valley deepening. Te sediments deposited in the caves help to reconstruct the morphologic succession and the paleoclimatic evolution. Moreover, they are the only means to date the caves and thus the landscape evolution. Caves appear as soon as there is an emersion of limestone from the sea and a water table gradient. Mesozoic and early tertiary paleokarsts within the alpine range prove of these ancient emersions. Hydrothermal karst seems to be more widespread than previously

Izvleček                                            UDK 551.435.84(234.3)

Philippe Audra, Alfredo Bini, Franci Gabrovšek, Philipp Häuselmann, Fabien Hobléa, Pierre-Yves Jeannin, Jurij Ku-naver, Michel Monbaron, France Šušteršič, Paola Tognini, Hubert Trimmel & Andres Wildberger: Razvoj krasa in jam v Alpah v luči paleoklime in paleotopografje

V članku predstavimo nova spoznanja o razvoju alpskih jam. Ta temeljijo na sintezi novih dognanj o procesih speleogeneze in rezultatih intenzivnih terenskih raziskav v Alpah v zadnjih desetletjih. Razvoj freatičnih delov jamskih sistemov poteka v bližini freatične površine, ki je vezana na položaj izvirov, ti pa so vezani na dno alpskih dolin. Torej je razvoj jam neposredno vezan na geomorfološki razvoj terena in poglabljanje dolin. Jamski sedimenti nosijo informacijo o zaporedju morfoloških in klimatskih dogodkov. Še več, določanje starosti jam in poteka razvoja površja, je možno edino z datacijo jamskih sedimen-tov. Razvoj jam se začne ob emerziji apnenca in vzpostavitvi hidravličnega gradienta. Mezocojski in zgodnje terciarni pa-leokras v območju Alp so dokaz starih emerzij. Hidrotermalni kras je očitno bolj razširjen, kot so domnevali v preteklosti. Te jame so bile pozneje preoblikovane z meteorno vodo, ki je zabrisala sledi zgodnjega hipogenega zakrasevanja. Ledeniki zavi-

1 équipe Gestion et valorisation de l’environnement, UMR 6012 “ESPACE” CNRS, University of Nice Sophia-Antipolis, 98 boulevard édouard Herriot, BP 209, 06204 Nice cedex, France (audra@unice.fr).

2 Dipartimento di Scienze della terra, Università di Milano, via Mangiagalli 34, 20133 Milano, Italy (alfredo.bini@unimi.it)

3 Karst research Institute ZRC SAZU, Titov trg 2, 66230 Postojna, Slovenia (gabrovsek@zrc-sazu.si)

4 Institut suisse de spéléologie et de karstologie (ISSKA), CP 818, 2301 La Chaux-de-Fonds, Switzerland (praezis@speleo.ch)

5 EDyTEM, Université de Savoie, 73376 Le Bourget cédex (Fabien.Hoblea @ univ-savoie.fr)

6 Institut suisse de spéléologie et de karstologie (ISSKA), CP 818, 2301 La Chaux-de-Fonds, Switzerland (info@isska.ch)

7 Hubadova ulica 16, 61000 Ljubljana, Slovenia (jurij.kunaver@siol.net)

8 Département de géosciences/géographie, ch. du Musée 4, Université de Fribourg, 1700 Fribourg, Switzerland (michel.monbaron@unifr.ch)

9 Dept. of Geology NTF, University of Ljubljana, 1001 Ljubljana, Slovenia (france.sustersic@ntfgeo.uni-lj.si)

10 via Santuario inferiore, 33/D, 23890 Barzago (LC), Italy (paolatognini@iol.it)

11 Draschestrasse 77, 1230 wien, Austria (Hubert.Trimmel@refex.at)

12 Dr. von Moos AG, Engineering Geology, 8037 Zürich, Switzerland (wildfsch@bluewin.ch) Received/Prejeto: 01.12.2006

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PHILIPPE AUDRA, ALFREDO BINI, FRANCI GABROVŠEK, PHILIPP HäUSELMANN, FABIEN HOBLéA, PIERRE-yVES JEANNIN, ...

presumed. Tis is mostly due to the fact that usually, hydrothermal caves are later reused (and reshaped) by meteoric waters. Rock-ghost weathering is described as a new cave genesis agent. On the contrary, glaciers hinder cave genesis processes and fll caves. Tey mainly infuence cave genesis indirectly by valley deepening and abrasion of the caprock. All present dat-ings suggest that many alpine caves (excluding paleokarst) are of Pliocene or even Miocene age. Progress in dating methods (mainly the recent evolution with cosmogenic nuclides) should permit, in the near future, to date not only Pleistocene, but also Pliocene cave sediments absolutely.

Key Words: Karst, Cave genesis, Alps, Glaciations, Messinian event, Paleoclimate, Paleotopography.

rajo procese speleogeneze in zapolnjujejo jame. Na razvoj jam vplivajo posredno, preko poglabljanja dolin in brušenja površja. Novejše datacije kažejo, da so številne jame v Alpah pliocenske ali celo miocenske starosti. Nove datacijske metode - predvsem metoda kozmogenih nuklidov - bodo omogočile absolutno datacijo sedimentov do pliocenske starosti. Ključne besede: kras, geneza jam, Alpe, poledenitve, mesinska stopnja.

INTRODUCTION

Progress in cave exploration and cave genesis studies (Audra 1994, Jeannin 1996, Palmer 2000) permitted to recognize the potential of caves for the study of landscape evolution, valley deepening and thus erosion rates and climate changes (Häuselmann et al. 2002; Bini et al. 1997). Most of the information that is sheltered within the cave’s morphology and sediments is no more available at the surface, mainly due to the intensive erosion, especially during the glaciations.

Tis article gives information about cave genesis and its potential for the reconstruction of the evolution

and timing of the landscape: Part I presents the latest results concerning cave genesis and their link with the landscape. Part II deals with new concepts about early cave genesis, including pre-existing karst systems (paleo-karst), hydrothermal karst, and pseudokarst. Many caves are older than the glaciations and glaciers generally are rather hindering cave genesis processes. Part III consequently presents evidences supporting a high age of many cave systems. In Part I V, ages obtained by diferent dating methods prove that karst genesis in the Alps started far before the quaternary, as far as the Cretaceous.

SETTING

Te Alpine belt extends from Nice (France) to Vienna Liechtenstein, Austria, Germany and Slovenia). Karsts (Austria) into seven countries (France, Switzerland, Italy, and caves are found in each country, the largest karst areas being located in periphery (Fig. 1). All massifs are dissected by deeply entrenched valleys which divide continuous structures into diferent physiographic units. Annual precipitation range from 1500 to more than 3000 mm.

Te French western Prealps consist of folded and thrusted massifs of mainly Cretaceous rocks. Te elevation ranges generally between

Fig. 1: map of the alpine karsts (dark color) with location of the mentioned massifs (karst areas afer: buzio & Faverjon 1996; mihevc 1998; Stummer & Pavuza 2001; Wildberger & Preiswerk 1997. map: d. Cardis).

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CAVE AND KARST EVOLUTION IN THE ALPS AND THEIR RELATION TO PALEOCLIMATE AND PALEOTOPOGRAPHy

1000 and 2000 m. Te Vercors displays a landscape of ridges and valleys, whereas the Chartreuse presents a steep, inverted relief.

Te Central Swiss Alps harbors the highest alpine karst areas at Jungfrau (3470 m ASL). Te Siebenhengste (2000 m ASL) and the Hölloch-Silberen (2450 m ASL) consist of nappes of Cretaceous and Eocene rocks.

Te Italian Southern Alps are located to the south of the Insubric Line. Te carbonate rocks range in age from Carboniferous to Cretaceous-Eocene. Tey are deformed and displaced by S-vergent thrusting and large scale folding. Te elevation ranges from 200 m to 2400 m ASL.

Te basics of cave genesis are beyond the scope of this paper. Te reader can refer to the most comprehensive and up-to-date work Speleogenesis: Evolution of Karst Aquifers (Klimchouk et al. 2000).

GENESIS OF CAVES AND MORPHOLOGy

OF PASSAGES RELATED TO wATER

TABLE POSITION

water fowing into limestone corrodes and erodes the rock. Driven by gravity and geological structure, it fows down more or less vertically, until it reaches either the karst water table or impermeable strata. Ten it continues fowing more or less horizontally towards the spring, collecting water from other lateral passages. water fowing in the vadose (unsaturated) zone can only erode the foor of a gallery creating a meandering canyon. On the other hand, water fowing within the phreatic (saturated) zone corrodes over its whole cross-section, giving a rounded cross-section (Fig. 2). Te morphologies that are preserved once the watercourses have been abandoned give information about the prevailing position of the phreatic zone during the genesis of the galleries.

~\s meander

^--' V                  floodwater level

tube

Fig. 2: An undulating phreatic tube is co-fed by a vadose meandering canyon, whose shape turns into a tube below the foodwater table. Te arrow marks the transition from vadose to phreatic.

Te Northern Calcareous Alps in Austria are composed of a slightly folded succession of Trias limestones and dolomites with a thickness of more than 1000 m. Large plateaus extend from 1800 to 2200 m ASL.

In the Slovenian Alps, the Julian and the Kamnik Alps correspond to the roots of the Austrian nappes. Tus the landscape is ofen similar, with plateaus and narrow steep ridges dominated by high peaks reaching more than 2800 m ASL.

RECOGNITION OF CAVE GENESIS PHASES AND RELATION TO THE SPRING

within the saturated zone, two geometric types of conduits prevail (Ford 1977, 2000): 1) the water table caves, represented by horizontal conduits located at the top of the saturated zone; 2) the looping caves, represented by vertically lowering and rising conduits, whose amplitude may reach as much as 300 m, or even more.

A “phase of cave genesis” corresponds to the network of active conduits related to a given (paleo)spring. As springs move together with valley bottoms, we usually fnd many diferent “phases of cave genesis” in a given karst region.

As described on fgure 2 the transition between phreatic conduits (elliptical shape) and vadose ones occurs at the top of the epiphreatic zone, i.e. more or less at the top level reached by water during highwater stages. Due to headlosses, highwater level is inclined towards the outlet of the system, namely the karst spring (Jeannin 2001, Häuselmann 2003). Most of the time conduits are located within a given range of altitudes (sometimes more than 300 m) below the (inclined) water table limit. Tese conduits go up and down (hence their name: “loops”) within this range and towards the spring. Sometimes main conduits of a given phase can be followed for kilometers and display a phreatic morphology all along. Sometimes the highest passages clearly show vadose entrenchment because they were located higher than the top of the epiphreatic zone, at least most of the time.

Reality is a little more complicated that exposed here (see Häuselmann et al. 2003 for instance), but the principle is the same. Te main exceptions to this model, linking quite directly the phases of cave genesis to the (paleo)spring positions, i.e. valley bottom, occur when

GENERAL CONCEPTS OF CAVE GENESIS

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PHILIPPE AUDRA, ALFREDO BINI, FRANCI GABROVŠEK, PHILIPP HäUSELMANN, FABIEN HOBLéA, PIERRE-yVES JEANNIN, ...

impervious barriers dam water somewhere inside the aquifer.

SUCCESSION OF CAVE GENESIS PHASES,

CAVE LEVELS RECORDING BASE LEVEL

CHANGES

If the spring lowers gradually, the cave system behind also adapts gradually by entrenchment to the new situation: no distinct phases exist. If the spring lowers in a stepwise manner, followed by a time of relative stability, the fowpath readjustment in the cave also occurs rapidly and a new cave genesis phase develops. Calculations show that, once a proto-conduit has been formed, caves may evolve very rapidly, in the order of 10’000 years, to reach penetrable size (Palmer 2000). Terefore, afer a new entrenchment of a valley, pre-existing or newly created soutirages (Häuselmann et al. 2003) allow for the water to reach the spring level quite quickly and a new water table, i.e. phase of cave genesis is created (Fig. 3). Former conduits, perched in the vadose zone afer the deepening of the karst system, are abandoned and remain dry (fossil passages). Provided that the cave genesis phases refect the deepening of the valleys through time, they give information for the reconstruction of paleorelief.

Fig. 3: Schematic fow system. black = main (epiphreatic) gallery; light grey = soutirages (downward) and upfow (upward); dark grey = perennial phreatic conduit.

Equivalent information at the surface is usually no longer present, mostly due to river or glacier erosion.

In some cases, the base level may rise again afer a period of deepening (e.g. post-messinian inflling of the overdeepened canyons in the southern part of the Alps; Felber & Bini 1997). Tis caused a fooding of pre-existing karst systems and a reactivation of previously vadose or abandoned passages (Tognini 2001).

THE RELATION BETwEEN MORPHOLOGy, CLIMATE, AND SEDIMENTS

Cave morphology depends on the position of the epi-phreatic water table. Te size of the passage, however, depends (among others, mostly geological factors) on time and fow rate. worthington (1991) puts forward that there is an “equilibrium size” of a phreatic passage for a given fow rate. Afer this size is reached, the passage hardly grows anymore, and a growth above this size is mainly dependent on an increase in fow rate, either by capturing another catchment, or related to an increase in precipitation. For example, in the Siebenhengste system, the size of the main conduits doubles between two phases (700 m and 660 m). Tis very probably corresponds to the capture of the Schrattenfuh catchment, which sig-nifcantly increased the size of the catchment area (Fig. 4). Conversely, a reduction in the catchment area due to valley entrenchment produces rearrangement of the cave system. Newly formed passages will be smaller than in the previous phase.

Beside the size of the conduits, sediments also provide direct information about the fow velocities, i.e. discharge rates in the conduits. Grainsize distribution of cave sediments and conduit size make it possible to assess paleodischarge rates quite precisely.

Fig. 4: N-S-projection of bärenschacht and St. beatus Cave with the recognized phases. Te numbers are the elevations ( in m ASL) of the corresponding spring. Phase 558 is the present one.

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CAVE AND KARST EVOLUTION IN THE ALPS AND THEIR RELATION TO PALEOCLIMATE AND PALEOTOPOGRAPHy

NEw CONCEPTS ABOUT CAVE GENESIS

THE INFLUENCE OF EARLy PHASES:

PRE-ExISTING KARST SySTEMS (PALEOKARST),

HyPOGENIC KARST AND PSEUDOKARST

Syn- and post-sedimentary paleokarsts

“Paleokarst” are features that are not related to any present water circulation and completely obstructed. Since most of the caves (including fossil tubes) are related to present rivers and valleys, they are not considered as paleokarst.

Some paleokarsts have been formed during or immediately afer the sedimentation of carbonate platforms (Upper Triassic, for example Calcare di Esino/Grigna; Dachsteinkalk/Northern Limestone Alps). Dolines, pockets and red paleosoils interfere within the cyclic sedimentation of the so-called loferitic succession. Under a premature diagenesis, dissolution and concretion produced evinosponges (Bini & Pellegrini 1998) and dolomite-flled fractures that contain iron oxides from paleosoils. In the Julian Alps, paleokarstic conduits have been flled with carbonate mud and later lithifed, so that – presently – a paleoconduit is just a portion of somehow diferently colored solid rock. Other paleokarst had been set up afer the emersion of the limestone strata. Tey are fossilized by Jurassic sediments (Swiss Prealps, Julian Alps), Upper Cretaceous sandstone (Siebenhengste), Eocene sands (Vercors), or Miocene conglomerates (Chartreuse).

Tose paleokarsts features may form highly porous discontinuities that may have guided the placement of later cave systems.

•  Hydrothermal caves related to tectonic build-up Some caves have a hydrothermal origin, which can

be recognized afer their typical corrosional cupolas originating from convection cells and their sediments like large calcite spar (Audra et al. 2002a; Audra & Hofmann 2004; Bini & Pellegrini 1998; Sustersic 2001; wild-berger & Preiswerk 1997). Tose hydrothermal upfows are usually located near huge thrust and strike-slip faults. Such karstifcations created well connected cave systems which later had generally been re-used by “normal” meteoric water fow afer uplif above the base level. Since this change has mostly deleted the marks of their origin, they are only conserved when rapidly fossilized.

•  Pseudokarst creating rock-ghosts (cave phantoms)

Models of apparent karst features created by processes other than pure dissolution are called pseudokarst. Te phantomisation (rock-ghost weathering) was recently described as a major agent of karstifcation in impure limestones (Vergari & quinif 1997). In such limestones fow remained guided by fractures but partially occurred in the matrix around the fracture. In a

favorable context, warm and humid climate and long-term stability of the base level, this type of fow could dissolve the limestone cement, but impurities remained in place, in place, preserving the parent material tex-

Fig. 5: Pseudoendokarst cave system in the marly-silicated moltrasio Limestone of mt. bisbino, Lake of Como (tognini 1999, 2001).

1 – Late Oligocene-Early miocene: Te tectonic structure was achieved during the neo-alpine phase. Uplif raised the area above sea level, producing a gentle relief dissected by valleys.

2-3 – middle-Late miocene: According to very long base level stability under warm and humid climate, deep soils develop. With very low gradient and water movements, weathering progressively penetrates deeply into the water-flled zone. Uplif gradually deepens the valleys.

4 – messinian: valleys dramatically entrench, water table lowers, inducing an active fow. Te weathered rock-ghosts are eroded away by piping, causing the formation of cave systems, which extend progressively in size and complexity. Steep hydraulic gradients prevent a further weathering at depth. Te present remnants of rock-ghosts mark the maximal depth (700 m) reached by weathering that corresponds to the present 500-600 m altitude. With a continuous entrenchment, pseudoendokarsts become perched and only “classical” cave system develop below.

5  – Early-middle Pliocene: Pseudoendokarstic caves systems stopped developing.

6 – Late Pliocene-Quaternary: Sequences of erosion and deposition are developing (e.g. lacustrine caves sediments recording the presence of the Adda glacier close to the caves entrances; speleothem deposition is enhanced during interglacials).

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tures and structures. Rock porosity increased up to 35%, causing a dramatic increase in hydraulic conductivity. Tis weathered material is called rock-ghosts, or phantoms. Te downstream part of such systems, close to the surface, can be eroded by piping because of the absence of cement. Tis may produce caves (Tognini 2001). Some peculiar features may point out their different origin (weathered walls, regularly spaced 3D network, brisk change in passage morphology, dead-end at gallery terminations with conservation of the ghost of the weathered host-rock). Afer the piping event, the rock-ghosts remained perched on an unweathered rock, in which only “classical” karst processes adapted to the new base level began to be active.

COMPLEx RELATIONSHIPS TO GLACIERS

Some older theories supported a direct relationship between glaciations and genesis of cave systems through glacial meltwater. However, recent datings (U/T, paleo-magnetism) and feldwork has clearly proven that many caves are older than the glaciations. Te role of the glaciers seems to be mostly limited to valley deepening, base level rising during glacial periods and related sedimentation in the conduits (Audra 1994, 2004; Bini 1994; Häuselmann 2002). Te genesis of new caves only takes place in certain contexts, where the glacial infuence often is only indirect.

Glacial processes mainly fll caves

In the Alps, glaciers were temperate with fowing water. As valley bottoms were flled by ice, base levels raised all along the valleys. Furthermore, tills obstructed the preexisting springs. Terefore, a large glacier body may have raised karstwater level by several hundreds of meters, for

instance 500 to 600 m in the Bergerhöhle/Tennengebirge (fg. 6). Such a rising karstwater level reactivated many older conduits, increasing drastically fow cross-sections and leaving only restricted fow velocities in each conduit. Fine-grained carbonate-rich sediments found in very many caves are good indicators of these stages. Since this carbonate four could obviously not be dissolved by the natural aggressivity of the water, it implies that a chemical erosion of cave walls was very probably negligible. Tis is confrmed by old speleothems, preceding such phases, that are hardly dissolved (Bini et al. 1998). Mechanical abrasion in the fooded zone is also improbable because of the small fow velocity. Terefore, it must be postulated that the genesis of deep-seated cave conduits is not favored by glaciations (Audra 1994, 2001a; Bini et al. 1998; Maire 1990).

In contrast, interglacials induce the presence of vegetation and soil at the surface. Both elements greatly enhance the CO2 content of the water (Bögli 1978), and reduce the amount of debris washed into the cave. So, water has a much higher initial acidity and can therefore enlarge caves (Audra 2004). During the same time, water from the fne fssures and matrix, which entered the system below the soil and epikarst, where pCO2 is high, is oversaturated with respect to calcite when it reached a (ventilated) cave passage. Terefore many speleothems formed. In some low valleys with fat bottoms, lakes flled the previously overdeepened valley and kept the water table high. Terefore, in spite of the sometimes considerable valley deepening by glaciers, the karst water table could never reach the total depth of the valley, blocking thus the genesis of deeper cave levels (Kanin). Nevertheless, in the South Alpine domain, the fuvial valley deepening may have allowed deep (and today submerged) karstifcation.

Fig. 6: Te Cosa Nostra-bergerhöhle system/tennengebirge, Salzburg Alps (Audra et al. 2002b). to the lef (3), relationship between cave passage altitude and old karst levels. Karst development began during the Oligocene beneath the Augensteine (1). during the miocene, horizontal systems developed with alpine water inputs (2), showing diferent levels (3) related to successive phases of stability: Ruinenhöhlen (4) and Riesenhöhlen (e.g. Eisriesenwelt – 5). Following Pliocene uplif, alpine systems developed (e.g. Cosa Nostra-bergerhöhle – 6). horizontal tubes at the entrance correspond to a miocene level (7). A shaf series (6) connect to horizontal tubes from bergerhöhle-bierloch (8), corresponding to a Pliocene base level (9). Te present water table at 700 m (10) pours into brunnecker Cave, which connects to the Salzach base level (11).

58 TIME in KARST – 2007

CAVE AND KARST EVOLUTION IN THE ALPS AND THEIR RELATION TO PALEOCLIMATE AND PALEOTOPOGRAPHy

Cave system

Massif

Difference in heigh, horizontal cave levels / present base level (m ASL)

Dating

Allogenic fluvial pebbles

Old sediments

- weathered soils

- presently removed covers

Partly eroded catchment, large dimensions not related to present topography, truncated by erosion

Presumed age of the system

References

Ch. du Goutourier

Dévoluy

2300 / 875 m

> 780 ka (paleomag.)

Tertiary weathered soils

Upper Miocene?

Audra 1996

Gr. Vallier

Vercors

1500 / 200 m

Tertiary, Lower Pleistocene glacial varves (paleomag.)

Tertiary weathered soils

yes

Upper Miocene

Audra & Rochette 1993

Réseau de la Dent de

Crolles

Chartreuse

1700 / 250 m

> 400 ka (U/Th)

Cretac. sandstones

yes

Upper Miocene?

Audra 1994

Gr. Théophile

Gdes Rousses

1900 / 1850 m

95 ka (U/Th)

Middle Pleistocene

Audra & Quinif 1997

Gr. de l’Adaouste

Provence

Stratigraphic correlation

Miocene pebbles

Artesian

Tortonian

Audra & al. 2002

Système du Granier

Chartreuse

1500 / 1000 m

> 1-1,5 Ma

(234U / 238U equilibr.,

paleomag.)

1,8-5,3 Ma

(cosmonucleides)

Upper cretac. and oligo.

limest.

- Cretac. sandstones

- weathered soils

yes

Upper Miocene?

Hobléa 1999; Hobléa

& Häuselmann 2007

Beatushöhle - Bärenschacht

Siebenhengste

890 / 558 m

> 350 ka

(U/Th)

Pleistocene

Häuselmann 2002

Siebenhengste

Siebenhengste

1900 / 558 m

4.4 Ma (cosmonucleides)

Pliocene

Häuselmann & Granger 2005

Jochloch

Jungfrau

3470 m

Lower Pleistocene? (palynology)

practically no catchment today

Lower Pleistocene

Wildberger &

Preiswerk 1997

Ofenloch

Churfisten

655 / 419 m

> 780 ka (paleomag.)

Pliocene

Müller 1995

Hölloch-Silberensystem

Silberen

1650 / 640 m

>350 ka (U/Th), <780 (paleomag)

Lower Pleistocene?

Battisti

Paganella

1600 m

> 1-1,5 Ma

(234U / 238U equilibr.)

Cherts from Eocene limestones

yes

Oligo-Miocene

Conturines

Dolomite

2775 m

> 1-1,5 Ma

(234U / 238U equilibr.)

yes

Oligo-Miocene

Frisia & al. 1994

Capana Stoppani, Tacchi-Zelbio

Pian del Tivano

900 / 200 m

> 350 ka (U/Th)

Boulders from glacial sinkholes

yes

Oligo-Miocene

Tognini 1999, 2001

Gr. dell’Alpe Madrona

Mte Bisbino

1000 / 200 m

> 350 ka (U/Th)

Miocene

Tognini 1999, 2001

Covoli di Velo Ponte di Veia

Mte Lessini

33-38 Ma (K/Ar)

yes

Eocene and Oligocene

Rossi & Zorzin 1993

Gr. Masera

Lario

200 / 361 m

≈ 2.6 to 7.2 Ma (cosmonucleides)

Fluvial pebbles

Pliocene or older

Häuselmann unpub. Bini & Zuccoli 2004

Gr. On the Road

Campo dei Fiori

805 / 300 m

> 1-1,5 Ma

(234U / 238U equilibr)

Oligo-Miocene

Uggeri 1992

Gr. Via col Vento

Campo dei Fiori

1015 / 300 m

> 350 ka (U/Th) Upper Plio. glacial sediments

Oligo-Miocene

Uggeri 1992

Gta. sopra Fontana Marella

Campo dei Fiori

1040 / 300 m

Middle Pleistocene (micro-fauna)

Conglomerate with crystalline pebbles

Ferralitic soils

yes

Oligo-Miocene

Zanalda 1994

Ciota Ciara – Cuitarun caves

Mte Fenara

Large miocene f uvial pebbles

yes

Oligo-Miocene

Fantoni & Fantoni

1991

Cosa Nostra-Bergerhöhle

Tennengebirge

1600-1000 / 500 m

> 780 ka (paleomag)

yes

Augensteine

yes

Miocene - Upper Pliocene

Audra & al. 2002

Mammuthöhle

Dachstein

1500-1300 / 500 m

yes

Augensteine

yes

Miocene

Trimmel 1961, 1992; Frisch & al. 2002

Eisriesenwelt

Tennengebirge

1500 / 600 m

yes

yes

Lower Pliocene?

Audra 1994

Feichtnerschacht

Kitzsteinhorn

2000 / 1000 m

118 ka (U/Th)

Pliocene?

Audra 2001, Ciszewski & Recielski 2001

Poloska jama

Mt Osojnica

750 / 500 m

yes

Crnelsko brezno

Kanin

1400 / 400 m

> 780 ka (paleomag) Glacial varves

Audra 2000

Snezna jama

Kamnik Alps

1600 / 600 m

1.8 to 3.6 or 5 Ma (paleomag)

yes

yes

yes

Miocene?

Bosak & al. 2002

tab. 1: Synthesis of information about the quoted caves systems

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As a conclusion, a warm climate induces passage growth and speleothem deposition, whereas a cold climate generally tends to obstruct the lower passages by sediments.

Glacial sediments covering older speleothems: cave systems may predate glaciations

Some cave sediments correspond to very old glaciations, according to paleomagnetic measurements that show inverse polarity: Ofenloch/Churfrsten (Müller 1995), grotte Vallier/Vercors (Audra & Rochette 1993), Crnel-sko brezno/Kanin (Audra 2000). Tese sediments ofen overlie successions of alterites or massive fowstone deposits, which in turn prove the existence of a warm and humid climate, thus showing that the cave systems predate those glaciations. Some of the old speleothems are more or less intensely corroded by fowing water postdating their deposition.

Cave development and glacial activity - Glacial abrasion at the surface and erosion in the va-dose zone. At the surface, the glacial activity is without doubt responsible for the abrasion of a variable amount of bedrock (50-250 m), which has surfaced old conduits that previously were deeply buried. Tis is manifested by wide open shafs, cut galleries and arches. During glacial melt, meltwater disappeared into distinct sectors. As soon as fractures were connected to preexisting conduits, they enlarged quickly and thus formed the “invasion vadose shafs” (Ford 1977), which can reach several hundred meters of depth: Granier, Silberen, Kanin (Ku-naver 1983, 1996). Te efectiveness of such meltwater is

Some existing caves and karst features clearly correspond to a strongly diferent topography than today. Tey are therefore supposed to be older. In the following paragraphs, the position and morphology of caves are compared to today’s landscape. Ten cave sediment characteristics are presented and discussed. In a third part, links between caves and well-recognized paleotopographies are explained. All those indications are clear evidences for a high age of cave systems.

CAVE SySTEMS VS. PRESENT TOPOGRAPHy

Perched phreatic tubes

Conduits with an elliptical morphology are sometimes perched considerably above the present base level (Tab. 1,

mainly due to its velocity in the vertical cascades as well as their abrasive mineral load originating from bedrock and till material.

- Some new cave systems appeared in the intra-Al-pine karst area due to glacial erosion. Tin limestone belts or marbles intercalated with metamorphic series were freed from their impervious cover by glacial erosion. Some caves are still in direct relationship with the peri-glacial fow, and act as swallowholes. Teir morphology refects the cascading waterfow and has a juvenile form: Perte du Grand Marchet/Vanoise, Sur Crap/Graubün-den (wildberger et al. 2001). At the Grotte Téophile/ Grandes Rousses, U/T datings evidenced that the cave was active at least along the two glacial-interglacial cycles that are marked by the sequence of passage-forming/fll-ing with gravel/sinter deposition (Audra & quinif 1997). Since cave development mainly occurred during inter-glacial, the efect of the glacier is only indirect, by eroding the impervious covers (Audra 2004).

- Te lower phases of huge cave systems are indirectly generated by glacial valley-deepening. while the uppermost cave systems are ofen older than the glacia-tions (infra), the lower passages are ofen of quaternary age, since they are related to valleys evidently deepened by glaciers. In this respect, glaciers are indirectly responsible for the creation of new cave passages (Siebenhengste, Chartreuse, Vercors). Tis strongly contrasts with the South Alpine domain, where valleys were deepened during the Messinian event. Here, glaciations contributed merely to the inflling of the preexisting valleys. Tus, most of the South Alpine cave systems are thought to be older than the glaciations.

3rd column). Tey developed close to a paleo base level, long before today’s valley deepening. At the Siebenhengste, the highest phases even show a fow direction opposite to the present one.

Caves intersected by current topography

Old perched caves are ofen segmented by a subsequent lowering of the surface. Two situations are usually found in the feld:

- Old phreatic caves at the surface of karst plateaus, which have been eroded by glacial abrasion (Grigna, Dolomites, Triglav, Kanin, Tennengebirge…)

- Old phreatic caves along valley fanks, obviously cut by the lowering of the topography (Adda, Adige, Salzach, Isère): Pian del Tivano, Mt. Bisbino, Mt. Tremez-

MORPHOLOGIC AND TOPOGRAPHIC EVIDENCES FOR A HIGH AGE

OF CAVE SySTEMS

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zo, Campo dei Fiori (Southern Alps), Paganella (Dolomites).

Dimensions too large with respect to the present catchment and climate

Te dimensions of some conduits are far too large compared to the present catchment area, thus proving that the older catchment areas had been much larger, but are now truncated by erosion (Eisriesenwelt/Tennengebirge (fg. 6); Antre de Vénus/Vercors; Snezna jama na Raduhi/ Kamnik Alps, caves at Pokljuka and Jelovica plateaus at Julian Alps, Siebenhengste, Pian del Tivano, Campo dei Fiori/Southern Alps).

Spring location vs. present base level

If the position of a spring is not due to a geologic perching above an impervious layer, it has to be close to base level (see part I). However, in some cases springs did not lowered down to today’s base level. In other cases springs are obviously located far below the base level. Tis can be explained by the following hypotheses:

- Some springs are perched, because the valley incision is very recent and rapid (Pis del Pesio/Marguareis).

- Others are presently submerged below the base level and hidden by alluvial fll or till (Emergence du Tour/Ara-vis; Campo dei Fiori). Tey were set into their place before the base level raised and they continue to function due to the high transmissivity of the sediment fll.

A specialty is given when old vertical vadose caves are suddenly stopped by the present water table, proving that the horizontal drains are at much greater depth and completely drowned. Typical vadose morphologies (spe-leothems, karren) are known in some drowned conduits (Grotta Masera, Grotta di Fiumelatte/Lake of Como; Fontaine de Vaucluse/Provence). Here, the spring location is adapted to the present base level, but the caves are proof that the base level may, in some cases, also rise. Tis is especially true for areas afected by the Messinian crisis (Bini 1994; Audra & al. 2004).

CAVE SEDIMENTS SHOwING EVIDENCE

OF A REMOTE ORIGIN, DIFFERENT CLIMATE

AND OLD AGE (tab. 1)

Old fuvial material

Te presence of some caves sediments is inexplicable with the present waterpaths. Big rounded pebbles found in caves perched high up on top of clifs mean that a valley bottom had to exist at this level. Aferwards, the valleys deepened so much that they are far below such perched massifs (Salzach/Salzburg Alps; Granier/Char-treuse). Ofen, gravels found in these caves have a petrog-

raphy and mineralogy that is not found in the present rocks. Tey are issued either from caprock that has disappeared a long time ago (Fontana Marella, Campo dei Fiori) or from distant catchments, as proven by fuvial pebbles (Augensteine/Northern Limestone Alps in Austria), quartz sandstones (Slovenian Alps), fuvioglacial sediments (Lake of Como). Dating of fuvial pebbles by cosmogenic nuclides from the Grotta Masera (Como), yielded a probable age comprised between 2.6 to 7.2 Ma, showing a pliocene age, or maybe older (Häuselmann unpub.; Bini & Zuccoli 2004). In the Granier system, this method yields ages comprised between 1.8 to 5.3 Ma (Hobléa & Häuselmann 2007).

Record of climatic changes in subterranean sediments

Ofen, the analysis of the sediments evidences climate changes, with a change from biostatic conditions, marked by the rarity of allogenic sediments, towards rhexistatic conditions, with lots of allogenic sediments. Tese sediments come from the erosion of soils in a context of climate degradation and general cooling. Tey usually are interpreted to refect the climatic change in the Pliocene, before the onset of the glaciations. Such sediments are present in most of the old cave phases, which therefore should be older than the end of the Pliocene: Grotte Vallier/Vercors; Tennengebirge (Audra 1994, 1995), Campo dei Fiori (Bini et al. 1997), Monte Bisbino (Tognini 1999, 2001). In the Dachstein-Mammuthöhle, which dates back to the Tertiary and shows a phreatic tube perched 1000 m above the Traun valley, fowstones grown during the interglacials interfn-ger with a series of debris-fow conglomerates of glacial origin (Trimmel 1992). In the Grotta di Conturines/Do-lomites (2775 m ASL), the mean annual temperatures deduced from the 18O of speleothems were between 15 and 25°, which implies that speleothemes deposited in a warmer climate within the Tertiary, probably also at a lower altitude than it is found today (Frisia et al. 1994). Furthermore, in many caves, either conduits or fowstones have been deformed by late Alpine tectonic movements: Grotta Marelli, Grotta Frassino/Campo dei Fiori (Uggeri 1992; Bini et al. 1992, 1993).

Dating results prove the antiquity of cave systems

Te calculated age of old speleothems are regularly above the U/T limits (700 ka, even 1.5 Ma according to the 234U/238U equilibrium (Bini et al. 1997); Tab. 1). Te pale-omagnetic measurements ofen show inverse magnetism, sometimes with multiple inversion sequences, proving of a very old age of the cave sediments (Audra 1996, 2000; Audra & Rochette 1993; Audra et al. 2002b). Te use of the new cosmonucleide method to date old quartz sediments also confrms this trend and yield ages reaching

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back to about 5 Ma (see the details for Siebenhengste example in this volume).

RELATIONS TO AN OLD TOPOGRAPHy

Te geomorphologic approach, which uses external markers of old base levels (paleovalleys, paleoshelves with associated sediments) that are well dated, ofers precious possibilities for the dating of karst systems. Sadly, correlations are almost impossible up-to-date due to the scarcity of such information. In the northern fank of the Alps, the glaciations ofen caused the remnants of an old topography to disappear. Te southern Alps, less glaciated and better studied in this context, ofer more possibilities, also thanks to the presence of guiding events like the Messinian incision and the following Pliocene marine highstand.

Old erosion surfaces

Te identifcation of old erosion surfaces is a precious tool in geomorphology. Large surfaces ofen top the relief and cut across very old caves that are difcult to link to an old drainage system because of their fragmented character. Te cave systems developing below those high surfaces are more recent, such as the stacked surfaces in the Vercors, of Eocene, infra-Miocene and Pliocene age (Delannoy 1997). Shelves along slopes, created by lateral corrosion of the rim of ancient depressions, have the same signifcance as perched valley bottoms. In Vercors, Pliocene caves could be associated on them, such as the Antre de Vénus and the Grotte Vallier (Delannoy 1997). In the area of Varese (Lombardy), the Oligo-Miocene surface that cuts across limestone, porphyritic rocks and granites, is dissected by the late Miocene valleys that had

PALEOKARST, A MILESTONE FOR OLD KARSTS

Te study of paleokarsts is a separate domain. No cave system has survived in its integrality from the periods predating the Miocene. In the Northern Limestone Alps of Austria, the possibility that caves of the highest level (Ruinenhöhlen) may be relicts of an oligocene karstif-cation has been discussed (Frisch et al. 2002). However, Paleogene paleokarsts are frequent, as evidenced by natural or artifcial removal of their flling:

- In Siebenhengste, upper Cretaceous paleotubes and fractures are found in Lower Cretaceous limestone,

been deepened during the Messinian (Bini et al. 1978, 1994; Cita & Corselli 1990; Finckh 1978; Finckh et al. 1984).

Morphological and sedimentological evidences of pre-pliocene paleovalleys

A fuvial drainage pattern of Oligo-Miocene age, incised in the relief, predated the Alpine tectonic events of the late Miocene. Te drainage originated in the internal massifs, cut through the calcareous border chains, and ended in alluvial fans in the molasse basins. In the border chains, perched paleovalleys are found more than 1500 m above the present ones (Salzburg Alps), as well as fu-vial deposits coming from siliceous rocks (Augensteine/ Northern Calcareous Alps; siliceous sands/Julian Alps (Habic 1992)), sometimes buried in caves near the valley slopes (Grotta di Monte Fenera/Piemont, Grotta Fontana Marella/Campo dei Fiori).

In the northern fank of the Alps, these valleys have been destroyed by the deepening of the hydrographic network, aided by the action of the glaciers. In the South, the old valleys have been deepened by the Messinian incision and flled by Pliocene sediments (Lake of Como/Adda, Varese, Tessin, Adige, Durance). As a consequence, the horizontal karstic drains that were linked to the old valleys had been truncated by slope recession, and are presently perched (Grotta Battisti/Paganella; Grotte Vallier/ Vercors; Pian del Tivano, Monte Bisbino (Tognini 2001); Campo dei Fiori (Uggeri 1992)). Te almost generally observed input of allogenic waters coming from impermeable rocks upstream, combined with a tropical humid climate with considerable foods, explains the giant dimensions of those caves.

flled with Upper Cretaceous Sandstone (Häuselmann et al. 1999).

- In many places, (Switzerland, Vercors, Chartreuse) vast pockets covering a karst relief and flling up some conduits can be observed.

- In Southern Alps, upper Eocene and lower Oli-gocene sediments have been found into large cavities inflled by basaltic intrusions (Covoli di Velo, Ponte di Veia/Monte Lessini) Teir age could be determined by K/Ar datings (Rossi & Zorzin 1993).

In several regions (Vercors and Chartreuse, Monte Lessini), karstifcation is more or less continuous from the Eocene onwards. However, the tectonic and paleo-

AGE OF ALPINE KARSTIFICATION: FROM PALEOKARSTS TO RECENT

MOUNTAIN DyNAMICS

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geographic changes have only lef dispersed paleokarsts. Since the Miocene on, several massifs emerged from the molasse basins, thus allowing a karstifcation that continues today.

ESTIMATION OF THE FIRST ExPOSURE ACCORDING TO MOLASSE PETROGRAPHy

Te main phase of karstifcation begins when suitable rocks are exposed at land surface. Since the oldest remnants of karst are ofen eroded, it is possible to calibrate the beginning of the karstifcation by the foreland sediments (mainly the Molasse), which contain limestone pebbles eroded away at the surface. However, absence of evidence is not evidence of absence: sedimentary gaps are frequent, and a karst in biostatic conditions does not spread detritic elements towards the foreland. As a general rule, the Miocene molasse registered the beginning of the last big karstifcation phase, earlier in Italy, later in Switzerland:

- Upper Oligocene-Lower Miocene (30 to 20 Ma) in the Southern Molasse, based on dated fuvial sediments located in paleovalleys (Gelati et al. 1988).

- Lower Miocene (20 Ma) in the molasse south of Grenoble, corresponding to the erosion of the emerged anticlines of the Vercors and Chartreuse (Delannoy 1997).

- Lower Miocene (20 Ma) in the Austrian Nord-Alpine molasse, corresponding to the erosion of the Augensteine cover, which is of Upper and Middle Oligocene age (Lemke 1984; Frisch et al. 2000).

- Upper Freshwater Molasse in the Eastern Swiss basin (Hörnli fan, Middle Miocene 17-11 Ma) which contains pebbles of the frst erosion of Helvetic nappes (Siebenhengste, Silberen, Speck 1953; Bürgisser 1980).

DATING THE yOUNGEST PHASES AND ExTRAPOLATION

Te most generally applied dating method for cave sediments is U/T. It makes it possible to date speleothems. In best cases, it allows for going back to as far as 700 ka – dating only the sediment contained within the cave and not the cave itself. Te use of paleomagnetic dating makes it possible, in some scarce cases, to push back the datable range to 2.5 Ma. Te use of cosmogenic isotopes (Granger et al. 2001) is the only recent method that opens new possibilities, having a dating range between 300 ka and 5 Ma. Another solution consists in dating lower cave phases that are supposed to be younger, and in progressively going up the phases towards the oldest cave systems, until reaching the limits of the used methods. From the calculated rate of valley deepening, one can then extrapolate

the age of the uppermost phases. Of course, such an approach can only give a general idea about the age.

Te lowermost phases of the Siebenhengste cave system, St. Beatus Cave and Bärenschacht, have been dated by U/T. Te following ages have been obtained: Phase 558 (youngest) began at 39 ka (max. 114 ka) and is still active today; Phase 660 was active between 135 and 114 ka; Phase 700 was active between 180 and 135 ka; and Phase 760 started before 350 ka and ended at 235 ka (Fig. 4). Tese age values indicate a general valley incision rate of 0.5 to 0.8 mm/a, with a tendency to slow down as the age gets higher. Extrapolation indicated an age of about 2.6 Ma for the oldest cave systems, at 1850 m ASL. Absolute cosmogenic dating yielded an age of 4.4 Ma for the oldest sediment, contained in the second-highest cave phase at 1800 m, showing a slower entrenchment in the older phases (Häuselmann & Granger 2005; see also this volume). Dating of the cave systems at Hölloch/Sil-beren gave maximal rates of valley incision in the range of about 1.5 to 3.5 mm/a.

RELATIVE UPLIFT RATES AND EROSION VOLUMES IN FORELAND SEDIMENTS

Uplif rates are generally calculated for long periods of time, taking the average of variable rhythms and integrating vast parts of the area, without taking into account block tectonics which can difer considerably from one massif to the other. In the same range, the estimated volume of the foreland basins only gives a global approach. Such results only may give a general frame for a validation. Modeling the fssion-track measurements of the Swiss Central Alps (Reuss valley) give an average uplif of 0.55 mm/a (Kohl, oral comm. 2000) comparable to calculations of recent uplif (0.5 mm/a; Labhart 1992) and consistent with the rates inferred from dating in caves. Uplif is maximal in the central parts of the mountain chains, therefore the rocks are more deeply eroded in this area. As a consequence, the oldest caves had to have disappeared from the central zones, compared to the border chains where they are better preserved due to the slower erosion.

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CONCLUSION

Te examples mentioned above are distributed throughout the Alpine belt. Terefore, the conclusions drawn here are valid for Alpine Caves at least, but they may be applied to other cave systems also. Te main following conclusions can be drawn from the above synthesis:

- In contrast to some earlier views, caves are not directly linked to glaciations. On the contrary, there is evidence that during glaciations caves are mainly flled with sediments, while they are enlarged during the inter-glacials. Te main infuence of glaciers upon cave genesis is the deepening of the base level valley, thus inducing a new cave genesis phase to be formed.

- U/T datings, coupled with paleomagnetism, inferred a Lower Pleistocene to Pliocene age for several cave sediments. Fossil or radiometric datings of solidifed cave flls (sandstone, volcanic rocks) gave ages reaching back to the Upper Cretaceous. It follows that caves are not inherent to the quaternary period, but are created whenever karstifable rocks are exposed to weathering. Due to later infll, however, most explorable caves range from Miocene to present age.

- we have shown that caves are related to their spring, which is controlled by a base level that usually consists of a valley bottom. So, the study of caves gives very valuable information about valley deepening processes and therefore about landscape evolution.

- Caves constitute real archives, where sediments are preserved despite the openness of the system. Te study of cave sediments gives information about paleo-climates. Moreover, the combination of cave morphology and datable sediments allow to reconstruct the timing of both paleoclimatic changes as well as landscape evolu-

tion between the Tertiary and today. Diferential erosion rates and valley deepenings can be retraced. Information of this density and completeness has disappeared at the surface due to the erosion of the last glacial cycles and the present vegetation.

- Correlations between well-dated cave systems can signifcantly contribute to the geodynamic understanding of the Alpine belt as a whole. Te location of most cave systems at the Alpine border chains is very lucky: since they are dependent on base level (in the foreland), recharge and topography (towards the central Alps). Tey inevitably registered changes in both domains. Caves are therefore not only a tool of local importance, but may have a wide regional/interregional signifcance.

- Te dating method by cosmogenic nuclides was recently applied in some French, Italian and Swiss alpine cave systems which partially contain pre-glacial fuvial deposits. Te dated sediments yielded ages ranging between 0.18 and 5 Ma, which are consistent with other approaches. Advances in modern dating techniques (cosmogenic isotopes, U/Pb in speleothems) therefore open a huge feld of investigations that will very signif-cantly contribute to the reconstruction of paleoclimates and topography evolution along the last 5, possibly 15 to 20 Ma.

- Te messinian event infuenced cave genesis over the whole southern and western sides of the Alps by overdeepening valleys. However, the subsequent base level rising fooded those deep systems creating huge deep phreatic aquifers and vauclusian springs (Audra et al. 2004).

ACKNOwLEDGEMENTS

PH, PyJ and MM acknowledge the Swiss National Science Foundation for support of the Habkern workshop

(Grant No. 21-62451.00) and for research support (Grant No. 2100-053990.98/1).

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COBISS: 1.01

ASPECTS OF THE EVOLUTION OF AN IMPORTANT

GEO-ECOSySTEM IN THE LESSINIAN MOUNTAIN

(VENETIAN PREALPS, ITALy)

POGLEDI NA RAZVOJ POMEMBNEGA GEO-EKOSISTEMA V GORAH LESSINI (BENEŠKE PREDALPE, ITALIJA)

Leonardo LATELLA1 & Ugo SAURO2

Abstract                               UDC 551.442:574.4 (234.323.4)

Leonardo Latella & Ugo Sauro: Aspects of the evolution of an important geo-ecosystem in the Lessinian Mountain (Venetian Prealps, Italy)

Te Grotta dell’Arena (476 V/VR), located in the Lessinian Mountain, at the elevation of 1512 m a.s.l., is a very important underground karst system. Although it is only 74 m long, several of the geological, geomorphological and environmental features of the High Lessinian underground karst are present in this cave. Te Grotta dell’Arena shares some common geological and faunistic characters with other important and well known karst systems. Tis cave has also one of the highest number of troglobitic species in all Venetian Prealps and some of them possibly originated in the pre-quaternary. From the geological point of view the cave is the expression of a contact karst, where diferent limestone types come in contact both stratigraphically and along tectonic structures. Te Grotta dell’Arena is located at the stratigraphic contact between the “Calcari del Gruppo di San Vigilio” and the “Rosso Ammonitico” and it is very close to a fault plane putting in vertical contact the two above formations with the “Biancone”, a kind of limestone closely stratifed and densely fractured, very sensible to frost weathering. It is interesting to note the presence of a good number of species of Tertiary, or more generally pre-quaternary, originate in the Grotta dell’Arena. Tis presence is possibly related to the geology of caves. In this paper the diferent kinds of underground karst systems in the Grottta dell’Arena and Lessinian Mountain, are analyzed and the relation with the cave fauna distribution are taken in consideration.

Key words: karst evolution, geomorphology, biospeleology, faunistic invasions, Venetian Prealps, Italy.

Izvleček                                UDK 551.442:574.4 (234.323.4)

Leonardo Latella & Ugo Sauro: Pogledi na razvoj pomembnega geo-ekosistema v gorah Lessini (Beneške Predalpe, Italija)

Jama Grotta dell’Arena (476 V/VR) v gorah Lessini, 1512 m n.m., je zelo pomemben podzemeljski kraški sistem. Čeprav je dolga le 74 m, vsebuje geološke, geomorfološke in okoljske elemente, značilne za kraško podzemlje Visokih Lessini. Grot-ta dell’Arena ima nekaj geoloških in favnističnih značilnosti skupnih z drugimi pomembnimi in znanimi kraškimi sistemi. Jama je med tistimi z največjim številom troglobiontskih vrst v vseh Beneških Predalpah, od katerih nekatere verjetno izvirajo izpred kvartarja. Z geološkega vidika predstavlja jama kontaktni kras, kjer so vzdolž stratigrafskega in tektonskega stika različni apnenci. Grotta dell’Arena je na stratigrafskem stiku med apnenci “Calcari del Gruppo di San Vigilio” in “Rosso Ammonitico” in je zelo blizu prelomne ploskve, vzdolž katere se vertikalno stikata omenjeni formaciji s formacijo “Bianco-ne”, to je vrsta drobnoplastovitega in gosto prepokanega, slabo odpornega apnenca. Zanimiva je prisotnost precejšnjega števila terciarnih oziroma splošneje predkvartarnih vrst. To je verjetno v zvezi z jamsko geologijo. V prispevku so podrobneje obravnavane različne vrste podzemskih kraških sistemov v sami jami Grottta dell’Arena kot tudi v gorah Lessini in tudi njihovi odnosi z razporeditvijo jamskega živalstva.

Ključne besede: razvoj krasa, geomorfologija, biospeleologija, invazija favne, Beneške Predalpe, Italija.

1 Museo Civico di Storia Naturale di Verona. Lungadige Porta Vittoria, 9, 37129 Verona, Italy. E-mail: leonardo.latella@comune.verona.it

2 Università degli Studi di Padova, Dipartimento di Geografa. Via del Santo 26, 35123 Padova, Italy. E-mail: ugo.sauro@unipd.it

Received/Prejeto: 21.12.2006

TIME in KARST, POSTOJNA 2007, 69–75

LEONARDO LATELLA & UGO SAURO

INTRODUCTION

Te Grotta dell’ Arena is registered with the number 476 in the Cadastre of the Caves of Veneto Region (the cave has been surveyed by A. Pasa in 1942, and GAS USV in 1972); the karst area is ML03 (Monti Lessini 03). Te cave is 74 m long with a diference in elevation of - 22 m. It is located in the Lessinian Mountain district of Bosco Chiesanuova, in Malga Bagorno area. G.C: 11° 06’ 02’’ E 45° 39’ 56” N, elevation 1512 m a.s.l.

Te Grotta dell’Arena is a signifcant kind of underground karst system in Lessinian Mountain in fact:

– it is a type of speleogenetic style in the morpho-dynamic context of the High Lessinians,

– several of the geological, geomorphological and environmental features of the High Lessinian underground karst are present in this cave and played a signif-cant role in karst evolution,

– some of the best known karst systems in the Les-sinian Mountain (Mietto & Sauro, 2000; Rossi & Sauro,

1977), such as the Abisso della Preta, the Covolo di Cam-posilvano, the Abisso del Giacinto, the Abisso dei Lesi, the Ponte di Veja, share some common characters with the Grotta dell’Arena,

– from the biospeleological point of view, this cave has one of the highest number of troglobitic species in all Venetian Prealps,

– several troglobitic species are endemic for the Grotta dell’Arena or the Lessinian Mountains and some of them possibly originated in the pre-quaternary.

Te Grotta dell’Arena is a large chamber, roughly elliptical in plane section, with a main diameter of about 50 m. Te roof coincides mostly with bedding planes. Te southern part of the foor is characterized by a large, asymmetrical, funnel-shaped depression, a kind of subterranean doline developed in the collapse debris.

Te chamber is situated a few meters below the topographical surface; it is connected to the surface through

Gastropoda

Opiliones

Diplopoda

Orthoptera

Zospeum sp.

Ischyropsalis strandi

Lessinosoma paolettii

Troglophilus sp.

Anellida

Copepoda

Collembola

Coleoptera

Marionina n.sp.

Speocyclops cfr. infernus

Onychiurus hauseri

Orotrechus vicentinus juccii

Araneae

Lessinocamptus caoduroi

Pseudosinella concii

Orotrechus pominii

Troglohyphantes sp.

Moraria n. sp.

Sincarida

Italaphaenops dimaioi

Pseudoscorpiones

Elaphoidella n. sp.

Bathynella sp.

Lessinodytes pivai

Chthonius lessiniensis

Isopoda

Amphipoda

Laemostenus schreibersi

Neobisium torrei

Androniscus degener

Niphargus galvagnii similis

Halberrria zorzii

Balkanoroncus boldorii

tab. 1: List of the cave-dwelling species in the Grotta dell’Arena.

Fig. 1: Te collapse depression called Arena. 70 TIME in KARST – 2007

Fig. 2: Te large chamber in the Arena cave. In the foreground the debris blocks, in the background the inner “doline”.

ASPECTS OF THE EVOLUTION OF AN IMPORTANT GEO-ECOSySTEM IN THE LESSINIAN MOUNTAIN

some narrow passages which start from an open collapse depression located on a slope, which resembles a Roman theatre (i.e. an “Arena”, hence the name of the cave) (Fig.1, Fig. 2). Te depression is the result of the collapse of part of the subterranean room.

To understand the signifcance of this cave it is necessary to:

– delineate the geological, geomorphological, and, in general, environmental characteristics of this cave,

THE ENVIRONM

Te Grotta dell’Arena had been previously defned not as a distinct structure, but as a window on a subterranean space, that allows us to see only some features of a karst system (Castiglioni & Sauro, 2002). In fact, the subterranean environment is a much more complex system, mostly hidden to the human perception.

From the geological point of view the cave is expression of a contact karst, where diferent limestone types come in contact both stratigraphically and along tectonic structures (Capello et al. 1954; Pasa, 1954; Sauro, 1973, 1974, 2001). In particular, the limestone formations present here are:

– “Calcari del Gruppo di San Vigilio” of lower-middle Jurassic, about 60 m in depth, pure both oolitic and bio-sparitic/–ruditic, or reef limestones, relatively densely fractured,

– “Rosso Ammonitico”, a condensed rock unit of middle- upper Jurassic age, about 30 m in depth, made up by nodular micritic limestone very resistant to erosion, crossed by widely spaced fractures,

– “Biancone”, a chalk type unit, from the lower and middle Cretaceous, 100-200 meters in depth, made up by whitish marly limestone closely stratifed and densely fractured, very sensible to frost weathering.

Te Scaglia Rossa formation of the upper Cretaceous, and the Eocene limestone, which lie above the Bi-ancone in the western and southern part of the plateau are not present in the studied area because they have been completely eroded. Below the “Calcari del Gruppo di San Vigilio” there is the formation “Calcari Grigi di Noriglio”, of lower Jurassic, which is about 300 m in depth and outcrops in the slopes of the main valleys, a kind of fuvio-karstic canyons.

Te Grotta dell’Arena is located at the stratigraphic contact between the “Calcari del Gruppo di San Vigilio” and the “Rosso Ammonitico” and it is very close to a fault plane putting in vertical contact the two above formations with the Biancone (Fig. 3). Te cover rocks of the cave are made mostly by the massive beds of lower Rosso

– reconstruct the framework of the spatial and temporal evolution of the High Lessini karst,

– taking into account the climatic and environmental changes of the external environment surrounding the cave that occurred during the Pleistocene.

– analyse the phyilogeographical and taxonomical afnities of the troglobitic elements of its fauna.

CONTExT

Ammonitico, whereas the inner cave is mostly developed inside the Calcari del Gruppo di San Vigilio. At the topographical surface, the line of the normal fault runs along

Fig. 3: Sketches of the Arena cave system:

I – Plan of the system; the grey corresponds to the biancone rock unit.

II  – vertical model of the karst system. Legend: 1) biancone formation, 2) Rosso Ammonitico, 3) Calcari del Gruppo di San vigilio and Calcari Grigi, 4) debris pipe in the cave, 5) bedding plane karst zone at the contact Rosso Ammonitico- Calcari del Gruppo di San vigilio, 6) fault plane karst zone, a) at the biancone side, b) at the Rosso Ammonitico side, 7) lateral fow inside and from the biancone aquifer, 8) vertical karst fow.

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a small valley, a few meters to the east of the cave; the displacement of the fault is about 100 m.

From the geomorphological point of view, Biancone is dissected by a network of dry valleys, whereas Rosso Ammonitico generates a rocky landscape with large fat karren separated by corridors, or rock cities of large blocks.

From the hydrological viewpoint, the water circulates difusely inside the dense network of discontinuities

SPATIAL AND TEMPORAL EVO

It is easy to understand that the Grotta dell’Arena results of diferent spatial and temporal processes which occurred as a consequence of several predisposing factors. In fact, the cave is at the same time, an example of litho-logical contact karst, of intra-stratal karst, of fault zone karst and of a subterranean hydrological transition from a dispersed and sub-horizontal water fow to a more concentrated and sub-vertical one.

Te Grotta dell’Arena system is fed by a lateral water fow coming from the Biancone aquifer and crossing the fault zone, facilitated by the westward dipping of the strata. Te speleogenesis of the cave has taken place in the lithological, tectonic and hydrological transition zone.

Each cave we visit represents a moment of a long history, it is like the picture of a movie. Surely the present aspect of this cave and of its collapsed part are the result of relatively recent processes, occurred mostly during the middle and upper Pleistocene. But the karst system of which the cave is expression has surely begun to develop much earlier.

Some caves, located in middle of the Lessinian plateau and in the Berici hills, are the result of the re-activation of old paleokarstic nets developed during the Paleo-gene (Rossi & Zorzin, 1989, 1991; Dal Molin et al. 2000); other caves with fllings from the early middle Pleistocene developed mostly during the lower Pleistocene. Te Grotta dell’Arena chamber seems to be related with the second group.

Te fault to the east side of the cave is a paleotec-tonic feature of Jurassic age, reactivated during the Cretaceous and later by the Alpine orogenesis during the Paleogene and the Neogene. Te area where the cave is located probably emerged from the sea during the Oli-gocene, as the southern part of the Lessinian plateau. Te erosion of the Eocene rock unit occurred during late Pa-leogene and early Neogene. Te Scaglia Rossa formation was probably eroded during middle to late Neogene. At the beginning of the quaternary these two formations

of the Biancone unit; the preferential fows is sub-parallel to the topographical surface and occurs mostly below the dry valley bottoms, but is also infuenced by the structural setting; vertical losses occur along the fault and fracture zones. In contrast, water circulation is more concentrated and mostly vertical in the Rosso Ammonitico.

TION OF THE KARST SySTEM

disappeared completely in the area (remnants of Scaglia are still present in the western High Lessinian).

A model showing the sequence of landscapes developed in the diferent rocks by the erosion can be created, based on present-day landscapes of other parts of the Lessini Mountains, where the eroded geological formations are still present. Tus in the southwestern Lessinian Mountain (High Valpolicella) there is an active hydro-graphic network with gorges entrenched in both Eocene Limestones and in the Scaglia Rossa.

Here, the early morphogenesis, afer the emersion and the uplif, has been mostly of the fuvial type, marked by the development of a network of valleys strongly controlled by the tectonic structure. So, a valley developed along the fault line. Following the incision of the Scaglia Rossa, the karst process begun to afect the fault zone. But, it is especially afer the erosion of the Scaglia Rossa that the aquifer hosted in the Biancone started to feed a new underground karst system located near to the fault zone of which the Grotta dell’Arena is the present day expression.

From this simple model it is possible to infer that the evolution of the underground karst system started since Neogene, probably since middle- upper- Miocene. Te transition from the fuvial environment to the karst environment has been accompanied by the development of a fuviokarstic milieu in the Biancone. In this milieu, which is still present, there is not surface runof except during exceptional events, but there is a difuse circulation inside the rock, for some aspects similar to that occurring below the river beds, inside the alluvial deposits (Fig. 4).

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Fig. 4: Sketch of the morphological evolution of the alti Lessini according with the erosional stages reached by the relief (progressive erosion of the rock units).

THE CLIMATE AND ENVIRONMENTAL CHANGES DURING THE PLEISTOCENE

Te Lessinian Mountain plateau was afected by the climatic and environmental changes of the Pleistocene. In the cave area there is no evidence of past development of local glaciers (the nearest local glacier was more than 1 km to the northwest). However, traces of strong perigla-cial processes, such as remnants of small rock glaciers, nivation niches, etc. are present (Sauro, 2002). During the last würm sporadic permafrost was present in the area. Te material resulting from the collapse of the Are-

na depression has been afected by cryoclastic processes, as shown by a large solifuction lobe located to the north side of the same hollow.

Te climate and enviromental change occurred in the Pleistocene, afected the colonization of the subterranean environment by some actual troglobitic species and shaped the distribution of the species that colonized this environments before the Pleistocene.

THE CAVE FAUNA AT PRESENT

Te cave fauna of the Grotta dell’Arena is characterized      ent times. Ancient elements of this fauna colonized the

by the presence of high number of troglobitic and en-      subterranean environments before the Pleistocene, and

demic species (Caoduro & Rufo, 1998). Colonization of      other species invaded the cave in diferent periods along

the cave by the troglobitic elements occurred in difer-      the quaternary.

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Today, this cave has a high number of cave-adapted animals. Of the 43 taxa known for the cave, 24 could be considered eucavernicolous species (sensu Rufo, 1955: eutroglophiles+troglobites). Te specialization index

Te subterranean karst of the alti Lessini is much more spatially developed than what is perceived by a speleologist. It consists not only in large pits and chambers but in a network of smaller cavities and fssures. In the two horizontal dimensions it is a kind of net, even if aniso-tropic, better developed along the fault zones and some bedding planes. In the vertical dimension the anisotropy is even greater, and the thickness overpasses one thousand of meters.

In the time dimension, this karst network has evolved progressively, even with diferent speeds infu-enced by the changes of the morphostructural setting and of the external environment. Te karst morphogenesis occurred as result of the co-occurrence of various favourable conditions.

Te hydro-geological condition of the alluvial deposits of the water courses of the early erosional stage, during middle Neogene, are no present here nowadays, but there are situation for some aspects similar both below the valley bottoms of the Biancone and in the difuse net of karst fssures developed inside this rock unit. Tis difuse aquifer is in contact with the more typical karst aquifer of the limestone of the Jurassic rock units.

Likewise, some of the larger karst pockets developed in the Eocene limestone, may have had some connections with the karst cavities in the Scaglia, and, along the main fault structures or volcanic structures, also with the karst voids in the Jurassic rock units.

we are grateful to Sandro Rufo for the helpful discussions and for the reading of the manuscript. we also thanks Augusto Vigna Taglianti for the informations re-

(eutroglobites/ eucavernicolous), has a value of 0.91, this means that 91% of the cave species in the Grotta dell’Arena are troglobionts.

Here, sudden and sharp changes of conditions of the underground environments have not occurred during the late Neogene and the Pleistocene. Even the abrupt climatic changes of the Pleistocene have had a limited infuence on the underground environments, according with the large thickness reached by it before the end of Neogene.

It is interesting to note the presence of a good number of species of Terziary, or generally pre-quaternary, origin in the Grotta dell’Arena. Te most important relict species are: balkanoroncus boldorii (Beier, 1931), Lessino-camptus caoduroi Stoch, 1997, Italaphaenops dimaioi Ghi-dini, 1964 and Lessinodytes pivai Vigna Taglianti e Sciaky, 1988 (Casale & Vigna Taglianti, 1975; Vigna Taglianti & Sciaky, 1988; Gardini, 1991; Galassi pers. com.).

Te presence and distribution of these species inside the caves of Lessinia (particularly the terrestrial species) has been usually related to certain environmental characteristic like temperature, humidity, air circulation etc. However, on the basis of the actual knowledge (Latella & Verdari, 2006), it appears that all these species are present in caves with a large range of temperatures, altitude and morphology. All these caves are developed inside, or in contact with, the Biancone or Scaglia (Cretaceous limestone) formations. It is likely that the geomorphology of the cave plays an important role not only in shaping the historical distribution, but also the actual presence, of cave animals in Lessinian area.

garding Trechinae, Diana Galassi for the informations on Copepoda and Beatrice Sambugar for the Anellida. Tanks to Cristina Bruno for the linguistic review.

FINAL REMARKS

ACKNOwLEDGMENTS

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REFERENCES

Caoduro, G. & Rufo, S., 1998: La Grotta dell’Arena, un biotopo di eccezionale interesse negli alti Lessini. La Lessinia ieri oggi domani: quaderno culturale 1998, 39-44.

Casale, A. & Vigna TAglianti, A., 1976: Note su Itala-phaenops dimaioi Ghidini (Coleoptera, Carabide). Bollettino del Museo Civico di Storia Naturale di Verona, 2 (1975): 293-314.

Capello, C.F., Nangeroni, G., Pasa, A., Lippi Boncampi, C., Antonelli, C. & Malesani, E., 1954: Les phéno-ménes karstiques et l’hydrologie souterraine dans certaines régions de l’ltalie. Assoc. Intern. Hydrol., vol. 37, n. 2, pp. 408-437, fgg. 5, Paris.

Castiglioni, B. & Sauro, U., 2002: Paesaggi e geosistemi carsici: proposte metodologiche per una didattica dell’ambiente. In: Varotto M. & Zunica M. (a cura di) – Scritti in ricordo di Giovanna Brunetta. Dipar-timento di Geografa “G. Morandini”, Università di Padova, 51-67.

Dal Molin, L., Mietto, P. & Sauro, U., 2000: Considera-zioni sul paleocarsismo terziario dei Monti Berici: la Grotta della Guerra a Lumignano (Longare - Vicen-za). Natura Vicentina 4, 33-48 (ISSN 1591-3791).

Gardini, G., 1991: Pseudoscorpioni cavernicoli del Vene-to (Arachnida). (Pseudoscorpioni d’Italia xIx). Bollettino del Museo Civico di Storia Naturale di Verona, 15 (1988): 167-214.

Latella, L. & Verdari, N., 2006: Biodiversity and bioge-ography of Italian Alps and Prealps cave fauna. Abstracts 18th International Symposium of Biospeleol-ogy, Cluj-Napoca, Romania, 10-5 July 2006: 9-10.

Mietto, P. & Sauro, U., (eds), 2000: Le Grotte del Veneto: paesaggi carsici e grotte del Veneto. Second edition, Regione del Veneto-La Grafca Editrice, 480 pp.

Pasa, A., 1954: Carsismo ed idrografa carsica del Gruppo del Monte Baldo e dei Lessini Veronesi. C.N.R., Cen-tro Studi per la Geografa Fisica, Bologna, Ricerche sulla morfologia e idrografa carsica, n. 5, 150 pp.

Rossi, G. & Sauro, U., 1977: L’Abisso di Lesi: analisi mor-fologica e ipotesi genetiche. Le Grotte d’Italia, (4) 6 1976): 73-100.

Rossi, G. & Zorzin, R., 1989: Fenomeni paleocarsici nei Lessinian Mountain Centrali Veronesi. La Lessinia ieri oggi domani: quaderno culturale 1989, 47-54.

Rossi, G. & Zorzin, R., 1991: Nuovi dati sui fenomeni pa-leocarsici dei Covoli di Velo (M.ti Lessini Verona). Atti xVI Congr. Naz. di Speleologia, Udine, 169-174.

Rufo, S., 1955: Le attuali conoscenze sulla fauna caver-nicola della regione pugliese. Memorie di Biogeo-grafa adriatica, 3: 1-143.

Sauro U., 2002: quando in Lessinia c’era il grande gelo. quaderno Culturale - La Lessinia ieri oggi domani - 2002, 85-94.

Sauro, U., 1973: Il Paesaggio degli alti Lessini. Studio geo-morfologico. Museo Civ. di St. Nat. di Verona, Mem. f. s., 6, 161 pp.

Sauro, U., 1974: Aspetti dell’evoluzione carsica legata a particolari condizioni litologiche e tettoniche negli Alti Lessini. Boll. Soc. Geol. It., 93, 945-969.

Sauro, U., 2001: Aspects of contact karst in the Venetian Fore-Alps. Acta Carsologica, Ljubljana, 30(2), 89-102, 2001.

Vigna Taglianti & Sciaky R., 1988: Il genere Lessinodytes Vigna Taglianti, 1982 (Coleoptera, Carabidae, Tre-chinae). Fragmenta Entomologica, 20 (2): 159-180.

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COBISS: 1.01

HISTORICAL BIOGEOGRAPHy OF SUBTERRANEAN BEETLES – “PLATO’S CAVE” OR SCIENTIFIC EVIDENCE?

ZGODOVINSKA BIOGEOGRAFIJA PODZEMELJSKIH HROŠČEV – »PLATONOVA JAMA« ALI ZNANSTVENI DOKAZ?

Oana Teodora MOLDOVAN1 & Géza RAJKA1

Abstract                                                 UDC 595.76:551.44

591.542

Oana Teodora Moldovan & Géza Rajka: Historical bioge-ography of subterranean beetles – “Plato’s cave” or scientifc evidence?

Te last two decades were particularly prolifc in historical bio-geography because of new information introduced from other sciences, such as paleogeography, by the development of quantitative methods and by molecular phylogeny. Subterranean beetles represent an excellent object of study for historical bio-geography because they are the group with the best representation in the subterranean domain. In addition, species have reduced mobility, display diferent degrees of adaptations to life in caves and many specialists work on this group. Tree processes have shaped the present distribution of the tribe Leptodirini (Coleoptera Cholevinae) in the world: dispersal, vicariance, and extinction. Terefore, three successive stages can be established in the space-time evolution of Leptodirini: (1) dispersal from a center of origin in the present area(s); (2) dispersal, extinction and vicariance among the present area(s); and (3) colonization and speciation in the subterranean domain. Te Romanian Leptodirini, especially those from western Carpathians is examined with respect to these processes. Teir pattern of distribution in diferent massifs and at diferent altitudes is discussed, with possible explanations from a historical biogeo-graphic point of view.

Key words: Historical biogeography, cave beetles, Leptodirini, Romania.

Izvleček                                                  UDK 595.76:551.44

591.542

Oana Teodora Moldovan & Géza Rajka: Zgodovinska biogeo-grafja podzemeljskih hroščev – jama »Platonova« ali znanstveni dokaz?

Zadnji dve desetletji sta bili za historično biogeografjo še posebej bogati, predvsem zaradi številnih novih informacij in dognanj paleogeografje, razvoja kvantitativnih metod ter molekularne flogenije. Podzemeljski hrošči so odličen model za proučevanje historične biogeografje, saj spadajo v tisto skupino organizmov, ki je v podzemlju najpogosteje zastopana. Hrošči iz podzemlja imajo zmanjšano mobilnost, razvili so številne načine prilagoditev na življenje v tem habitatu. S to skupino organizmov se ukvarjajo številni raziskovalci po svetu. Na trenutno razširjenost vrst rodu Leptodirini (Coleoptera Cholevinae) so vplivali trije procesi: disperzija, vikarianca in izumiranje. V prostorsko-časovnem razvoju Leptodirinov se lahko pojavijo tri zaporedne faze: (1) razširjanje iz izvornega mesta na sedanje/a poročje/a, (2) razširjanje, izumrtje in vi-karianca med sedanjimi območji, ter (3) kolonizacija in spe-ciacija v podzemeljskih habitatih. S tega vidika smo proučevali Leptodirine iz Romunije, s poudarkom na vrstah iz zahodnih Karpatov. V prispevku je opisan vzorec razširjenosti hroščev v različnih gorskih predelih ter na različnih nadmorskih višinah. V razpravo smo z vidika historične biogeografje vključili tudi verjetno interpretacijo.

Ključne besede: zgodovinska biogeografja, speleobiologija, Leptodirini, Romunija.

1 Institutul de Speologie “Emil Racovitza”, Cluj Department, Clinicilor 5, P.O.Box 58, 400006 Cluj-Napoca, Romania; e-mail: oanamol@hasdeu.ubbcluj.ro

Received/Prejeto: 04.12.2006

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INTRODUCTION

Te Greek philosopher, Plato (428-348 BC), in his book, Te Republic, tells about Socrates teaching lessons of wisdom. One of these is about human beings kept in a cave with one source of artifcial light coming from behind. Te idea of the allegory is that we might have a wrong perception about what is reality, or, that most people live in a world of ignorance because they rely only on their narrow experiences and rely on their own truths. Another possible interpretation of Plato’s allegory is that we might be wrong if we consider concepts and perceived objects on the same level. Historical biogeog-raphy is a science based on concepts and suppositions and there is no direct evidence available in the attempt to build credible scenarios about past and present animal distributions. However, development of this science on circumstantial evidence ensures better understanding of the objects under study.

Biogeography studies geographic distribution of organisms. Tis simple defnition describes an extremely complex science. Geology, geography and various branches of biology defne a discipline that is continuously developing. Te Swiss botanist de Candolle (1820) was the frst to speak about ecological and historical bio-geography as separate branches of biogeography. Tey difer mainly in what concerns spatial and temporal scales. Historical biogeography reports on evolutionary processes over millions of years, mostly on a global scale (Crisci 2001). Pleistocene glaciations are sometimes collectively considered a separate or intermediary branch between historical and ecological biogeography. Te last two decades were particularly prolifc in papers on historical biogeography due largely to new information introduced from other sciences, such as paleogeography, by the development of quantitative methods (Morrone &

Crisci 1995) and by the development of molecular phy-logeny.

Morrone & Crisci (1995) and Crisci (2001) defne the biogeographic processes that modify the spatial distribution of taxa and recognize nine basic approaches to historical biogeography: (1) Identifcation of the centers of origin, or the existence of “Eden” where diferent lineages of all living beings moved from by dispersal to the present areas; (2) Panbiogeography, which plots the distribution of diferent taxa on maps, connecting their distribution areas together with lines; (3) Phylogenetic biogeography and (4) Cladistic biogeography, both assuming correspondence between taxonomic relationships and area relationships; (5) Parsimony analysis of endemicity that classifes areas by their shared taxa; (6) Event-based methods; (7) Phylogeography; (8) Ancestral areas; and (9) Experimental biogeography.

Te evolution of subterranean animals is a process that can be presumed but not directly proven. Te origin, migration and colonization of the subterranean realm can be explained by a multitude of arguments and indirect evidences which support or falsify the proposed hypotheses. Te role of historical biogeography is to explain the way subterranean animals gain their present distribution, using available data from biology and other sciences. Trough this process, we can gain a new insight into the mechanisms of colonization that have afected some of the extreme areas or habitats which exist in the subterranean domain. Chronologically, the history of a taxonomic group (like the beetles), or of a phyletic lineage must begin with its origin. To understand present distribution patterns and why some areas were colonized and others were not, we must frst establish temporal and spatial reference points.

SUBTERRANEAN COLEOPTERA ExAMPLES IN HISTORICAL BIOGEOGRAPHy

Tere are several reasons why subterranean beetles represent an excellent object of study for historical biogeog-raphy:

1. Tey are the best represented group in the subterranean karst environment or domain, with many species inhabiting caves and the mesovoid shallow substratum (also called MSS, see Juberthie et al. 1980);

2. Most species are terrestrial and therefore have reduced mobility; and while they are not limited to limestone/karst areas, most taxa inhabit caves;

3. A group whose representatives that display different degrees of adaptations to life in caves. Some of

the lines have endogean and hypogean species, of which the last is more or less adapted to subterranean environment.

4. Tey are a well known group, with many specialists studying various aspects of their biology, including taxonomy, adaptations, behavior and molecular phylogeny.

Two families encompass most of the world’s subterranean beetles, the Trechinae (predator Carabidae) and the Cholevinae (detritivorous and saprophagous Leiodi-dae). Our example is from one of the best represented subterranean tribe of Cholevinae, the Leptodirini (for-

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mer Bathysciini). According to ecological biogeography, Leptodirini are presently distributed in caves, MSS, and other dark and humid habitats, such as litter and moss, mostly in the Palearctic region.

For historical biogeography the life of the tribe Lep-todirini begins in the Paleozoic. Te present distribution of Leptodirini can only be explained through wegener’s theory of continent drif and the dispersal, vicariance and extinction processes. Dispersal was the main concept in biogeography before wegener and it explains the area of a population by the mechanisms of migration and crossing over geographical barriers. Extinction means the death of local populations, species or even supraspecifc taxa, and its role in biogeography has not always been recognized. Vicariance represents the splitting of an ancestral population into several subpopulations, which will later evolve into species through isolation. Tese three processes have shaped the present distribution of Leptodiri-ni, and three successive stages can be established in the space-time evolution of this group:

I. Dispersal from a center of origin in the present area(s);

II. Dispersal, vicariance, and extinction among the present area(s);

III. Colonization and speciation in the subterranean domain.

Fig. 1: historical biogeography of ancestors of Leptodirini, which migrated from Gondwana (a) together with continental microplates (b), up to Eurasia (c), from there dispersed west to the mediterranean region (d) (modifed from Giachino et al. 1998): areas covered by Leptodirini are represented by grey ellipses.

I. According to Giachino & Vailati (1998) the ancestral family of Oricatopidae inhabited the southern part of the Gondwana supercontinent (Fig. 1). Descending from this family, ancestors of Leptodirini and other tribes migrated at the end of Paleozoic to the what is now the south of Eurasia on the microplates that broke of from Gondwana. Tus, Eurasia was colonized by the ancestors of Leptodirini 120–150 Ma ago. More recently, 50-65 Ma ago, the group dispersed from northeast, through the central south of Asia, up to eastern Eurasia and then toward the west, along the Mediterranean basin. Epigean individuals successively migrated at the surface, and they were probably pre-adapted to low, constant temperatures and high humidity. Jeannel & Leleup (1952) provide excellent examples for preadaptated ancestors of pselaphid beetles, afer studying high altitude (2000-2900 m) beetles on Mount Kivu (Congo). At this level, the species are exclusively humic inhabitants, deepened at few centimeters in humus, where proper conditions, such as constant temperature (10°C) and high humidity, are fulflled. Tey also described a species with similar adaptations to those inhabiting caves, and also found deeper, under the humus.

II. Te second phase of evolution of the group probably happened before the Miocene, and possibly in the late Oligocene. Te dispersal of beetles was from Asia, along

the Miocene Alpine chain, whose remains are the Cantabric chain, Pyrenees, Central French Massif, Alps, Dinarides, Balkans, Pindus chain, Peloponnesus chain, and Pontic Alps. Aferwards, some species colonized the Apennines, Jura, Carpathians, Rodops, Taurus, Caucasus and Mediterranean inlands (Giachino et al. 1998). Due to major geological and geographical transformations of the landscape, extinction and vicari-ance alternated during the next periods. A large and continuous distribution area of epigean and probably endogean ancestors of Leptodirini that migrated from east was then fragmented, even before the colonization of the subterranean domain. New paleogeographic data about the evolution of the Paratethys from Late Eocene to Pliocene has been recently published (Steininger & Rögl 1985, Popov et al. 2004), and it appears that paleoconfguration of the Paratethys shaped the distribution of Leptodirini in Europe.

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III. Te third stage is represented by colonization and speciation in the subterranean domain. Two scenarios were proposed for explaining the mechanisms of underground colonization by epigean and endogean representatives of various groups of fauna (Holsinger 2000, 2005):

(1) Te climatic-relict model, in which preadapted or adapted animals were “forced” or constrained by climatic fuctuations to fnd refuge in caves. Te best documented are the Pleistocene glacial-interglacial periods. Eventually, surface ancestors of these successful colonizers went extinct. Tis model not only fts temperate climate regions, but also any region that has previously sustained drastic climatic changes.

(2) Te adaptive-shif model is mostly applied to lava tubes and tropical karst regions. Proposed by How-arth (1981), it explains the active colonization by pre-adapted ancestors and exploitation of new and empty niches to avoid competition. In this model, adaptation to the new environment does not depends on physical isolation from surface ancestors, as is necessaryin the previous model.

In our opinion, colonization of the subterranean domain is an active process, as is the case of empty niche colonization anywhere on Earth. Climatic changes have made important contributions in shaping the distribution areas and breaking of gene fow with surface relatives. Climatic changes can also interrupt energetic fow between surface and subterranean environments, leading to extinction of populations on one or both sides. Tis apparently happened in parts of the world directly affected by or covered by Pleistocene glaciers.

Bellés (1991) enumerates three reasons for cave colonization:

1. Survival, when external stress determines animals to fnd refugee in caves;

2. Opportunism or colonization of an empty space;

3. Convenience or escaping surface competition which uses the same trophic resources.

Peck (1980), Vailati (1988) and Juberthie (1988) proposed scenarios for cave colonization by beetles in the family Leiodidae from North America and Europe. Juberthie’s model uses complex data from studies on the ecology, ethology, genetics, tectonics, paleoclimate and geology of species from the Speonomus delarouzeei complex (Leiodidae: Cholevinae: Leptodirini). Tese species inhabit the MSS and caves on Mount Canigou in the French Pyrenees. Te history of this complex begins with the frst glacial period (2.3 Ma), when high altitude species separated from those at low altitude in the Mediterranean climate. Te two species, S. brucki

and respectively S. delarouzeei are characterized by different mating behavior, by reproductive isolation and by genetic distance. Tere are also diferences in fecundity and egg development speed at diferent temperatures. Tus, depression of temperature during glaciation selected cold resistant genotypes at 1000 m altitude, where annual mean temperature in caves is today 8-10°C, while S. delarouzeei remained at low altitude at temperatures of 14°C. During glacial periods, the forest belt displaced several hundred meters downslope on Mount Canigou and was replaced by steppe vegetation. Cracks, voids, MSS and even caves formed during these periods, while flling happened during interglacial periods. At altitudes between 500 and 1000 m two other species, S. emiliae and S. charlottae, inhabit subterranean habitats. S. emil-iae lives in the MSS at 720 m altitude and is presumed to be the ancestor of S. brucki, and probably populated caves and MSS at diferent altitudes. S. emiliae migrated together with the forests during glacial periods through cracks and MSS down to the present altitude. Te isolation of this species and S. brucki, which formed a population at high altitude, happened by inflling of the MSS and related cracks and crevices. Similar mechanism acted in a previous period for separating S. charlottae from ancestors of S. brucki.

By comparing cuticular hydrocarbons (pheromones that act at short distance or by contact) of species of the S. delarouzeei complex, Moldovan (1997) and Moldovan et al. (2003) obtained a diferent composition in the mountain species S. brucki and the Mediterranean species, S. delarouzeei: shorter chains in the frst one and longer in the second. S. emiliae, at an intermediate altitude, displays a mixture of short and long molecules in the cu-ticular hydrocarbon cocktail. Te result can be explained by temperature infuence on cuticular hydrocarbon composition. A small variation in temperature can change hydrocarbon composition even from the frst generation (Toolson et al. 1990). For subterranean beetles, adaptation to a new climate can rapidly change the pheromone composition, thus representing an important mechanism of isolation that acts prior to mating. Climate changed the distribution of populations on the slope of Canigou Mountain through migrations of ancestral populations. Consequently, composition in cuticular hydrocarbons changed and preceded genetic mutations. Hydrocarbon changes become stable if climate is maintained over long periods of time, eventually causing isolation of populations and genetic mutations. Terefore, speciation of subterranean inhabitants can occur without the existence of physical barriers as proposed in Juberthie’s model.

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REFERENCE MARKS IN HISTORICAL BIOGEOGRAPHy OF ROMANIAN LEPTODIRINI

with its geographic position in eastern Europe, Romania is very rich in subterranean fauna for a non-Mediterranean country. Tis is due to the special features defned as follows (Moldovan et al. 2005):

1. Te geographic position of the country, with climatic and fauna infuences from various regions;

2. Te reduced total surface of limestone; karst areas are distributed along the Carpathians and in Dobrogea, covering only 2% of the surface of Romania (Onac & Cocean 1996);

3. Te high number of caves/surface units; even if the covered surface is so small, the speleological potential is high, with almost 12,000 caves discovered prior to 1989 (Goran 1989);

4. Te distribution of caves at low altitude, with 27% of karstic rocks at altitudes below 500 m and 47% up to 1000 m a.s.l. (Bleahu & Rusu 1965);

5. Te patchy distribution of limestone, with small outcrops scattered especially in western and southern regions. From an ecological point of view Romanian karst forms small continental islands between non-karstic rocks, which act as natural barriers to migration of subterranean organisms. Each area represents an island to its inhabitants, which in turn leads to isolation and promotes evolution and formation of new species. Te discovery of the MSS has added new insights into the availability of subterranean habitats, but it can explain only short distance migrations between geographically close areas.

Fig. 2: Genera of Leptodirini distributed in the Western and Southern Carpathians of Romania.

Te above-mentioned features explain the fragmentation of the initial distribution area of surface ancestors of cave animals and speciation processes. It also explains the high number of genera and species for a country at 45° northern latitude. Other countries at the same latitude are much poorer in species (e.g., Austria - 2 species, Switzerland – 1 species), even though their limestone areas in these countries are larger.

Romanian Leptodirini is represented by 8 genera and 6 subgenera with 50 species and 46 subspecies, composed of 1 epigean, 10 endogean and 85 strictly caver-nicolous taxa. Concerning the distribution of subterranean beetles, the Romanian Carpathians can be divided in three geographical units: western, Southern and Eastern Carpathians. Te last unit has few caves and no representatives of Leptodirini. More than half of the karst surface of the country belongs to the western unit (the Apuseni Mountains). Tis region also has the highest degree of speciation with 63 taxa in the genera drimeotus, Pholeuon and Protopholeuon. Tese species inhabit caves and the MSS. More genera but fewer species are found in the Southern Carpathians: the epigean monospecifc mehadiella, and the 34 taxa of subterranean banatiola, Sophrochaeta, Closania and tismanella (Fig. 2).

Te origin of Romanian Leptodirini is strictly linked to dispersal of ancestral lineages that inhabited the Alpine Miocene chain and to a Paratethys evolution. Jean-nel (1924, 1931) and Decu & Negrea (1969) suggested a Dinaric origin for the Romanian Leptodirini, based on morphological similarities, and especially on features of the male geni-talia. Tis theory explains the colonization of the Apuseni Mountains through the Bohemian massif, and direct colonization of the Southern Carpathians from the Dinarides. Diferences between the two phy-letic lineages (western drimeotus and Southern Sophrochaeta) justi-fed this hypothesis, which is also supported by new paleogeographic data (Steininger & Rögl 1985, Popov et al. 2004). when these diferent waves of colonization occurred is questionable, because direct Dina-rides-Carpathians connection is either very old or too recent.

Migration of Asian ancestors of Cholevinae was not possible until the Upper Oligocene-Early Miocene, when a Dinarian-Pelagonian-

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Anatolian landmass was formed, and linked to the rest of Europe by the recurring Slovenian corridor. Tis was the frst connection between the Dinarides and Carpathians and lasted until Lower Badenian (16 Ma) when the Central Paratethys was fooded. It provided the possibility of populating the Southern Carpathians by Dinaric lineages, which was also at the time of Carpathian system development (Fig. 3). In Upper Ottnangian (17-18 Ma), the basin of the Paratethys was profoundly altered and a connection between the Alps and the Carpathians was established. Te frst Alps-Bohemian Massif-Carpathians connection provided conditions for the Apuseni Mountains colonization through the Bohemian massif. In Lower Badenian (15-16 Ma) a major transgression temporarily interrupted the connection between the Carpathians and the Bohemian Massif. Later, in Middle Badenian (14-15 Ma), the connection was defnitively established. A connection between the Dinarides and the Carpathians was also established during the Messinian crisis (5-6 Ma) but cannot explain the processes of Southern Carpathian colonization and speciation. Subterranean beetles are less mobile, even if they can migrate over relatively short distances through the non-calcareous MSS. Supposing that epigean and edaphobiont forms migrated and colonized this region, it is improbable to admit that adaptation to deep subterranean habitats and speciation could have occurred in such a short period of time.

In conclusion, the Dinaric origin of subterranean Romanian beetles can be explained by a frst migration wave of a Dinaride lineage over the Southern Carpathians and a later one through the Bohemian massif of a lineage that colonized the Apuseni Mountains. Both lineages are morphologically linked to Dinaric species, with some peculiar features in the drimeotus western lineage. An additional migration from the southwest during the Messinian crisis also could have been possible but only for species less adapted to caves. Te next step in the evolution of the Apuseni beetles was subterranean domain colonization. Te processes and mechanisms that could have driven the subterranean colonization were presented in the previous section.

we also analyzed spatial distribution of species and subspecies of the Drimeotus phyletic lineage to obtain information which can be corroborated with available taxonomic and molecular data. Romanian Leptodirini ofer good material for studying speciation and vicari-ance processes, because it involves insular distribution, which is diferent from the large, continuous limestone surfaces such as those of the Dinarides and the Pyrenees, where speciation has occurred in the absence of geographical barriers. Te Apuseni Mountains are inhabited by three genera (Protopholeuon, Pholeuon and drimeo-tus), belonging to the drimeotus phyletic lineage (Fig. 4).

Fig. 3: Evolution of the Paratethys in Upper Ottnangian (a), middle badenian (b) and Lower badenian (c) (Cluj is located in North-Western Romania) (simplifed afer Rögl & Steininger 1984): grey – marine realms, dark grey – evaporitic basins, light grey – important areas with fuvio-terrestrial sedimentation and/or lignite formation, white – continental realms, - basins narrowed post-sedimentation by tectonic processes.

Te lineage is monophyletic (Bucur 2003) and suggests a common ancestor, probably epigean. Protopholeuon, which is monospecifc, inhabits the Metaliferi Mountains, while the other two genera have larger distribution. Most species of Pholeuon and drimeotus occur in the Pa-durea Craiului and the Bihor mountains. Pholeuon also

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has sub-genera in the Codru-Moma unit, while drimeo-tus is in the Metaliferi and the Trascau Mountains. Each mountain is inhabited by a diferent sub-genus. It is possible that future searches will enlarge the distribution of drimeotus also in Codru-Moma. (Te frst and last specimen of Drimeotus in the Metaliferi was found as recently as 2001 in a cave well known for Protopholeuon and this was afer several trapping episodes where Protopholeuon/ drimeotus ratio was 150/1.)

Fig. 4: distribution of Leptodirini in the Western Carpathians (Apuseni mountains): ■k - drimeotus, - Pholeuon, - Protopholeuon, grey areas - karst.

Comparing the largest geographical units in the Apuseni, Padurea Craiului and Bihor, the number of species and subspecies of less adapted drimeotus and the more adapted Pholeuon is diferent between genera and between units. drimeotus (20 species and 12 subspecies) has higher specifc diversity in both units and lower sub-specifc diversity than Pholeuon (6 species and 20 subspecies). Tis can be explained by the diference in adaptation and diferent histories of the two genera. Pholeuon, very adapted, is less mobile and very few individuals were found in MSS or under rocks. Preadapted ancestors of Pholeuon colonized deep subterranean environment in the entire area and since then small modifcations have occurred. Lacking competition, infra-generic differentiation of Pholeuon is slow. drimeotus, less adapted and relatively mobile between limestone areas, is under

stronger climatic and biologically stronger selective pressures, which explains larger distribution areas and higher specifc diversity. Tere are also diferences between the Padurea Craiului and the Bihor drimeotus, with more than two-thirds of the species in the frst mountains. In Padurea Craiului the climate is warmer and less humid, with caves at lower altitude than in Bihor. Terefore, migration and gene fow between populations inhabiting diferent limestone areas or caves are limited and specia-tion is stronger. Te more humid and colder Bihor Mountains allows superfcial migrations and gene interchange between geographically close populations.

Te altitudinal distribution of Leptodirini was frst discussed by Jeannel (1952), who mentioned the presence of the same genus and even same species at the surface at 1500 m altitude, under the rocks at 1000 m, and strictly cavernicolous at 500 m. A sound analysis of the distribution published by Decu (1980) emphasizes the lack of correlation between body size and altitude. we found diferent results, given in Table 1. For drimeotus, correlation between altitude and body length or relative length of antennae is negative for Padurea Craiului samples, and positive for Bihor samples. An approach that links geography to morphology is the kriging method, which uses a topographic representation of the data sets. Using the Golden Sofware Surfer 8 we obtained the maps in Fig. 5. As one can see, the vectors defne centers of origin at about 500-700 m altitude. Ancestors of the drimeotus lineage probably inhabited superfcial habitats between 500 and 1000 m altitude. Colonizing caves at lower or higher altitude induced body increase, a process explained by lack of competition and/or decrease of temperature. Body growth, as a result of cave colonization, is not only known for subterranean beetles. Te t test showed no signifcant diference in body length between populations of Padurea Craiului and Bihor. Te same test on the relative length of antennae gives shorter antennae in Bihor than in the Padurea Craiului samples. Tis can be due to the fact that the higher Bihor Mountains are inhabited by populations less confned to cave, compared to the Padurea Craiului. Pholeuon has the same tendencies as drimeotus, with a negative correlation of body length and altitude in Padurea Craiului and

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a positive correlation in Bihor, and the antennae length decrease with altitude.

tab. 1: Linear regression (y) and coefcient of determination (R2) at drimeotus (13 populations) and Pholeuon (6 populations) from the Padurea Craiului and the bihor mountains (Western Carpathians): bL body length, AL/bL antenna/body lengths ratio.

Altitude (m)

0-499

500-999

> 1000

Drimeotus

BL

y = -0.0003X + 4.4511 R2 = 0.0096

y = 0.0004x + 4.1025 R2 = 0.2337

y = 0.0007x + 3.5404 R2 = 0.3301

AL/BL

y = -8E-05X + 0.5969 R2 = 0.1077

y = 3E-05x + 0.5327 R2 = 0.0195

y = 0.0001x + 0.4088 R2 = 0.2449

Pholeuon

BL

y = -0.0001X+ 3.9152 R2 = 0.0239

y = 0.0031x + 2.142 R2 = 0.7849

y = 1E-04x + 4.6179 R2 = 0.0150

AL/BL

y = -1E-04x + 0.8619 R2 = 0.2445

y = -0.0002X + 0.9593 R2 = 0.7847

y = -0.0001x + 0.9044 R2 = 0.2529

Mantels test is a regression in which variables are matrices summarizing pairwise similarities among sample locations. Geographic distance was used as a predictor variable, and morphological features of populations belonging to drimeotus and Pholeuon, from the Padurea Craiului Mountains, as dependant distance matrices. For α = 0.01, the test gives strong correlation for drimeotus samples (Fig. 6) and no correlation for Pholeuon. For the moment, we cannot explain this result, although presumptions can be formulated.

Fig. 5: Antennae relative length (a) and altitude (b) variations in geographical coordinates for 15 populations of drimeotus s. str. (red dots) of Padurea Craiului mountains, in 3d and vectorial overlayed representations.

Mantel’s test (xLSTAT 2006.5 sofware) was also used to correlate geographic distance with morphological features, such as body and relative antennae lengths.

Fig. 6: histogram representing results of the mantel test on representatives of drimeotus s. str. from Padurea Craiului.

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CONCLUSIONS

Plato’s allegory still raises questions in historical bioge-ography of cave beetles, but new scientifc acquisitions will also enhance the chances for a more objective view in explaining the history of one group or another and what shaped their present distribution.

we have only presented few results and further research must take into consideration more populations and the surface of the populated area, as in insular studies. In caves, as well as on oceanic islands, the number of endemics can be related to the size of the area. Studies of Barr (1985) and Culver et al. (1973) applied the insular theory of McArthur & wilson to karst areas, which have the characteristics of continental islands separated by non-calcareous “seas”. Tus, the number of subterranean species is strongly correlated with the surface of the limestone.

Te recent interest in biogeographic studies has resulted from conservation necessities, especially in the last

we are grateful to John Holsinger and David Culver for valuable suggestions, our colleagues Gheorghe Racovita and Tudor Tamas for useful discussions, and Andrej Mi-

Barr Jr., T.C., 1985: Pattern and process in speciation of trechine beetles in eastern North America (Coleop-tera: Carabidae: Trechinae). In: Ball, G.E. (ed.) Phy-logeny and zoogeography of beetles and ants, Junk, Dordrecht, 350-407.

Bellés, x., 1991: Survival, opportunism and convenience in the processes of cave colonization by terrestrial faunas. In: Ros, J.D. & N. Prat (eds.) homage to Ramon margalef; or, Why there is such pleasure in studying nature. – Oecol. Aquat. 10 325-335.

Bleahu, M. & T. Rusu, 1965: Carstul din Romania. O scurta privire de ansamblu. – Lucr. Inst. Speol. “E. Racovita” 4 59-73.

Bucur, R., Kosuch, J. & A. Seitz, 2003: Molecular phylo-genetic relationships of Romanian cave Leptodiri-nae (Coleoptera: Cholevidae). – Atti. Mus. Civ. Stor. Nat. Trieste 50 231-265.

decade. For example, the concept of habitat fragmentation became one of the priority themes of conservation researches. Te concept is considered ambiguous, and empirical studies demonstrate a wide variety of direct and indirect efects, even with opposing implications (Haila 2002). Te efects of habitat fragmentation are considered extremely dangerous for species and population preservation, and are ofen mentioned when establishing protection areas for rare and vulnerable species.

From a biospeleological point of view, habitat fragmentation represents one of the main mechanisms that enhanced speciation processes in reduced areas (at least for terrestrial fauna). Tis idea, diferent from the conservationist concern, can be extremely useful in solving protection problems. Unfortunately, none of the main contributions in conservation biology mentions caves and cave fauna as examples of survival in small, fragmented areas.

hevc, Liviu Buzila and Alexandru Imbroane for advice and maps.

de Candolle, A. P. , 1820: Géographie botanique. In: dic-tionnaire des Sciences Naturelles F.G. Levrault, Strasbourg, 18 359-422.

Crisci, J.V., 2001: Te voice of historical biogeography. – J. Biogeogr. 28 157-168.

Culver, D., Holsinger, J. R. & R. Baroody, 1973: Toward a predictive cave biogeography: the Greenbrier valley as a case study. – Evolution 27, 4 689-695.

Decu, V. , 1980: Analyse de la repartition selon l’altitude des coléoptères cavernicoles Bathysciinae et Trechi-nae des Carpates de Roumanie.-Mém. Biospéol. 7 99-118.

Decu, V. & S. Negrea, 1969: Aperçu zoogéographique sur la faune cavernicole terrestre de Roumanie. – Acta Zool. Cracov. 14, 20 471-546.

Giachino, P. M., Decu, V. & C. Juberthie, 1998: Coleop-tera Cholevidae. In: Juberthie, C. & V. Decu (eds.) Encyclopaedia biospeologica, Fabbro Saint-Girons, France, 1083-1122.

ACKNOwLEDGEMENTS

REFERENCES

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Giachino, P.M. & D. Vailati, 1993: Revisione degli Ane-madinae Hatch, 1928 (Coleoptera Cholevidae).– Mus. Civ. Stor. Nat. Brescia, Monografa di “Natura Bresciana” 18 1-314.

Goran, C., 1989: La spéléogramme de la Roumanie.-Mis-cell. Speol. Rom. 1: 335-346.

Haila, y., 2002: A conceptual genealogy of fragmentation research: from island biogeography to landscape ecology.-Ecol. Appl. 12 312-334.

Holsinger, J.R., 2000: Ecological derivation, colonization, and speciation. In: wilkens, H., Culver, D.C. & w.F. Humphreys (eds.) Subterranean ecosystems. Ecosystems of the world 30, Elsevier, Amsterdam, 399-415.

Holsinger, J. R., 2005: Vicariance and dispersalist bio-geography. In: Culver, D. C. & white w. B. (eds.) Encyclopedia of Caves, Elsevier Academic Press, 591-599.

Howarth, F.G., 1981: Non-relictual terrestrial troglobites in the tropic Hawaiian caves. Proc. 8th Internat. Congr. Speleol., Bowling Green, Kentucky (USA), 2 539-541.

Jeannel, R., 1924: Monographie des Bathysciinae.–Arch. Zool. Exp. Gén. 63 1-436.

Jeannel, R., 1931: Origine et évolution de la faune cav-ernicole du Bihar et des Carpathes du Banat.-Arch. Zool. Ital., Atti xI Congr. Internaz. Zool. Padova, 1930. 16 47-60.

Jeannel, R. & N. Leleup, 1952: L’évolution souterraine dans la region méditerranéenne et sur les Mon-tagnes du Kivu.-Notes Biospéologiques 7 7-13.

Juberthie, C., Delay, B. & M. Bouillon, 1980: Sur l’existence d’un milieu souterrain superfciel en zone non cal-caire.-C. R. Acad. Sc. Fr. 290 49-52.

Juberthie, C., 1988: Paleoenvironment and speciation in the cave beetle complex Speonomus delarouzeei (Coleoptera, Bathysciinae).-Int. J. Speleol. 17 31-50.

Moldovan, O., 1997: Reconnaissance des sexes et isole-ment reproductif chez les coléoptères bathysciinae souterrains: approche taxonomique, biochimique et expérimentale, PhD thesis, «Paul Sabatier» University, Toulouse (France), 130 pp.

Moldovan, O.T., Juberthie, C., Jallon, J.-M. & H. Alves, 2000: Importance of cuticular hydrocarbons for speciation in the Speonomus delarouzeei complex (Coleoptera: Cholevidae: Leptodirinae).-Evolution & Adaptation 6 110-115.

Moldovan, O.T., Iepure, S. & A. Persoiu, 2005: Biodiversity and protection of Romanian karst areas: the example of interstitial fauna. In: Stevanović, Z. & P. Milanović (eds.), Water resources and environmental problems in karst. Proc. Internat. Conf. & Field

Semin., Belgrade & Kotor (Serbia & Montenegro), 13-19 September 2005, p. 831-836, Belgrade.

Morrone, J.J. & J.V. Crisci, 1995: Historical biogeography: Introduction to methods.-Annu. Rev. Ecol. Syst. 26 373-401.

Onac, B.P. & P. Cocean, 1996: Une vue global sur le karst roumain.-Kras i Speleologia 8, 17 105-112.

Peck, S.B., 1980: Climatic change and the evolution of cave invertebrates in the Grand Canyon, Arizona.– Nat. Speleo. Soc. Bull. 42 53-60.

Popov, S.V., Rögl, F., Rozanov, A.y., Steininger, F.F., Shcherba, I.G. & M. Kovac, 2004: Lithological-Pa-leogeographic maps of Paratethys Late Eocene to Pliocene. Courier Forschungsinstitut Senckenburg, Band 250, Frankfurt am Main, 46 pp., maps 1-10.

Rögl, F. & F.F. Steininger, 1984: Neogene Paratethys, Mediterranean and Indo-pacifc seaways. Implications for the paleobiogeography of marine and terrestrial biotas. In: Brenchley, P. (ed.) Fossils and Climate, John wiley & Sons Ltd. 171-200.

Steininger, F.F. & F. Rögl, 1985: Paleogeography and pal-inspastic reconstruction of the Neogene of the Mediterranean and Paratethys. In: Dixon, J.E. & A.H.F. Robertson (eds.), Te Geological Evolution of the Eastern Mediterranean, Special Publication of the Geological Society, No. 17, Blackwell Scientifc Publications, Oxford, pp. 659-668.

Toolson, E.C., Markow, T.A., Jackson, L.J. & R.w. Howard, 1990: Epicuticular hydrocarbon composition of wild and laboratory-reared drosophila mojavensis Patterson and Crow (Diptera: Drospophilidae).-Annls. Ent. Soc. Am. 83 1165-1176.

Vailati, D., 1988: Studi sui Bathysciinae delle Prealpi centro-occidentali. Revisione sistematica, ecologia, biogeografa della “seria fletica di boldoria” (Co-leoptera Catopidae).–Mus. Civ. Stor. Nat. Brescia, Monografa di “Natura Bresciana” 11 1-331.

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wHAT DOES THE DISTRIBUTION OF STyGOBIOTIC COPEPODA (CRUSTACEA) TELL US ABOUT THEIR AGE?

KAJ NAM POVE RAZŠIRJENOST STIGOBIONTSKIH

CEPONOŽNIH RAKOV (CRUSTACEA: COPEPODA)

O NJIHOVI STAROSTI?

David C. CULVER1 & Tanja PIPAN2

Abstract                                                        UDC 595.3-15

591.5:595.3

David C. Culver & Tanja Pipan: What Does the Distribution of Stygobiotic Copepoda (Crustacea) Tell Us About Teir Age?

Geographic distribution of stygobionts is ofen used to estimate age of a group by assuming vicariant speciation with little or no subsequent dispersal. we investigated the utility of using distributional data for Slovenian stygobiotic copepods by assuming that dispersal is a way to measure age of a species. we list some species of Copepoda that, on the basis of their range and frequency of occupancy within their range, should be older. Body size is not predictor either of range or frequency of occupancy. Key words: Speleobiology, Copepoda, stygobionts, dispersal biogeography.

Izvleček                                                         UDK 595.3-15

591.5:595.3

David C. Culver & Tanja Pipan: Kaj nam pove razširjenost stigobiontskih ceponožnih rakov (Crustacea: Copepoda) o njihovi starosti?

Ob predpostavki, da je nastajanje novih vrst posledica vikari-ance, brez naknadne disperzije, se za ocenjevanje starosti živalskih skupin pogosto uporablja geografska razširjenost sti-gobiontov. Ob domnevi, da je disperzija merilo za določanje starosti vrst, smo proučevali primernost podatkov o razširjenosti stigobiontskih kopepodov v Sloveniji. Na osnovi analize obsega naselitve in pogostosti naseljevanja znotraj območja smo v prispevku priložili seznam nekaterih vrst ceponožnih rakov, ki naj bi bile evolucijsko starejše. Telesna velikost ne določa obsega naselitve in pogostosti pojavljanja.

Ključne besede: speleobiologija, Copepoda, stigobionti, dis-perzijska biogeografja.

INTRODUCTION

Te distribution of stygobionts has ofen been used to infer the age of a fauna. Te general procedure has been to assume that little or no migration has occurred, and that the extant distribution represents the site of original colonization and isolation in subterranean habitats. Te vicariance biogeographic view, now dominant in modern biogeography (e.g., Crisci, Katinas, and Posadas 2003) largely supplanted the old idea of centers of origin with species dispersing out from this central place (Matthew

1915). Given the reduced opportunities for dispersal of subterranean animals, it is not surprising that there have been a number of studies that show a correspondence between ancient shorelines and current distributions, especially Tethyan and Paratethyan distributions (Culver and Pipan in press). In some cases, it has been possible to match distributions to historical events and to obtain support from molecular clock data (see Verovnik, Sket, and Trontelj 2004). However, not all subterranean dis-

1 Department of Biology, American University, 4400 Massachusetts Ave., Nw, washington D.C., U.S.A.; e-mail: dculver@american.edu

2 Karst Research Institute ZRC-SAZU, Titov trg 2, SI-6230 Postojna, Slovenia; e-mail: pipan@zrc-sazu.si

Received/Prejeto: 27.11.2006

TIME in KARST, POSTOJNA 2007, 87–91

DAVID C. CULVER & TANJA PIPAN

tributions can be explained solely by vicariance. A particularly interesting example is the cirolanid isopod An-trolana lira Bowman. In general, subterranean cirolanids are found near to marine shores (Botosaneanu, Bruce, and Notenboom 1986), suggesting a marine ancestor with vicariant isolation. But, A. lira is found in caves in the Appalachian Valley of Virginia and more than 200 km from not only the present ocean shore, but from any ocean dating back at least to the Paleozoic (Holsinger, Hubbard, and Bowman 1994).

In this contribution, we take a dispersalist rather a vicariance view of subterranean biogeography. we consider a model of colonization and isolation as follows. A species colonizes and is isolated in a subterranean site. As adaptation occurs, the species occupies more sites in the vicinity of the colonization. Tat is, the frequency of occupancy of subterranean sites increases. In the next stage, the species expands its range, with a high occupan-

cy of suitable sites in its range. Finally, as other species also evolve, the original species may be out-competed or it may become specialized in response to competition. In this scenario, it will then occupy a lower frequency of sites within its range. Tus, we can rank the ages of species in increasing age as follows:

1. Species with small ranges and occupying few (sometimes only one) sites

2. Species with small ranges but occupying a high frequency of sites within its range

3. Species with large ranges and occupying a high frequency of sites within its range

4. Species with large ranges and occupying a low frequency of sites within its range.

we examine this hypothesis using distributional data of subterranean copepods from Slovenia (see Pipan 2005), and make assess the utility of this approach.

METHODS AND MATERIALS

From information in Pipan (2005) and Culver, Pipan, and Schneider (in press) we generated list of stygobiotic copepods from seven Slovenian caves, with information on ranges, frequency of occupancy of well-sampled caves, and average body size. Ranges were categorized into three groups:

1. Slovenian endemics

2. Balkan endemics

3. European endemics

4. Cosmopolitan species To measure frequency of occupancy, we used data

from Pipan (2005), which was intensive enough that it is likely that most species were found (Pipan and Cul-

ver in press). Body sizes were taken from original species descriptions and direct measurement by T P. Data were available for 37 species.

Analysis was done by grouping ranges into two categories (Small—categories 1 and 2 and Large—categories 3 and 4), frequency of occupancy into two categories (Low—1 to 3 caves and High—4 to 7 caves), and size into two categories (Small—less than the overall mean of 0.61 and large—greater than or equal to the overall mean of 0.61). Te resulting 2x2 contingency tables were analyzed for independence using Fisher’s Exact Test in JMPTM (Sall, Creighton, and Lehman 2005).

RESULTS

Available data for the 37 species of stybobiotic copepods are shown in Table 1. In Table 2, all species are categorized into four groups based on range and occupancy. Tere was no signifcant diference between observed and expected although there was a small excess of species with large ranges that were also found in a high frequency of caves. Tose species hypothesized to be the oldest (large ranges, low occupancy) were:

• Acanthocyclops kieferi

• Acanthocyclops venustus stammeri

• diacyclops clandestinus

• dicyclops languidoides

• Elaphoidella elaphoides

• morariopsis scotenophila Te group hypothesized to be the next oldest are

those with large ranges and high occupancy:

• Elaphoidella jeanneli

• bryocamptus balcanicus

• Acanthocyclops venustus

• Parastenocaris nolli alpina

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wHAT DOES THE DISTRIBUTION OF STyGOBIOTIC COPEPODA (CRUSTACEA) TELL US ABOUT THEIR AGE?

tab. 1: Stygobiotic copepod species found in seven well-sampled caves in Slovenia. See Pipan (2005) and Culver et al. (in press).

Species Name/Taxonomic Authority

Mean Body Size

No. Caves Occupied

Range

Acanthocyclops kieferi (Chappuis, 1925)

0.73

2

3

Acanthocyclops venustus (Norman & Scott, 1906)

1.07

1

3

Acanthocyclops venustus stammeri (Kiefer, 1930)

1.07

5

3

Bryocamptus balcanicus (Kiefer 1933)

0.40

4

3

Bryocamptus borus Karanovic & Bobic, 1998

1

2

Bryocamptus pyrenaicus (Chappuis, 1923)

0.80

7

3

Bryocamptus sp.

2

1

cf. Stygepactophanes sp.

0.35

3

1

Diacyclops charon (Kiefer, 1931)

1.00

7

2

Diacyclops clandestinus (Kiefer, 1926)

0.40

3

4

Diacyclops hypogeus (Kiefer, 1930)

0.50

2

1

Diacyclops languidoides (Lilljeborg, 1901)

0.80

3

4

Diacyclops slovenicus (Petkovski, 1954)

0.68

3

1

Echinocamptus georgevitchi (Chappuis, 1924)

0.70

1

2

Elaphoidella cvetkae Petkovski, 1983

0.75

4

2

Elaphoidella elaphoides (Chappuis, 1924)

0.60

1

3

Elaphoidella franci Petkovski, 1983

0.64

1

1

Elaphoidella jeannelli Chappuis, 1928

0.60

4

3

Elaphoidellakarstica Dussart & Defaye (1990)

1

1

Elaphoidella sp. A

2

1

Elaphoidella sp. B

2

1

Elaphoidella stammeri Chappuis, 1936

0.62

4

1

Maraenobiotus cf. brucei

0.60

1

1

Metacyclops postojnae Brancelj, 1990

>0.61

1

2

Moraria sp. A

2

1

Mor aria sp. B

1

1

Moraria stankovitchi Chappuis, 1924

0.55

2

2

Morariopsis dumonti Brancelj, 2000

0.39

2

1

Morariopsis scotenophila (Kiefer 1930)

0.49

3

4

Nitocrella sp.

0.50

2

1

Parastenocaris cf. andreji

0.40

2

1

Parastenocaris nolli alpina (Kiefer, 1938)

0.42

5

3

Parastenocaris sp. A

0.40

2

1

Parastenocaris sp. B

0.40

4

1

Parastenocaris sp. C

0.40

2

1

Speocyclops infernus (Kiefer 1930)

0.47

6

2

Troglodiaptomus sketi Petkovski, 1978

0.88

3

2

we investigated whether there was a body size bias      pan and Culver 2006). In any case, there was no relation-for occupancy or range size. Smaller copepods might be      ship between frequency of occupancy and body size and able to disperse more easily but they may also be more      no relationship between range and body size (Table 3). subject to the vagaries of water movement in epikarst (Pi-

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DAVID C. CULVER & TANJA PIPAN

tab. 2: Number of species of stygobiotic copepods in categories of large and small range and high and low frequency of site occupancy. Numbers in parentheses are the expected numbers. Observed and expected numbers do not signifcantly difer (p=0.21, Fisher’s Exact test).

High Occupancy

Low Occupancy

Large Range

4 (2.4)

5 (6.6)

Small Range

6 (7.6)

22 (20.4)

tab. 3: Number of species of stygobiotic copepods in categories of high and low frequency of site occupancy (A), large and small range (b) and body size. Numbers in parentheses are the expected numbers. Neither association was statistically signifcant (p=0.71 for A, p=0.71 for b, Fisher’s Exact test).

A.

High Occupancy

Low Occupancy

Large Body Size

5 (4.3)

8 (8.7)

Small Body Size

5 (6.7)

12 (11.3)

B.

Large Range

Small Range

Large Body Size

5 (4.5)

8 (8.5)

Small Body Size

5 (5.5)

11 (10.5)

we have created a list of copepod species that, according to the hypothesis outlined in the introduction, should be older than other stygobiotic copepod species discussed in this study. Unfortunately, we know of no detailed phy-logeny that would allow for such a comparison but we think that it would make for a very interesting study to do so. what is known about copepod phylogeny is that the Cyclopoida seem to be a more recent group than the Harpacticoida, accoding to the phylogeny of Huys and Boxshall (1991). Te fact that cyclopoids are over-represented among species with large ranges (Table 4) contradicts the hypothesis put forward. Of course, just because

Te authors were supported by funds from the Center for Subterranean Biodiversity of the Karst waters Insti-

Finally, we investigated the taxonomic position of the putative older species, i.e., those with larger ranges. Of the ten species listed above, fve are cyclopoids and fve are harpacticoids. Tere is an excess of large ranged cyclopoids but the diference was only signifcant at p~0.10 (Table 4). Acanthocyclops is especially noteworthy. All three stygobiotic species (A. kieferi, A. venustus, and A. venustus stammeri) had large ranges. In contrast none of the three species of Moraria (m. stankovitchi, sp. A, and sp. b) have large ranges. Te lone calanoid species (troglodiaptomus sketi) also has a small range.

tab. 4: Relationship between range and taxonomic group (Cyclopoida vs. harpacticoida). Expected numbers are given in parentheses. Te relationship was marginally signifcant (p~0.10, Fisher’s Exact test).

Large Range

Small Range

Cyclopoida

5 (2.8)

5 (7.2)

Harpacticoida

5 (7.2)

21 (18.8)

cyclopoids as a group are younger does not mean that the species are all younger than harpacticoids. Alternatively, it may be that harpacticoids are in general being outcom-peted by cyclopoids, and this has resulted, not only in reduction in occupancy frequency, but also in range contraction.

we think that examination of the kinds of distribution patterns (range size and occupancy) discussed here will yield interesting results. Tis analysis would enrich phylogeography studies as well as provide additional hypotheses about the origin and evolution of subterranean groups.

tute and the Ministry of Higher Education, Science, and Technology of the Republic of Slovenia.

DISCUSSION

ACKNOwLEDGEMENTS

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REFERENCES

Botosaneanu, L., N. Bruce, & J. Notenboom., 1986: Isopoda: Cirolanidae, pp. 412-421, in L. Botosanea-nu [ed.] Stygofauna mundi. E.J. Brill, Leiden, Te Netherlands.

Crisci, J.V., L. Katinas, & P. Posadas., 2003: historical bio-geography. An Introduction. p. 250, Harvard Univ. Press, Cambridge.

Culver, D.C., T. Pipan., & K. Schneider., in press: Vicari-ance, dispersal, and scale in the aquatic subterranean fauna of karst regions. Freshwater biology

Culver, D.C., & T. Pipan., in press: Subterranean ecosystems. In S.A. Levin [ed.] Encyclopedia of biodiversity, second edition. Elsevier, Amsterdam.

Holsinger, J. R., D. A. Hubbard, Jr , & T. E. Bowman., 1994: Biogeographic and ecological implicationd of newly discovered populations of the stygobiont iso-pod crustacean Antrolana lira Bowman (Cirolani-dae). journal of Natural history 28, 1047-1058.

Huys, R., and G. Boxshall., 1991: Copepod evolution. p. 468, Te Ray Society, London,

Matthew, w.D., 1915: Climate and evolution. Annals of the New york Academy of Sciences 24, 171-318.

Pipan, T., 2005: Epikarst – a Promising habitat. 100 p. Karst Researach Institute at ZRC-SAZU, ZRC Publishing, Postojna.

Pipan, T., & D.C. Culver., 2006: Copepod distribution as an indicator of epikarst system connectivity. hydro-geology journal

Pipan, T., & D.C. Culver., in press: Regional species richness in an obligate subterranean dwelling fauna— epikarst. journal of biogeography.

Sall, J., L. Creighton, & A. Lehman., 2005: jmP Start Statistics. Brook/Cole—Tomson Learning, Belmont, California.

Verovnik, R., B. Sket, & P. Trontelj., 2004: Phylogeog-raphy of subterranean and surface populations of water lice Asellus aquaticus (Crustacea: Isopoda). molecular Ecology 13, 1519-1532.

TIME in KARST – 2007 91

COBISS: 1.01

HOw TO DATE NOTHING wITH COSMOGENIC NUCLIDES KAKO DATIRATI PRAZNINE S KOZMOGENIMI NUKLIDI

Philipp HäUSELMANN1

Abstract                                           UDC 539.16:552.5(494)

Philipp Häuselmann: How to date nothing with cosmogenic nuclides

A cave is a natural void in the rock. Terefore, a cave in itself cannot be dated, and one has to resort to datable sediments to get ideas about the age of the void itself. Te problem then is that it is never very certain that the obtained age really is coincident with the true age of the cave. Here, we present the use of a method which couples sedimentary and morphologic information to get a relative chronology of events. Datings within this relative chronology can be used for assessing ages of forms, processes, and sediments, and the obtained dates also fx some milestones within the chronology, which then can be used to retrace, among other things, paleoclimatic variations. For many cave systems, the dating limits of the most widely used U/T method on speleothems are too low (350 to max. 700 ka) to get ages that inform us about the age of the cave. Te recent use of cosmogenic nuclides on quartz-containing sediment permits to push the datable range back to 5 Ma. while the theoretical background is explained elsewhere (Granger, this volume), we concentrate on the Siebenhengste example (Switzerland). Key words: relative chronology, cosmogenic nuclides, cave dating methodology, Siebenhengste.

Izvleček                                            UDK 539.16:552.5(494)

Philipp Häuselmann: Kako datirati praznine s kozmogenimi nuklidi

Jame predstavljajo praznino v kamninski masi in jim kot takim ne moremo določiti starost. Zato z datiranjem jamskih sedimen-tov sklepamo tudi o starosti jame, pri čemer seveda ne moremo trditi, da je dobljena starost tudi prava starost jame. V članku predstavimo metodo pri kateri z združitvijo sedimentarnih in morfoloških izsledkov sklepamo o relativni kronologiji dogodkov. Datiranje v oviru relativne kronologije lahko uporabimo za določevanje starosti različnih oblik, procesov in sedimentov. Dobljene rezultate pa lahko uporabimo kot pomembne mejnike v kronologiji, npr. pri intepretaciji klimatskih sprememb. Veliko jam je starejšiih od zgornje meje starosti (350 do 700 ka), ki jo lahko določimo z uran-torijevo metodo, ki je zelo razširjena. V zadnjem času se zato uveljavlja metoda datacije s kozmogenimi nuklidi, ki omogoča datiranje dogodkov do starosti 5 Ma. Ker je teoretično ozadje te metode predstavljeno drugje (npr. Granger v tej številki), se tu omejimo le na uporabo metode v jamskem sistemu Siebenhengste (Švica).

Ključne besede: relativna kronologija, kozmogeni nuklidi, metodika datiranja jam, Siebenhengste.

INTRODUCTION

For many cave scientists, it might not be evident that a while the sediments found within the cave give variable

cave does not exist - only the surrounding rock gives existence to the void called cave. Terefore, a cave cannot be dated by conventional methods (Sasowsky 1998), but one has to use datable sediments. In karstic caves, the age of the surrounding rock gives a maximal age of the cave,

ages from today (in the case of still active speleothems) up to the last stages of speleogenesis (in the case of spe-cifc sand deposits dated by cosmogenic nuclides) and therefore to the age of nothing itself.

1 Swiss Institute of Speleology and Karst studies SISKA, c.p. 818, 2301 La Chaux-de-Fonds, Switzerland, Fax 0041 32 913 3555, e-mail: praezis@speleo.ch

Received/Prejeto: 11.12.2006

TIME in KARST, POSTOJNA 2007, 93–100

PHILIPP HäUSELMANN

Tis paper contains two parts. In the frst part, the concept of relative chronology is explained. Te link between morphology and sediment succession leads to a relative chronology of erosional and depositional events. Any dating of sediment with the purpose of studying the age of nothing basically requires such a relative chronology, which places the obtained data into a timeframe.

In the second part, the dating of sandy cave sediments with cosmogenic nuclides is briefy presented. Es-

THE CONCEPT OF RE

INTRODUCTION Geologists and other scientists are usually aware of the laws of stratigraphy, which say that a younger sediment overlies an older one. Tese laws are the base of a relative chronology. Tis chronology is normally used to assess the correctness of an obtained age - the numerical value has to be concordant with stratigraphy, or the dated age may not be correct. Most of the time, this principle is used with stalagmites, where the obtained ages must be older at the base and younger at the top (e.g. Spötl et al. 2002).

Morphological indications, on the other hand, also give chronological information. A keyhole passage informs us that a phreatic phase was followed by a vadose one. Successions of speleogenetic phases are found in many cave systems. while some of them indicate base level rises (Audra et al., 2004), most of them indicate a downcutting of the regional base level (uplif, valley deepening, e.g. Ford & williams 1989; Rossi, Cortel & Arcenegui 1997). Tis in itself is also a chronological information: the oldest cave passages are on top, the youngest ones near the present baselevel.

Te difculty now is to connect the sediments of several, basically independent, sedimentary profles and to link them with the morphological succession of the cave passages. Tus, the sedimentary profles are not independent from each other, and a relative chronology of erosional and depositional events over the whole cave can be made.

ExAMPLE Figure 1 shows a real situation encountered in St. Beatus Cave (Switzerland):

To the right side is a typical keyhole passage which proves that a phreatic initiation of the ellipse on top was followed by a canyon incision. In the middle part of the fgure, the meander gradually disappears and is replaced by a more or less elliptic passage that continues towards

pecially when dealing with sands, a relative chronology is very important to date only meaningful sediments. Te theoretical background is only very briefy presented, and the reader is referred to Granger (this volume) for more thorough information. Te Siebenhengste example, the use of the relative chronology, and the obtained results are presented in more detail.

TIVE CHRONOLOGy

the lef side of the fgure. we see therefore a transition of a vadose feature into a phreatic one, and thus an old water level. In the profle to the right, we observe fowstone deposition that was truncated by the river incising the meander. Terefore, the fowstone predates the canyon, but postdates the initial genesis of the elliptic passage to the right. Te meander changes into an elliptic passage, thus the two forms are contemporaneous. Consequently, the older fowstone disappears in the area of this transition. within all the passages, silts were deposited. Tey are younger than the meander incision, and younger than the passage to the lef, and prove of an inundation of the whole cave. Stalagmites grow on the silts and are partially still active. Tis example can be written as a table (Tab. 1).

--------------------------------------

Phreatic genesis of top ellipse

-------------------------------------- Water level lowering

Deposition of fowstone Erosion of fowstone Erosion of meander

-------------------------------------- Water level lowering

Silt deposition

Stalagmite growth

--------------------------------------

tab. 1: Chronology of erosional and depositional events (Fig. 1)

Tis table is a frst relative chronology that links the sediments and the morphology of the cave.For practical reasons, the table presenting the chronology of events in a large cave system is not rewritten with each sedimentary succession found. Instead, the single sedimentary sequence is coupled with morphology, and is written as a column in the table. Te next sedimentary sequence, again coupled with morphology, is written as another column. Tus, the above example would then look like Table 2.

94

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HOw TO DATE NOTHING wITH COSMOGENIC NUCLIDES

Sequence at left

Sequence at right

Phreatic genesis Phreatic genesis Phreatic genesis Water level lowering Silt deposition Stalagmite growth

Phreatic genesis of top ellipse Water level lowering Deposition of fowstone Erosion of fowstone Erosion of meander

Silt deposition Stalagmite growth

tab. 2: Chronological table with columnar writing of Fig. 1

ExPANSION If we continue up- and downstream of that profle, we fnd several other morphological indications and sedimentary successions, each of them having a link with our initial profle - until we encounter the next paleo-water-level and thus the next morphological change. Tere, the links have to be established again. Te table thus slowly grows and gets more complete.

Of course, the example presented above is an ideal case. Ofen, the passages lack some information, thus making it difcult to establish an unambiguous chron-Table 3: A more complicated example from St. Beatus Cave

Lower passage

Phreatic genesis

Water level lowering

Pebble deposition

Speleothem

Erosion

Sand deposition

Speleothem

Sand deposition

Silt deposition

Pebble deposition

Sand deposition

Silt deposition

Erosion

Speleothem

Erosion

Silt deposition

Speleothem

Erosion

Silt deposition

?

?

Upper passage

Phreatic genesis

Water level lowering

Speleothem

Silt deposition

Speleothem

Silt deposition

Speleothem

Silt deposition

Erosion

Speleothem

Silt deposition

?

ological table. Table 3 give an example: here, the upper passage lacks incision of a canyon. Terefore, it is not clear whether the sediments found in the upper passage were all deposited while the lower passage was still in its initial genesis, or whether the sediments can be partly correlated. In this case, a relative correlation of the sediments by observation only is not possible: some absolute dates have to be obtained. Of course, these ages have to be in stratigraphic order of both the sediment succession and the morphologic indications. Te above example had been dated by U/T on speleothems. Te resulting table is presented in Table 4. Here, the speleothems with roughly the same age have been grouped together. Ten, laminated silt deposits that are thought to be a product of glacial damming (Bini, Tognini & Zuccoli 1998; Audra et al., this volume), are parallelized, inferring that the whole cave was fooded in such conditions. Of course, some uncertainties still persist. Table 4: The more complicated example, dated and expanded

Lower passage

Phreatic genesis Water level lowering Pebble deposition Speleothem Erosion

Sand deposition Speleothem (235 ka) Sand deposition Silt deposition Pebble deposition Sand deposition Silt deposition Erosion

Speleothem (180 ka) Erosion

Silt deposition

Speleothem (91 ka)

Erosion

Silt deposition

Upper passage

Phreatic genesis Water level lowering Speleothem (>350 ka) Silt deposition

Speleothem (337 ka)

Silt deposition

Speleothem (114 ka) Silt deposition Erosion Speleothem (99 ka)

Silt deposition

tab. 3: A more complicated example from St. beatus Cave

tab. 4: Te more complicated example, dated and expanded

TIME in KARST – 2007 95

PHILIPP HäUSELMANN

Fig. 1: Schematic section through a part of St. beatus Cave (Switzerland), showing the relationship between sediments and morphology.

wHy A RELATIVE CHRONOLOGy?                  parallelized all the sedimentary sequences, it is possible Te huge advantage of such a table of relative chronology      to make a synthetic and dated sediment profle of the is that it ofers more control on the correct stratigraphic      whole cave, which can then be used to get information order than single sections, in ideal cases also the cave      on climatic variations and the presence or absence of gla-genesis can be dated, and last but not least, when having      ciers damming the cave’s exit (Häuselmann 2002).

DATING wITH COSMOGENIC NUCLIDES

INTRODUCTION Cosmogenic nuclides are generated by the interaction of cosmic rays (mainly protons, neutrons, and muons) with atoms in the Earth’s atmosphere and lithosphere. Te production rate of cosmogenic isotopes depends on the intensity of the cosmic rays, which is subject to change. Te atmosphere then absorbs most of the primary rays and thus causes production rates to depend on elevation. Finally, the geometry of the sample location (and eventual snow or soil cover) also has its efects. Te radioactive nuclides most widely used for dating purposes are 10Be and 26Al produced in quartz.

THE PRINCIPLE AND POSSIBILITIES OF BURIAL DATING Burial dating of cave sediments is a relatively new technique that indicates the time sediment has been underground (Granger, Fabel & Palmer 2001). It relays on the radioactive decay of the nuclides that were previously accumulated when the sediment was exposed at the surface. whereas the intensity of the cosmic rays may vary with time, the ratio of produced 10Be to 26Al remains always approximately 1:7. Te 10Be/26Al ratio can thus be calculated from the production rates and radioactive decay. If a sample that contains 10Be and 26Al is washed underground to sufcient depth to be shielded from further radiation, the nuclide concentrations diminish. Since 26Al has a half-life of 720 ka,

opposed to the one of 10Be of 1.34 Ma, the ratio of 1:7 is gradually lowered. Measurement of that ratio therefore gives a direct indication of the time the sample remained underground.

Of course, several prerequisites have to be fulflled in order to get a burial age:

- First of all, the sediment must contain quartz that was irradiated sufciently prior to burial. Te grain size should be minimally fne sand (otherwise the cleaning process also eliminates the quartz), but may reach pebble size without problem.

- Ten, burial should ideally be 20-30 m below the surface to be sufciently shielded from radiation.

- In order to make a measurement meaningful, the stratigraphic relationship of the sampled sand with the passage and other sediments should be clearly established - the relative chronology is needed.

Burial dating has a range from about 100’000 years up to 5 Ma. Afer that time, the amount of remaining isotopes is usually too small to be measured accurately (Granger & Muzikar 2001). It is one of only a few radio-metric methods that date lower quarternary and Pliocene deposits. It is of great interest for cave dating, frst because many old caves were created in the Pliocene or even earlier, and second because caves are very efective at shielding the sediment from further cosmic ray bombardment. As with other cave-dating methods, burial dating may also be used to date the age of the passage,

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Caves of the region Siebenhengste - Hohgant

Perspective view from 370g, as of January, 2002 Only the most important passages shown

Spring for 1440 - 558 Aare valley

Fitzlischacht

I

0.5

1           1.5 km

mi*

Siebenhengste

IA201IISHPT

Spring for 1950-1505 Eriz

Hohgant

"~760 558

St. Beatus Caves

Bärenschacht

Haglätsch by HRH & toporobot

Fig. 2: Projection (370 degrees) of the Siebenhengste caves with the speleogenetic phases. Stars indicate sampling places for cosmogenic dates. From häuselmann & Granger (2005), modifed.

thus indicating valley deepening rates and evolution of the surface outside the cave.

THE SIEBENHENGSTE ExAMPLE we used burial dating to date the old passages of the Siebenhengste cave system in Switzerland. Te Siebenhengste region is situated in the north-western part of the Alps, adjacent to the molasse basin. From Lake Tun, the mountain range extends to the Schrattenfuh, 20 km away. Te cave region is one of the longest and deepest worldwide, with the Réseau Siebenhengste-Hohgant

Fig. 3: Plot of ages (vertical) versus altitude (horizontal).

having 154 km length and -1340 m depth. Te caves comprise 14 diferent speleogenetic phases, which can be related to paleo-valley bottoms (Jeannin, Bitterli & Häuselmann 2000). Te highest and oldest fve phases (at presumed spring elevations of >1900, 1800, 1720, 1585, and 1505 m a.s.l.) had their springs in the Eriz valley (Fig. 2). Te next phase, at 1440 m, shows a change in fow direction of 180°. Te spring was then located in the area of Lake Tun. Te infuence of today’s Aare valley (the site of Lake Tun today) therefore became predominant. All subsequent springs (at 1145, 1050, 890, 805, 760, 700, 660, and 558 m a.s.l.) drained towards the Aare valley.

In the area between Lake Tun and Hohgant, a total of 23 sites were selected for sampling (see Fig. 2: stars indicate sites). Selection was made on the basis of a relative chronology, and care has been given to ensure that either the oldest possible sediment, or a series in stratigraphic order, was sampled. Due to the limited amount of time in which sampling could be done, the relative chronology is incomplete (Tab. 5), although the main events were retraced. 21 samples were analysed (Häuselmann & Granger 2005). Te results show a great diversity of ages, ranging from 118 ka up to

TIME in KARST – 2007 97

Faustloch

Bätterich

PHILIPP HäUSELMANN

bold = morphologic event (a 0 denotes phreatic genesis, a v vadose enlargement), italic = dated event

A201 ShP low SHP up Haglätsch A2TR A2CHU A2NS

RBL

L18

Faustloch Beatus Age

Interpretation

18000 18000 18000

SHP 7 Sediment

Erosion Erosion

SHP2 SHP 3 Silt

18000

4.39

2.35

17200 Flowst. Flowst. Silt              lake           Silt

Erosion Erosion Erosion

Flowst.

17200

17200

Sand

Erosion

A201 SHP5 Sand Silt

1.9-1.84

Sand

Silt

15850

15850 15850

15850

15850

Erosion Parag.?

Flowst. Flowst.

Silt

Flowst.

Erosion

lake

SHP1 Flowst.

SHP6 HGLP Flowst. Flowst.

Erosion Erosion Canyon

HGLS

Paragen. epiphreatic

L18 Silt

1.54-1.60

1.04-1.09 (.93?)

SHP4

HGLT A2TR A2CHU A2NS

1505/14400

Flowst. RBL2

Erosion

RBL1

10500

1505/14400 0.78-0.80 (.93?) 0.63

10500

1050V

8900

Flowst.

flooding

FSTL

8050 7600

0.47

BG23

0.23

BG1

0.18

BG20

0.16

8900

8050 7600

tab. 5: Relative chronology of events around the Siebenhengste

1500

1000

500

1             2            3             4

6 Burial age (10 years)

4.4 Ma (Tab. 6). Te surface sample (MwA) has a burial age of 106 ± 176 ka. Tus, the value is indistinguishable from zero, and we may assume that the sample was never buried. Te sample from St. Beatus Cave (BG1) has an age of 182 ± 122 ka. Its true value, bracketed by U/T

Fig. 4: Rate of valley lowering in the Siebenhengste. Only maximum and minimum ages are displayed; however the valley deepening rates as well as the knickpoint at ~800 ka are easily visible.

98 TIME in KARST – 2007

5

A relative chronology of events, albeit incomplete, coupled with burial age dating by cosmogenic nuclides, permitted to obtain a continuous history of valley incision in the Alps. Such data cannot be obtained in the same precision with other methods or at the surface. Te results presented here are the frst cosmogenic dates for an Alpine cave system in a glacially infuenced area. Te results indicate an onset of karstifcation in the Siebenhengste before 4.4 Ma, that is in the Pliocene or even earlier. Together with U/T dates obtained earlier (Häuselmann 2002), the history of the Siebenhengste cave system and

HOw TO DATE NOTHING wITH COSMOGENIC NUCLIDES

ages, should be between 160 and 235 ka, which is again the case. Tese values indicate that the method yields young ages where expected.

A difculty for dating with cosmogenic nuclides is mobility of the sediment. For instance, recent sand can be transported into a fossilized cave by a food and then be deposited. Our results show that this process happens: for any speleogenetic phase, there is a range of ages observed (Fig. 3). However, Fig. 3 also indicates that the re-mobilization and re-deposition of old sediments is rarely observable: if this would be the case, we would expect a random distribution of ages throughout the phases. However, the maximum age decreases with the next lower phase. we can thus construct a gradual valley lowering with time which is represented in Fig. 4. we see a knickpoint in the line connecting the ages: this knickpoint occurs at around 800 ka and 1500 m. Tis point refects a dramatic increase in valley deepening rate and coincides with the change in fow direction from Eriz to the Aare valley.

tab. 6: Results of dating.

its surrounding environment can be traced back over a huge time span.

Te construction of a complete relative chronology is very time-consuming, but can be extremely rewarding given the information one can extract from the cave. If speleogenetic phases, which are related to the overall geomorphic evolution of an area, can be expanded by such relative chronologies as well as absolute dates, the rate, duration, and extent of valley deepenings can be assessed, and a paleoclimatic history can be drawn as well.

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REFERENCES

Audra, Ph., L. Mocochain, H. Camus, E. Gilli, G. Clauzon & J.-y. Bigot, 2004: Te efent of the Messinian Deep Stage on karst development around the Mediterranean Sea. Examples from Southern France. - Geo-dinamica Acta, 17, 6, 27-38.

Bini, A., P. Tognini, & L. Zuccoli, 1998: Rapport entre karst et glaciers durant les glaciations dans les val-lées préalpines du Sud des Alpes. - Karstologia, 32, 2, 7-26.

Ford, D.C. & P. williams, 1989: Karst geomorphology and hydrology. Chapman & Hall, London, 601 p.

Granger, D.E, D. Fabel & A.N. Palmer, 2001: Pliocene-Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic 26Al and 10Be in Mammoth Cave sediments. - GSA Bulletin, 113, 7, 825-836.

Granger, D.E. & P.F. Muzikar, 2001: Dating sediment burial with in-situ produced cosmogenic nuclides: theory, techniques, and limitations. - Earth and Planetary Science Letters, 188, 269-281.

Häuselmann, Ph., 2002: Cave genesis and its relationship to surface processes: Investigations in the Siebenhengste region (bE, Switzerland). - PhD thesis, Université de Fribourg, 168 p.

Häuselmann, Ph. & D.E. Granger, 2005: Dating of caves by cosmogenic nuclides: Method, possibilities, and the Siebenhengste example (Switzerland). - Acta Carsologica, 34, 1, 43-50.

Jeannin, P.-y., T. Bitterli, T. & Ph. Häuselmann, 2000: Genesis of a large cave system: the case study of the North of Lake Tun system (Canton Bern, Switzerland). In: A. Klimchouk, D. C. Ford, A. N. Palmer, & w. Dreybrodt (Eds.), Speleogenesis: Evolution of Karst Aquifers, pp. 338-347.

Rossi, C., A. Cortel & R. Arcenegui, 1997: Multiple pa-leo-water tables in Agujas Cave System (Sierra de Penalabra, Cantabrian Mountains, N Spain): Criteria for recognition and model for vertical evolution. - Proceedings 12th Int. Congress of Speleology, La Chaux-de-Fonds, Switzerland, 1, 183-187.

Sasowsky, I.D., 1998: Determining the age of what is not there. - Science, 279, 1874.

Spötl, C., M. Unterwurzacher, A. Mangini & F.J. Long-stafe, 2002: Carbonate speleothems in the dry, inneralpine Vinschgau valley, northernmost Italy: witnesses of changes in climate and hydrology since the last glacial maximum. - Journal of Sedimentary Research, 72, 6, 793-808

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UPPER CRETACEOUS TO PALEOGENE FORBULGE

UNCONFORMITy ASSOCIATED wITH FORELAND BASIN

EVOLUTION (KRAS, MATARSKO PODOLJE AND ISTRIA;

Sw SLOVENIA AND Nw CROATIA)

ZAKRASELA PERIFERNA IZBOKLINA POVEZANA Z RAZVOJEM

ZGORNJEKREDNO-PALEOGENSKEGA PREDGORSKEGA

BAZENA; KRAS, MATARSKO PODOLJE IN ISTRA

(JZ SLOVENIJA IN SZ HRVAŠKA)

Bojan OTONIČAR1

Abstract                                   UDC 551.44.551.7(497.4-14)

552.541.551.7(497.4-14)

Bojan Otoničar: Upper Cretaceous to Paleogene forbulge unconformity associated with foreland basin evolution (Kras, Matarsko Podolje and Istria; SW Slovenia and NW Croatia)

A regional unconformity separates the Cretaceous passive margin shallow-marine carbonate sequence of Adriatic Carbonate Platform from the Upper Cretaceous and/or Paleogene shallow-marine sequences of synorogenic carbonate platform in southwestern Slovenia and Istria (a part of southwestern Slovenia and northwestern Croatia). Te unconformity is expressed by irregular paleokarstic surface, locally marked by bauxite deposits. Distinctive subsurface paleokarstic features occur below the surface (e.g. flled phreatic caves, spongework horizons…). Te age of the limestones that immediately underlie the unconformity and the extent of the chronostratigraphic gap in southwestern Slovenia and Istria systematically increase from northeast towards southwest, while the age of the overlying limestones decreases in this direction. Similarly, the deposits of synorogenic carbonate platform, pelagic marls and fysch (i.e. underflled trinity), deposits typical of underflled peripheral foreland basin, are also diachronous over the area and had been advancing from northeast towards southwest from Campan-ian to Eocene. Systematic trends of isochrones of the carbonate rocks that immediately under- and overlie the paleokarstic surface, and consequently, of the extent of the chronostratigraphic gap can be explained mainly by the evolution and topography of peripheral foreland bulge (the forebulge). Te advancing fexural foreland profle was the result of vertical loading of the foreland lithospheric plate (Adria microplate) by the evolving orogenic wedge. Because of syn- and post-orogenic tectonic processes, and time discrepancy between adjacent foreland basin deposits and tectonic (“orogenic”) phases it is difcult to defne the exact tectonic phase responsible for the evolution of the foreland complex. According to position and migration of the subaerially exposed forebulge, distribution of the foreland

Izvleček                                    UDK 551.44.551.7(497.4-14)

552.541.551.7(497.4-14)

Bojan Otoničar: Zakrasela periferna izboklina povezana z razvojem zgornjekredno-paleogenskega predgorskega bazena; Kras, Matarsko podolje in Istra (JZ Slovenija in SZ Hrvaška)

V jugozahodni Sloveniji in Istri so kredna karbonatna zaporedja Jadranske karbonatne platforme pasivnega obrobja Jadranske mikroplošče ločena z regionalno diskordanco od zgornjekrednih in paleogenskih karbonatnih zaporedij sino-rogene karbonatne platforme. Razgibano paleokraško površje, ki diskordanco označuje, je lokalno prekrito z boksitom. Pod površjem se pojavljajo različne podpovršinske paleokraške oblike, med drugim večje zapolnjene freatične jame in diskretni horizonti drobnih prepletajočih se kanalčov. Starost apnencev neposredno pod paleokraškim površjem in obseg stratigrafske vrzeli v jugozahodni Sloveniji in Istri sistematično naraščata od severovzhoda proti jugozahodu, nasprotno pa starost apnencev, ki paleokraško površje pokrivajo v tej smeri upada. Preko obravnavanega območja so med campanijem in eocenom od severovzhoda proti jugozahodu napredovala tudi sedimentna zaporedja sinorogenih karbonatnih platform (karbonatne kamnine Kraške grupe) ter pelagičnih laporjev in fiša, ki predstavljajo sedimente podhranjenega predgorskega bazena. Sistematične trende izohron karbonatnih kamnin, ki ležijo neposredno pod in nad paleokraškim površjem in posledično razpona stratigrafske vrzeli lahko v veliki meri razložimo z evolucijo in topografjo periferne predgorske izbokline. Napredujoči feksurni predgorski profl je nastal zaradi vertikalne obremenitve predgorske litosferske plošče (Jadranske mikroplošče) z nastajajočim orogenim klinom. Zaradi sočasnih in postorogenih tektonskih procesov ter časovnega neskladja med sedimenti sosednjih predgorskih bazenov in med različnimi tektonskimi (»orogenimi«) fazami tega dela zahodne Tetide v kredi in paleogenu, je opredelitev tektonske faze, ki je neposredno odgovorna za evolucijo obravnavanega predgorja otežena. Glede na položaj in migracijo periferne iz-

1 Karst Research Institute ZRC SAZU, Titov trg 2, Si-6230 Postojna, Slovenia, e-mail: otonicar@zrc-sazu.si Received/Prejeto: 01.02.2006

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BOJAN OTONIČAR

related macrofacies and orientation of tectonic structures, especially of Dinaric nappes, and Dinaric mountain chain I suggest that the foreland basin complex in western Slovenia and Istria was formed during mesoalpine (“Dinaric”) tectonic phase due to oblique collision between Austroalpine terrane/Tisia micro-plate and Adria microplate when probably also a segmentation of the foreland plate (Adria microplate) occurred. Key words: forebulge unconformity, paleokarst, chronostrati-graphic gap, fysch, Adriatic Carbonate Platform, synorogenic carbonate platform, foreland basin, Adria microplate, Dinaric orogene, Cretaceous, Paleogene, Sw Slovenia, Istria.

Plate tectonics theory had a crucial impact on our understanding of sedimentary basins, and consequently, of carbonate sedimentary systems. Plate tectonics determines not only the gross architecture (dimension and shape) and lithological/structural characteristics of carbonate platforms (Bosellini, 1989), but also their evolution and the longevity. Tose characteristics are largely defned by specifc geotectonic setting in which certain carbonate platform begin to grow. Carbonate platform(s), which colonize certain area through longer or shorter period of geologic history, constantly change its/their position in relation to the equator and plate boundaries and pass through diferent phases of the wilson cycle. Te sedimentary and diagenetic character of the carbonate platform(s) constantly change(s) during this journey and at a stretch, the platform evolution may be stoped. In this case, the area formerly inhabited by the carbonate platform may fall under conditions which are not favourable for considerable carbonate production. In one scenario it may immediately afer the deposition or later in the geologic history be uplifed, subaerially exposed and karstifed. Similarly as the plate tectonics governs the sedimentary evolution of the carbonate platforms, it may also determins their diagenetic evolution, including karsti-fcation. Te gross architecture, lithological/structural caharacteristics, and the evolution and the longevity of the uplifed area with subaerially exposed carbonate platform are mainly dependent on its geotectonic position regard to plate boundaries, former geodynamics and consequently topography of the area, especially of the carbonate platform. Although important for the appearance of the karstic landscape, the efects of other variables, such as climate and ground water level, may be just superimposed on the geotectonically predisposed framework.

bokline, razporeditev makrofaciesov podhranjenega predgor-skega bazena ter usmerjenost tektonskih struktur, predvsem Dinarskih pokrovov, in Dinarskega gorstva v celoti domnevam, da je nastal predgorski sistem v zahodni Sloveniji in Istri med mezoalpidsko (»Dinarsko«) tektonsko fazo, kot posledica bočne kolizije med Avstroalpidskim terranom in/ali Tisa mikroploščo ter Jadransko mikroploščo, pri čemer je verjetno prišlo tudi do segmentacije Jadranske mikroplošče.

Ključne besede: diskordanca, paleokras, kronostratigrafska vrzel, fiš, Jadranska karbonatna platforma, periferna predgorska izboklina, sinorogena karbonatna platforma, predgorski bazen, Jadranska mikroplošča, Dinarski orogen, kreda, paleogen, jugozahodna Slovenija, Istra.

Each karstic landscape carries its specifc geotecton-ic signature which can be read from and explained with specifc evolution of karstic features and a karst system as a whole. In addition, studies of sedimentary successions of rocks that under- and overlie the (paleo-) karstic surface and that of the adjacent sedimentary basins as well as the general geologic conditions of the region may signifcantly improve our knowledge on geodynamics of the uplifed area.

Te paper documents an example of paleokarst that occurred during the uplif of the Adriatic Carbonate Platform (sensu Vlahović et al., 2005) in the distant foreland region of the evolving collision related orogenic belt between the Adria microplate (sensu Stampfi et al., 1998) and the Austroalpine terrane and/or Tisia micro-plate (sensu Neugebauer et al., 2001) in the Late Cretaceous and the Early Paleogene.

Te study is based on 36 geological profles from the karstic regions of southwestern Slovenia, both Slovenian and Croatian part of Istria peninsula and the area between Trieste bay and Italian-Slovenian border in northeastern Italy (Figs. 1, 2). To get a whole picture of conditions that dominated the region during the emersion period, I expend the area of interest to syno-rogenic carbonate platform that onlap the paleokarstic surface and to siliciclastic fysch regions of afore mentioned areas and the adjacent regions of western Slovenia and northeastern Italy (along the border between Italy and Slovenia).

Te aim of this work is to show the causes of the uplif and subaerial exposure of the northwestern part of the Cretaceous Adriatic Carbonate Platform in Late Cretaceous and Early Paleogene. Te data presented here were provided mainly from the studies of paleogeograph-ic and topographic extent of the emersion, stratigraphy of the carbonate successions that immediately under- and

INTRODUCTION

102

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UPPER CRETACEOUS TO PALEOGENE FORBULGE UNCONFORMITy ASSOCIATED wITH FORELAND BASIN EVOLUTION

Fig. 1: Geographical position and simplifed geological map of the western Slovenia and Istria showing major structural elements (modifed from Placer, 1999).

overlain the paleokarstic surface, stratigraphy and sedi-      time of the uplif is correlated with events on the adjacent mentology of the onlapping synorogenic carbonate plat-      plate boundaries of the western Tethian domain (tradi-form and adjacent deeper marine basin as well as from      tional “orogenic phases”) and global eustatic curve. regional geotectonic and general geologic situation. Te

GEOLOGy OF THE AREA

Te geology of southwestern Slovenia and Istria has been carbonate successions of diferent Cretaceous formations studied from the late 19th century on. Since that time also from shallow-marine limestones of the Upper Creta-a regional unconformity which separates shallow-marine ceous/Lower Paleogene Liburnia Formation or Eocene

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BOJAN OTONIČAR

Fig. 2: Simplifed lithostratigraphic columns of Cretaceous to Eocene successions in southwestern Slovenia and Istria (NW Croatia and SW Slovenia), with one column from NW Italy. Authors of original geological columns are listed below:

1) šribar (1995); Rižnar (1997), 2) drobne (1977, 1979), 3) drobne et al. (1988, 1996); šribar (1995); jurkovšek et al. (1996), 4) jurkovšek et al. (1996), 5) drobne (1981); jurkovšek et al. (1996), 6) jurkovšek et al. (1997), 7) hamrla (1959); drobne (1977, 1979); Pavlovec et al. (1991), 8) hamrla (1959, 1960); jurkovšek et al. (1996), 9) brazzatti et al. (1996), 10) hamrla (1960); drobne et al. (1991); jurkovšek et al. (1996), 11) hamrla (1959); buser & Lukacs (1979); delvalle & buser (1990); jurkovšek et al. (1997); this study, 12) drobne (1977); delvalle & buser (1990), 13) delvalle & buser (1990); šribar (1995); buser & Radoičić (1987), 14) šikić et al. (1972); drobne (1977), 15) drobne (1977); this study, 16) drobne (1977, 1981); hottinger & drobne (1980); drobne & Pavlovec (1979); drobne et al. (1991); turnšek & drobne (1998); this study, 17) drobne (1977), 18) šikič et al. (1972); drobne (1977), 19) biondić et al. (1995), 20) šikić et al. (1972); drobne (1977), 21) šikić et al. (1968); drobne (1977), 22) Pleničar et al. (1969); drobne (1977); Gabrić et al. (1995), 23) Pleničar et al. (1969); drobne (1977), 24) hamrla (1959); Pleničar et al. (1973); drobne (1977); velić & vlahović (1994); matičec et al. (1996), 25) šikić et al. (1968); drobne (1977); hottinger & drobne (1980); drobne et al. (1991), 26) matičec et al. (1996), 27) tarlao et al. (1995), 28) buser & Lukacs (1972); drobne (1977); hottinger & drobne (1980); matičec et al. (1996), 29) Polšak & šikić (1973); drobne (1977), 30) drobne et al. (1991), 31) - 34) matičec et al. (1996), 35) šikić et al. (1968); magaš (1973); šikić et al. (1973); šikić & Polšak (1973); höttinger & drobne (1980); Otoničar et al. (2003), 36) Polšak (1970); drobne (1977); matičec et al. (1996).

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Alveolina-Nummulites Limestone has been known. Te Liburnia Formation, Alveolina-Nummulites Limestone and intermediate Trstelj Beds represent the Kras Group (Košir, 2003) (Fig. 3), which corresponds to the lower unit of the underflled peripheral foreland basin stratigraphy (i.e. the lower unit of the “underflled trinity” of Sinclair, 1997). Tus the unconformity represents a megasequence boundary and typically separates the underlying passive margin carbonate succession from the overlying deposits of the synorogenic carbonate platform at periphery of the foreland basin (Košir & Otoničar, 2001). Te synorogen-ic carbonate platform was fnally buried by prograding hemipelagic marls (i.e. the middle unit of the “underflled trinity” of Sinclair, 1997) and deep-water clastics (fysch) (i.e. the upper unit of the “underflled trinity” of Sinclair, 1997) (Fig. 3). Because the name of the carbonatre platform that overlie the unconformity has not been defned yet, I will use in this paper only the general geodynamic term – i.e. the synorogenic carbonate platform.

Fig. 3: Generalized stratigraphic column of Upper Cretaceous-Eocene succession in the Kras (Karst) and matarsko podolje regions, SW Slovenia, showing major lithostratigraphic units (modifed from Košir, 2004).

Te unconformity is expressed by an irregular paleokarstic surface, locally marked by bauxite depos-

its. Although the unconformity has been repeatedly mentioned, no systematic study of paleokrast has been performed. Relatively numerous papers on biostratig-raphy, especially on the carbonate successions of the Kras Group, have been published (see list of references attached to Fig. 2), yet not more than few attempts on explanation of the sedimentology of the paleokarstic deposits and onlapping beds have been done (Otoničar, 1997; Debeljak et al., 1999; Durn et al., 2003). Only occasionally, the geotectonic conditions under which the paleokarst (uplif) evolved have been briefy mentioned (Košir & Otoničar, 2001; Otoničar & Košir, 2001; Durn et al., 2003).

Tectonically, the discussed area corresponds to three macrotectonic units, the Southern Alps, the Ex-

Fig. 4: Illustrative geological map showing distribution of fysch deposits and major structural elements in western Slovenia. Te map is based mainly on data from basic geological maps of yugoslavia, 1:100.000, sheets beljak & Ponteba (jurkovšek, 1986), Udine-tolmin & videm (Udine) (buser, 1986), Kranj (Grad & Ferjančič, 1974), Gorica (buser et al., 1968), Postojna (buser et al., 1967), trst (Pleničar et al., 1969) and Ilirska bistrica (šikić et al., 1972). Copyright: Geološki zavod Slovenije (Geological survey of Slovenia), 2002 – All rights reserved.

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Fig. 5: A) Paleogeographical map showing major geotectonic units at Santonian-Campanian boundary in western tethys and central Atlantic (modifed from Neugebauer et al., 2001). b) Geotectonic and paleogeographic units of Adria microplate and adjacent areas.

ternal Dinarides and the Dinaric foreland (Placer, 1999) (Fig. 1). while the fysch-related sediments can be followed across the all three units (Fig. 4), the unconformity and the overlying carbonate successions of the Kras Group correspond to the most external thrust unit of the Dinaric fold and thrust belt – the northwestern External Dinarides in southwestern Slovenia, Italian part of the Kras plateau and northeastern Istria, and to more stable foreland domain of the Dinaric mountain belt in other parts of Istria (Figs. 1, 2).

Te nappe structure of northwestern part of the External Dinarides comprises fve successively lower and younger thrust units from northeast to southwest: Trnovo Nappe, Hrušica Nappe, Snežnik Trust Sheet, Komen Trust Sheet and Kras Trust Edge (Placer, 1981, 1999, 2002) (Fig. 1).

Te External Dinarides and the Dinaric foreland correspond to the northwestern part of the Cretaceous Adriatic Carbonate Platform and the Upper Cretaceous-Eocene synorogenic carbonate platform which occupied northeastern part of the Adria microplate s.s. (Fig. 5). In the Cretaceous the area of present day Southern Alps

was a part of deeper marine realm which comprised the Slovenian Basin formed in the Middle Triassic (Cousin, 1981; Buser, 1989) and the area of former Julian Carbonate Platform which was drowned in the Lower and Middle Jurassic (Cousin, 1981; Buser, 1989).

Te geologic and paleogeographic situation started to change severely in the Late Cretaceous (see below). It is important to note, that the described region is recently confned from the north side by the Periadriatic fault zone, from the west by the deposits of the Southern Alpine Molasse Basin and from the south and southwest by the Adriatic Sea and its sediments (Fig. 1).

To understand the mechanisms that governed the uplif and emersion, regional geotectonic conditions of the wider area of the Late Cretaceous-Early Paleogene western Tethys were taken into consideration.

During the Mesozoic, the area between Eurasia and Gondwana or the western part of the extensive Tethys bay of the Pangea was occupied by more or less uniform Adria microplate surrounded by smaller tectonic units or terranes (Fig. 5). with regard to major geotectonic events, the extent and shape of Adria microplate was

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changing constantly through the geologic history. Te results of these events (e.g. tecto-sedimentary successions or cycles) could be correlated between geographically and geologically distant parts of the Adria microplate.

Afer substantial Permian to Middle Triassic and Triassic/Jurassic extensional tectonics, the Adria domain became encircled by oceanic bays and dissected by numerous deepwater basins and drowned carbonate platforms (Fig. 5). It is considered that since Early Jurassic the Adriatic Carbonate Platform had been isolated by deeper marine realms (Vlahović et al., 2005).

At the Middle/Late Jurassic boundary compression-al tectonic regime prevailed over the peri-Adriatic region. It was caused by the beginning of closure (subduction) of the adjacent oceanic bays of the western Tethys. During the Late Jurassic and Cretaceous gentle broad-scale positive and negative lithospheric defections periodically occurred on the Adriatic Carbonate Platform. Te defections were expressed by coexistence of karstic areas and somewhat deeper marine intra-platform basins (Tišljar et al., 1995; 1998; Vlahović et al., 2005). Distinctive defections correspond to period of ophiolite emplacement [e.g. the Late Jurassic/Early Cretaceous obduction of ophiolite suite of the Dinaric Tethys on the E margin of the Adria microplate (Pamić et al., 1998; 2000)] and distant collisions [e.g. the mid-Cretaceous Eoalpine orogenesis in the Pelso/Austroalpine/Tisia domain (Faupl & wagreich, 2000; Neugebauer et al., 2001)]. Topographic disunity over the platform gave rise to irregular facies distribution and thickness of carbonate successions of diferent parts of the platform.

In the investigated area both surface and subsurface pale-okarstic features occur. In places the paleokarstic surface is denoted by surface karst forms like karrens, dolines and depressions of decimetric amplitude (Fig. 6a). Pedogenic features and enlarged root-related channels characterize the upper part of the vadose zone, the epikarst. Vadose channels, shafs and pits penetrate up to a few tens of meters bellow the paleokarstic surface, where they may merge with originally horizontally oriented phreatic cavities. Te latter comprise characteristics of caves forming in fresh/brackish water lenses. At least some of them may be defned as fank margin caves (Fig. 6b, 6c). In extensive outcrops, the remains of such caves can be followed as much as few hundreds of meters along strike. In one case a breccia body which was defned as paleokrastic cave related deposit (Otoničar et al., 2003), is so extensive that was used even as mappable unit for Basic geologic map of

Signifcant interruptions of carbonate successions are also related to global eustatic oscillations and/or oceanic anoxic events, but they are mainly superimposed on tectonically induced changes of relative sea-level.

Tus before the beginning of the uplif of northern part of the Adriatic Carbonate Platform in the Late Cretaceous and the synchronous onset of fysch sedimentation in the area north and north-eastern of the platform, the whole region was already topographically distinctly heterogeneous. Flysch started to deposit in deeper marine basin with partly inherited bathymetry from former deeper marine domain of Slovenian Basin and drowned Julian Carbonate Platform (Fig. 5). Deeper marine realms with more or less uninterrupted sedimentation had still encircled the carbonate platform from its western and southwestern side (Vlahović et al., 2005) (darker grey area on Fig. 5).

Later tectonic activity which shortened the area and displaced diferent parts of the region, prevent more accurate interpretation of geotectonic conditions at those time. Namely, except the substantial shortening of the region due to diferent “thrusting” phases of Alpine oro-geney, the area north from the Periadriatic Fault Zone was displaced for at least 100 km eastward during the Miocene (Ratschbacher et al., 1991; Frisch et al., 1998; Vrabec & Fodor, 2006), in some estimates up to 500 km (Haas et al., 1995). It should be noted that western Istria (i.e. Dinaric Foreland on Figure 1) experienced signif-cant counterclockwise rotation most likely between the end of Miocene and the earliest Pliocene (Márton et al., 1995; Márton, 2006).

yugoslavia 1:100.000 (see Magaš, 1965). Te cavities are usually irregular and elongated in shape, and could be up to few tens of meters long and up few meters high (Fig. 6b). Depending on locality, the phreatic cavities were found in diferent positions regarding to the paleokrastic surface, the lowest one some 75 meters below it. Te cavities had been subsequently partly reshaped and entirely flled with sediments and fowstones in the upper part of the phreatic, epiphreatic and vadose zones (Figs. 6b, 6c). Similarly, the vadose channels and voids are also flled by sediments and fowstones, but they usually difer from these of phreatic cavities in higher content of noncar-bonate material, lower δ13C values of carbonate material and more distinctive pedogenic modifcation. Te denudation had frequently exposed flled paleokarstic subsurface cavities on the paleokarstic surface, where they may be identifed only by the remains of their fll (Otoničar

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et al., 2003) (Fig. 6c). Te internal sediments and fow-stones ofen occur as grains in deposits that cover the paleokarstic surface or fll subsurface paleokarstic cavities of diferent generations. Paleokarstic surface with its depressions as well as subsurface channels and voids are ofen covered and flled by bauxite deposits which were locally exploited (Fig. 6d) (Gabrić et al., 1995).

Certain limestone lithofacies of immediate cover of the unconformity are commonly locally confned, sug-

Fig. 6: A) Paleokarstic surface is locally denoted by small scale depressions (motorway road-cut at Kozina village, SW Slovenia). Note colour contrast between Upper Cretaceous shallow marine limestone of the Lipica Formation and dark grey palustrine limestone of the Liburnia Formation. hammer for scale is about 30 cm high. b) horizontally oriented cave of irregular shape largely flled with reddish-stained calcareous mudstone/siltstone (Podgrad, matarsko Podolje, SW Slovenia). Te maximal height of the cave is approximately 4 meters. Te cave deposits are artifcially marked by reddish transparent colour on the photograph. C) breccia body represents a part of flled roofess paleokarstic phreatic cave at Koromačno in Istria, NW Croatia. (1,8 m tall geologist for scale in the upper right corner) d) Excavated paleokarstic cavity (vadose shaf?) originally flled with bauxite (minjera, Istria, NW Croatia).

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gesting highly irregular topography of the karstic surface before the beginning of transgression. In places it is clear that the incipient transgression involved gradual increase of groundwater table and, eventually, ponds or “blue holes” were formed in karstic depressions (Durn et al., 2003). In the Kozina site (southwestern Slovenia) during the “blue hole” stage of the transgression, a paleokarstic

pit was flled by coarse grained breccia with vertebrate remains, mainly dinosaurian and crocodilian bone fragments and teeth (Debeljak et al., 1999, 2002). Generally, the cover sequence (i.e. the Liburnian Formation of Maastrichtian and early Paleogene age) is characterized by restricted, marginal marine and palustrine lithofacies, which frequently show pedogenic modifcations.

EVOLUTION OF THE PERIPHERAL BULGE (THE FOREBULGE)

Besides the research on paleokarst related phenomena, the study of sedimentary successions of the host rock in which the paleokarstic features occur and those that overlie the paleokarstic surface is of crucial importance to understand the uplif of substantial part of the Adriatic Carbonate Platform above the sea-level in the Late Cretaceous and Paleogene. To explain the mechanisms that govern the uplif, regional and global geotectonic and eu-static conditions were taken into consideration, too.

STRATIGRAPHy

Te age of the limestones that immediately underlie the unconformity and the extent of the chronostratigraphic gap in southwestern Slovenia and Istria systematically increase from northeast towards southwest (Figs. 2, 7a, 7b), while the age of the overlying limestones decrease in this direction (Figs. 2, 7c). In western part of Istria the orientation of the isochrones is slightly diferent and

VN. »im

a

i

If

^^+jSijf/ / / / J^ I

h

Fig. 7: A) Isochrones of carbonate rocks that immediately underlie the unconformity. b) Isochrones of the extent of the chronostratigraphic gap. C) Isochrones of carbonate rocks that immediately overlie the unconformity. Isochrones in all fgures are in ma. major structural elements of the area (see Fig. 1) and positions of the geological profles used in the research (see Fig. 2) are also shown in the fgures.

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shows a dome-like topography of the forebulge. Te isochrones represent a statistic result acquired by kriging in Surfer programme version 8.00 (© Golden Sofware, Inc.). Te data were provided from 36 geological profles from the karstic regions of southwestern Slovenia, both Slovenian and Croatian part of Istria peninsula and the area between Trieste bay and Italian-Slovenian border in northeastern Italy (Figure 2 and red dots on Figures 7a, 7b, 7c).

Te youngest rocks below the unconformity belong to mid-Campanian and occur in the central and northeastern part of the Kras (Karst) plateau (the Komen thrust sheet) (Fig. 1) (Jurkovšek et al., 1996) and close to Postojna (the Snežnik thrust sheet) (Fig. 1) (Šribar, 1995; Rižnar, 1997) in southeastern Slovenia, while the oldest one, Valanginian and Hauterivian in age, crop out in the western part of Istria (Matičec et al., 1996) (Figs. 2, 7a).

Te beds that cover the unconformity correspond to diferent ages, litofacies, members and formations. As mentioned afore, the age trend of the immediate cover is opposite to that of the footwall. In this case the oldest rocks occur in southwestern Slovenia and belong to the youngest stage of the Late Cretaceous - the Maastrich-tian. Towards southwest, progressively younger deposits onlap the paleokarstic surface (Figs. 2, 7c). However, the youngest strata that onlap the unconformity don’t ft exactly with the oldest one immediately below it. with regard to described situation, the chronostratigraphic gap increases considerably from few Ma on the Kras plateau (southwestern Slovenia) to more than 80 Ma in western Istria (Figs. 2, 7b).

Te lithofacies of the lower part of the cover sequence (Te Liburnian formation) frequently show features typical of subaerial exposure surfaces, including calcrete, pseudomicrokarst, brecciated horizons and karstic surfaces. Locally, the lowermost subaerial exposure surface of the Liburnija Formation, which shows karstic topography of decimetric amplitude, and the main paleokarstic surface form a composite unconformity. Sporadically, thin coal beds and seams occur in the lower part of the sequence. Although the stratigraphy of the Kras Group, “Transitional Beds” and Flysch (Fig. 3) shows overall deepening of the basin, prominent subaerial exposure surfaces also occur in carbonate successions of Trstelj Beds and Alveolina-Nummulites Limestone (Košir & Otoničar, 1997; Košir, 2003). Much thicker successions of paralic sediments with more frequent unconformities and marsh related sediments occur in southwestern Slovenia and northeastern Istria in comparison with other parts of Istria, yet local variation can be signifcant (Figs. 2, 8). In western Istria, where the chronostratigraphic gap is the most extensive, the foraminiferal limestones frequently lie directly on the paleokarstic surface (Matičec

at al., 1996). Te thickness of the Kras Group generally decreases from northeast toward southwest, although also in this case signifcant deviations may occur (Figs. 2, 8).

Te point where the unconformity pinch-out towards the foreland basin occurs somewhere between the northeastern part of the Kras plateau on the Komen Trust Sheet and some 10 km (approximately 25 km in original position – see Placer, 1999) distant Mt. Nanos on the Hrušica nappe (Fig. 1). From this point on towards the foreland basin, the uplif of the forebulge didn’t take place because the area was so close to the orogene that experienced only a subsidence. Here, the sedimentary succession of the Adriatic Carbonate Platform gradually passes into progressively deeper-marine carbonate succession of synorogenic carbonate platform. Namely, on the Mt. Nanos at Campanian-Maastrichtian boundary, the deepening of the shallow marine carbonate platform without any evidence of preceding emersion is documented (Šribar, 1995).

Further towards the northeast, in the Julian Alps (the eastern part of the Southern Calcareous Alps) and in the most northern part of recent Dinaric mountain belt in western Slovenia and northeastern Italy (the Trnovo Nappe), the turbiditic siliciclastic sediments (fysch) started to deposit in Campanian and Maastrichtian over the rocks of diferent lithology, age and origin (Pavšič, 1994). Flysch ofen overlies deeper marine pelagic marls of “scaglia” type and alodapic carbonates, which were receiving the material from Adriatic Carbonate Platform. It is important to note that in this part of western Slovenia deep-marine basin existed before fysch or above mentioned deeper marine pelagic marls started to deposit. However, the oldest pelagic marls (pre-fysch deposits) which overlie the Upper Cretaceous shallow marine carbonates of the northeastern margin of the Adriatic Carbonate Platform also belong to Maastrichtian. Similar as I stated for chronostratigraphic gap, the pelagic marls and fysch deposits are also diachronous over the area. From northeast toward southwest, successively younger strata onlap the pre-foreland basin deposits (Fig. 4).

Te successions of pelagic marls and especially si-liciclastic fysch were periodically interrupted by deposition of calcarenitic and calcruditic beds/megabeds, locally even of olistostrome character. Tose beds were supplied by turbiditic currents from the fault-related escarpments of distorted and seismically active marginal areas of former Adriatic Carbonate Platform (Skaberne, 1987; Tunis & Venturini, 1987) and later also from outer parts of synorogenic carbonate platforms (distally steepened ramps?) (Fig. 9).

Te synorogenic carbonate and siliciclastic deposits of other parts of External Dinarides (e.g. Dalmatia) are

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Fig. 8: Lithostratigraphic columns for three adjacent sites in matarsko Podolje and mt. Slavnik (SW Slovenia). Note signifcant variations in thickness of lithostratigraphic units and in time span of stratigraphic gap.

younger than these described here. Tey started to deposit not before Eocene (Marjanac & Ćosović, 2000) and probably represent deposits of diferent foreland system or at least of diferent segment of the one described here.

DISCUSSION

Systematic trends expressed by isochrones showing the age of the carbonate rocks that immediately under- and overlie the paleokarstic surface (Figs. 7a, 7c), and consequently, the extent of the chronostratigraphic gap (Fig. 7b), can be explained mainly by the evolution and topography of peripheral foreland bulge (the forebulge) (Fig. 9).

when the foreland continental lithospheric plate is vertically loaded by the fold and thrust belt, it responds with fexure. In front of the evolving orogen an asymmetric foreland basin is formed; the deepest part of the basin (the foredeep) is located adjacent to the orogenic wedge (Fig. 9). Because of the isostatic rebound on vertical loading of the lithosphere, the opposite side of the basin (opposite to the orogenic wedge) is instantaneously upwarped and the bulge with subtle relief is formed, the

peripheral bulge or the forebulge. Te bulge is especially well expressed in early, fysch stage of the foreland basin evolution (Crampton & Allen, 1995). while the wavelength of the defection is approximately the same for both, foreland basin and peripheral bulge, the amplitude of the basin subsidence is typically much greater as the uplif of the bulge (Crampton & Allen, 1995; Miall, 1995). If the conditions are suitable, synorogenic carbonate platforms with distinctive ramp topography may colonise the gentle slope of the forebulge toward the fore-deep (Dorobek, 1995).

Signifcantly, as the whole complex of the orogenic wedge advances forelandward, the fexural profle produced by the orogenic wedge advances with it. Topography of the forebulge is controlled by numerous factors, among which the rigidity of the foreland lithospheric plate and the rate of emplacement of the load are the most important (Allen & Allen, 1992; Dorobek, 1995; Miall, 1995). An expected maximal height of the forebulge above the sea level (if the foreland plate is at or close to sea-level prior to fexural loading) would be in the range of up to a few tens to few hundreds meters (Crampton &

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Fig. 9: Schematic block diagram of foreland basin complex showing the position of the orogenic wedge, foredeep and forebulge with distribution of macrofacies belts before plate convergence ended (modifed from bradley & Kidd, 1991).

Allen, 1995; Miall, 1995). According to topography of the forebulge, the rate of erosion (see white, 2000) and the style of migration of the orogenic wedge, the area of maximal denudation should occur in the central part of the region, which is over-passed by the bulge (Crampton & Allen, 1995). In addition, non-fexural deformations (e.g. reactivation of pre-existing heterogeneities, enhanced defections because of horizontal in-plane stresses…) and inherited topography may signifcantly infuence the evolution and topography of the forebulge (Allen & Allen, 1992; Dorobek, 1995; Miall, 1995; Crampton & Allen, 1995).

On Mt. Nanos (Hrušica Nappe; Fig. 1) shallow water rudist limestone of the Adriatic Carbonate Platform gradually passes over limestone with orbitoidiform larger foraminifera into pelagic marls without any emersion at the base of the deepening sequence – the erosional gap reduces to conformity. Te age span of this transition falls within a period of the shortest documented chronostrati-graphic gap between the northeastern part of former Adriatic Carbonate Platform and the overlying synogen-ic carbonate platform (Fig. 2), which extends from mid-Campanian to Late Maastrichtian. Maastrichtian in age are also the oldest pelagic marls which in places directly overlie the Upper Cretaceous shallow water carbonates of former northeastern margin of the Adriatic Carbonate Platform. Although the oldest turbiditic siliciclastic fysch was deposited in a basin with inherited deeper marine bathymetry (former Slovenian Basin) its Campan-ian and Maastrichtian age could be correlated with other incipient foreland related deposits and phenomena. with regard to these criteria and trends of unconformity related isochrones elsewhere (Figs. 2, 7a, 7b, 7c), I suggest

that northern part of the Adriatic Carbonate Platform had thrived more or less prosperously till the end of Campanian, when an initial uplif of the forebulge occurred. Te carbonate sediments that had originally been deposited till that time, and are now missing in carbonate successions immediately below the unconformity, had been erased during the paleokarstic period by the karstic denudation processes.

According to topography of the forebulge and advancing nature of the foreland geodynamic complex as a whole, the most extensive denudation is expected in the central area over which the forebulge migrates. Te western part of Istria, where the chronostratigraphic gap is the largest and the beds immediately below the unconformity are the oldest (Fifs. 2, 7a, 7b), most probably corresponds to this zone. However, in an ideal conceptual/mathematical model of the forebulge unconformity, the amount of erosion should remain more or less constant over vast area in the central part of the region over-passed by the bulge, and decreases on its distal slope towards back-bulge basin (Crampton & Allen, 1995). Instead, in western Istria the isochrones of the beds underlying the unconformity show distinctive condensation compared to situation in northeastern Istria and southwestern Slovenia (Fig. 7a). I suggest that this is not the result of rapid increase of the amount of footwall eroded but rather of denudation of primarily much thinner Cretaceous carbonate successions in western Istria. Namely, in this part of Istria the carbonate successions are relatively thin (Matičec et al., 1996), partly because of repeating emersions throughout the Cretaceous (Velić et al., 1989) and partly because of reduced accommodation space of Cretaceous shallow marine environments. Evidence of considerable Late Jurassic and Cretaceous land areas in the vicinity of western Istria (probably ofshore form its recent west coast), came also from dinosaur record (footprints and bones) (Della Vecchia et al., 2000; Mauko & Florjančič, 2003; Mezga et al., 2003) and distribution of sedimentary fa-cies of the adjacent peritidal to deeper marine environments of intraplatform basins (Tišljar et al., 1995; 1998). why was the area of western Istria beeing preferentially uplifed during the Cretaceous is still questionable, but the reasons for defections should be searched at adjacent plate boundaries where their reorganisation and difer-ent collision-related events and processes (see Faupl & wagreich, 2000; Neugebauer et al., 2001) produced hori-

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zontal in-plane stresses that may be transmitted many hundreds of kilometers inboard of actual collision (Zei-gler et al., 1995).

It is also possible that the central zone of the foreb-ulge and the slope towards back-bulge basin in their fnal position occurred ofshore of recent Istrian west coast. However, we should be aware that the Late Cretaceous Adriatic Carbonate Platform was surrounded from the western side by deeper marine interplatform basins (Vlahović et al., 2005) what might considerably afected the appearance of the forebulge and the back-bulge area.

Although the “abnormal thickness” of denuded stratigraphy in western Istria is mainly the result of previous sedimentary history, some uncertainties may also arise from diferential uplif/subsidence of certain parts of the forebulge. Evidence for diferential subsidence along reactivated ancient tectonic structures is for example well documented in carbonate successions of the Kras Group, where the thickness of chrono- and lithostratigraphic units may vary considerably over short distances (Figs. 2, 8).

In conclusion I suggest that the denudation exposed the oldest carbonate rocks in the western Istria partly because of specifc evolution (migration) and topography of the forebulge and partly because of primarily thinner carbonate successions in this part of Istria compared to more northeastern parts of the investigated area.

Te rate of transgression over the paleokarstic surface is expressed by the isochrones of the strata that onlap the unconformity (Fig. 7c). while the large scale diachro-nism of the onlapping strata shown in Figure 7c is the result of specifc large-scale topography and migration of the forebulge as a whole, local smaller scale spatial differences in the onlap pattern (not observable in Figure 7c) are due to shorter oscillations of relative-sea level and deposition over topographically irregular paleokarstic surface (e.g. dolines, shafs… – a “blue hole phase” of the transgression). Te pattern of the isochrones shown in Figure 7c suggests that the transgression during its earlier stages (southwestern Slovenia and northeastern Istria) was slower compared to its later stages (western Istria). Although subsequent tectonic deformations, such as tectonic shortening, faulting and rotation, substantially afected the area, the rate of the onlap in southwestern Slovenia and northeastern Istria is estimated to about 2-3 km/Ma while in southwestern Istria to about 4-5 km/Ma. we should be aware that some apparent anomalies, especially at terminations of the isochrones may be the result not only of later tectonic deformations of the area but also of limited number of data points which are not uniformly distributed, spatially confned area of the investigation along the strike of the forebulge and defectiveness of statistic method (kriging) used. Slightly diferent orienta-

tion of the isochrones in western part of Istria compared to those in southwestern Slovenia and northeastern Istria (Figs. 7a, 7b, 7c) may also be the result of diferent syde-positional or synorogenic orientation of the prevailing stresses (see Marinčić & Matičec, 1991; Matičec et al., 1996) during the Cretaceous and Paleogene and later counterclockwise rotation of the area (see Márton et al., 1995 amd Márton, 2006). In spite of all that, the reasons for diferent stratigraphic pinch-out rate are many sided and may arise from diferential rheologic and structural characteristics of the foreland plate itself, events at collision zone and adjacent plate boundaries, sublithospheric processes and external reasons like eustatic sea-level oscillations and climate changes. In our case it is difcult to determine the exact reason for the increasing rate of the onlap in Lower Eocene, not only because diferent processes may lead to the same result, but also because they can act simultaneously.

Long term sea-level fall (i.e. second-order cycle of Haq et al., 1987) may for example slow-down the onlap rate and vice-versa long term sea-level rise may increase the onlap rate. If we observe the eustatic curve for the Cretaceous and Paleogene (Haq et al., 1988) we can notice that the rate of the onlap is in relatively good agreement with mid-Campanian to Late Paleocene second-order fall and Early Eocene rise of the sea-level. However, the foreland basin should progressively widen and pinch-out migration rate would increase also if, for example, the orogenic wedge loaded a progressively stronger elastic lithosphere (Allen & Allen, 1992).

Although not all local variations of relative sea-level oscillations and so the onlap rate could be identifed from isochrones in the Figure 7c, they could be observed in the feld. Namely, the subaerial exposure surfaces that periodically interrupt the carbonate sedimentation of the Liburnia Formation refect relative sea-level falls. Short term falls (i.e. third-order cycles of Haq et al., 1987), which were documented in Late Maastrichtian, Late Pa-leocene and Early Eocene (Haq et al., 1988), could cause these unconformities.

On the other hand, a few other processes may infu-ence the rate of the onlap. Te forebulge should increase in height and migrate toward the orogenic wedge over time if the foreland lithosphere behaves viscoelastical-ly even when the load is unchanging (Tankard, 1986). However, estimations for time constants of the viscous relaxation of stresses are longer than actual amount of time available for the forebulge migration (Allen & Allen, 1992; Dorobek, 1995). Variation in onlap rate may refect also changes in sediment supply, or within the orogenic wedge, such as the formation of a new thrust complex (Crampton & Allen, 1995) or transition from passive to active thrusting phase. An increase in com-

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pressive in-plane stress produced during convergence also might enhance uplif of the forebulge and causing shoreline regression along its fank (Allen & Allen, 1992; Dorobek, 1995).

Evidence of short term sea-level oscillations could also be recognized from the specifc evolution of the pa-leokarst, especially phreatic caves. If the majority of lenticular caves with irregular walls and discrete horizons of spongework or swisse-cheese like vugs on young carbonate islands originated at/in fresh/brackish water lenses (see Mylroie & Carew, 1995), then in our case the major part of the cavities had been emplaced in the vadose zone prior to submergence and burial. Namely, the caves are frequently completely flled with deposits originated in vadose zone, like fowstone and bauxite, or they had been opened to the paleokarstic surface by complete denudation of the roof (i.e. roofess caves of Mihevc, 2001). If the water-level is stagnant and the forebulge migrates, than in the conceptual sense only those phreatic cavities developed below that forebulge fank that facing towards back-bulge basin should be uplifed in the vadose zone before subsidence. On the contrary, phreatic caves developed below the fank facing the foreland basin and the advancing orogenic wedge should sufer nothing but subsidence and subsequent burial. Teoretically it is possible that because of the advancing character of the forebulge, caves formed in diferent sides of the forebulge may occur in the same karstic profle. Phreatic cavities developed below the fank facing towards the back-bulge region should be uplifed and modifed in the vadose zone. Subsequently, afer the crest of the forebulge migrates over the back-bulge fank, the “back-bulge” phre-atic caves should re-immerge into phreatic zone, but this time below the fank facing towards the foreland basin. It is important to note that frequently observed multiphase modifcations of originally phreatic caves could also be the result of the same causes of relative sea-level oscillations that govern the onlap character of the beds that overlie the unconformity (e.g. relaxation of the viscoelas-tic bulge, formation of a new thrust complex, increase of horizontal in-plane stress, eustatic sea-level fall…).

Te carbonate platform was subsequently re-established and fnally buried by prograding deeper-marine clastics (pelagic marls and fysch) of the migrating foreland basin (Fig. 9). As it has been already discussed, shallow-water carbonate successions that cover the unconformity may yield a considerable amount of information about relative sea-level oscillations and geodynamics of the forebulge.

Paralic/shallow-marine successions with frequent unconformities and palustrine deposits of the Liburnia Formation (Fig. 3) are usually much thicker in southwestern Slovenia and northeastern Istria than in central

and western Istria (Fig. 2). Tere the paleokarstic surface is frequently directly overlain by foraminiferal limestones (Matičec at al., 1996). Te general trend of thickness and the rate of transition from shallow to deep marine environments (drowning) (Fig. 2) are in good agreement with the rate of the onlap (Fig. 7c) and should be the result of the same processes that caused the diferentiations in the onlap pattern. I suggest that the anomalies in thickness and facies distribution that could be in places quite distinctive may arise from reactivation of inherited geological structures due to the approaching orogenic wedge.

It has been discussed already, that the orogenic phases could be recognised from structural and stratigraphic data even in areas that are located at some distance from the source of tectonic activity at plate boundaries (e.g. collision and orogenesis). Because of later tectonic deformations it is sometimes difcult to defne the exact tectonic phase which afects the area and the actual source of tectonic activity.

In our case, the structural and stratigraphic data indicate the evolution of migrating synorogenic foreland basin complex, which should be the result of collision processes and the evolution of the advancing orogenic wedge (see e.g. Allen & Allen, 1992; Crampton & Allen, 1995; Miall, 1995). At frst sight it seems normal to link the foreland complex to tectonic phase that generated structures by mainly NE-Sw compression (mesoalpine phase of some authors; see Doglioni & Bosellini, 1987) and gave rise to Dinaric mountain belt during its fnal stages. However, the Dinaric orogenic belt of which fnal uplif occurred during the Oligocene-Miocene (Vlahović et al., 2005) is supposed to be the result of collision between Tisia and Adria microplates with onset of collision during the Eocene (Pamić et al., 1998; Pamić, 2002), what is also the age of the oldest synorogenic deposits of the “coastal” part of the External Dinarides (Marjanac & Ćosović, 2000). On the contrary, although the nappe structures of western Slovenia and Late Cretaceous – Pa-leogene compressional deformations of northeastern Italy indicate NE-Sw or ENE-wSw compression, and so “Dinaric” orientation of prevailing regional stress, the oldest foreland basin deposits in these regions are much older than those of other parts of the External Dinarides and belong to the latest stages of Late Cretaceous (Pavšič, 1994; Doglioni, 1987; Doglioni & Bosellini, 1987). As it is shown on Figure 4 the age distribution of fysch deposits indicates the advancing nature of foreland basin from northeast towards southwest what is in accordance with “Dinaric” orientation of the prevailing regional stress. while south of Zagreb-Zemplen fault line, the remnants of oceanic lithosphere (i.e. ophiolite melange) as well as subduction and collision related rocks of Internal Dinarides (i.e. the Sava-Vardar zone by Pamić et

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al, 1998), which could be linked to closing processes of the Vardar Ocean and collision between Tisia and Adria (Pamić, 2000) are widespread, north of Zagreb-Zemplen line no such rock has been found so far. It seems possible that in central Slovenia, in prolongation of the Sava-Var-dar zone, such rocks have been buried by Tertiary sediments and Southern Alpine nappes. In addition, on the NNE side the nappe structure of western Slovenia was cut from its “root zone” by Periadriatic fault. Te “root zone” should be displaced for at least 100 km eastward during the Miocene (Ratschbacher et al., 1991; Frisch et al., 1998; Vrabec & Fodor, 2006).

Although, the structural and sedimentary features of eoalpine tectonic phase which culminated in mid-Cretaceous orogeny in the Austroalpine domain (Faupl & wagreich, 2000) and also afected the central and western part of the Italian Southern Alps (Doglioni, 1987; Doglioni & Bosellini, 1987) mostly pre-date the foreland related features and sediments described here, it should

In spite of all structural and depositional heterogeneities and subsequent tectonic deformation of the area the paleokarstic unconformity marked by distinctive surface and subsurface paleokarstic features exhibits characteristics typical of a forebulge unconformity:

1)   From northeast towards southwest the unconformity cuts progressively older units which are onlapped by progressively younger shallow water carbonates; the chronostratigraphic gap progressively increases.

2)   Deepening upward sequences of synorogenic ramp-like carbonate systems overlie the unconformity. In marginal parts of the former Adriatic Carbonate Platform towards the foreland basin, a deepening upward sequence is documented also without intermediate unconformity – here the sequence is conformable because the orogenic wedge was so close that the area experienced only subsidence and forbulge uplif had no taken place.

3)   Te foreland basin with siliciclastic turbiditic fysch deposits was developing synchronously with the forebulge and synorogenic carbonate platforms. It was also advancing synchronously in the same direction as they were forebulge and synorogenic carbonate platforms. Te stratigraphy overlying the unconformity (i.e. underflled trinity) representing subsidence in under-flled peripheral foreland basin.

4)   Evidence of contemporary seismic activity arises from periodic carbonate resediments (megabeds, olistostromes) fnd in siliciclastic fysch successions.

be noted that in Istria Tertiary tectonic cycle (from Eocene on) display distinctively diferent orientation of the prevailing stress than Mesozoic one (Marinčić & Matičec, 1991; Matičec et al., 1996).

In conclusion, the foreland basin complex in western Slovenia and Istria was probably formed during me-soalpine (“Dinaric”) tectonic phase, although some infu-ences of eoalpine tectonic phase could be important in earlier stages of its evolution. Te time discrepancy and also the exact orientation of prevailing regional stress are probably the result of oblique collision between Adria and Tisia microplates (and/or Austroalpine terrane?) and/or segmentation of the foreland plate (see Ricci-Luc-chi, 1986; Allen & Allen, 1992).

Oligocene to recent tectonic events especially in Dinarides and Apennines, and conter-clockwise rotation of Adria importantly modifed the area formerly occupied by the forebulge, but this is already beyond the scope of this paper.

Tey were supplied by turbiditic currents from the fault related escarpments of the forebulge slope (reactivated ancient faults). Besides fexural upwarping because of the isostatic rebound on vertical loading of the foreland lithosphere, other smaller scale fexural and non-fexural deformations signifcantly infuenced the evolution and appearance of the forebulge (incuding its diagenesis and karstifcation), lithofacies distribution and thickness of the carbonate successions above the unconformity. At least some infuence of eustatic sea-level oscillations cannot be excluded.

5) Te subaerially exposed area and the facies belts of progressive forelandward advancing shallow-marine, pelagic, and turbiditic depositional environments ahead of the orogenic front are roughly parallel to the Dinaric mountain chain. However, the Dinaric foreland-related system supposedly began to evolve during the Eocene when Tisia and Adria microplates began to collide what is much later comparing to Late Cretaceous onset of foreland basin evolution and forebulge uplif in western Slovenia and Istria. In Istria the orientation of the prevailing regional stress during Cretaceous tectonic cycle difers signifcantly from Eocene one. I suggest that the foreland basin complex in western Slovenia and Istria was probably formed during mesoalpine (“Dinaric”) tectonic phase, due to oblique collision of Adria and Ti-sia microplates (and/or Austroalpine terrane?) and segmentation of the foreland plate.

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Stampfi, G. M., Mosar, J., Marquer, D., Marchant, R., Baudin T. & Borel, G., 1998: Subduction and obduc-tion processes in the Swiss Alps.- Tectonophysics, 296, 1-2, 159-204.

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Šikić, D., Polšak, A. & Magaš, N., 1968: Osnovna geološka karta SFRJ. List Labin [Kartografsko gradivo]. 1:100.000. Zvezni geološki zavod, Beograd.

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A REVIEw OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS AND ASSOCIATED SUPRASTRATAL DEFORMATION

MEDSEBOJNO ZDRUŽENI PORUŠENI PALEOKRAŠKI JAMSKI SISTEMI IN DEFORMACIJE NAD NJIMI LEŽEČIH PLASTI –

PREGLED

Robert G. LOUCKS1

Abstract                                                           UDC 551.44

Robert G. Loucks: A Review of Coalesced, Collapsed-Paleo-cave Systems and Associated Suprastratal Deformation

Coalesced, collapsed-paleocave systems and associated supra-stratal deformation appear to be prominent diagenetic/struc-tural features in carbonate sections at/near composite unconformities. Te basic architecture of the system can be divided into two sections. Te lower karsted section, where high-density cave formation took place, is preserved as massive breccias commonly displaying a rectilinear pattern in map view. Te overlying suprastratal deformation section is characterized by large, circular to linear sag structures containing faults and fractures. Regional distribution of coalesced, collapsed-cave systems commonly appears as large-scale (hundreds to thousands of square kilometers in area), rectilinear patterns with areas of concentrated, coalesced breccias separated by relatively undisturbed host rock. Tis pattern may refect development of the paleocave system along fracture swarms. Collapsed-paleocave systems are large, complex features that show broad-scale organization. Te complete paleocave system may need seismic data or large, mountain-scale outcrops to de-fne their architecture and distribution.

Key Words: Paleocaves, Paleokarst, karst, suprastratal deformation, cave systems.

Izvleček                                                            UDK 551.44

Robert G. Loucks: Medsebojno združeni porušeni paleokraški jamski sistemi in deformacije nad njimi ležečih plasti – pregled

Medsebojno združeni porušeni paleokraški jamski sistemi in deformacije nad njimi ležečih plasti predstavljajo izrazite dia-genetsko/strukturne oblike karbonatnih zaporedij v bližini sestavljenih geoloških nezveznosti. Osnovno zgradbo posameznega sistema lahko razdelimo na dva dela. Spodnji zakraseli del, kjer je gostota jam velika, je ohranjen v obliki masivnih breč, ki pogosto kažejo v tlorisu vzorec sestavljen iz ravnih odsekov. Za deformirane plasti, ki prekrivajo porušene jamske sisteme, so značilne velike skledaste do škatlaste uleknine, ki jih sekajo prelomi in razpoke. Regionalno gradijo združeni paleokraški jamski sistemi tega tipa vzorec velikega merila (zajemajo območja velika stotine do tisoče kvadratnih kilometrov), sestavljen iz ravnih odsekov in vključuje območja zgoščenih združenih brečastih teles, ločenih z relativno neprizadeto prikamnino. Tak vzorec lahko kaže na razvoj paleokraškega jamskega sistema vzdolž razpok-linskih con. Porušeni paleokraški jamski sistemi predstavljajo velike kompleksne pojave, ki odražajo organiziranost velikega merila. Za opredelitev zgradbe in razprostranjenosti popolnega paleokraškega jamskega sistema teh dimenzij potrebujemo podatke seizmičnih raziskav ali izdanke dimenzij gorovja. Ključne besede: pelokraški jamski sistemi, paleokras, deformacije, jamski sistemi.

1 Bureau of Economic Geology , John A. and Katherine G. Jackson School of Geosciences, Te University of Texas at Austin, University Station Box x, Austin, Texas 78713-8924 U.S.A., Fax: 512-471-0140 , email: bob.loucks@beg.utexas.edu

Received/Prejeto: 27.11.2006

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ROBERT G. LOUCKS

INTRODUCTION

At several composite unconformities in the stratigraphic record, carbonate sections display extensive karsting that leads to multiple development of cave systems (Esteban, 1991). Tese cave systems underwent extensive collapse and mechanical compaction with burial. Deformation of the overlying strata is associated with burial collapse of the cave system. Te efects of this suprastratal deformation can be noted 700+ m up section above the karsted interval.

Tis review will describe the evolution of cave systems during burial and what the characteristics of the cave systems are at diferent stages of burial. Also the

characteristics of suprastratal deformation will be described. Paleocave systems have been investigated by several authors including Lucia (1968, 1995, 1996), Loucks and Anderson (1980, 1985), Kerans (1988, 1989, 1990), wilson et al. (1991) wright et al. (1991), Candelaria and Reed (1992), Loucks and Handford (1992), Lucia et al. (1992), Kerans et al. (1994), Hammes et al. (1996), Maz-zullo and Chilingarian (1996), McMechan et al. (1998), Loucks (1999, 2001, 2003), Loucks et al. (2000, 2004), Loucks and Mescher (2001), McMechan et al. (2002), and Combs et al. (2003). Te review will mainly synthesize material from these studies.

CLASSIFICATIONS OF CAVE PRODUCTS AND FACIES

Loucks (1999) and Loucks and Mescher (2001) produced classifcations of cave products and cave facies. Loucks (1999) used a ternary diagram (Fig. 1) to show the relationships between crackle breccias, mosaic breccias, chaotic breccias, and cave sediments. Crackle breccias are highly fractured rock, with thin fractures separating the clasts and only minor displacement existing between the clasts. Mosaic breccias show more displacement than crackle breccias, but the clasts can still be ftted back together. Chaotic breccias are com-

ton

§3

Crackle breccia

I gravel | *ä •• % »!_••

Cave-sediment fill

Matrix-rich: clast-supported: chaotic breccia

Matrix-supported chaotic breccia

cd

Cave sediment with chips, slabs, and blocks

Fig. 1: Cave-sediment flls and breccias can be separated into three end members: crackle breccia, chaotic breccia, and cave-sediment fll. modifed from Loucks (1999) and reprinted by permission of the AAPG whose permission is required for further use.”

posed of mixtures of clasts that have been transported vertically by collapse or laterally by fuvial or density-fow mechanisms. Clasts show no inherent association with their neighbors. Chaotic breccias grade from matrix-free, clast-supported breccias; through matrix-rich, clast-supported breccias; to matrix-rich, matrix-supported breccias. Cave-sediment fll can consist of any material, texture, or fabric.

Loucks and Mescher (2001) proposed a classifcation of six common paleocave facies (Fig. 2): (1) Undisturbed strata, which are interpreted as undisturbed host rock. In this facies bedding continuity is excellent for tens of hundreds of meters. (2) Disturbed strata that are disturbed host rock around the collapsed passage. Bedding continuity is high, but it is folded and ofset by small faults. It is commonly overprinted by crackle and mosaic brecciation. (3) Highly disturbed strata, which is collapsed host rock adjacent to or immediately above passages. (4) Coarse-clast chaotic breccia that is interpreted as collapsed-breccia cavern fll produced by ceiling and wall collapse. It is characterized by a mass of very poorly sorted, granule- to boulder-sized chaotic-breccia clasts approximately 0.3 to 3 m long that form a ribbon-to tabular-shaped body as much as 15 m across and hundreds of meters long. It is commonly clast

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supported, but can contain matrix material. (5) Fine-clast chaotic breccia interpreted as laterally (hydro-dynamically) sorted, transported-breccia cavern fll. Characterized by a mass of clast-supported, moderately sorted, granule- to cobble-sized clasts with varying amounts of matrix. Clasts can be imbricated or graded. Resulting bodies are ribbon-to tabular-shaped and are as much as 15 m across and hundreds of meters long. (6) Cave-sediment cavern fll that can be carbonate and/or silici-clastic debris of any texture or fabric and commonly displaying sedimentary structures.

Fig. 2: Six basic cave facies are recognized in a paleocave system and are classifed by rock fabrics and structures. modifed from Loucks and mescher (2001) and reprinted by permission of the AAPG whose permission is required for further use.”

EVOLUTION OF CAVE PASSAGES

Knowledge of the processes by which a modern cave lapsed paleocave passage in the subsurface is necessary passage forms at the surface and evolves into a col- to understand the features of paleocave systems. Loucks

(1999) described this evolutionary process (Fig. 3), and the review presented here is mainly from that investigation.

A cave passage is a product of near-surface karst processes that include dissolutional excavation of the passage, partial to total breakdown of the passage, and sedimentation in the passage (Fig. 4). During later-burial cave collapse, mechanical compaction takes place.

Cave-ceiling crackle breccia

Breakout dome

Burial cave-ceiling crackle breccia

Crackle/mosaic breccia

Burial cave-wall crackle breccia

breakdown breccia

Cave-ceiling collapse and further dissolution

Transported breccia and sediment

Mechanical compaction

Sag, faults, and fractures

Fig. 3: Schematic diagram showing evolution of a single cave passage from its formation in the phreatic zone of a near-surface karst environment to burial in the deeper subsurface. modifed from Loucks (1999) and reprinted by permission of the AAPG whose permission is required for further use.”

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Initial passages form in phreatic and/or vadose zones (Fig. 3). Passages are excavated where surface recharge is concentrated by preexisting pore systems, such as bedding planes or fractures (Palmer, 1991), that form a continuous link between groundwater input, such as sinkholes, and groundwater output, such as springs (Ford, 1988). Cave passages are under stress from the weight of

Karst towers

Vadose canyon (passage)

Cave-sediment fill Solution-enlarged fractures

Phreatic zone

Phreatic tube (passage)

Stream sediment

Chamber (room)

Cave-ceiling Cave-floor crackle breccia breakdown breccia

Fig. 4: block diagram of a near-surface modern karst system. Te diagram depicts four levels of cave development (upper-right corner of block model), with some older passages (shallowest) having sediment fll and chaotic breakdown breccias. modifed from Loucks (1999) and reprinted by permission of the AAPG whose permission is required for further

overlying strata. A tension dome, or zone of maximum shear stress, is induced by the presence of the passage or cavity (white, 1988). Stress is relieved by collapse of the rock mass within the stress zone. Tis collapse produces chaotic breakdown breccia on the foor of the cave passage (Figs. 3 and 4). Te associated stress release around the cavity produces crackle and mosaic breccias in the adjacent host rock.

As cave-bearing strata are buried, extensive mechanical compaction begins, resulting in collapse of the remaining void (Fig. 3). Multiple stages of collapse occur over a broad depth range. Meter-scale bit drops in wells (indication of cavernous pores) are not uncommon down to depths of 2,000 m and are observed to occur to depths of 3,000 m (Loucks, 1999). Te collapsed passages become pods of chaotic breccia (Fig. 3). Te areal cross-sectional extent of brec-ciation and fracturing afer burial and collapse is greater than that of the original passage because the adjacent fractured and brecciated host rock has become part of the brec-ciated pod. Sag features, faults, and fractures (Fig. 3) occur over the collapsed passages.

Sediment-filled passages Breakout dome Breakdown pile

EVOLUTION OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS

A coalesced, collapsed-paleocave system can be divided into two parts: (1) a lower section of strata that contains collapsed paleocaves and (2) an upper section of strata that is deformed to varying degrees by the collapse and compaction of the section of paleocave-bearing strata (Fig. 5). Te deformed upper section of strata is termed suprastratal deformation (Loucks, 2003) and is discussed in a later section.

Cave systems are composed of numerous passages. If the areal density of passages is low, the collapsed cave system will feature isolated, collapsed passages (nonco-alescing paleocave system; Fig. 6). If the cave system has a high density of passages, as is common at composite third-order unconformities (Esteban, 1991; Lucia, 1995;

Fig. 6: Schematic diagram showing burial and collapse of low-density cave system (noncoalescing, collapsed-cave system) and reprinted by permission of the AAPG whose permission is required for further use.”

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Active cave systems

Unconformity

4

Phase 1:

Modern cave system

Phase 2:

Multiple near-surface cave systems

developed below composite

Sg2k Composite unconformity

Phase 3:

Coalesced, collapsed-paleocave system

100 to >1000 m

Loucks, 1999), then upon burial and collapse the system can form large-scale, coalesced, brecciated and fractured breccia bodies upon burial and collapse that are the amalgamation of many passages and intervening disturbed host rock (coalescing paleocave system; Fig. 5). Te bodies are hundreds to several thousands of meters across, thousands of meters long, and tens of meters to more than 100 m thick. Internal spatial complexity is high, resulting from the collapse and coalescence of numerous passages and cave-wall and cave-ceiling strata.

Fig. 5: Schematic diagram showing the stages of development of a coalesced, collapsed-paleocave system. modifed from Loucks et al., (2004) and reprinted by permission of the AAPG whose permission is required for further use.”

SUPRASTRATAL DEFORMATION

Collapse and compaction of cave systems provide potential for development of large-scale fracture/fault systems that can extend from the collapsed interval upward to more than 700 m (Kerans, 1990; Hardage et al., 1996a; Loucks, 1999, 2003; McDonnell et al., in press). Tese fracture/fault systems are not related to regional tectonic stresses.

Large-scale suprastratal deformation occurs above the collapsed-cave system. As the cave system collapses during burial, overlying strata will sag or subside over the collapsed area. Tis phenomenon is well documented in mining literature (Kratzsch, 1983; wittaker and Reddish, 1989). Kratzsch (1983, p. 147) presented a diagram (Fig. 7) that shows the stress feld above a collapsed mine passage and associated subsidence. Te overlying stress feld widens from the edges of the excavation, and the overlying strata are under compression directly over the excavation. Near the edges of the excavation, between a vertical line extending from the edge of the cavity and the limit line, strata are under extension (tension). within this zone of stress the overlying strata have the potential to sag, creating faults and fractures for some distance upward, depending on the mechanical properties of the strata and the thickness of the beds within the strata. Fig. 8 is a scatterplot showing a number of examples of the

magnitude of subsidence over coal mines. Te graph indicates that subsidence is recorded at horizons more than 800 m above the cavity. Tese data indicate the magnitude of the efect that the collapse of a cavity can have on overlying strata.

et

Extension »I

Compression

,- . . Extension

Collapsed mine

Fig. 7: diagram of a collapsed mine showing collapsed breccia zone and suprastratal deformation. Te center of the subsidence trough is under compression, whereas the wings are under extension. modifed from Kratzch (1983).

Applying the above concept of stress felds over cavities to the collapse of a cave passage during burial sug-

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ROBERT G. LOUCKS

gests that similar stress felds will develop. As the cave passage collapses, it has the potential to afect a consider-

1000

500 400

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100

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able number of overlying strata. within a cave system, numerous passages will collapse with burial. Each passage will develop a stress feld above it, and these stress felds will interact to create a larger, combined stress feld. Tis concept was presented by wittaker and Reddish (1989; p. 47), who detailed instances in which multiple mining excavations are collapsing. Te stress feld above a collapsing cave system will be complex because the different cave passages do not collapse and compact uniformly over time. As local areas collapse, diferent stress felds will develop, producing fractures and faults related to that individual stress feld. Resulting suprastratal deformation will show variable fracture and fault patterns within an overall subsidence sag. A unique circular fault pattern above collapsed cave systems is recognized by cylindrical faults (Hardage et al., 1996a; Loucks, 1999; McDonnell et al., in press).

Fig. 8: Scatterplot showing thickness of overburden that can be afected by mine collapse. Graph shows a trend of greater subsidence with less overburden.

MEGASCALE ARCHITECTURE PATTERNS OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS

Coalesced, collapsed-paleocave systems are megascale diagenetic/structural features that can afect more than 700 m of section and be regional in scale. As discussed earlier, the karsted section refects the coalescing of collapsed breccias that formed by collapse of passages and associated disturbed host rock. Te vertical extent of the breccias commonly afects the upper 100 m of section (Loucks and Handford, 1992; Loucks 1999) and as much as 300 m of the total section (Lucia, 1996). Te intensity of brecciation can vary throughout the afected interval. Kerans (1990), Loucks (1999), Loucks et al., 2004), and many others have published descriptions of collapsed, brecciated paleocave zones. Fig. 9 shows examples of cave facies from the Lower Ordovician Ellenburger Group in central Texas (Loucks et al., 2004).

Te regional pattern of the collapsed paleocave system is commonly rectilinear (Loucks, 1999). Tis rectilinear pattern is probably an artifact of the original cave system developing along an early-formed fracture system. In a detailed study of a paleocave system in the

Fig. 10: Slice map through a collapsed-paleocave system in the Lower Ordovician Ellenburger Group in central texas. modifed from Loucks (2004) and reprinted by permission of the AAPG whose permission is required for further use.”

\

Quarry wall

1000 ft

300 m

Undisturbed host rock

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Fractured and

brecciated

rock (coalesced,

collapsed cavern)

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1

4

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A REVIEw OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS AND ASSOCIATED SUPRASTRATAL DEFORMATION

Lower Ordovician in central Texas, Loucks et al. (2004) presented maps (Fig. 10) and cross sections of the three-dimensional, fne-scale architecture of a coalesced, col-lapsed-paleocave system. Te coalesced, collapsed-pas-sage breccias range in size to as much as 350 m and are separated by disturbed and undisturbed host rock ranging in size up to 200 m. Lucia (1995) also presented a map of brecciated collapsed passages (Fig. 11) from outcrops in the Franklin Mountains of far west Texas, which displays a crude rectilinear pattern.

Tis rectilinear pattern can be seen on seismic data as well. Loucks (1999) presented seismic-based maps

from Benedum feld in west Texas that display a rectilinear pattern of sags and circular faults induced by collapse of the Ellenburger paleocave system below (Fig. 12). A similar rectilinear pattern is evidenced on seismic data in Boonsville feld (Fig. 13) in the northern Fort worth Basin in Texas (Hardage et al., 1996a; McDonnell et al., in press). In both the Benedum and Boonesville datasets, suprastratal deformation afects up to 700 m of section above the karsted interval (Figs. 12 and 13).

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Fig. 9: Representative cores from paleocave facies. (a) Crackle-fractured disturbed host rock. (b) Collapsed chaotic breccia with large slabs and cave-sediment fll. (c) transported chaotic breccias in carbonate cave-fll matrix. Sample on right is under Uv light. Samples from Lower Ordovician Ellenburger Group in central texas. modifed from Loucks (2004) and reprinted by permission of the AAPG whose permission is required for further use.”

TIME in KARST – 2007 127

ROBERT G. LOUCKS

(a)

Sag (suprastratal deformation)

Upper Ordovidan Montoya

Silurian Ftisseiman

Upper Ortoviasn

Montoya

Paleocave trends

Approximate area of Great McKelligon Sag (above photograph)

■ Brecciated McKelligon Canyon, Cindy, and Ranger Peak Formations

] Brecciated Ranger Peak Formation ___ Unbrecciated El Paso Group

Fig. 11: (a) Photograph of the Great mcKelligon Sag in the Franklin mountains of far West texas. Photograph and general interpretation are from Lucia (1995) but have been modifed by current author. Tis outcrop is an outstanding example of a collapsed-paleocave system with associated overlying suprastratal deformation. (b) map produced by Lucia (1995) of several paleocave systems within the Franklin mountains. Paleocave trend lines are by current author.

CONCLUSIONS

Coalesced, collapsed-paleocave systems are megascale diagenetic/structural features that can afect more than 700 m of section and be regional in scale. Te architecture of the complete system can be divided into the lower collapsed zone, where the dense system of caves formed and collapsed with later burial, producing a complex zone of brecciation. Te upper, suprastratal deformation section formed during the collapse of the karsted section.

Te overlying strata were generally lithifed, but the sag also afected concurrent sedimentation patterns (Hard-age et al., 1996b). Te deformation in the deformed su-prastratal zone consists of normal, reverse, and cylindrical faults and fractures (Loucks, 1999; McDonnell et al., in press). It is important to emphasize that large-scale structural features can develop above karsted zones and not be related to regional tectonic stresses.

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3000 ft

j

900 m

A REVIEw OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS AND ASSOCIATED SUPRASTRATAL DEFORMATION

(a)

(b)

fusse -EUenburger Marker

Collapsed-paleocave zones            -<----------»

(shown by missing reflections)            ~300 m

Fig. 12: 3-d seismic example over an Ellenburger paleocave system from benedum feld in West texas. (a) Second-order derivative map in the Fusselman interval displaying sag zones produced by Ellenburger paleocave collapse. (b) Seismic line showing missing sections (collapse in Ellenburger section), cylindrical faults, and sag structures. Suprastratal deformation is >1,000 f thick in this section. modifed from Loucks (1999) and reprinted by permission of the AAPG whose permission is required for further use.”

Coalesced, collapsed-paleocave systems and associated suprastratal deformation are complex systems, and large-scale outcrops or datasets are necessary to defne them. However, with the model presented in this paper, individual data points can lead to recognition that the system is a coalesced, collapsed-paleocave feature.

TIME in KARST – 2007 129

ROBERT G. LOUCKS

(a)

N

\

1500 m

(b)

|Sag|

Top Üiddo-i-

Forestburg^i

lop Ellenburger ^~

200 m ^—^ - * 7. '-ml

Fig. 13: Suprastratal deformation sag features in post-Lower Ordovician Ellenburger strata in Fort Worth basin in north texas. (a) Curvature map at mississippian Forestburg Limestone horizon displaying sag features and faults produced by collapse in the Ellenburger interval. From mcdonnell et al. (in press). (b) 3d seismic line at 1:1 scale showing sag features produced by paleocave collapse in the Ellenburger section. Line-of-section location is shown by dashed line in Fig. 13a.

ACKNOwLEDGEMENTS

I would like to express my appreciation to Angela McDonnell for reviewing this manuscript. Lana Deiterich edited the text. Published with the permission of the Di-

rector, Bureau of Economic Geology, John A. and Kath-erine G. Jackson School of Geosciences, Te University of Texas at Austin.

130 TIME in KARST – 2007

A REVIEw OF COALESCED, COLLAPSED-PALEOCAVE SySTEMS AND ASSOCIATED SUPRASTRATAL DEFORMATION

REFERENCES

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Combs, D. M., R. G. Loucks, & S. C. Ruppel, 2003: Lower Ordovician Ellenburger Group collapsed paleocave facies and associated pore network in the Barnhart feld, Texas.- in T. J. Hunt & P. H. Lufolm, Te Permian Basin: back to basics: west Texas Geological Society Fall Symposium: west Texas Geological Society Publication No. 03-112, 397-418.

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Hammes, Ursula, F. J. Lucia, & Charles Kerans, 1996: Reservoir heterogeneity in karst-related reservoirs: Lower Ordovician Ellenburger Group, west Texas.-in E. L. Stoudt, ed., Precambrian-Devonian geology of the Franklin Mountains, west Texas—analogs for exploration and production in Ordovician and Silurian karsted reservoirs in the Permian Basin: west Texas Geological Society, Publication No. 96-100, 99-117.

Hardage, B. A., D. L. Carr, D. E. Lancaster, J. L. Simmons Jr., R. y. Elphick, V. M. Pendleton, & R. A. Johns, 1996a: 3-D seismic evidence of the efects of carbonate karst collapse on overlying clastic stratigraphy and reservoir compartmentalization.- Geophysics, 61, 1336-1350.

Hardage, B. A., D. L. Carr, D. E. Lancaster, J. L. Simmons, Jr., D. S. Hamilton, R. y. Elphick, K. L. Oliver, & R. A. Johns, 1996b: 3-D seismic imaging and seismic attribute analysis of genetic sequences deposited in low-accommodation conditions.- Geophysics, 61, 1351-1362.

Kerans, Charles, 1988: Karst-controlled reservoir heterogeneity in Ellenburger Group carbonates of west Texas.- reply: American Association of Petroleum Geologists Bulletin, 72, p. 1160-1183.

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Loucks, R. G., 1999: Paleocave carbonate reservoirs: origins, burial-depth modifcations, spatial complexity, and reservoir implications.- American Association of Petroleum Geologists Bulletin, 83, 1795-1834.

Loucks, R. G., 2001: Modern analogs for paleocave-sedi-ment flls and their importance in identifying paleo-cave reservoirs.- Gulf Coast Association of Geological Societies Transactions, 46, 195-206.

Loucks, R. G., 2003: Understanding the development of breccias and fractures in Ordovician carbonate reservoirs.- in T. J. Hunt & P. H. Lufolm, Te Permian Basin: back to basics: west Texas Geological Society Fall Symposium: west Texas Geological Society Publication No. 03-112, 231-252.

Loucks, R. G. & J. H. Anderson, 1980: Depositional fa-cies and porosity development in Lower Ordovician Ellenburger dolomite, Puckett Field, Pecos County, Texas.- in R. B. Halley & R. G. Loucks, eds., Carbonate reservoir rocks: SEPM Core workshop No. 1, 1-31.

Loucks, R. G. & J. H. Anderson: 1985, Depositional fa-cies, diagenetic terrains, and porosity development in Lower Ordovician Ellenburger Dolomite, Puckett Field, west Texas.- in P. O. Roehl & P. w. Choquette, eds., Carbonate petroleum reservoirs: Springer-Verlag, 19-38.

Loucks, R. G. & R. H. Handford, 1992: Origin and recognition of fractures, breccias, and sediment flls in paleocave-reservoir networks.- in M. P. Candelaria & C. L. Reed, eds., Paleokarst, karst related diagenesis and reservoir development: examples from Or-dovician-Devonian age strata of west Texas and the Mid-Continent: Permian Basin Section SEPM Publication No. 92-33, 31-44.

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Loucks, R. G. & P. Mescher, 2001: Paleocave facies clas-sifcation and associated pore types.- American Association of Petroleum Geologists, Southwest Section, Annual Meeting, Dallas, Texas, March 11-13, CD-ROM, p.18.

Loucks, R. G., P. Mescher, & G. A. McMechan, 2000: Architecture of a coalesced, collapsed-paleocave system in the Lower Ordovician Ellenburger Group, Dean word quarry, Marble Falls, Texas.- Final report prepared for the Gas Research Institute, GRI-00/0122, CD-ROM.

Loucks, R. G., P. Mescher, & G. A. McMechan, 2004: Tree-dimensional architecture of a coalesced, col-lapsed-paleocave system in the Lower Ordovician Ellenburger Group, Central Texas.- American Association of Petroleum Geologists Bulletin, 88, 545-564.

Lucia, F. J., 1968: Sedimentation and paleogeography of the El Paso Group.- in w. J. Stewart, ed., Delaware basin exploration: west Texas Geological Society Guidebook No. 68-55, 61-75.

Lucia, F. J., 1995: Lower Paleozoic cavern development, collapse, and dolomitization, Franklin Mountains, El Paso, Texas.- in D. A. Budd, A. H. Saller, and P. M. Harris, eds., Unconformities and porosity in carbonate strata: American Association of Petroleum Geologists Memoir 63, 279-300.

Lucia, F. J., 1996: Structural and fracture implications of Franklin Mountains collapse brecciation.- in E. L. Stoudt, ed., Precambrian-Devonian geology of the Franklin Mountains, west Texas-Analogs for exploration and production in Ordovician and Silurian karsted reservoirs in the Permian basin: west Texas Geological Society 1996 Annual Field Trip Guidebook, wTGS Publication No. 96-100, 117-123.

Lucia, F. J., Charles Kerans, & G. w. Vander Stoep, 1992: Characterization of a karsted, high-energy, ramp-margin carbonate reservoir: Taylor-Link west San Andres Unit, Pecos County, Texas.- Te University of Texas at Austin, Bureau of Economic Geology Report of Investigations No. 208, p. 46.

Mazzullo, S. J. & G. V. Chilingarian, 1996: Hydrocarbon reservoirs in karsted carbonate rocks.- in G. V. Chil-ingarian, S. J. Mazzullo, & H. H. Rieke, eds., Carbonate reservoir characterization: a geologic-engineering analysis, Part II: Elsevier, 797-685.

McDonnell, A., R.G. Loucks, & T. Dooley, (in press): quantifying the origin and geometry of circular sag structures in northern Fort worth Basin, Texas: paleocave collapse, pull-apart fault systems or hydrothermal alteration?.- American Association of Petroleum Geologists Bulletin.

McMechan, G. A., R. G. Loucks, P. A. Mescher, & xia-oxian Zeng, 2002: Characterization of a coalesced, collapsed paleocave reservoir analog using GPR and well-core data.- Geophysics, 67, 1148-1158.

McMechan, G. A., R. G. Loucks, x. Zeng, & P. A., Me-scher, 1998: Ground penetrating radar imaging of a collapsed paleocave system in the Ellenburger dolomite, Central Texas.- Journal of Applied Geophysics, 39, 1-10.

Orchard, R. J., 1975: Prediction of the magnitude of surface movements.- in Proceedings, European Congress on Ground Movement, 39-46.

Palmer, A. N., 1991: Origin and morphology of limestone caves.- Geological Society of America Bulletin, 103, 1-21.

white, w. B., 1988: Geomorphology and hydrology of karst terrains.- Oxford University Press, New york, p. 464.

wilson, J. L., R. L. Medlock, R. D. Fritz, K. L. Canter, & R. G. Geesaman, 1992: A review of Cambro-Orodovi-cian breccias in North America.- in M. P. Candelaria & C. L. Reed, eds., Paleokarst, karst related diagenesis and reservoir development: examples from Or-dovician-Devonian age strata of west Texas and the Mid-Continent: Permian Basin Section SEPM Publication No. 92-33, 19-29.

wittaker, B. N. & D. J. Reddish, 1989: Subsidence; Occurrence, Prediction and Control: Elsevier, Development in Geotechnical Engineering, No. 56, p.528.

wright, V. P. , M. Esteban, & P. L. Smart, eds., 1991: Pal-aeokarst and palaeokarstic reservoirs: Postgraduate Research for Sedimentology, University, PRIS Contribution No. 152, p.158.

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NAJSTAREJŠE JAME NA SVETU: KAKO SO SE OHRANILE IN KAJ NAM LAHKO POVEDO?

R. Armstrong L. OSBORNE1

Abstract                                                    UDC 551.44(091)

R. Armstrong L. Osborne: Te world’s oldest caves: - how did they survive and what can they tell us?

Parts of an open cave system we can walk around in today are more than three hundred million years old. Common sense tells even enthusiasts like me that open caves this old should not still exist, but they do! Teir survival can be partly explained by extremely slow rates of surface lowering, but this is not sufcient by itself. Isolation by burial and relative vertical displacement by faults are probably also required. Now one very old set of caves have been found, are there more of them? what can they tell us? Key words: speleology, oldest cave, survival of old caves.

Izvleček                                                   UDK 551.44(091)

R.A.L. Osborne: Najstarejše jame na svetu: kako so se ohranile in kaj nam lahko povedo?

Deli odprtega jamskega sistema, po katerem se lahko danes sprehajamo, so stari več kot 300 milijonov let. Zdrav razum celo takemu navdušencu, kot sem jaz, pove, da tako stare odprte jame ne morejo obstajati, a vendar so! Da so se ohranile, je lahko deloma vzrok v izredno počasnem zniževanju površja, toda to samo po sebi ni dovolj. Jama je morala biti najbrž tudi zasuta in s tem odrezana od sveta, potreben pa je bil tudi relativen navpičen premik ob prelomih. Zaenkrat je bil najden en sam niz zelo starih jam, ali jih je morda še več? Kaj nam lahko povedo?

Ključne besede: speleologija, najstarejša jama, ohranitev starih jam.

INTRODUCTION

In June 2004, when I last spoke here at Postojna about dating ancient caves and karst I found it difcult to not to reveal the exciting discovery which this paper follows (see Osborne, 2005). My collaborators and I had been convinced since mid 2001 that sections of Jenolan Caves in eastern Australia had formed 340 million years ago. we had to ensure that our story was published and that we could convince others. Te issue was not whether the

dates themselves were correct, but did the evidence really mean that the caves containing the clays were of such a great age. Tis took four years of intensive work on the clays and additional dating.

Now afer the publication of the results (Osborne et al, 2006), and the following media interest; it seems appropriate to refect on the signifcance and implications of the survival of Early Carboniferous open caves.

1 R.A.L. Osborne, Faculty of Education and Social work, A35, University of Sydney, NSw 2006, Australia; e-mail: a.osborne@edfac.usyd.edu.au

Received/Prejeto: 27.11.2006

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R. ARMSTRONG L. OSBORNE

THE POTENTIAL FOR CAVES/SECTIONS OF CAVE

TO HAVE A GREAT AGE Despite many years of working on palaeokarst, I initially found the Early Carboniferous (340 Ma) K-Ar dates for unlithifed clays in Jenolan Caves incredible (Figure 1).

Fig. 1: Plastic illite–bearing clay, mustard yellow, in the River Cave, jenolan Caves, NSW Australia. Te < 2µm fraction of this clay was K-Ar dated by Osborne et al., (2006) at 357.30 ± 7.06 ma.

As I pointed out in 2004 (Osborne, 2005), some Permian landforms do survive relatively intact in Australia. Even a Late Carboniferous age would not have been too surprising, as a Late Carboniferous landsurface has been exhumed at Jenolan from below the overlying Permo-Trias-sic Sydney Basin.

An Early Carboniferous age seemed challenging for two main reasons:

1 Te 340 Ma age sits in the middle of the accepted timing for the last folding event in the area (350-330 Ma). Not only the caves, but also the relatively undeformed and well-lithifed caymanite deposits they intersected had to be younger than this event. Te clay dates upset

the accepted chronology for the area and suggested that the last folding was older than previously thought. 2 Te 340 Ma age is older than the accepted emplacement age for the adjacent Carboniferous granites (320 Ma). Te plateau surface adjacent to the caves intersects granite plutons. why didn’t the process that exposed the plutons wipe out the ancient caves?

My opponents believed that while other landforms in Australia were old, the caves were not. Tey argued that there was no demonstrably old sediment in the caves. I have already discussed this argument elsewhere (Osborne, 1993a, 2002, 2005). Te Early Carboniferous clays from Jenolan are the frst evidence for ancient sediments in Australian caves accessible to humans, but they make the problem of the survival of ancient caves even more difcult, because they are so very old.

If we think about the geological history of karstif-cation at Jenolan then the formation of caves in the Carboniferous should not be surprising. Te best dates for the Jenolan Caves Limestone put it in the Latest Silurian (Pridoli, 410-414 Ma)(Pickett, 1982).

As well as telling us about the 340 Ma event, the KAr clay dating indicated that the limestone underwent a pre-tectonic period of cave development in the Early Devonian before 390 Ma when the caves were flled with the unconformably overlying volcaniclastics. Tere was also a post-tectonic period of ancient speleogenesis before a marine transgression flled the second generation of caves with lime-mud and crinoidal debris. I suspect if we had announced a third-phase of lithifed palaeokarst some 340 million years old at Jenolan, there would have been little reaction, although the problem of its survival and the problem with the timing of folding would have been the same as the problems with our relict sediments. It would not be surprising for limestone anywhere in the world to have undergone speleogenesis some 70 Ma afer its deposition. Te development of a modern cave in Late Cretaceous limestone is hardly unusual.

So, what is the problem? I suspect that while geo-morphologists think surface lowering will destroy old caves, many geologists expect that:

1  open caves fail relatively quickly by breakdown (by analogy with mines and quarries)

2  palaeokarst caves only survive because they are flled with rock; the rock supports the roof preventing destruction due to breakdown.

3  cave sediments become lithifed quickly, so old unlithi-fed relic sediments cannot exist

Tese ideas are refuted by the fndings of palaeo-karst workers, surface cavers and the oil industry so I will not expand on them here, rather I will concentrate on geomorphological challenges to the survival of 340 million year old caves.

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HOw COULD THEy SURVIVE?

wHy CAVES MAy SURVIVE LONGER THAN SURFACE LANDFORMS Landforms are always under threat from the processes of weathering, incision and surface lowering. weathering in the normal sense of the word is irrelevant in karst since, except in the case of Nadja’s incomplete solution (Zupan-Hajna, 2003), carbonate weathering results in almost total removal of the rock mass. Incision may re-activate or expose ancient caves, but will rarely afect enough of the rock mass to lead to the destruction of ancient caves. It is surface lowering that is the greatest threat to ancient caves and the main process that leads to their late stage modifcation into unroofed caves. what processes may protect caves from surface lowering?

Protection by the rock mass

Since caves form below the surface, there is a thickness of rock between them and the zone where surface lowering is progressively removing the surface of the Earth. Tis means that caves have a head start in survival compared with surface landforms of the same age. Caves unroofed at the surface are always substantially older than the surface in which they are exposed.

Isolation and “karst resistance”

Not a lot happens once a cave space enters the vadose zone, there may be breakdown or speleothem deposition, but many cave openings just sit there, inactive while the water is directed through active conduits at a lower level.

Te “god” that protects cave walls

Apart from speleothem and lithifed sediments that may outlive all of the cave they formed in (Figure 2), it is the walls of a cave that survive the longest, right up to the very last stage of an unroofed cave (Figure 3).

why don’t the cave walls fail and simply fall into the void beside them and why don’t they allow the whole cave to fll with speleothem during its siesta in the vadose zone? Some process must protect cave walls from failure and penetration by potentially lethal vadose fow. I am indebted to Andrej Mihevc for the concept of a ‘”god” that protects cave walls’. I am sure this god is a useful addition to the karst panoply.

Tree factors are probably important for the survival of cave walls, particularly in teleogenic karsts: -

•  rock strength

•  Slow and gentle cave excavation, leading to gradual stress release (caves are not mines or tunnels)

•  Degassing and precipitation from seeping water makes cave walls self-sealing

Fig. 2: Speleothem, exposed on surface above dip Cave, Wee jasper, NSW, Australia. Cave entrance can be seen top of photo. Tis speleothem has outlived all of the cave it formed in.

Some cave walls do fail for a variety of reasons. we can observe this in many breakdown chambers and it is possible to recognise the sources of the weakness in the walls that resulted in their failure.

Lack of substantial entrances

Some caves, e.g. cryptokarst caves of thermal /hydrother-mal origin, may have no entrances or very poor connection to the surface. If there is no entrance or surface connection then surface processes cannot get in and modify the cave.

Entrance Blockages

It is very easy for cave entrances to become blocked. Pro-grading entrance facies talus cones reaching the ceiling, talus from the surface or breakdown, growth of fow-stone masses, logs, vegetation and biogenic deposits such as guano piles can all easily block cave entrances. with a small amount of vadose cementation, these blockages can become efectively permanent and the cave can become isolated.

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Fig. 3: Looking towards the surviving cave wall from the foor of an Carso, Italy.

Protection by flling

If a cave is flled with easily removed material, it is possible for the cave to remain “fossilized” for a geologically signifcant time and then become exhumed. If the fll is impermeable to vadose seepage, it will not become cemented. Even if it is cemented, if the fll contains minerals that are unstable when exposed to oxygen-rich vadose water it can be removed from the cave with little efect on the enclosing walls.

Protection by cover/burial

Cover by sediments, volcaniclastics or lava fows can protect not only the caves, but also surface karst land-forms. For the process to be efective, the cover must be removed without a great efect on the underlying older karst. It helps if the cover consists of relatively weak rock or of rock that is easily weathered. An outstanding example of this process is the burial by Permian basalt and later exhumation of the Shinlin karst in southern China.

DENUDATION RATES Both biblical prophets and geomorphological pioneers predicted a fat future, the “rough places a plain” of Isaiah 40:4 and the peneplanation of w. M. Davis. while peneplanation may be out of favour, surface lowering is a real phenomenon. Te problem for survival of old caves is that even with the slowest rates of surface lowering most Mesozoic and all Palaeozoic caves should have been destroyed, except those that have been deeply buried and later exhumed following tectonic movements.

In some parts of Australia, extremely low denudation rates apply. wilford (1991) reported rates as low as 0.5 metres per million years in the Ofcer Basin of western Australia over the last hundred million years.

unroofed cave, trieste

Surface lowering rates in the eastern Australian highlands, where Jenolan Caves are located, are said to range between 1-10 metres per million years (Bishop 1998). If this is so, then the limestone exposed at the surface today in these areas was between 65 and 650 metres below the surface at the end of the Meso-zoic. while these rates are slow by world standards, they are not slow enough to account for the survival of extremely old features.

Surface lowering and early incision may be slower than we think

Studies of past erosion rates in the Shoalhaven Catchment in eastern Australia by Nott et al., (1996) show that we must approach incision and

denudation with some care. Teir relevant fndings are

that:

• summit lowering and scarp retreat were insignifcant when compared to the process of gorge extension

•  the rate of summit lowering was 250 times less and the rate of scarp retreat was 15 times less than the rate of headward advancement of gorges

•  stream incision in the plateau upstream of the erosion head is very slow compared to the rate of gorge extension

•  there was “insignifcant lowering of the interfuves throughout the Cainozoic” (Nott et al., 1996, p 230)

•  “Over the long term, the highlands…will become considerably more dissected well before they decrease substantially in height or are narrowed” (Nott et al., 1996, p 224)

Te stream incision rate is important when we consider the age of relict caves. If incision rates early in the history of the landscape are much slower than at later stages, present incision rates will lead us to seriously underestimate the age of relict caves located high in the sides of valleys.

If lowering of interfuves, i.e. surface lowering, is much slower than incision, scarp retreat and nick-point recession then plateau karst, high level caves and surface caves exposed on hilltops could be very much older than we have previously thought. In dissected terrains the caves will not just be as old as the hills, but considerably older.

TECTONIC PROCESSES ARE NECESSARy FOR

ExTREME SURVIVAL

Low denudation rates, low relief and low rainfall, the

Australian trifecta, can only go so far to preserve old

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landforms. Stephen Gale recognised this point: “Although low rates of denudation are an important factor in ensuring the survival of ancient landscapes, this alone is inadequate as an explanation of the maintenance of landforms over ten and even hundreds of millions of years” (Gale, 1992, p 337). Gale went on to discuss how denudation needed to be localized if old landsurfaces were to survive. One way the landsurface can be isolated from surface lowering is through the relative adjustment of adjacent blocks by faulting.

Te Fault-Block Shufe

Te problem at Jenolan is the elevation of the old caves relative to the adjacent plateau surface. Te plateau surface to the south of Jenolan Caves exposes and intersects post-tectonic Carboniferous granites, thought to be 320 million years old. Figure 4 is a cartoon drawn to explain in simple terms how the caves may have survived.

Te caves must have been relatively close to the surface when the cupolas formed and the volcanic ash that formed our old clays entered them (Step 1 in Figure 4).

Fig. 4: Cartoon of postulated events at jenolan Caves to explain the survival of caves with Carboniferous clays

1  Cave excavated by thermal processes following folding of limestone

2  volcano erupts; tephra falls to ground and enters caves.

3  Fine tephra begins to fll caves and reacts with water in caves to produce clay minerals. Tese clays have been dated at 340 million years.

4  volcano stops and begins to be eroded. Te caves are full of clay. Granite intrudes the rock near the caves (? 320 ma).

5  Te rock mass containing the granite moves up along the fault, while the rock mass containing the caves moves down.

6  Late Carboniferous: At least 8 kilometres thickness of rock is eroded away, probably partly by glaciation. Tis cuts of the top of the granite and brings the cave back close to the surface.

7  Late mesozoic: valleys erode into the surface and a new stream cave forms below the level of the flled cave. Te clays, still sof, are undermined. Tey fall down and are carried way by the stream.

8  today: Almost all of the 340 million year old clay has now been removed from the caves, small remnants are found and dated.

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R. ARMSTRONG L. OSBORNE

Even if the granites did form close to the surface, something between hundreds of metres and a few kilometres of rock must have been removed from the plateau surface to expose the granite. Tis amount of surface lowering should have removed any older caves, particularly those shallow enough to fll with surface-derived sediment.

For the caves to survive there must have been a relative change in elevation between the mass of rock intruded by the granite and the mass of rock hosting the caves (Step 5 in Figure 4) before signifcant regional denudation took place.

For the sake of simplicity and because the history is not well understood, several steps have been lef out

when speaking here in 2004 (Osborne, 2005) I suggested a number of characteristics of localities where one might expect to fnd very old caves, interestingly Jenolan has only some of these. So how might we recognize “funny old caves” and ancient cave sediments?

“ABNORMAL CAVES” AND “ABNORMAL” SECTIONS OF “NORMAL” CAVES My work on palaeokarst in caves and on non-fuvial cave morphology frequently takes me to caves that others regard as unusual. Te Carboniferous clays from Jenolan are found in cupolas and other non-fuvial sections of the caves. Interestingly, these same sections of cave also intersect caymanite palaeokarst.

Fieldwork on non-fuvial morphology in Europe during 2005 took me to Belianska Cave in Slovakia and Račiška pečina in Slovenia. Co-incidentally, (or not) these are the same localities where Pavel Bosak and co-workers have found the oldest relict cave sediments in Europe (see Bella et al., 2005 & Bosák et al., 2005).

Non-fuvial caves, the per ascensum caves of Ford (1995), are characterised by being isolated from or poorly integrated with the modern hydrological system. Some have no natural entrances, while others have poor connection or secondary breakdown entrances. Tis gives them a head start in the survival stakes when compared with fuvial caves. Generally odd caves may survive longer than normal ones.

THE OLDEST CAVES ARE NOT ALwAyS AT THE TOP when I frst discovered the caymanite deposits in Jenolan Caves in the 1980s, I could not understand why they were intersected by cave passages at low levels in the limestone mass, not by (older) high-level passages. I did not realize

in Figure 4 between Step 6 and Step 7. In the Late Carboniferous, the upper sections of the present valleys were incised and fuvial caves formed. Tese flled with gla-ciofuvial sediment and the whole landscape was buried under the Sydney Basin.

In the late Mesozoic, the Sydney Basin was stripped back and the valleys re-juvenated. New fuvial caves formed below the level of the old flled ones (Step 7 in Figure 4). Underhand stoping has now removed most of the old clay and only tiny remnants of clay remain in the caves.

then that while level in the landscape is a good indicator of the age of fuvial caves, it has little to do with the age

Fig. 5: Palaeokarst sandstone flling spar-lined tube intersected by more recent cave in the entrance area of Lucas Cave, jenolan Caves, NSW, Australia. Te strongly cemented sandstone is younger than the plastic clay shown in Figure 1.

wHERE ARE THE OTHER OLD CAVES?

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of non-fuvial caves. In fuvial caves you look to the top for the old sections of cave, but in non-fuvial caves, you must look high and low.

RECOGNISING OLD SEDIMENTS How can we recognise very old relict sediments in caves? Te old clays at Jenolan were not found by looking for old material, we were originally looking for unusual minerals. Te clays that looked diferent contained larger than normal amounts of illite and so we were able to date them. Afer the frst old date, samples were chosen strategically, to get the maximum amount of chronological information from the minimum number of samples. Tis was only possible because there were existing pal-aeokarst and cave morphology stratigraphies to test (Os-borne, 1999).

GEOLOGICAL HISTORy OF THE CAVES During the 1980s and 1990s, the aim of my research on palaeokarst was to show that speleogenesis and karstif-cation in eastern Australia had a geological history (Os-borne 1984, 1986, 1991b, 1993 a & b, 1995, 1999). Tat is, palaeokarst deposits intersected by “modern” accessible (open) caves indicate repeated periods of cave development at the same locality over periods of hundreds of millions of years. Cavities flled with strongly lithifed palaeokarst deposits represented the older periods of cave development.

Te discovery of 340 million year old clays in open accessible caves at Jenolan (Osborne et al., 2006) demonstrated something signifcantly diferent. Te open caves themselves, not just cavernous karsts, can have developmental histories extending over geologically signifcant periods of time (i.e. hundreds of million years).

Not much happens during the life of an old cave; they just snooze like an old pet cat. Sometimes dramatic events above, below or beside the cave may wake it from its slumber and leave their mark for us to fnd in the future.

GEOLOGICAL HISTORy FROM THE CAVES Much has been said about the potential of the strati-graphic, geomorphic and climatic record in caves. Even the most generous previous estimates for the age of caves (not palaeokarst) suggested that such evidence would be limited largely to the younger end of the Cainozoic, and might perhaps in places like eastern Australia with old landscapes extend to the late Mesozoic. Te survival of Palaeozoic open caves presents a new vista of using caves

Unconsolidated Relict Sediments May Be Older than Lithifed Palaeokarst Deposits

In my last presentation here, I raised the idea of the lithi-fcation trap: the idea that strongly lithifed cave deposits and palaeokarsts may be younger than some unconsoli-dated or uncemented cave sediments (Osborne, 1995). Tis makes sense if we think about fowstone growing over mud and recognise that cementation, rather than compaction is the main agent of lithifcation in caves. Above ground geologists ofen fnd this idea conceptually challenging.

At Jenolan Caves, a crystal-lined cave passage is flled with strongly cemented sandstone (Figure 5). we have no problem with the sandstone being younger than the crystal, but stratigraphy suggests that this sandstone is younger than the unconsolidated clay shown in Figure 1.

as a source of geological information. Both ancient caves and palaeokarst deposits could contain records of “missing sequences” for which there is no other record. while there has been signifcant progress in reading the ancient record of palaeokarst, lack of suitable dating techniques and a lack of expectation make geological history from the caves an open and uncultivated feld.

Evidence for Global Events

Cave sediment research, particularly in the UK and Australia, began with a focus on a geological problem of global signifcance. Today we call it the Pleistocene extinction. Te protagonists at the time saw it in terms of the “deluge” and the extinction or not of “antediluvian” faunas (see Osborne 1991a). Caves were an obvious focus for this research as Pleistocene vertebrate fossils occur in great abundance in the red earths of caves throughout the globe.

If the surface of some interfuves dates back to the Mesozoic, then ancient caves have the potential to contain evidence of the K-T boundary. what signal should we expect to fnd in the caves from the K-T event and how would we recognise it? Commentators have suggested that the K-T event involved dramatic changes in the pH of meteoric water, with strongly acidic rain falling from the sky. If this were sustained it should have lef an imprint of extreme surface karstifcation and enhanced vadose and fuvial speleogenesis. Given how efectively caves have trapped Pleistocene loess, we might also expect to fnd iridium-rich silt in caves that were open at the K-T boundary. I don’t know if anyone has looked, but perhaps they should.

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Caymanites & unknown transgressions

Lazlo Korpas has been able to make great progress in understanding the evolution of the karst of Hungary by dating caymanites, because these contain fossils and they correlate with magnetostratigraphy (Korpas, 1998, Korpas et al., 1999). Caymanites provide very useful evidence for marine transgressions (Korpas, 2002).

Caves intersect caymanites in at least six karst areas in eastern Australia. None of the caymanites have been directly dated. Te 340 Ma old caves at Jenolan intersect caymanites, indicating a minimum age. Te eastern Australian caymanites indicate one or more marine transgressions, probably in the Early Carboniferous for which there is no other geological evidence.

Volcaniclastic cave sediments/palaeokarst

Given the close physical relationship between stratovol-canoes and carbonate terrains in island arcs and active margins, volcaniclastic cave sediments and palaeokarst deposits should be common in both modern and ancient island arcs and active margins. Tere seems, however, to

we still know very little about extremely ancient caves. Tere are good prospects for making new geological discoveries in very old caves. All we have to do is identify funny old sediments in funny old caves, ascertain their meaning and fnd ways to date them. Tis sounds easy, but it is not.

Te Jenolan team consisted of a karst geologist, a dating guru (essential so there is no argument about the technical aspects of the dates) and two mineralogists. It

be scant reference to such deposits in the literature. Perhaps this is due to the concentration of karstological effort on Tethyan karsts.

Volcaniclastic cave sediments and palaeokarst deposits should be expected to occur around the Pacifc rim, particularly in volcanically active island arcs e.g. Indonesia, Philippines, Malaysia, Japan, New Zealand and in southern Europe (Mts Etna and Vesuvius). Tey should also be expected where I work in the early Palaeozoic island arc environments of the Tasman Fold Belt of eastern Australia. while andesitic and silicic stratovolca-noes are likely to be the most common sources of tephra for volcaniclastic deposits in caves and karst depressions, basaltic tephra can also fll caves.

Five volcaniclastic palaeokarsts and volcaniclastic relict sediment deposits, including the 340 million year old clays, have now been recognised in eastern Australia (Table 1). It seems likely that more will be recognised, given that many of the cavernous Palaeozoic limestones are overlain by volcaniclastics.

took six frustrating years and a sponsor with deep pockets to get the work completed and published.

A new world of geology of and from ancient caves awaits those with a stout heart, a thick skin, a good sponsor and eyes for caves and sediments that don’t seem quite right; something like the qualifcations for Antarctic explorers.

tab. 1: volcaniclastic Palaeokarst and Relict Cave Sediments in eastern Australia

Type

Likely Age

Karst Area

Chemistry

Reference

Pk

? Tertiary

Crawney Pass

Basaltic

observed by author

Pk

Mid Devonian

Jenolan

Silicic

Osborne et al. 2006

R

Early Carboniferous

Jenolan

Silicic

Osborne et al. 2006

Pk

Mid Devonian

Wombeyan

Silicic

Osborne, 1993

Pk

?

Wellington

Silicic

Osborne in prep

Pk = palaeokarst

R= relict cave sediment

SPECULATION

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ACKNOwLEDGEMENTS

Tis paper was presented at the Time in Karst symposium at the Karst Research Institute, Postojna, Slovenia in March 2007. Te University of Sydney Overseas Travel Grant Scheme and Top-Up funding for the Faculty of Education and Social work supported attendance at the symposium. Tis paper arises from the dating of clays at Jenolan Caves (Osborne et al., 2006). Many thanks are due to my co-workers, Horst Zwingmann, Ross Pogson and David Colchester.

Final corrections to the Jenolan Clay paper were made in Europe in the second half of 2005. I wish to

thank colleagues in the Czech Republic, Hungary, Slovakia and Slovenia for their assistance and support. work on Belianska Cave with Pavel Bella, Peter Gazik, Jozef Psotka and Stanislav Pavlarčik assisted in developing the ideas presented here. Other inspiration came when Karel Žác showed me the caves of the Bohemian Karst and Lazlo Korpas showed me his caymanite sequences and well-dated unconsolidated old sediment. Andrej Mihevc engaged in lively discussions about surface lowering, the “god that protects cave walls” and the origins and survival of Račiška pečina. Penney Osborne read the drafs.

REFERENCES

Bella, P., P. Bosák, P. , J. Glazek, D. Hercman, T. Kiciniska, & S. Pavlarcik., 2005: Te antiquity of the famous Belianska Cave (Slovakia). Abstracts, 40th International Speleological Congress, Athens-Kalamos 21-28 August 2005: 144-145.

Bishop, P. , 1998: Te eastern highlands of Australia: the evolution of an intraplate highland belt. Progress in Physical Geography 12, 159-182.

Bosák, P. , P. Pruner, A. Mihevc, N. Zupan-Hajna, I. Hora-cek, J. Kadlec, O. Man, & P. Schnabl., 2005: Palaeo-magnetic and palaeontological research in Račiška pečina Cave, Sw Slovenia. Abstracts, 40th International Speleological Congress, Athens-Kalamos 21-28 August 2005: 204.

Ford, D.C., 1995: Paleokarst as a target for modern karst-ifcation. Carbonates and Evaporites 10, 2, 138-147.

Gale, S.J., 1992: Long-term landscape evolution on Australia. Earth Surface Processes and Landforms,17, 323-343.

Korpas, L., 1998: Palaeokarst Studies in hungary. Geological Institute of Hungary, Budapest.

Korpas, L., 2002: Are the palaeokarst systems marine in origin? Caymanites in geological past, pp.415-424, in F. Gabrovšek [ed.] Evolution of Karst: From Prek-arst to Cessation, Založba ZRC, Ljubljana.

Korpas, L., M. Lantos, & A. Nagymarosy., 1999: Timing and genesis of early marine caymanites in the hydrothermal palaeokarst system of Buda Hills, Hungary. Sedimentary Geology 123, 9-29.

Nott, J., R. young, & I. McDougall., 1996: wearing down, wearing back and gorge extension in the long-term denudation of a highland mass: quantitative evidence from the Shoalhaven catchment, southeast Australia. journal of Geology 104, 224-232.

Osborne, R.A.L., 1984: Multiple karstifcation in the Lachlan Fold Belt in New South wales: Reconnaissance evidence. journal and Proceedings of the Royal Society of New South Wales 107, 15-34.

Osborne, R.A.L., 1986: Cave and landscape chronology at Timor Caves, New South wales. journal and Proceedings of the Royal Society of New South Wales 119, 1/2, 55-76.

Osborne, R.A.L., 1991a: Red earth and bones: Te history of cave sediment studies in New South wales, Australia. journal of Earth Sciences history 10, 1, 13-28.

Osborne, R.A.L., 1991b: Palaeokarst deposits at Jenolan Caves, N.S.w. journal and Proceedings of the Royal Society of New South Wales 123, 3/4, 59-73.

Osborne, R.A.L., 1993a: A new history of cave development at Bungonia, N.S.w. Australian Geographer 24,1, 62-74.

Osborne, R.A.L., 1993b: Te history of karstifcation at wombeyan Caves, New South wales, Australia, as revealed by palaeokarst deposits. Cave Science 20, 1, 1-8.

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Osborne, R.A.L., 1995: Evidence for two phases of Late Palaeozoic karstifcation, cave development and sediment flling in southeastern Australia. Cave and Karst Science 22, 1, 39-44.

Osborne, R.A.L., 1999: Te origin of Jenolan Caves: Elements of a new synthesis and framework chronology. Proceedings of the Linnean Society of New South Wales 121, 1-26.

Osborne, R.A.L., 2002: Paleokarst: Cessation and Rebirth?, pp. 97-114. In F. Gabrovšek [ed.], Evolution of karst: from prekarst to cessation, Založba ZRC, Ljubljana. p. 97-114.

Osborne, R.A.L., 2005: Dating ancient caves and related palaeokarst. Acta carsologica 34, 1, 51-72.

Osborne, R.A.L., H. Zwingmann, R. E. Pogson, & D.M. Colchester., 2006: Carboniferous Cave Deposits from Jenolan Caves, New South wales, Australia. Australian journal of Earth Sciences 53, 3, 377-405.

Pickett, J., 1982: Te Silurian System in New South wales. bulletin of the Geological Survey of New South Wales 29, 1-264

wilford, G.E. 1991: Exposure of land surfaces, drainage age and erosion rates, pp. 93-107. In C.D. Ollier [ed.], Ancient Landforms. Belhaven, London.

Zupan-Hajna, N., 2003: Incomplete Solution: Weathering Of Cave Walls And Te Production, transport And deposition Of Carbonate Fines, Založba ZRC, Ljubljana. p. 167.

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KLASTIČNI SEDIMENTI V JAMAH – NEPOPOLNI ZAPIS

KRAŠKIH PROCESOV

Ira D. SASOwSKy1

Abstract                                                 UDC 552.517:551.7

Ira D. Sasowsky: Clastic sediments in caves – imperfect recorders of processes in karst

Clastic sediments have played an important role in deciphering geologic history and processes since the inception of the discipline. Early studies of caves applied stratigraphic principles to karst deposits. Te majority of cave deposits are breakdown and alluvium. Te alluvial materials have been successfully investigated to determine ages of caves, landscape evolution, paleoen-vironmental conditions, and paleobiota. Rapid stage changes and the possibility of pipe-full fow make cave deposits diferent than surface deposits. Tis and other factors present difculties with interpreting the cave record, but extended preservation is aforded by the “roofng” of deposits. Dating by magnetism or isotopes has been successful in many locations. Caves can be expected to persist for 10 Ma in a single erosive cycle; most cave sediments should be no older than this.

Key words: clastic sediments, paleoclimate, sedimentology, stratigraphy, dating.

Izvleček                                                  UDK 552.517:551.7

Ira D. Sasowsky Klastični sedimenti v jamah – nepopolni zapis kraških procesov

Že od nekdaj so klastični sedimenti pomembno orodje pri razbiranju geološke zgodovine. V zgodnjih študijah so uporabili načela stratigrafje tudi pri raziskovanju jamskih sedimentov . Glavnino jamskih sedimentov sestavljajo podori in aluvij. Raziskave aluvija so se uspešno izkazale pri dataciji jam, določanju razvoja površja, paleookolja in paleontologije. Zaradi možnega tlačnega toka in hitrih sprememb stanj, so jamski sedimenti drugačni od površinskih. To, poleg ostalih dejavnikov, predstavlja težave pri interpretaciji zapisov, ki jih hranijo jame. Po drugi strani pa je obstojnost jamskih sedimentov daljša zaradi zavetja, ki jim ga nudi jama. Po vsem svetu poznamo številne uspešne datacije jamskih sedimentov z magnetizmom ali izotopi. Jame znotraj erozijskega cikla vzdržijo do10 milijonov let, zato naj jamski sedimenti ne bi bili znatno starejši. Ključne besede: klastični sedimenti, paleoklima, sedimen-tologija, stratigrafja, datiranje.

INTRODUCTION

Geology is undeniably a science of history, and since the earliest practice of the discipline, that history has been revealed in clastic sedimentary deposits. william Smith, for example, created maps of the sedimentary rocks in England in the late 1700’s, and established a relative chronology of their deposition using stratigraphic position and fossils. It has been natural, therefore, that karst scientists examine clastic deposits in caves, in order to explore

geologic time. In doing so, they are in large part applying the same principles and techniques developed by classical stratigraphers. An early example of this was a study by Kukla and Ložek (1958) examining the processes of cave sediment deposition and preservation. In the present day, work such as that by Granger et al. (2001) and Polyak et. al. (1998) builds upon those classical techniques and applies laboratory methods to develop absolute chronolo-

1 Ofce for Terrestrial Records of Environmental Change, Department of Geology and Environmental Science, University of Akron, Akron, OH 44325-4101, USA.

Received/Prejeto: 24.01.2007

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gies. Tese chronologies in turn have allowed insight to such processes as river incision, water-table lowering, and landscape/climate linkages.

Tis paper is a brief evaluation of clastic sediments as they apply to deciphering historical processes and events

MATERIALS A

Te processes that result in clastic sedimentation in caves are quite varied. Reviews and details including classif-cation of deposits are presented in several texts (white, 1988; Ford and williams, 1989; Sasowsky and Mylroie, 2004). A perspective is given here.

A useful broad-level classifcation is genetic, and based upon whether the clastic material originated within the cave (autogenic) or was carried in from the surface (allogenic). Te former class is mainly bedrock breakdown (incasion), but encompasses fne grained sediments sourced from insoluble residue during phre-atic enlargement, collapse of secondary mineralization (speleothems), and so forth. Allogenic sediments include alluvium, windblown material, animal feces, fossil matter, till, etc.

In practice, the most commonly occurring materials by far are bedrock breakdown and alluvium. Consequently, autogenic cave sediments are mainly limestone. Allogenic sediments are usually resistant siliciclastics, because carbonates do not typically persist in the fuvial environment.

Tere is no satisfying overall term for the clastic deposits found in caves. Te word “soil” has been applied to the fne grained deposits, but this is a misnomer by most defnitions, and is not recommended. Cave fll and cave earth have also been used. Regolith seems applicable in spirit, but, because this material does not strictly “….form(s) the surface of the land ....” (Jackson, 1997) some may object to such usage.

BREAKDOwN

Te collapse of cave bedrock walls and ceilings results in material that is angular, and ranges in size from sand to boulders. It is possible many times to visually ft larger blocks to their point of origin on the adjacent cave walls and ceilings. Te process of breakdown is not a common occurrence on human timescales. Only a few cases of present-day natural failure have been documented. For example, in Mammoth Cave, Kentucky only one large collapse was noted in 189 years of mining and tourism (May et al., 2005). However, on geologic timescales, the proc-

in karst terrane. Advantages and problems of working with these unique deposits are presented. For purposes of this paper, the “age” of a given cave sediment refers to the time of deposition of the material in the cave.

D PROCESSES

ess is pervasive and evident in most caves. Failures occur along existing planes of weakness (joints, faults, bedding planes). Causes of collapse can include removal of underlying support (particularly loss of buoyancy caused by the transition from phreatic to vadose conditions), removal of overlying arch support, cryoclastism (wedging by ice), and secondary mineral wedging (white and white, 2003). Triggering by earthquakes has also been observed, for example in Sistem Zeleške Jame-Karlovica (personal communication, F. Drole). Davies (1951) published an early analysis of expected collapse parameters in the cave environment. Tis was expanded on by white (1988, p. 232) to evaluate stability of ceilings relative to limestone bed thickness. Greater spans can be maintained by thicker beds. Jameson (1991) provides a comprehensive overview and classifcation of breakdown.

Breakdown is frequently most prolifc at 1) the intersections of cave passages, presumably due to the greater span lengths present at such points, and 2) where the cave is close to the surface, due to lack of thinning of the span and resulting decreased competency. In evaluations of causes for passage terminations (white, 1960) it was noted that many cave passages ended in breakdown blockage (referred to by explorers as “terminal breakdown”).

Although pervasive, breakdown has not found sig-nifcant utility for deciphering earth history in karst ter-ranes.

ALLUVIUM

Alluvium enters caves by sinking stream, and occasionally by colluvial mechanisms. Te transport processes are for the most part similar to those in surface channels. Te full range of sediment sizes are seen, structures such as cross-bedding and pebble imbrications develop, and cut-and-fll stratigraphy is possible. However, there are two important diferences exhibited for stream fow in caves when compared to most surface channels. First, channel width is severely constrained by bedrock walls. Tis promotes rapid stage increase during fooding, akin to that of slot canyons in surface streams (Fig. 1). Second,

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Fig. 1: Subterranean stream channels are typically narrow, and have no foodplain (a). Tis leads to rapid stage changes. Similar conditions in the surface environment are only seen in slot canyons such as the virgin River, Utah, USA (b).

because the channel is roofed over, it is possible to have confned (pipe-full) rather than open channel fow. Taken in conjunction, the results of these two conditions are the likelihood of high fow velocities, and the possibility of upwards phreatic fow. A striking example of rapid

stage change is seen in Hölloch, Switzerland, where rises of 250 m in a single food have been recorded (wildberger and Preiswerk, 1997; Jeannin, 2001). Cases of phreatic lifs are seen in many cave systems. In Castleguard Cave (Rocky Mountains, Canada) a seasonally active lif of 9 m is observed (Schroeder and Ford, 1983). In that situation well-rounded cobbles are accumulated at the base, where they reside until communition reduces them suf-ciently to allow transport up the lif tube.

Te composition of the alluvium refects the source of the material, as well as some other factors. It is interesting to note that a high proportion of clay sized material found in cave alluvium is actually fne-grained silica, not a clay mineral (white, 1988). Te residuum found on the surface of many karst terranes frequently contains high amounts of clay and chert. Te clay results from insoluble residues of the weathered limestone. Te chert behaves in a very persistent way, being found throughout cave passages.

INFORMATION REVEALED

In the investigation of clastic sedimentary deposits, either cave related or not, answers are sought to such questions as: How old? what was the paleoenvironment? what was the fow direction? what organisms were present? Tese in turn allow an understanding of geologic history, environments of deposition, past climates, and potential for sedimentary deposits to act as mineral and fuel reservoirs.

In the case of cave studies, it is primarily the frst question which has been addressed. Caves can only be numerically dated by the deposits that they hold, and this age is usually reported as a minimum value. Alluvial materials are considered superior to speleothems in this undertaking, because they are emplaced much earlier in the existence of the cave. Once a date has been obtained, subsequent inferences such as rates of river incision, denudation, and so forth, can then be made based upon the relation of the cave to the landscape. Dating has been accomplished by radiocarbon, magnetism, and cosmo-genic isotopes.

Paleoenvironmental information is revealed through studies of sedimentary structures and sequences, as well as via analyses of clay mineralogy and environmental magnetism. Paleohydrology can be deduced using traditional stratigraphic indicators such as cross-bedding, pebble imbrication, etc. Fossil deposits of organisms are actually rather rare within caves – most cave depsits are barren of these materials. Signifcant deposits are known, though, and many excavations made in caves (particularly in the entrance facies) serve as irreplaceable records of terrestrial fauna.

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LIMITS ON TIMESCALE

Caves are erosional landforms, which have a limited period of existence. Excluding those caves which have been subjected to burial, this places a practical limit on their duration as potential recorders of nearby processes. In any case, the cave sediments can be no older than the cave they are emplaced in (Sasowsky, 1998). Terefore, the ultimate limit on preservation of sediments within a cave is the persistence (lifetime) of the cave in the environment.

In most limestone terranes epigenetic processes occur, with dissolution taking place both at the surface (forming pavements, dolines, etc.) and in the subsurface (forming caves). As base level lowers, denudation of the upland surfaces is also occurring and uppermost caves are eventually breached and destroyed. In certain settings examples of various states of decay can be seen in the landscape, and the sedimentary flls of breached (unroofed) caves may even be observed (e.g. Šušteršič, 2004). In settings such as the Appalachian Valley and Ridge, hundreds of meters of carbonate have been denuded from anticlinal valleys (white, 1988), and one may imagine extensive systems of caves which have been obliterated with no remaining trace.

Bounds on the expected lifetime of an epigene cave may be evaluated by considering the two main control-

Fig. 2: Teoretical persistence of caves in an erosional environment. Te length of time that a given cave will exist depends upon the initial depth of formation (position on y-axis) and the denudation rate (slope of line). Gray regions envelope a range of reasonable denudation pathways for two examples. In case A, a cave formed at 200 m depth, the expected lifetime is 2.5 to 10 ma. For a cave formed at 100 m depth (case b), the lifetime is reduced to 1.25 to 5 ma. Solid sloping lines are the average denudation rate, 69 m/ma, for 33 major drainage basins (calculated from data in Summerfeld and hulton, 1994).

ling factors: initial depth of formation and rate of land surface lowering (denudation, Fig. 2). Although caves may form at any depth, a practical limit of 300 m is reasonable, and the majority of caves are much shallower (Milanovic, 1981). Note that this “depth” is not correlative to the frequently reported mapped depth of caves, which refers to the maximum vertical extent of survey. In the context of the present evaluation, depth is the position below surface (thickness of overlying rock) at a given point in the cave. Denudation rates can be quite variable, and tend to correlate with rainfall (white, 1988, p. 218). Envelopes of expected cave persistence can be constructed (Fig. 2) using these 2 parameters. Based upon this calculation, epigene caves would usually exist in the erosive environment for up to 10 Ma.

In practice, dating has not yet resulted in identifca-tion of caves this old within the present erosional cycle. Paleomagnetic dating has been used back to 4.4 Ma (Cave of the winds, Colorado, USA; Luiszer, 1994). Cosmogen-ic isotope dating has documented cave sediments as old as 5.7 (±1.1) Ma (Bone Cave, Tennessee, USA; Anthony and Granger, 2004). Te absence of older values may be a consequence of limitations of dating methods, or refect the relative dearth of older caves in the environment, or both. Te challenges of paleomagnetic dating include absence of fne-grained sediments, lack of uninterrupted sedimentation, and uncertainties of correlation with the global magnetic polarity scale. Cos-mogenic dating is constrained by the absence of quartzose sediments, uncertainties in parent isotope values, and the cost/efort of analyses.

If consideration is extended beyond the present erosional cycle, flled and buried caves (paleokarst) are found in the rock record. Such materials have been recognized in many places, and the flls described in some detail (e.g. Loucks, 1999). Interest has been strong in the context of exploration for minerals or petroleum. Tese deposits also represent a potential trove of information on far past hydrologic and environmental conditions because of their capacity to preserve.

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RESOLUTION, CONTINUITy, AND VERACITy

Stratigraphers have traditionally examined marine or paralic sediments because of their resolution, continuity, and veracity. Compared to terrestrial deposits, marine/ paralic strata are much more laterally and vertically extensive, they are of economic interest, and they potentially function as continuous recorders for long periods of time. Terrestrial deposits are of interest though, particularly because they contain information about the on-continent setting. within the terrestrial environment lacustrine deposits and fuvial terraces have seen the greatest attention as recorders of Cenozoic paleo-conditions. Lakes probably represent the highest quality records in the terrestrial environment – their environment many times is one of high preservation potential. Lacustrine deposits can be sampled by coring; duplication of cores can serve as a quality control; accumulation rates can be rapid; sediment properties are well tied to local environmental conditions; and spatial variability is usually well understood. Terraces tend to preserve a partial record of

the fuvial environment, depending upon regional uplif or down-cutting of the stream.

In comparison, most caves contain spatially irregular deposits that can be afected by factors such as plugging of swallets, extreme fow events, and back-fooding. Hydrologic complexity is common (Bosák et al., 2003), even more so than surface fuvial environments. Analysis of the paleohydrology of the depositional setting through cave passage morphometry is usually necessary, and may be quite time consuming if detailed maps are not available. Stratigraphic sections may be discontinuous, and require compilation. Caves are difcult sampling locations, due to logistics, remoteness, lack of light, and constraints on sampling equipment transport.

Nevertheless, the cave environment is one that provides some advantages in recording the history of a region. Te greatest advantage is that of potential preservation. Because caves are “roofed over” deposits are likely to be protected (at least on intermediate time scales), from

Fig. 3: Comparison of sedimentary records from Lake baikal, Russia (3 columns on lef), and Cave of the Winds, USA (3 columns on right). baikal data used with permission from King and Peck, 2001. Cave of the Winds data used with permission from Luiszer, 1994.

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IRA D. SASOwSKy

Fig. 4: Episodic inflling and removal of sediments is commonly observed in caves. In this section of Windy mouth Cave (West virginia, USA) a diamict was almost completely removed afer being covered with fowstone. Te conduit is presently dry.

surfcial erosion. Tis is particularly germane for the fu-vial deposits. weathering and erosion of surface fuvial terraces is commonplace. In the cave, such materials may sit undisturbed for years. For example, in xanadu Cave, Tennessee, USA, a pristine, non-indurated fuvial deposit that is greater than 780 ka was sampled (Sasowsky, et al.,

1995). Although rare, in exceptional settings the quality of the cave record may approach that of lakes (Fig. 3). Conditions amenable to this are stable recharge confguration, diffuse recharge, minimal variation of discharge, and deep circulation. In Figure 3 two exceptional records are compared. Te Lake Baikal record was constructed from cores taken on watercraf. In that setting, about 40 m of sediment accumulate in 1 Ma. In contrast, at Cave of the winds the accumulation rate is slower by more than an order or magnitude.

In many settings caves appear to undergo episodic flling and excavation (Fig. 4). In certain cases this may be locally controlled by catastrophic storms (e.g. Doehring and Vierbuchen 1971). However, the presence of broadly similar deposits/incisions within many caves in a region supports the idea that cave clastic materials refect regional paleoclimatic conditions. Tese deposits hold much information that will be revealed with continued advances in conceptual frameworks and improved laboratory methods.

REFERENCES

Anthony, D.M. & D.E. Granger, 2004: A Late Tertiary origin for multilevel caves along the western escarpment of the Cumberland Plateau, Tennessee and Kentucky, established by cosmogenic 26Al and 10Be. - Journal of Cave and Karst Studies, v. 66, no. 2, p. 46-55.

Bosák , P. , P. Pruner, & J. Kadlec, 2003: Magnetostratigra-phy of cave sediments: Application and limits. - Studia Geophysica et Geodaetica, v. 47, p. 301-330.

Davies, w. E., 1951: Mechanics of cavern breakdown. -National Speleological Society Bulletin, v. 13, p. 36-43.

Doehring, D.O. & R.C. Vierbuchen, 1971: Cave Development during a catastrophic storm in the Great Valley of Virginia. - Science, v. 174, no. 4016, p. 1327-1329.

Ford, D.C. & P. w. williams, 1989: Karst geomorphology and hydrology. - Unwin Hyman, London, 601 p.

Granger, D.E., D. Fabel, D. & A.N. Palmer, 2001: Pliocene–Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmo-genic 26Al and 10Be in Mammoth Cave sediments. - Geological Society of America Bulletin, v. 113; no. 7, p. 825-836.

Jackson, J.A. (ed.), 1997: Glossary of geology. - 4th ed., American Geological Institute, Falls Church, Virginia, 769 p.

Jameson, R.A., 1991: Concept and classifcation of cave breakdown: An analysis of patterns of collapse in Friars Hole Cave System, west Virginia: - In, Kast-ning, E.H. and Kastning, K.M. (eds.), Appalachian Karst. - National Speleological Society, Huntsville, Alabama, USA, p. 35-44.

Jeannin, P.-y., 2001: Modeling fow in phreatic and epi-phreatic karst conduits in the Hölloch cave (Muo-tatal, Switzerland). - water Resources Research, v. 37, no. 2 , p. 191-200.

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King, J. & J. Peck, 2001: Use of paleomagnetism in studies of lake sediments: In: Last, w.M. & J.P. Smol, (eds.), Tracking environmental change using lake sediments” Volume 1: Basin analysis, coring and chronological techniques. - Kluwer Academic Publishers, Dordrecht, p. 371-389.

Kukla, J. & V. Ložek, 1958: K promlematice vyzkumu jeskynnich vyplni (To the problems of investigation of the cave deposits). - Českoslovensy Kras, v. 11, p. 19-83.

Loucks, R.G., 1999: Paleocave carbonate reservoirs: Origins, burial-depth modifcations, spatial complexity, and reservoir implications. - AAPG Bulletin, v. 83; no. 11; p. 1795-1834.

Luiszer, F. G., 1994: Speleogenesis of Cave of the winds, Manitou Springs, Colorado: In Sasowsky, I. D., and Palmer, M. V. (eds.) Breakthroughs in karst geomi-crobiology and redox geochemistry (Special Publication 1). - Charles Town, west Virginia, Karst waters Institute, p. 91-109.

May, M.T., K.w. Kuehn, C.G. Groves, C.G., & J. Meiman, 2005: Karst geomorphology and environmental concerns of the Mammoth Cave region, Kentucky. - American Institute of Professional Geologists 2005 Annual Meeting Guidebook, Lexington, Kentucky, 44 p.

Milanovic, P. T., 1981: Karst Hydrogeology (translated from the yugoslavian by J. J. Buhac). - water Resources Publications, Littleton, Colorado, 434 p.

Polyak, V.J., w.C. McIntosh, N. Güven, N., & P. Provencio, 1998: Age and origin of Carlsbad Cavern and related caves from 40Ar/39Ar of alunite. - Science, v. 279, no. 5358, p. 1919 - 1922

Sasowsky, I.D., 1998: Determining the age of what is not there. - Science, v. 279, no. 5358, p. 1874

Sasowsky, I. D. & J.w. Mylroie (eds.), 2004: Studies of cave sediments: Physical and chemical recorders of climate change. - Kluwer Academic/Plenum Publishers, New york, 329 p.

Sasowsky, I. D., w.B. white, & V.A. Schmidt, 1995: Determination of stream incision rate in the Appalachian Plateaus by using cave-sediment magnetostratigra-phy. - Geology, v. 23, no. 5, p. 415-418.

Schroeder, J. & D.C. Ford, 1983: Clastic sediments in Cas-tleguard Cave, Columbia icefelds, Canada. - Arctic and Alpine Research, v. 15, no. 4, p. 451-461.

Summerfeld, M. A., & N.J. Hulton, 1994: Natural controls of fuvial denudation rates in major world drainage basins. - Journal of Geophysical Research, v. 99(B7), p. 13,871–13,884.

Šušteršič, F., 2004: Cave sediments and denuded caverns in the Laški Ravnik, classical Karst of Slovenia: In: Sasowsky, I.D. and Mylroie, J.w. (eds.), Studies of cave sediments: Physical and chemical recorders of climate change. - Kluwer Academic/Plenum Publishers, New york, p. 123-134.

white, w. B., 1960: Termination of passages in Appalachian Caves as evidence for a shallow phreatic origin. - Bulletin of the National Speleological Society, v. 22, no. 1, p. 43-53.

white, w.B., 1988: Geomorphology and hydrology of karst terranes. - Oxford University Press, 464 p.

white, w.B. & E.L. white, 2003: Gypsum wedging and cavern breakdown: Studies in the Mammoth Cave System Kentucky. - Journal of Cave and Karst Studies, v. 65, no. 1, p. 43-52.

wildberger, A. & C. Preiswerk, 1997: Karst and caves of Switzerland. - SpeleoProjects, Basil, Switzerland, 208 p.

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ANALySIS OF LONG-TERM (1878-2004) MEAN ANNUAL DISCHARGES OF THE KARST SPRING FONTAINE DE VAUCLUSE

(FRANCE)

ANALIZA DOLGOČASOVNEGA (1878-2004) POVPREČNEGA LETNEGA PRETOKA KRAŠKEGA IZVIRA FONTAINE DE

VAUCLUSE (FRANCIJA)

Ognjen BONACCI1

Abstract                                                     UDC 556.36(44)

Ognjen Bonacci: Analysis of long-term (1878-2004) mean annual discharges of the karst spring Fontaine de Vaucluse (France)

Statistical analyses have been carried out on a long-term (1878-2004) series of mean annual discharges of the famous karst spring Fontaine de Vaucluse (France) and the mean annual rainfall in its catchment. Te Fontaine de Vaucluse is a typical ascending karst spring situated in the south-eastern region of France. Te spring has an average discharge of 23.3 m3/s. Te average annual rainfall is 1096 mm. Its catchment area covers 1130 km2. Using the rescaled adjusted partial sums (RAPS) method the existence of next fve statistically signifcant difer-ent sub-series was established: 1) 1878-1910: 2) 1911-1941; 3) 1942-1959: 4) 1960-1964; 5) 1965-2004. Te diferent spring discharge characteristics during this long period (1878-2004) can be caused by natural climatic variations, by anthropogenic infuences, and possibly by climate changes. At this moment it should be stressed that objective and scientifcally based reasons for diferent hydrological behaviour in fve time sub-periods could not be found.

Keywords: karst hydrology, mean annual discharges, annual catchment rainfall, karst spring, Fontaine de Vaucluse, France.

Izvleček                                                      UDK 556.36(44)

Ognjen Bonacci: Analiza dolgočasovnega (1878-2004) povprečnega letnega pretoka kraškega izvira Fontaine de Vaucluse (Francija)

V prispevku predstavim statistično analizo časovne vrste povprečnega letnega pretoka in letnih padavin v zaledju slavnega izvira Fontaine de Vaucluse v Franciji. Fontaine de Vaucluse je tipični kraški izvir pri katerem voda priteka iz velike globine. Nahaja se v jugovzhodni Franciji. Povprečni pretok izvira je 23,4 m3/s. Povprečna količina letnih padavin v zaledju, ki meri 1130 km2, je 1096 mm. Z uporabo metode umerjenih delnih vsot (RAPS) smo določili pet statistično pomembnih različnih podobdobij: 1) 1878-1910: 2) 1911-1941; 3) 1942-1959: 4) 1960-1964; 5) 1965-2004. Vzrokov za različne pretoke preko celotnega obdobja (1878-2004) je lahko več; npr. klimatske spremembe in antropogeni vplivi. V tem trenutku moramo poudariti, da objektivne znanstvene razlage za različne hidrološke značilnosti v petih podobdobjih še ne poznamo.

Ključne besede: hidrologija krasa, povprečni letni pretok, količina letnih padavin, kraških izvir, Fontaine de Vaucluse, Francija.

INTRODUCTION

Te Fontaine de Vaucluse represents one of the most      et al., 1992b). Te karst system of the Fontaine de Vauc-famous and most important karst springs on the Earth.      luse is characterised by an approximately 800 m unsatu-It is located in the south-eastern karst region of France      rated zone. Emblanch et al., (1998) and Emblanch et al., (Figure 1), about 30 km eastward of the town of Avignon.      (2003) stressed important role of this zone for the transIt represents the only fow exit from the 1500 m thick      formation of rainfall into runof. Te Fontaine de Vauc-karst aquifer of Lower Cretaceous limestone (Blavoux      luse karst spring catchment area is estimated to be 1130

1 Faculty of Civil Engineering and Architecture, University of Split, 21000 Split, Matice hrvatske 15, Croatia, E-mail: obonacci@ gradst.hr

Received/Prejeto: 27.11.2006

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OGNJEN BONACCI

km2 (Cognard-Plancq et al., 2006a; 2006b). Te average catchment altitude is 870 m a. s. l. Te average annual air temperature of the catchment is 9,6 °C.

Fig. 1: Location map of karst spring Fontaine de vaucluse.

Te Fontaine de Vaucluse is typical ascending karst spring (Michelot & Mudry 1985; Blavoux et al., 1991/1992; 1992a). Its limestone channel ranges in diameter from 8 to 30 m (Mudry & Puig, 1991). Te lowest

Te climate in the catchment is Mediterranean. Rainfall distribution over the year as well as over the large spring catchment is irregular. Intensive and signifcant rainfall events occurred during autumn and spring, while summer and winter are generally dry. Interannual fuctua-tions of rainfall on the catchment are very high.

In order to defne an historical homogeneous catchment rainfall database Cognard-Plancq et al., (2006b) used six rainfall gauging stations. Te mean elevation of these stations is 445 m a. s. l., while the mean elevation of the spring catchment is 870 m a. s. l. Transformation of the measured monthly rainfall to the altitude of 870 m a. s. l. was made. Te average annual catchment rainfall in the 1878-2004 period is 1096 mm, while the minimum and maximum observed values were 641 mm (1953) and 1740 mm (1977) respectively.

Data series with linear trend line of the annual rainfall on the Fontaine de Vaucluse catchment for the period 1878-2004 are presented in Figure 2. Te increasing

depth reached by diver was -308 m below the gauging station datum of 84.45 m a. s. l. Tis depth is still not at the bottom of the ascending karst channel.

Te maximum water level measured at the gauging station was 24.10 m above the datum, the minimum was a few centimetres below the datum. Te rate of the maximum discharge of the spring has never been precisely measured, but it is estimated that it cannot exceed 100 m3/s (Blavoux et al., 1991/1992; 1992a). Cognard-Plancq et al. (2006b) state that maximum spring discharge varies between 100 and 120 m3/s. Tis surmise identifes a karst spring with limited discharge capacity (Bonacci 2001). Te historical minimum discharge is 3.7 m3/s (Blavoux et al., 1991/1992).

Every karst aquifer has complex hydrodynamic behaviour. Te Fontaine de Vaucluse karst system responses to rainfall quite rapid in comparison with the large recharge area. Te peak of hydrograph occurred 24 to 72 hours afer the rainfall events. Te spring water level and discharge recessions are slow, which can be explained by the existence of a large storage capacity of the aquifer (Cognard-Plancq 2006b).

Te primary objective of the investigation was to defne sub-periods with diferent hydrological behaviour of the Fontaine de Vaucluse karst spring during 127 years period (1878-2004), analysing time series of mean annual spring discharges. It should be the frst step in explanation of this extremely important and interesting phenomenon.

trend of the catchment rainfall of 1.045 mm per year is not statistically signifcant but should not be neglected in further analyses.

Fig. 2: time data series of annual rainfall P at the Fontaine de vaucluse catchment with trend line for the period 1878-2004.

ANALySIS OF CATCHMENT ANNUAL RAINFALL TIME SERIES

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ANALISIS OF MEAN ANNUAL DISCHARGES TIME SERIES

Data series with linear trend line of the mean annual spring discharges q for the period 1878-2004 are presented in Figure 3. Te decreasing trend of the mean annual discharges of 0.0468 m3/s per year is not statistically signifcant. Te average annual catchment discharge in the 1878-2004 period was 23.3 m3/s, while the minimum and maximum observed values were 7.61 m3/s (1990) and 53.4 m3/s (1915) respectively.

Fig. 3: time data series of mean annual discharges Q at the Fontaine de vaucluse karst spring with trend line for the period 1878-2004.

It should be stressed that annual catchment rainfall during the same period has an increasing trend. In Figure 4 linear regression between the mean annual the Fontaine de Vaucluse discharges q and the Fontaine de Vaucluse catchment annual rainfall P is shown. Te linear correlation coefcient is only 0.713, which is relatively low. A special problem is that the regression line cut abscissa line at 222 mm of annual rainfall P, which is relatively low value. Explanation of so unusual rainfall-runof relationship can be found in fact that accuracy of discharges and rainfalls are not very high, and maybe

the value of catchment area of 1130 km2 is not precisely defned.

It should be stressed that determination of exact catchment area in karst is one of the greatest and very ofen unsolved problems. Tis may be the case with the catchment of the Fontaine de Vaucluse spring. Te weak relationship between runof and rainfall means that some others factors (probably: air temperature, groundwater level, interannual rainfall distribution, changes of catchment area during the time, preceding soil wetness, anthropological infuences, climate change etc) have infuence on it.

A time series analysis can detect and quantify trends and fuctuations in records. In this paper the Rescaled Adjusted Partial Sums (RAPS) method (Garbrecht & Fernandez 1994) was used for this purpose. A visualisation approach based on the RAPS overcomes small systematic changes in records and variability of the data values themselves. Te RAPS visualisation highlights trends, shifs, data clustering, irregular fuctuations, and periodicities in the record (Garbrecht & Fernandez 1994). It should be stressed that the RAPS method is not without shortcomings. Te values of RAPS are defned by equation:

t-l ^Y

where Y is sample mean; is standard deviation; n is number of values in the time series; (k=1, 2…,n) is counter limit of the current summation. Te plot of the RAPS versus time is the visualisation of the trends and fuctuations of yt.

Time data series of Rescaled Adjusted Partial Sums (RAPS) for mean annual spring discharges in the period 1878-2004 are given in Figure 5. Terefore, the total data

Fig. 4: Linear regression between the mean annual the Fontaine de vaucluse discharges Q and annual the Fontaine de vaucluse catchment rainfall P.

Fig. 5: time data series of the Rescaled Adjusted Partial Sums (RAPS) for mean annual discharges Q for the period 1878-2004 with designated next fve sub-periods: 1) 1878-1910; 2) 1911-1941; 3) 1942-1959; 4) 1960-1964; 5) 1965-2004.

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series was divided into next fve subsets: 1) 1878-1910; 2) 1911-1941; 3) 1942-1959; 4) 1960-1964; 5) 1965-2004. Cognard-Plancq et al., (2006a; 2006b) defned the same fve stationary sub-periods using diferent methodology. Five time data sub-series of the Fontaine de Vau-cluse karst spring mean annual discharges q with trend lines for fve defned sub-periods are shown in Figure 6. In order to investigate statistically signifcant diferences between the averages of fve time sub-series for q and P the t-test was used. Te neighbouring averages of discharges for all fve sub-series are statistically signifcant at

Fig. 6: Five time data sub-series of the Fontaine de vaucluse karst spring mean annual discharges Q with trend line for fve defned sub-periods.

Te rescaled adjusted partial sums (RAPS) method established existence of next fve statistical, and hydrologi-cal signifcant diferent time sub-series: 1) 1878-1910: 2) 1911-1941; 3) 1942-1959: 4) 1960-1964; 5) 1965-2004. Variations in the Fontaine de Vaucluse karst spring hy-drological regime during relatively short period of 127 years are very strong and cannot be neglected. Anthropogenic impacts are probably the main cause of such behaviour of the mean annual spring discharges time series analysed, but the natural pattern of drought and wet years is also possible. Land-use changes and overexploitation of surface water and groundwater at the spring catchment on hydrological regime of the Fontaine de Vaucluse spring certainly exists. Teir exact quantifcation during analysed period is extremely questionable due to missing of many parameters. Strict division of natural and anthropogenic infuences on the hydrological regime is hardly possible.

The significant changes of spring discharge characteristics during 127 years long period (1878-2004) can be caused by natural climatic variations,

Fig. 7: Linear regressions between mean annual discharges Q and annual catchment rainfall P defned for fve diferent sub-periods.

the 5 % and even more 1 %. At the same time the neighbouring sub-series averages of the catchment rainfall are not statistically signifcant.

Figure 7 shows fve linear regressions between mean annual discharges q and annual catchment rainfall P de-fned for fve diferent sub-periods. It can be seen that linear correlation coefcients for all sub-series, except for third (1942-1959) and fourth (1960-1964) ones are higher than the linear correlation coefcient for whole time series.

by anthropogenic influences, and possibly by climate changes. It is extremely hard, but at the same time extremely practically and theoretically important, to find correct and scientifically based explanation of this phenomenon.

Cognard-Plancq et al., (2006a) consider that rain-fall-runof data have shown the large impact of clima-tologic variations on the hydrogeological system. Tey conclude that the underground storage zone is an important infuence on karst spring outfow, which depends on rainfall amount over 2 or 3 previous years. Investigations made in this paper do not confrm this statement.

Correct answers on many questions dealing with changes in hydrological-hydrogeological regime of the Fontaine de Vaucluse karst spring cannot be done using only annual data. Some processes can be explained measuring and analysing climatologic, hydrologic, hydrogeo-logical and geochemical interactions in shorter as well as larger time increments. Te problem is that most of parameters required for these analyses were not monitored in the past.

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More accurate and precise delineation and defni-tion of the Fontaine de Vaucluse spring catchment should be done. It is possible that its catchment area changes as a function of groundwater level. Tis means that ground-water level measurements in deep piezometers should be organized across the catchment. Te second task which should be considered in further analyses is detailed analysis of infuence of rainfall distribution during the year on the spring runof. Tis can have very strong infuence on the relationship between rainfall and runof, especially in karst areas.

Te author thanks to Anne-Laure Cognard-Plancq and Christophe Emblanch from Laboratoire d’Hydrogéologie, Faculté des Sciences, Université d’Avignon et Pays de

Blavoux, B., Mudry, J. & Puig, J.-M., 1991/1992: Bilan, fonctionnement et protection du système karstique de la Fontaine de Vaucluse (sud-est de la France). Geodinamica Acta, 5 (3), 153-172., Paris.

Blavoux, B., Mudry, J. & Puig, J.-M., 1992a: Te karst system of the Fontaine de Vaucluse (Southeastern France). Environ. Geol. water. Sci., 19 (3), 215-225.

Blavoux, B., Mudry, J., & Puig, J.-M., 1992b: Role du con-texte geologique et climatique dans la genese et le fonctionnement du karst de Vaucluse (Sud-Est de la France). In: H Paine, w Back (eds.) Hydrogeology of Selected Karst Regions. IAH International Contributions to Hydrogeology, Vol. 13, 115-131.

Bonacci, O., 2001: Analysis of the maximum discharge of karst springs. Hydrogeol. J., 9, 328-338.

Cognard-Plancq, A.-L., Gévaudan, C. & Emblanch, C., 2006a: Apports conjoints de suivis climatologique et hydrochimique sur le rôle de fltre des aquifères karstiques dans l’étude de la problématique de changement climatique; Application au système de la Fontaine de Vaucluse. Proceedings of the 8th Conference on Limestone Hydrogeology. Neucha-tel, Sep. 21-23, 2006, 67-70.

It can be stated that main dilemmas about variations of mean annual discharges of the Fontaine de Vaucluse karst spring during 127 years long period have not been solved. Tey should be explained using number of different procedures and climatic as well as other indicators, and performing further detailed measurements and analyses. Te paper presents the need for interdisciplinary analyses incorporating several approaches and techniques. For the sustainable development and the protection of such valuable water resource it is very important to establish prerequisites for the defnition of a causes and consequences of its hydrological changes.

Vaucluse 84000 Avignon, 33 Rue Louis Pasteur, France, which kindly provide me with data analysed in this paper.

Cognard-Plancq, A.-L., Gévaudan, C., &, Emblanch, C., 2006b: Historical monthly rainfall-runof database on Fontaine de Vaucluse karst system: review and lessons. IIIéme Symposium International Sur le Karst „Groundwater in the Mediterranean Coun-tries“, Malaga, Spain. In: J J Duran, B Andreo, F y Carrasco (eds.) Karst, Cambio Climatico y Aguas Subterraneas. Publicaciones des Instituto Geological y Minero de Espana. Serie: Hidrogeologia y Aguas Subterrraneas, N°18: 465-475.

Emblanch, C., Puig, J. M., Zuppi, G. M., Mudry, J., & Bla-voux, B., 1998: Comportement particulier lors des montées de crues dans les aquifères karstiques, mise en évidence d’une double fracturation et/ou de circulation profonde: Example de la Fontaine de Vau-cluse. Ecologae Geol. Helv., 92: 251-257.

Emblanch, C., Zuppi, G. M., Mudry, J., Blavoux, B. & Batitot, C., 2003: Carbon 13 of TDIC to quantify the role of the unsaturated zone: Te example of the Vaucluse karst systems (Southeastern France). J. of Hydrol., 279 (1-4): 262-274.

ACKNOwLEDGEMENT

REFERENCE

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Garbrecht, J. & Fernandez, G. P. , 1994. Visualization of Mudry, J., Puig, J.-M., 1991: Le karst de la Fontaine de trends and fuctuations in climatic records. water             Vaucluse (Vaucluse, Alpes de Haute-Provence,

Resources Bulletin, 30 (2): 297-306.                                    Drôme). Karstologia, 18 (2): 29-38.

Michelot, C. & Mudry, J., 1985: Remarques sur les exu-toires de l’aquifère karstique de la Fontaine de Vau-cluse. Karstologia, 6(2): 11-14.

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TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

ČASOVNO USKLAJEVANJE RAZVOJA JAMSKIH PROSTOROV IN SEDIMENTACIJA V JAMI CAVE OF THE wINDS, MANITOU

SPRINGS, COLORADO, ZDA

Fred G. LUISZER1

Abstract                                       UDC 551.3:551.44:550.38

550.38:551.44 Fred G. Luiszer: Timing of Passage Development and Sedimentation at Cave of the Winds, Manitou Springs, Colorado, USA.

In this study the age of the onset of passage development and the timing of sedimentation in the cave passages at the Cave of the winds, Manitou Springs, Colorado are determined. Te amino acid rations of land snails located in nearby radiometri-cally dated alluvial terraces and an alluvial terrace geomorphi-cally associated with Cave of the winds were used to construct an aminostratigraphic record. Tis indicated that the terrace was ~ 2 Ma. Te age of the terrace and its geomorphic relation to the Cave of the winds was use to calibrate the magne-tostratigraphy of a 10 meter thick cave sediment sequence. Te results indicated that cave dissolution started ~4.5 Ma and cave clastic sedimentation stopped ~1.5 Ma.

Key words: Cave of the winds, Manitou Springs, magneto-stratigraphy, aminostratigraphy, land snails.

.Izvleček UDK 551.3:551.44:550.38

550.38:551.44 Fred G. Luiszer: Časovno usklajevanje razvoja jamskih prostorov in sedimentacija v jami Cave of the Winds, Manitou Springs, Colorado, ZDA

Članek se osredotoča na začetek razvoja jamskih prostorov in časovno sosledje sedimentacije v jami Cave of the winds, Manitou Springs, Kolorado. V bližini jame se nahajajo aluvialne terase, ki so bile datirane z radiometrično metodo. Z geomorfološko metodo so bile povezane z jamo Cave of the winds. V teh aluvialnih terasah so bili najdeni fosilni ostanki kopenskih polžev, na katerih so bile opravljene datacije z aminokislinami, ki so pokazale starost ~ 2 Ma let. Starost aluvialnih teras in njihova geomorfološka povezava z jamo Cave of the winds, sta služila kot izhodišče za natančnejšo časovno umestitev 10 metrov debele sekvence jamskih sedimentov, ki so bili magnetostratigrafsko opredeljeni. Raziskava je pokazala, da se je raztapljanje v jami pričelo pred ~4.5 Ma leti, medtem ko se je odlaganje klastičnih sedimentov prenehalo pred ~1.5 Ma let. Ključne besede: Cave of the winds, Manitou Springs, ZDA, magnetostratigrafja, aminostratigrafja, kopenski polži.

INTRODUCTION

Cave of the winds, which is 1.5 km north of Manitou Springs (Figure 1), is a solutional cave developed in the Ordovician Manitou Formation and Mississippian williams Canyon Formation. Commercialized soon afer its discovery in the1880s it has been visited by millions of visitors in the last 125 years. As part of an extensive study (Luiszer, 1997) of the speleogenesis of the cave the timing

of passage development and sedimentation needed to be determined. Te task of dating the age of caves has always been an enigma because dating something that has been removed is not possible. Sediments deposited in the cave passages, however, can be dated, which then can be used to estimate the timing of the onset of cave dissolution and when the local streams abandoned the cave.

1 University of Colorado, Boulder, Department of Geological Sciences, Campus Box 399, Boulder, CO 80302, USA. Received/Prejeto: 13.12.2006

TIME in KARST, POSTOJNA 2007, 157–171

FRED G. LUISZER

A specially constructed coring device was utilized to core several locations in the cave. Te natural remnant magnetization (NRM) of samples taken from the cores were use to construct a magnetostratigraphic record. Tis record by itself could not be used to date the age of the sediments because sedimentation in the cave stopped sometime in the past and part of the record was missing. An alluvial terrace, which overlies the Cave of the winds, is geomorphically related to the cave. Te age of the alluvial terrace, which had not been previously dated, can be used to determine the age of the youngest stream deposited sediments in the cave. An abundant number and variety of land snails were found when this alluvium was closely searched. Biostratigraphy could not be used to determine the age of the terrace because all of the snail species found were extant, however, the amino acid rations of the snails collected from this terrace and nearby radiometrically dated terraces were used to construct an aminostratigraphy that was used to date the alluvium. Once the age of the terrace was determined the age of the youngest magnetic chron of the magnetostratigraphic record could be assigned thus enabling the dating of cave dissolution and sedimentation.

FIELD AND LABOR

Amino Acid Dating

Snails were collected from outcrops of the Nussbaum Alluvium, and from younger radiometrically dated alluvia (Fig. 2) for the purpose of dating the Nussbaum Alluvium by means of amino-acid racemizatio.

Approximately 50 kg of sandy silt was collected at each site. To minimize sample contamination, washed plastic buckets and fresh plastic bags were used. Te samples were loaded into containers with a clean metal shovel and with minimal hand contact. In the lab, the samples were disaggregated by putting them in buckets flled with tap water and letting them soak overnight.

Te samples were then washed with tap water through 0.5-mm mesh scree. Following air drying, the mollusks were hand picked from the remaining matrix by means of a small paint brush dipped in tap water. Te mollusks were then identifed. Only shells that were free of sediment and discoloration were selected for further processing. Tese shells were washed at least fve times in distilled water while being sonically agitated. Te amino-acid ratios were determined on a high-performance liquid chromatograph (HPLC) at the Institute of Arctic and Alpine Research (University of Colorado, Boulder).

Colorado

oDenver

/

^/El Paso /^ County \^

(25)

Cave'.of the Winds j^24s-ö^—Colorado Springs

Manitou Springs

v25/

Fig. 1: Location of study area.

ORy PROCEDURES

Paleomagnetism

A coring device was used to sample the cave sediments at six cored holes in the Grand Concert Hall (Fig. 3). Te core samples were obtained by means of a coring device in which a hand-powered hydraulic cylinder drives a stainless-steel, knife-edged barrel down into the sediments. Up to 40 cm of sediment could be cored each trip into the hole without sediment distortion. Samples were also collected from hand-dug pits at Mummys Alcove and Sniders Hall (Fig. 3). Additionally, samples were collected from a vertical outcrop in Heavenly Hall (Fig. 3). Te pits and outcrops were sampled for paleomagnetic study by carving fat vertical surfaces and pushing plastic sampling cubes into the sediment at stratigraphic intervals ranging from 3.0 to 10.0 cm. Te samples were oriented by means of a Brunton compass.

Te core barrel and all pieces of drill rod that attached to the barrel were engraved with a vertical line so that the orientation of the core barrel could be measured with a Brunton compass within ±2°. A hand-operated hydraulic device was used to extract the sediment core from the barrels. As the core was extruded, a fxed thin wire sliced it in half, lengthwise. Plastic sampling cubes were then pushed into the sof sediment along the center line of the fat surface of the core half at regular intervals

158

TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

Figure 2. GEOLOGY MAP OF COLORADO SPRINGS AND MANITOU SPRINGS AREA

with locations of snail collection sites. Geology adapted from Trimble and Machette, (1979).

(EARLY PLEISTOCENE)

(CRETACEOUS)

TRIASSIC,

(precambian)

or amino acid

4 KILOMETERS

(generally ~5.0 cm). Te samples at Sniders Hall, Mum-mys Alcove, and Hole 1 were taken with 3.2 cm3 sampling cubes; all other samples were taken with 13.5 cm3 cubes. In the lab, the NRM (Natural Remanent Magnetization) of all samples was initially measured. Subsequently, the samples were subjected to alternating-feld (A. F.) demagnetization and remeasured. All samples were frst demagnetized at 10, and then at 15 millitesla (mT). Some samples at the bottom of Hole 5 that displayed aberrant inclinations and declinations were additionally demagnetized at felds up to 30 mT. All remanence measurements were made on a Schonstedt SSM 1A spinner magnetometer with a sensitivity of 1x10-4 A/m. Repeat measurements indicate an angular reproducibility of ~2° at an intensity of 1x10-6 A/m2.

Age Of Cave Passages

Because Cave of the winds is an erosional feature, its exact age cannot be determined. However, geologic and geomorphic features related to the cave can be used to bracket the age of incipient and major cave development. Solution breccia in the Manitou Formation indicate that there may have been some Middle Ordovician to Devonian cave development (Forster, 1977). Sediment-flled paleo-caves and paleo-sinkholes at Cave of the winds in-

dicate Devonian to Late Mississippian karst development (Hose & Esch, 1992). Subsequent Cenozoic dissolution along some of these paleokarst features has resulted in the formation of cave passage (Fish, 1988). Between the Pennsylvanian and Late Cretaceous, about 3000 m of sediments, which contain abundant shale beds, were deposited over the initial cave. Very little, if any, cave development could take place during this period of deep burial under the thick blanket of the nearly impervious rock.

Te Laramide Orogeny, beginning in the Late Cretaceous (~75 Ma, Mutschler et al., 1987), was associated with the uplif of the Rocky Mountains. Te up-lif, which included the Rampart Range and Pikes Peak, caused the activation of the Ute Pass and Rampart Range Faults (Morgan, 1950; Bianchi, 1967). In the Manitou Springs area, movement on the Ute Pass Fault resulted in the folding, jointing and minor faulting of the rocks (Hamil, 1965; Blanton, 1973). Te subsequent fow of corrosive water along the fractures related to the folding and faulting would produce most of the passages in Cave of the winds and nearby caves. Uplif during the early Laramide Orogeny increased the topographic relief in the Manitou Springs area, resulting in the initiation of erosion of the overlying sediments and also increased

TIME in KARST – 2007 159

jp

'. es

(LATE

jb

jlo

3s

2\

jrf

i

N

<p

N38

<Pr

FOUNTAIN FORMATION (PENNSYLVANIAN)

Pf

WCr

ypp

Xgnc

W104*SS

4 MILES

FRED G. LUISZER

Figure 3. Map Of Cave Of The Winds, Manitou Springs, Colorado showing locations of samplings sites.

Modified from Paul Burger, 1996

Snider Hall

Cliffhanger Entrance

Manitou Grand Cavern Entranc (Sealed)

' Passage below main cave (in red).

1 Passage above main cave (in red).

the local hydraulic head. Te erosion of some of the impervious shale along with the increased hydraulic head may have initiated some minor water fow through the joints and faults, causing incipient dissolution. However, in the frst 25 m. y. of the Laramide Orogeny, erosional stripping almost equaled uplif (Tweto, 1975) resulting in a subdued topography with a maximum elevation of about 1000 m (Epis and Chapin, 1975). It was unlikely, therefore, that a large hydraulic head existed--a necessary hydraulic head that would have had to be present to force through the rock the large volumes of water needed for development of a large cave system.

A Late Miocene-Early Pliocene alluvial deposit on the Rampart Range, 18 km northwest of Manitou Springs, indicates renewed Miocene-Pliocene uplif, which in some places was up to 3000 m (Epis and Chapin, 1975). At the same time, movement along the Ute Pass Fault caused redirection of Fountain Creek from its former position near the above-mentioned alluvial deposit to its present position (Scott, 1975). Valley entrenchment along the Ute Pass Fault by Fountain Creek, in conjunction with uplif, created the hydraulic head needed to drive the mineral springs, the mixing zone, and limestone dissolution (Luiszer, 1997). It is likely, therefore, that the age for the onset of major dissolution at Cave of the winds is probably Late Miocene-Early Pliocene (7 Ma to 4 Ma).

Age Of Cave Fill

Sedimentation in the cave appears to have been contemporaneous with passage development. Tere are a few problems in proving this chronology. One is the lack of datable materials in the sediments, such as fossils or volcanic ashes. Preliminary study of the sediments indicated that magnetic reversal stratigraphy (mag-netostratigraphy) might be useful in dating the sediments. Te use of this method, however, presents another problem: it requires that the polarity sequence be constrained by at least one independent date.

Te Nussbaum Alluvium, which crops out east of the cave and is ~20 m higher in elevation, is apparently related to coarse sediments present at the top of sediment sequences in Cave of the winds. If an age can be assigned to the Nussbaum Alluvium and the relationship of the Nussbaum Alluvium to the coarse sediments in the cave deciphered, then an independent date can be assigned to at least one polarity reversal in the cave. Te age of the Nussbaum Alluvium will be dealt with frst, because the age of the Nussbaum Alluvium is poorly constrained. Various authors have assigned that range from Late Pliocene to early Pleistocene (Scott, 1963; Soister, 1967; Scott, 1975). For the purpose of correlating the Nussbaum Allu-

Natural Entrance

Tunnel Entrance

160 TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

vium with a paleomagnetic reversal, a more accurate date of the Nussbaum Alluvium was needed. Tis problem was solved by aminostratigraphy.

Aminostratigraphy

Most amino acids exist as two forms: L- and D-isomers (Miller & Brigham-Grette, 1989). In a living organism, the amino acids are L-isomers. Afer the death of an organism, the amino acids racemize, which is the natural conversion of the L-isomers into D-isomers. Eventually the amino acids in the dead organism equilibrate to a 50/50 mixture of L- and D-isomers. Te amino acids used in the present study are D-alloisoleucine and L-isoleucine (A/I). Tese amino acids are somewhat more complex, because L-isoleucine actually changes to a different molecule, D-alloisoleucine. Tis reaction, similar to racemization, is called epimerization (Miller and Brigham-Grette, 1989).

Te rate at which this reaction takes place is a function of temperature. For example, if the burial-temperature history for a group of mollusks of diferent ages has been the same, the ratio of the two amino acids – alloiso-leucine and isoleucine (A/I) – in the mollusk shells can be used for relative dating and in some cases, absolute dating (Miller and Brigham-Grette, 1989). Because temperature controls the rate of racemization, the temperature history of buried fossils must be considered before using A/I to derive ages.

Solar insolation, fre, altitude, and climate can efect the burial temperature of fossils. Diurnal or seasonal solar heating of fossils buried at shallow depths may accelerate racemization and increase the apparent age of the samples (Goodfriend, 1987; Miller and Brigham-Grette, 1989). Terefore, samples should be obtained from depths that exceed 2 m (Miller and Brigham-Grette, 1989). During the intense heat associated with a fre, racemization can also be greatly accelerated. For example, charcoal, which has a 14C age of ~1500 years, found with snails at Manitou Cave suggests that the snails were exposed to a forest fre before being transported into the cave. If so, the A/I of the snails may be anomalously high for their age.

Te altitude of the collection site can also afect ra-cemization rates. For example, snails in this study were collected at altitudes between 1890 and 2195 m above sea level. Because of the normal adiabatic efect, the highest site averages about 1.7° C less than the lowest site. Another temperature variable is long-term climate change. For example, the Nussbaum Alluvium has probably been exposed to episodes of higher or lower temperatures for much longer periods of time than the younger alluvia. Because post-depositional thermal histories are impossible to ascertain, the burial temperature for all alluvia in this study are assumed to be the same.

Mollusks Results

In all, over 10,000 mollusks, which included one species of slug, one species of clam, and 24 species of snail, were identifed and counted. Te tabulated number for each species is the number of shells that could be iden-tifed. For example, the Louviers site had ~3,000 snails that could not be identifed because they were too small (juvenile) or broke. Because of the small weight of the individual snails (0.3 to 5.0 mg) in relation to the 30 mg necessary for testing, only abundant species that occurred at multiple sites could be used for the amino-acid study. Te species chosen for the Nussbaum (Black Canyon) were vallonia cyclophorella and Pupilla muscorum and from the Verdos, vallonia cyclophorella and Gastro-copta armifera (Table 1). All of the alloisoleucine and isoleucine (A/I) ratios of the snails along with laboratory identifcation numbers are tabulated in Table 2A. Table 2B contains the average and standard deviation of the A/I of selected snails from each site.

Discussion Of A-I Ratios

Te epimerization rates of the four species used in this study are very similar. Tis is indicated in Table 2A by the comparable A/I values of diferent snail species at the same sample location. Moreover, shell size did not appear to greatly afect the A/I. For example, the average Gastro-copta armifera shell weighs 5 mg; the vallonia cyclophore-lla 1 mg; yet, the A/I for these shells from Manitou Cave are similar (Table 2A).

Te snails from the Verdos Alluvium, which include the Starlight, Fillmore, and Colorado City sites (Locations on Fig. 2), were used to test the A/I reproducibility of samples from one site and to compare the A/I from the diferent sites. Extra efort was put into assuring that the amino acid ratios of snails from Verdos Alluvium were as accurate as possible, because any errors in their A/I determination would greatly amplify the inaccuracies of the extrapolated age of the Nussbaum Alluvium (Fig. 4). Terefore, the Starlight site was sampled three times and the Fillmore site, twice. Although each of the two sub-sites at Colorado City were sampled twice, the scarcity of val-lonia cyclophorella and Gastrocopta armifera necessitated combining all snail shells of similar species from the entire site and from both sampling trips. One Starlight-site sample (Table 2A, Lab # AAL-5768) was excluded from the fnal curve ftting because it had an anomalously high ratio as compared to the others from that site. Te snails that made up this sample (AAL-5768) may have been from an older reworked alluvium or there may have been a problem with their preparation or analysis.

Te data from the Colorado City site were also excluded from the fnal curve ftting, primarily because the A/I of the two species were very diferent from each other

TIME in KARST – 2007

161

FRED G. LUISZER

1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0

Black Canyon

Starlight

and Filmore

HIGH A/I CURVE FIT Age = 1064.2y2 + 782.3y - 11.2

AVERAGE A/I CURVE FIT Age = 1268.6y2 + 863.8y - 10.0

LOW A/I CURVE FIT Age = 2002.4y2 + 782.0y - 4.2

0

500

1000

1500

2000

2500

AGE (ka) Figure 4. The A/I of snails from the Starlight and Filmore (Verdos Alluvium), Chesnut (Louviers Alluvium), Centennial (Piney Creek), and Modern Flood Plain sites are used for curve fitting. The diamonds represent the curve fit of the average A/I. The circles and squares represent the curve fits of +/- one standard deviation of the A/I. The A/I of the snails from the Black Canyon site with the appropriate equations are used to extrapolate the age of the Nussbaum Alluvium (1.9+0.4/-0.2 Ma).

and both A/I were much lower than those from the Starlight and Fillmore sites. Teir low A/I would indicate that the Colorado City site may actually be either the Slocum or Louviers Alluvium. Te anomalously low ratios, of course, could also be the result of contamination from modern shells or organic material.

Determination of anomalously high or low ratios would be impossible without multiple sampling. Taking one sample per site would have been useless for this study. Two samples per site was acceptable when the A/I ratios were about the same for both species. with 12 samples from the Verdos Alluvium, it was quite appropriate to discard the highest and lowest ratios.

Age Of Te Alluvia

Te higher A/I of the snails from Black Canyon site, which is mapped as Nussbaum Alluvium, indicates that it is older than the other alluvia (Table 2A). Furthermore, by ascertaining the ages of the younger alluvia, plotting those against their relative A/I ratio, and ftting a curve to the resultant plot, a equation can be derived that can be used to calculate the approximate age of the Nussbaum Alluvium.

Snails from the modern food plain (Fig. 2) were used to ascertain the A/I ratio of modern snails. About 50% of the snails at this site were alive when collected.

Te live snails were not analyzed because the fesh, which may have diferent amino-acid ratios than the shells, might have contaminated the shell A/I ratios. Empty shells were used for analysis and assumed to be about one year old. Tere is a possibility that the modern shells were reworked from older sediments such as the Piney Creek Alluvium. However, the abundant live snails mixed with the dead snails of the same species suggests that all snail specimens were contemporaneous.

Te Piney Creek Alluvium site (Fig. 2) has been mapped as Piney Creek and Post-Piney Creek (Trimble and Machette, 1979). Charcoal collected from the Piney Creek site (location on Fig. 2) was 14C dated at 1542 ± 130 years old (Table 3) indicating that the site should be mapped as Post-Piney Creek Alluvium. Te snails collected at Manitou Cave, which have relatively high A/I ratios, were initially thought to be about the same age as dated deposits at Narrows Cave. Narrows Cave is located ~0.4 km north of Manitou Cave contains food deposits intercalated with fowstone that has been dated and found to have a maximum uranium-thorium age of 32 ± 2 Ka (Table 3). Tey were thought to be the same age because the snails at Manitou Cave and the deposits at were both deposited by paleo-foods and both had similar heights above williams Canyon Creek. However, charcoal associated with the snails in Manitou Cave was 14C dated with an age of 1552 ± 75 years (Table 3). Apparently, either young charcoal mixed with old snails during the paleo-food or the snails were afected by a forest fre that induced anomalously high A/I ratios. Tis conficting evidence made it necessary to exclude the Manitou Cave data from the curve ftting.

Te Louviers Alluvium site was mapped by Trimble and Machette (1979). Elsewhere in Colorado the Louviers has been dated at 115 Ka by Machette (1975). Szabo (1980) gave a minimum age of 102 Ka and inferred that the maximum age was ~150 Ka. Te Fill-more, Colorado City, and Starlight sites are all mapped as Verdos Alluvium (Trimble and Machette, 1979), which, in the Denver area, contains the 640-Ka Lava Creek B ash near its base (Sawyer et. al., 1995; Izett et. al., 1989; Machette, 1975). Because the Lava Creek B ash gives the maximum age for the Verdos Alluvium,

162 TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

tab. 1: Species identifed, their location, and amount of shells counted.

Modern Flood Plain

Centennial

Manitou Cave

Chesnut

Filmore (Verdos)

Starlight ( Verdos)

Colorado City

Black

Canyon

(Nussbaum)

East ( Verdos)

West (Verdos)

Carychium exiguum (Say)

8

3

105

35

18

5

Cionella lubrica (Muller)

20

3

1

0

2

1

Columella alticola (ingersoll)

4

0

1

0

Derocerus spp.

1

0

4

1

Discus whitneyi

4

1

4

0

Euconulus fulvus (Muller)

16

2

20

2

2

1

Fossaria parva (Lea)

19

2

3

1

8

3

10

3

Gastrocopta armifera (Say)

1

0

1

0

47

7

5

1

38

7

17

7

5

2

Gastrocopta cristata Pilsbry

1

0

1

0

15

6

19

6

10

3

Gastrocopta holzingeri (Sterki)

6

2

6

1

96

39

37

12

3

1

Gastrocopta pellucida (Pfeifer)

1

0

193

27

3

1

6

2

3

1

136

28

Gastrocopta procera (Gould)

6

2

5

1

35

6

5

2

14

5

3

1

Gyraulus parvus (Say)

2

1

53

13

Hawaiia minuscula (Binney)

23

6

43

5

82

12

134

14

84

14

12

5

20

7

12

3

26

5

Oreohelix spp.

28

4

Oxyloma spp.

20

2

6

2

5

2

Physa spp.

1

0

10

3

Pisidium casertanum (Poli)

13

4

200

50

Pupilla muscorum (Linne)

70

18

174

22

20

3

4

0

2

0

9

4

12

4

2

1

52

11

Pupoides albilabris (C.B. Adams)

7

1

4

2

8

3

Pupoides hordaceous (Gabb)

133

28

Pupoides inornata Vanatta

35

9

7

1

1

0

130

22

3

1

6

2

9

2

7

1

Stagnicola spp.

10

3

Succinea spp.

4

1

45

8

3

1

Vallonia

cyclophorella

(Sterki)

250

64

579

72

197

28

381

39

240

41

60

24

20

7

32

8

123

26

Vertigo gouldi and ovata

1

0

4

1

390

39

Zonitoides arboreus (Say)

1

0

96

14

1

0

7

3

20

7

15

4

6

1

TOTAL

394

100

809

100

713

100

989

100

585

100

248

100

304

100

397

100

483

100

#

%

#

%

#

%

#

%

#

%

#

%

#

%

#

%

#

%

TIME in KARST – 2007

FRED G. LUISZER

tab. 2A: Alloisoleucine and isoleucine (A/I) ratios of snails.

Sample Location

Species

Lab Number

Results

Average

Standard Deviation

Modern

P

AAL-5990

0.020

0.022

0.021

0.001

Modern

V

AAL-5989

0.021

0.020

0.021

0.001

Centennial

P

AAL-5970

0.023

0.021

0.022

0.001

Centennial

V

AAL-5969

0.024

0.032

0.028

0.004

Manitou Cave

G

AAL-5993

0.042

0.056

0.051

0.050

0.006

Manitou Cave

P

AAL-5992

0.039

0.044

0.041

0.041

0.002

Manitou Cave

V

AAL-5991

0.043

0.069

0.056

0.013

Chesnut

GO

AAL-5972

0.106

0.124

0.115

0.009

Chesnut

V

AAL-5971

0.106

0.103

0.105

0.002

Colorado City

G

AAL-5986

0.154

0.210

0.163

0.176

0.025

Colorado City

V

AAL-5985

0.076

0.083

0.080

0.004

Fillmore 1

G

AAL-5976

0.279

0.274

0.277

0.003

Fillmore 1

V

AAL-5975

0.298

0.275

0.287

0.012

Fillmore 2

G

AAL-5988

0.239

0.233

0.236

0.003

Fillmore 2

V

AAL-5987

0.283

0.270

0.277

0.007

Starlight

P

AAL-5768

0.423

0.414

0.420

0.419

0.004

Starlight

V

AAL-5767

0.276

0.317

0.296

0.296

0.017

Starlight 1

G

AAL-5974

0.302

0.322

0.312

0.010

Starlight 1

V

AAL-5973

0.307

0.231

0.224

0.254

0.038

Starlight 2

G

AAL-5978

0.292

0.298

0.295

0.003

Starlight 2

V

AAL-5977

0.246

0.244

0.245

0.001

Black Canyon

P

AAL-5766

0.502

0.531

0.543

0.529

0.526

0.015

Black Canyon

V

AAL-5765

0.545

0.545

0.546

0.544

0.515

0.576

0.545

0.018

V = Vallonia cyclophorella P = Pupilla muscorum G = Gastrocopta armifera GO = Vertigo gouldii and Vertigo ovata

the inferred maximum age of ~150 Ka was assigned to the Louviers Alluvium. Te interpolated age of the

tab. 2b: Average values and standard deviation of A/I ratios of selected snails from each site.

Nussbaum Alluvium, therefore, represents its maximum age.

Parabolic Curve Fitting

Ages and A/I data (Table 2B ) from four of the younger alluvia, together with A/I data from the Nussbaum, were used to extrapolate the age of the Nussbaum. Various authors have applied linear and parabolic curve ftting to amino acid data for both interpolation and extrapolation of age (Miller & Brigham-Grette, 1989). Mitterer & Kriausakul (1989) have employed the parabolic function (y=x2) with good results. Applying the generalized parabolic equation (y=A+Bx+Cx2) to my data resulted in a better curve ft than the specialized parabolic function (y=x2). Use of the specialized parabolic function assumes that the A/I ratio starts at 0.0 and that at an initial age near zero, the racemization rate is infnitely large. Te data from my study area suggest that both of these assumptions are invalid (Table 2B and Fig. 4).

Ignoring the A+Bx terms appears to have little efect on curve ftting of relatively young snails (<100 Ka). Te generalized parabolic function, however, was used in this study because the age of the Nussbaum Alluvium is extrapolated 3 to 4 times beyond the oldest calibration point. Parabolic-curve fts for the average ratio with error bars of one standard deviation indicate

an extrapolated age for the Nussbaum Alluvium of 1.9

+0.4/-0.2 Ma (Fig. 4).

tab. 3: Uranium-thorium and 14C dates.

Average - standard deviation

Average

Average + standard deviation

Modern Flood Plain

0.020

0.021

0.022

Centennial

0.021

0.025

0.029

Chesnut

0.103

0.110

0.117

Filmore and Starlight

0.249

0.275

0.301

Black Canyon

0.523

0.536

0.549

Centennial site

Manitou Cave

14C Age (years B.P.)

1495 ± 130

1505 ± 75

Lab. Number*

GX-15992

GX-15993

*Krueger Enterprises Inc.

Uranium-thorium Age** (years B.P.)

Narrows Cave

32,000 ± 2,000

**Dan Muhs, U.S.G.S., 1990, per. comm.

164 TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

Extrapolating a date that is 3 to 4 times more than the maximum calibration date is a practice generally frowned up. I believe that by carefully collecting and handling samples, obtaining precise analysis of the ami-no acids, acquiring the best age determinations of the younger deposits, and curve ftting with the generalized parabolic function, I have ameliorated problems usually associated with such extrapolation. Te 1.9-Ma date for the Nussbaum Alluvium is appropriate only for the unit mapped in the Manitou Springs area; it may not be correlative with the type section in Pueblo, Colorado. Te date, 1.9 +0.4/-0.2 Ma, which is the most accurate date available for the Nussbaum Alluvium, was used to calibrate the magnetostratigraphy of the sediments in Cave of the winds.

Magnetostratigraphy

Rocks and unconsolidated sediments can be magnetized by the magnetic feld of the earth (Tarling 1983), acquiring natural remanent magnetization (NRM). A type of NRM in sediments is detrital remanent magnetization (DRM), which is formed when the magnetic grains of a sediment, such as magnetite or hematite, are aligned with the earth’s magnetic feld during or soon afer deposition (Verosub, 1977). Te DRM of a sediment has the same orientation as and its intensity is proportional to, the earth’s magnetic feld (Verosub, 1977).

Te magnetic feld of the earth has reversed many times in the past (Tarling, 1983). Polarity time scales have been constructed by compiling the reversals and the radiometrically derived dates of the rock in which the reversals are preserved, (Mankinen & Dalrymple, 1979; Harland et. al., 1982; Hailwood, 1989; Cande and Kent, 1992).

Tere are several ways to use this time scale to date sediments. By assuming that the top of a sediment section starts at the present and sedimentation has

been uninterrupted, such as in deep ocean basins, it is a simple matter of counting the reversals and correlating them with the polarity time scale. Because of erosion or a hiatus in deposition, however, the top of many sediment sections will have an older age that must be ascertained by some other technique before reversals in the section can be correlated with the polarity time scale.

Another way of dating sediments is by pattern matching. If the sedimentation rate of an undated section is constant or known and there are many reversals (5-10), the polarity record can be matched to the pattern of the polarity time scale to provide dating. Tis is possible because the timing of reversals is apparently random (Tarling, 1983). Terefore, the timing of a sequence of reversals is seldom repeated. Both of these techniques mentioned here were used to refne the age of the sediments at Cave of the winds.

Paleomagnetic Results

All the paleomagnetic data from Hole 6 are presented to give an example of all the raw data from all sampling sites and how the samples responded to demagnetization (Table 4). Inspection of the complete data set revealed that all samples responded very similarly to demagnetization. Te complete data set of sites included in this study as well as other miscellaneous sites not used in this study are available from the author on computer storage disks. Sample depth and magnetic declination afer 15-mT AF demagnetization from each site were used to correlate the magnetic polarity within and between the Grand Concert Hall and nearby Heavenly Hall (Fig. 5). An exception to use of the 15-mT-AF demagnetization is Hole 5, where samples from 6.5 to 10.0 m were subjected to 20-, 25-, and 30-mT-AF demagnetization. Te higher felds were applied in an attempt to remove secondary overprints. Even with the increasing demagnetization,

Sniders Hall 5=-

Hole 5

Hole 1

(See Figure 3 for locations of pits and holes.)

Hole 3

Hole 4

Hole 6

Figure 5. Cross-section and correlation of the magnetic declination of sampled pits and cored holes from the Grand Concert Hall and Heavenly Hall.

Hole 2

Mummys Alcove

A'

Heavenly Hall

TIME in KARST – 2007 165

A

FRED G. LUISZER

tab. 4: Complete Paleomagnetic results of hole 6, Grand Concert hall

Sample Number

Depth cm

Natural

10 mT

15 mT

Dec.

Inc.

Int.

Dec.

Inc.

Int.

Dec.

Inc.

Int.

11

80

-10

62

1.2E-4

-21

55

5.4E-5

-14

58

4.7E-5

12

93

-30

45

1.5E-4

-7

54

6.8E-5

-16

52

5.0E-5

13

105

-11

52

2.0E-4

-4

52

1.2E-4

-9

60

1.1E-4

14

118

-23

27

1.5E-4

-23

26

1.1E-4

-24

24

9.7E-5

21

121

-14

44

1.8E-4

-21

40

1.2E-4

-20

39

9.6E-5

22

131

-11

46

2.7E-4

-7

39

1.7E-4

-6

40

1.5E-4

23

141

-0

41

1.4E-4

-13

34

7.2E-5

-7

37

6.6E-5

24

151

4

42

3.2E-4

3

38

2.1E-4

2

38

1.8E-4

31

154

-11

40

3.8E-4

-15

32

2.1E-4

-14

34

1.9E-4

32

163

-27

40

2.2E-4

-21

38

1.4E-4

-24

36

1.3E-4

33

172

-24

41

2.6E-4

-29

36

1.8E-4

-30

35

1.6E-4

34

182

-17

40

2.5E-4

-19

38

1.7E-4

-20

37

1.6E-4

41

184

-18

38

4.4E-4

-18

40

3.1E-4

-18

39

2.9E-4

42

194

-15

41

1.8E-4

-24

42

1.1E-4

-20

36

9.6E-5

43

204

-17

58

1.4E-4

-45

62

4.7E-5

-50

64

3.4E-5

44

213

165

-32

1.1E-4

162

-28

9.9E-5

162

-29

9.1E-5

51

216

115

11

7.0E-5

149

-9

6.1E-5

156

-11

5.7E-5

52

226

155

-29

9.5E-5

165

-36

1.OE-4

168

-35

9.2E-5

53

236

-14

52

7.4E-5

144

75

1.4E-5

149

59

1.1E-5

54

246

30

50

1.3E-4

54

30

5.5E-5

62

30

5.0E-5

61

249

81

47

6.7E-5

114

14

4.6E-5

119

3

3.7E-5

62

257

-2

51

1.2E-4

34

41

2.3E-5

36

16

1.0E-5

63

264

176

58

2.7E-5

164

-7

2.3E-5

170

-16

2.3E-5

64

271

177

-18

5.0E-5

184

3

6.4E-5

183

3

6.2E-5

71

273

-12

88

6.7E-4

169

-9

4.7E-5

172

-8

4.5E-5

72

281

203

14

3.9E-5

142

12

7.4E-5

144

8

7.0E-5

81

283

127

-11

1.2E-4

131

-19

9.6E-5

131

-18

8.6E-5

82

294

150

-17

6.4E-5

156

-21

6.2E-5

158

-24

5.2E-5

83

305

93

16

5.4E-5

130

-16

5.2E-5

128

-17

4.5E-5

84

316

59

30

2.2E-5

140

-34

2.2E-5

142

-38

2.0E-5

91

319

28

62

7.2E-5

82

47

2.2E-5

100

29

1.7E-5

92

329

85

67

4.5E-5

148

5

3.8E-5

154

-2

3.5E-5

93

339

-2

53

5.5E-5

41

61

1.4E-5

41

56

1.3E-5

94

349

17

75

6.3E-5

140

34

2.5E-5

162

26

2.2E-5

101

352

101

-26

5.4E-5

159

15

4.5E-5

153

3

4.1E-5

102

362

81

76

5.2E-5

131

33

2.0E-5

150

17

1.5E-5

103

372

67

79

7.7E-5

139

-1

2.6E-5

137

-6

3.2E-5

104

382

178

11

4.7E-5

179

-16

4.7E-5

186

-21

4.7E-5

111

385

170

24

5.5E-5

165

-3

4.9E-5

165

-2

4.5E-5

112

396

159

-12

3.7E-5

156

-30

3.5E-5

157

-29

3.3E-5

113

407

184

-10

3.9E-5

174

-32

4.8E-5

172

-32

4.5E-5

166 TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

Sample Number

Depth cm

Natural

10 mT

15 mT

Dec.

Inc.

Int.

Dec.

Inc.

Int.

Dec.

Inc.

Int.

121

420

-37

-30

2.4E-5

-70

-57

1.2E-5

-49

-54

1.0E-5

122

431

228

52

2.5E-5

214

25

1.4E-5

208

18

1.1E-5

123

439

-44

55

3.1E-5

249

16

1.1E-5

266

16

1.1E-5

124

451

126

3

2.1E-5

145

-32

2.2E-5

142

-36

1.9E-5

131

453

211

7

1.6E-5

136

-38

9.8E-6

164

-55

9.8E-6

132

463

172

37

1.5E-5

144

-43

2.4E-5

147

-40

1.9E-5

133

472

69

-21

9.3E-6

149

-46

1.6E-5

152

-50

1.6E-5

134

481

263

19

5.4E-6

167

-32

1.3E-5

177

-28

1.2E-5

141

484

115

8

1.9E-5

183

-35

1.4E-5

174

-40

1.1E-5

142

493

189

-6

7.2E-5

188

-19

5.8E-5

192

-22

5.1E-5

143

503

176

62

2.1E-5

158

23

9.6E-6

163

20

8.2E-6

144

512

68

35

1.3E-5

186

-36

6.3E-6

175

-36

6.6E-6

151

514

-19

40

3.4E-5

-39

15

8.3E-6

-15

15

5.9E-6

152

525

41

70

4.7E-5

139

66

1.8E-5

146

60

1.6E-5

153

535

-6

46

8.1E-5

-4

33

3.3E-5

-7

36

2.6E-5

154

545

189

33

1.2E-4

185

21

1.1E-4

182

21

1.1E-4

161

547

173

57

2.8E-5

186

2

2.4E-5

187

-0

2.4E-5

162

558

208

7

2.6E-5

200

-28

3.8E-5

201

-28

3.2E-5

163

568

10

68

1.7E-5

206

-25

9.1E-6

211

-33

1.1E-5

171

570

146

73

4.4E-5

175

27

2.9E-5

173

31

2.7E-5

172

580

255

54

10.0E-6

190

-46

1.5E-5

176

-43

1.6E-5

173

591

131

63

4.3E-5

161

14

2.1E-5

160

10

2.2E-5

174

601

39

67

2.2E-5

148

14

6.4E-6

150

2

7.4E-6

181

603

92

52

7.9E-6

163

-18

6.4E-6

135

-31

4.9E-6

182

613

2

69

2.6E-5

152

87

1.2E-5

113

78

8.2E-6

183

624

-44

19

2.1E-5

-69

-45

1.7E-5

-67

-53

1.4E-5

184

634

-16

5

1.6E-5

267

-55

1.1E-5

-86

-59

8.6E-6

191

636

106

60

2.0E-6

112

-37

3.0E-6

160

1

1.4E-6

192

646

-38

7

2.3E-5

-54

-26

1.8E-5

-55

-40

1.2E-5

193

657

2

47

2.6E-5

-4

19

5.7E-6

-26

-27

3.0E-6

194

667

14

64

4.3E-5

42

63

1.6E-5

45

61

1.1E-5

201

669

8

45

4.5E-5

25

43

2.5E-5

24

45

1.6E-5

202

677

22

84

5.0E-5

183

84

2.6E-5

192

80

1.8E-5

203

685

48

52

3.3E-5

74

50

1.7E-5

78

44

1.2E-5

204

692

25

48

1.9E-5

56

25

6.3E-6

78

-17

1.6E-6

however, the declination of the deeper samples at Hole 5 have greater variability than those of shallower samples (Fig. 5). Additionally, the polarity results from Hole 5 are shown in Fig. 6, which also shows the correlation with the known paleomagnetic record and stratigraphy of the cave sediments.

Criteria For Reversal Assignment

Sequences of samples that had an average declination of ~0.0° and an average inclination of ~35.0° were assigned to normal polarity. Te ideal inclination for DRM in the Manitou Springs area should be ~60°. Te low values recorded at Cave of the winds are considered to be the

TIME in KARST – 2007 167

FRED G. LUISZER

Declination

°šg

1.5

2.5

3.0

3.5-

Floor

Angular limestone r blasts up to 50 cm contains silt, clay, small (bat) and large bones near base. Appears to be

artificial fill.__________

Flows tone

Brown, laminated, micaceous silt contains clay intraclasts.

Brown, laminated, micaceous silt interbedded with mottled red clay. Mostly silt near top and clay near bottom. Beds dip 20 degress east.

Reddish brown clay contains red, brown, purple, green and blue mottles.

Normal Polarity

Reversed Polarity

Green Clay

Clay Intra clast

Figure 6. Paleomagnetic correlation and stratigraphy of Grand Concert Hall Hole 5. Paleomagnetic time scale adapted from Harland and others (1982).

result of inclination error resulting from sediment compaction (Verosub, 1977). Sequences of samples that had an average declination of ~180° were assigned a reversed polarity. In most cases, inclinations of these samples were variable, ranging mostly between -35.0° and +10.0°. Because of this variability, the sample declinations were used to determine reversals (Fig. 5). Tese anomalous inclinations appear to be related to post-depositional acquisition of remanent magnetization.

Efects Of Post-Depositional Remanent Magnetization On Sediments

Most post-depositional remanent magnetization (PDRM) is the result of realignment of the magnetic particles during compaction and especially dewatering, both of which can take place thousands to millions of years afer deposition (Verosub, 1977). A possible explanation of the variability of the inclination of the reversed

samples is that these samples were compacted and dewatered during a normal polarity interval, overprinting a normal component. Te de-watering and compaction may have occurred rather quickly following rapid draining of the water in the cave passages related to downcut-ting by Fountain Creek. Mud cracks present in the top two meters of the sediments at the Grand Concert Hall combined with their mostly normal polarity (Fig. 6) indicate that this is a plausible explanation. Further micro-sampling and precision analysis would be necessary to ascertain the mechanism responsible for the difference in the inclinations.

Chemical remanent magnetization (CRM) may also be a contributing factor to the inclination anomalies. Alteration and oxidation of iron-bearing minerals in the sediments may contribute to the CRM. Tis could only be a factor in the top two meters of coarse sediments (Fig. 6), which contain unaltered minerals; because the general oxidizing conditions and neutral to slightly alkaline pH of percolating cave waters through these sediments would preclude mobilization or precipitation of iron oxides. Te underlying soil-derived clays, which have already undergone prolonged oxidation before being deposited in the cave, are chemically stable and would not be vulnerable to CRM.

Paleomagnetic Correlation

Because there are no independent dates on the cave sediments, correlation of the magnetic polarity record of the Cave of the winds sediments with the accepted polarity time scale is difcult. It requires matching the sequence of known polarity events with the Cave of the winds record. Te age of the Nussbaum Alluvium, which is apparently related to the uppermost coarse cave sediments, however, can be used to help constrain the paleomag-netic correlation. Te relationship of the Nussbaum Alluvium to the detrital sediments in Cave of the winds will be discussed in detail.

As discussed previously, the clay is deposited in the cave below the phreatic-vadose interface where sediment-laden streams enter water-flled passages. Te

Reddish brown clay contains yellow and purple mottles. Contains limestone and purple sandstone clasts.

Thin bed (5 cm) of Mn-Fe-oxides and solution residue.

Chert

sm>

168 TIME in KARST – 2007

2.

4.

Limestone

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

South

A. ~2 Ma

Fountain Creek

North

Williams Canyon Creek

Text in green are sediments that are being deposited in the cave.

* = Grand Concert Hall, Cave Of The Winds ----------------- = outline of cavern

I = Nussbaum Alluvium

South

B. ~1.8 Ma                          North

Williams Canyon Creek

Fountain Creek

South

C. Present

Fountain Creek

Figure 7. Schematic cross sections showing the sequence of changes in the water table, topographic setting, and depositional phases over the last ~2 Ma.

Nussbaum Alluvium was being deposited at the same time that clay was being deposited in the Grand Concert Hall the (Fig. 7A). As Fountain Creek downcut and moved to the south, the water table dropped (Fig. 7B). Te drop in the water table coincided with drop in the water depth in rooms like the Grand Concert Hall. As the water depth dropped, the velocity of the water passing through the room increased. Te increased stream en-

ergy changed the sedimentation regime from clay deposition to silt, sand, and gravel deposition (Fig. 7B). Fluvial sedimentation at Cave of the winds stopped as Fountain Creek moved further to the south and downcut further (Fig. 7C). Te relationship between the Nussbaum Alluvium and the sediments in the cave indicate that the silt-clay interface in the Grand Concert Hall took place afer the Nussbaum was deposited. More specifcally, the silt-clay interface should be the same age as the Nussbaum Alluvium minus the time it took for Fountain Creek to downcut and drop the water table to the level of the Grand Concert Hall (Fig. 7B).

Te sediment foor of the Grand Concert Hall, where the paleomagnetic data was obtained, is about 20 m below the Nussbaum Alluvium. Te age of the Nussbaum Alluvium (~1.9 Ma) and its height above modern streams (200 m) provides an estimate of the average down-cutting rate of 10.5 cm/1000 years. Accordingly, accumulation of coarse sediments in the cave 20 m below the Nussbaum Alluvium probably would have begun ~1.7 Ma.

Te estimated 1.7 Ma age of the clay-coarse sediment interface correlates well with the onset of the Olduvai Subchron at 1.9 Ma ( ~2.2 m depth, Fig. 6). Tis is the most probable correlation. Alternatively, one could match the normal-polarity sequence (1.0 to 2.2 m depth, Fig. 6) with the Jaramillo Subchron (Harland et al., 1982) or the Gauss Chron (Fig. 6). Tese correlations, however, would result in an age of ~1.0 Ma or ~ 2.6 Ma, respectively, for the clay-coarse-sediment interface, which is estimated to be 1.7 Ma, thereby making these alternate correlations unlikely.

North

TIME in KARST – 2007 169

FRED G. LUISZER

Te complete paleomagnetic correlation shown on Fig. 6 follows from correlation of the normal-polarity interval between 1.0 and 2.2 m in depth with the Olduvai Subchron. According to the correlation suggested here,

the oldest cave sediment was deposited about 4.3 Ma, a date that agrees quite well with the previously discussed probable age of the major onset of cave formation (7 Ma to 4 Ma).

CONCLUSIONS

Cave of the winds is a phreatic cave dissolved from the calcite-rich Manitou, williams Canyon, and Leadville Formations. Dissolution occurred along joints associated with Laramide faulting and folding. Paleokarst features, such as sediment-flled fssures and caves, indicate that some of the passages at Cave of the winds are related to cave-forming episodes that started soon afer the deposition of the Ordovician Manitou Formation and continued to the beginning of the Cretaceous Laramide Orogeny. Most speleogenesis, however, occurred in the last ~5.0 Ma.

Te Nussbaum Alluvium was assigned an age of ~1.9 Ma by means of aminostratigraphy. Te age of the Nussbaum Alluvium and its relation to coarse grained sediments at Cave of the winds were used to fx an age of ~1.7 Ma for the onset of coarse grained sedimentation in the cave. Tis enabled the identifcation of the Olduvai Polarity Subchron in the coarse grained sediments. Correlation of the magnetostratigraphy of cave sediments with the accepted polarity time scale indicates that the dissolution of cave passage started ~4.2 Ma and stopped ~1.5 Ma.

REFERENCES

Blanton, T. L., 1973: Te Cavern Gulch Faults and the Fountain Creek Flexure, Manitou Spur, Colorado [M.S. thesis]: Syracuse University, New york, 90 p.

Bianchi, L., 1967: Geology of the Manitou-Cascade Area, El Paso County, Colorado with a study of the permeability of Its crystalline rocks [M.S. Tesis]: Golden, Colorado School of Mines.

Cande, S. C., and D. Kent., 1992: A new geomagnetic polarity time scale for the Late Cretaceous and Ceno-zoic: Journal of Geophysical Research, 97, 10, 13- 17.

Epis, R. C., and C.E. Chapi, 1975: Geomorphic and tectonic implications of the Post-Laramide, Late Eocene Erosion surface in the Southern Rocky Mountains, in Curtis, B.F., ed., Cenozoic History of the Southern Rocky Mountains: Geological Society of America Memoir 144, 45-74.

Fish, L., 1988: Te real story of how Cave of the winds Formed: Rocky Mountain Caving, 5, 2, 16-19.

Forster, J. R., 1977: Middle Ordovician subaerial exposure and deep weathering of the Lower Ordovician Manitou Formation along the Ute Pass Fault zone: Geological Society of America Abstracts with Programs, 9, 722.

Goodfriend, G. A., 1987: Evaluation of amino-acid race-mization/epimerization dating using radiocarbon-dated fossil land snails: Geology 15, 698-700.

Hailwood, E. A., 1989: Te role of magnetostratigraphy in the development of geological time scales; Pale-oceanography, 4, 1, 1-18.

Hamil, M. M., 1965: Breccias of the Manitou Springs area, Colorado [M.S. thesis]: Louisiana State University, 43 p.

Harland, w. B., et al., 1982: A geologic time scale: Cambridge, Great Britain, Cambridge University Press, 66 p.

Hose, L. D., & Esch, C. J., 1992: Paleo-cavity flls formed by upward injection of clastic sediments to lithostat-ic load: exposures in Cave of the winds, Colorado [abs.]: National Speleological Society Convention Program, Salem, Indiana, p.50

Izett, G. A., Obradovich, J. D., & H.H. Mehnert., 1989: Te Bishop Ash Bed (Middle Pleistocene) and some older (Pliocene and Pleistocene) chemically and mineralogically similar ash beds in California, Nevada, and Utah: U. S. Geological Survey Bulletin, 1675, 37 p.

Luiszer, F. G., 1997: Genesis of Cave of the winds, Mani-tou Springs, Colorado, [Ph. D. thesis]: Boulder, University of Colorado, 112 p.

Machette, M. M., 1975: Te quaternary geology of the Lafayette quadrangle, Colorado, [M. S. thesis]: Boulder, University of Colorado, 83 p.

170 TIME in KARST – 2007

TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA

Mankinen, E. A., & Dalrymple, G. B., 1979: Revised geomagnetic polarity time scale for the interval 0-5 m. y. B. P. ; Journal of Geophysical Research, 84, B2, 615-626.

Miller, G. H., & Brigham-Grette, J., 1989: Amino acid geochronology: Resolution and precision in carbonate fossils in INqUA quat. Dating Methods, Rutter and Brigham-Grette Eds. Pergamon Press.

Mitterer, R. M., & Kriausakul, 1989: Calculation of amino acid racemization ages based on apparent parabolic kinetics: quaternary Science Reviews, 8, 353-357.

Morgan, G. B., 1950: Geology of williams Canyon area, north of Manitou Springs, El Paso County, Colorado (Masters thesis): Golden, Colorado School of Mines, 80 p.

Mutschler, F. E., Larson, E. E., & R.M. Bruce: 1987: Laramide and younger magmatism in Colorado-New petrologic and tectonic variations on old themes: Colorado School of Mines quarterly 82, 4, 1-47.

Sawyer, D. A. et al., 1995: New chemical criteria for quaternary yellowstone tephra layers in central and western North America: Geological Society of America Abstracts with Programs, 27, 6, 109.

Scott, G. R., 1963, Nussbaum Alluvium of Pleistocene(?) age at Pueblo, Colorado. U. S. Geological Survey Professional Paper, 475-C, C49-C52

Scott, G. R., 1975, Cenozoic surfaces and deposits in Curtis, B. F., ed., Cenozoic History of the Southern Rocky Mountains: Geological Society of America Memoir 144, 227-248.

Soister, E., 1967, Relation of Nussbaum Alluvium (Pleistocene) to the Ogallala Formation (Pliocene) and to the Platte-Arkansas divide, Southern Denver Basin, Colorado. U. S. Geological Survey Professional Paper 575-D, p.D39-D46.

Szabo, B. J., 1980, Results and assessment of uranium-series dating of vertebrate fossils from quaternary alluviums in Colorado: Arctic and Alpine Research, 12, 95-100.

Tarling, D. H., 1983, Palaeomagnetism; principles and applications in geology, geophysics and archaeology: Chapman and Hall Ltd., London, 379 p.

Trimble, D. E., & Machette, M. M., 1979, Geologic map of the Colorado Springs-Castle Rock Area, Front Range Urban Corridor, Colorado; U. S. Geological Survey, 1:100,000, Map I-857-F

Tweto, O., 1975, Laramide (Late Cretaceous-Early Tertiary) Orogeny in the Southern Rocky Mountains in Curtis, B.F., ed., Cenozoic History of the Southern Rocky Mountains: Geological Society of America Memoir 144, 1-44.

Verosub, K. L., 1977, Depositional and post-depositional processes in the magnetization of sediments: Reviews of Geophysics and Space Physics, 15, 129-143.

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COBISS: 1.01

HOw LONG DOES EVOLUTION OF THE TROGLOMORPHIC FORM TAKE? ESTIMATING DIVERGENCE TIMES IN ASTyANAx

MExICANUS

KAKO DOLGO TRAJA EVOLUCIJA TROGLOMORFNIH OBLIK? OCENJEVANJE DIVERGENČNIH ČASOV PRI ASTyANAx

MExICANUS

Megan L. PORTER1, Katharina DITTMAR2 & Marcos PéREZ-LOSADA3

Abstract                                                     UDC 551.44:597

591.542

Megan L. Porter, Katharina Dittmar & Marcos Pérez-Losada: How long does evolution of the troglomorphic form take? Estimating divergence times in Astyanax mexicanus

Features including colonization routes (stream capture) and the existence of both epigean and cave-adapted hypogean populations make Astyanax mexicanus an attractive system for investigating the subterranean evolutionary time necessary for acquisition of the troglomorphic form. Using published sequences, we have estimated divergence times for A. mexicanus using: 1) two diferent population-level mitochondrial datasets (cyto-chrome b and NADH dehydrogenase 2) with both strict and relaxed molecular clock methods, and 2) broad phylogenetic approaches combining fossil calibrations and with four nuclear (recombination activating gene, seven in absentia, forkhead, and α-tropomyosin) and two mitochondrial (16S rDNA and cytochrome b) genes. Using these datasets, we have estimated divergence times for three events in the evolutionary history of troglomorphic A. mexicanus populations. First, divergence among cave haplotypes occurred in the Pleistocene, possibly correlating with fuctuating water levels allowing the colonization and subsequent isolation of new subterranean habitats. Second, in one lineage, A. mexicanus cave populations experienced introgressive hybridization events with recent surface populations (0.26-2.0 Ma), possibly also correlated with Pleistocene events. Finally, using divergence times from surface populations in the lineage without evidence of introgression as an estimate, the acquisition of the troglomorphic form in A. mexicanus is younger than 2.2 (fossil calibration estimates) – 5.2 (cytb estimate) Ma (Pliocene).

Key words: Astyanax mexicanus, divergence time, troglomor-phy, subterranean, evolution.

Izvleček                                                      UDK 551.44:597

591.542

Megan L. Porter, Katharina Dittmar & Marcos Pérez-Losada: Kako dolgo traja evolucija troglomorfnih oblik? Ocenjevanje divergenčnih časov pri Astyanax mexicanus

Značilnosti, ki vključujejo tudi kolonizacijske poti in obstoj tako epigejičnih kot hipogejičnih populacij vrste Astyanax mexica-nus, ji omogočajo, da predstavlja zanimiv sistem za proučevanje evolucije in časa, potrebnega za razvoj podzemeljskih troglo-morfnih oblik. Za A. mexicanus smo na podlagi že objavljenih sekvenc ocenili divergenčni čas ob uporabi: 1) dveh različnih populacijskih mitohondrialnih podatkovnih baz (citokrom b in NADH dehidrogenaze 2), obe z natančno in sproščeno metodo molekularne ure, in 2) razširjenega flogenetskega pristopa v kombinaciji s fosilno kalibracijo ter štirimi jedrnimi geni (rekombinacijski aktivacijski gen, »forkhead kontrolni gen« in α-tropomiozin) in dvema mitohondrialnima genoma (16S rDNA in citokrom b). Ob uporabi navedenih podatkovnih baz smo ocenili divergenčni čas za tri dogodke v zgodovini razvoja troglomorfnih populacij A. mexicanus. Prvič, razhajanje med podzemeljskimi haplotipi se je zgodilo v Pleistocenu, verjetno v odvisnosti od nihanja vode, ki je omogočilo kolonizacijo in posledično izolacijo v novih podzemeljskih habitatih. Drugič, verjetno je v povezavi s pleistocenskimi dogodki pri eni liniji podzemeljskih populacij A. mexicanus prišlo do introgresivne hibridizacije s takratnimi površinskimi populacijami (0.26-2.0 Ma). Z uporabo divergenčnega časa površinskih populacij tistih linij, ki ne kažejo introgresije ocenjujemo, da je troglomorfna oblika A. mexicanus mlajša od 2,2 (ocene fosilne kalibracije) do 5,2 milijona let (cytb ocena) (Pliocen).

Ključne besede: Astyanax mexicanus, divergenčni čas, troglo-morfzem, podzemlje, speleobiologija, evolucija.

1 Dept. of Biological Sciences, University of Maryland Baltimore County, Baltimore, MD, USA; e-mail: porter@umbc.edu

2 Dept. of Molecular Biology, University of wyoming, Laramie, wy, USA

3 GENOMA LLC, 50E woodland Hills, Provo, UT 84653-2052, USA

Received/Prejeto: 06.12.2006

TIME in KARST, POSTOJNA 2007, 173–182

MEGAN L. PORTER, KATHARINA DITTMAR & MARCOS PéREZ-LOSADA

INTRODUCTION

Understanding the evolution of the cave form has fascinated biologists interested in subterranean faunas since Darwin. Termed ‘troglomorphy’, the suite of progressive and regressive characters associated with cavernicolous animals can be observed in the worldwide convergence of form found in the cave environment, exhibited in similar structural, functional, and behavioral changes across diverse taxonomic groups. Much of the debate over troglo-morphy has centered on the evolutionary mechanisms responsible for character regression, generally argued to be either neutral mutation or natural selection. Several studies, (Gammarus minus - Culver et al., 1995; Astyanax mexicanus – Jefery, 2005) have shown eye degeneration is the result of selection, and, in the case of A. mexica-nus, is caused by the pleiotropic efects of natural selection for constructive traits. Another, less studied, aspect of understanding troglomorphy is the evolutionary time required to gain the cave form. Because it is generally dif-fcult to pinpoint the time of subterranean colonization and isolation from surface ancestors, few troglomorphic species ofer the opportunity for quantitative estimates of the evolutionary time spent in the subterranean realm. Terefore, the time of cave adaptation is thought of in relative terms, where the degree of eye and pigment reduction indicates the period of cavernicolous evolution and therefore the relative phylogenetic age of each species (Aden, 2005).

In evolutionary studies of cave adaptation, Asty-anax mexicanus has become a model system (Jefery, 2001). Te advantageous features of A. mexicanus as a model system include the existence of both surface and troglomorphic cavefsh populations, with several cave fsh populations having evolved constructive and regressive changes independently (Jefery, 2001). Furthermore, since the discovery of the species in 1936 (Hubbs & Innes, 1936), there has been an extensive amount of research devoted to characterizing developmental, phylogenetic, taxonomic, and biogeographic aspects of the species (Jef-fery, 2001; Mitchell et al., 1977; wiley & Mitchell, 1971;). In terms of being a model system for understanding the evolution of the troglomorphic form, A. mexicanus has at least one additional favorable attribute. Te primary mode of A. mexicanus subterranean colonization is via

stream capture, with most of the captured surface drainages no longer supporting epigean populations (Mitchell et al., 1977). Tese captures provide discrete colonization events correlated with divergence time from surface populations and therefore with the time of subterranean evolution.

Molecular studies that have looked at A. mexicanus phylogeography indicate that at least two independent invasions of surface Astyanax have occurred (Dowling et al., 2002a; Strecker et al., 2003, 2004). Tese two distinct A. mexicanus genetic lineages consist of cave fsh from La Cueva Chica, La Cueva de El Pachón, El Sótano de yerbaniz, El Sótano de Molino, El Sótano de Pichijumo, and La Cueva del Río Subterráneo (lineage A) and from La Cueva de los Sabinos, El Sótano de la Tinaja, La Cueva de la Curva, and El Sótano de Las Piedras (Lineage B) with diferent evolutionary histories - Lineage A clusters with closely related epigean populations while lineage B has no closely related epigean counterparts. Te close association of Lineage A to epigean populations (as estimated by mitochondrial markers) is thought to be the result of either recent subterranean colonization or refect recent introgressive hybridization with surface populations, while lineage B is considered to be a more ancient colonization event from surface populations that are extinct in the region (Dowling et al., 2002a; Strecker et al., 2004). Although the evolutionary histories of different hypogean A. mexicanus populations are complex, the two lineages ofer the unique opportunity to estimate the divergence time required for the evolution of the tro-glomorphic form based on discrete times of colonization and the previous molecular studies of their phylogeogra-phy. At least one other study has estimated lineage ages in A. mexicanus populations; however, this study was based on a single gene molecular clock estimate and did not specifcally estimate the divergence times of the cave populations (Strecker et al., 2003). Here we use three different sets of publicly available sequence data and known fossil calibrations and apply multiple phylogenetic approaches to estimate the age of cave colonization and stream capture events, and to provide an estimate of the time necessary to acquire the troglomorphic form in A. mexicanus.

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METHODS

Sequence Data

Data were acquired from Genbank (http://www.ncbi. nlm.nih.gov/) from previously published studies of A. mexicanus and characiform fshes (Tab. 1). Tese studies provided three diferent datasets, consisting of: 1) population-level haplotype datasets for the mitochondrial cy-tochrome b (cytb; Strecker et al., 2004) and NADH dehy-drogenase 2 (ND2; Dowling et al., 2002a) genes, and 2) a species-level dataset of four nuclear (recombination activating gene – RAG2; seven in absentia – sina; forkhead – fh; and α-tropomyosin - trop) and two mitochondrial genes (16S rDNA and cytb) from representatives within the Otophysi (Calcagnotto et al., 2005). Divergence times from all three data sets were estimated and compared.

Species-level Phylogenetic Analyses

Te species-level dataset included selected Otophysi, Characiformes, and Characidae sequences (see Tab. 1), and was analyzed using Anotophysi species as outgroups. Representative A. mexicanus cytb haplotype sequences from the Strecker et al., (2004) study were included in the dataset of characiform species to estimate divergence times based on fossil calibrations for comparison with population-based estimates utilizing substitution rates. Alignments of protein-coding regions were trivial and were accomplished using amino acid translations. Sequences of the trop gene spanned an intron, which was removed due to signifcant length variation (70-836 bp) leading to ambiguous alignments. Te alignment of the 16s rDNA gene was generated using the E-INS-i accuracy-oriented strategy of MAFFT v.5 (Katoh et al., 2005). All of the individually aligned genes were then concatenated to form a single dataset consisting 3770bp in length. Te concatenated dataset was analyzed with PAUP* 4.0b10 (Swoford, 2000) using maximum parsimony and implementing the parsimony ratchet method (Nixon, 1999) using a batch fle generated by PAUPRat with the default parameters for 5000 replicates (Sikes & Lewis, 2001).

Divergence time estimation

Population analysis. Dates of divergence were inferred for A. mexicanus lineage A and B cave fsh populations using the cytb and ND2 datasets with BEASTv1.4 (Drummond & Rambaut, 2003). Because the cytb and ND2 haplotype datasets were generated from diferent studies, they cannot be combined. Terefore, each dataset was used to

independently estimate the divergence times of the A. mexicanus cave-adapted haplotype sequences. Each dataset was analyzed using both strict and relaxed clock models (Drummond et al., 2006) tested under constant and skyline models of population growth. As part of BEAST divergence time estimation, either a calibration point (fossil or geologic) or a gene-specifc substitution rate is required. Because there are no geologic dates corresponding to A. mexicanus populations invading subterranean systems, substitution rates were used. For each gene, the range of substitution rates calculated for other freshwater fsh were used. For cytb, mean substitution rates ranged from 0.005 to 0.017 substitutions/site/million year (my) (Bermingham et al., 1997; Burridge et al., 2006; Dowling et al., 2002b; Perdices & Doadrio, 2001; Sivasundar et al., 2001; Zardoya & Doadrio, 1999) and for ND2 mean substitution rates ranged from 0.011 to 0.026 substitutions/site/my (Near et al., 2003; Mateos, 2005). Tese independent rates were used to calibrate the rate of evolution of our datasets by either fxing the rate to the lowest and highest value estimated for each gene or using strong prior distributions on the substitution rates. Two independent MCMC analyses 2x107 steps long were performed sampling every 2,000th generation, with a burn-in of 2x106 generations. All the Bayesian MCMC output generated by BEAST was analyzed in Tracer v1.3 (Drummond & Rambaut, 2003).

Likelihood-based AhRS method. we used the likelihood heuristic rate-smoothing algorithm of (yang, 2004) as implemented in PAML3.14 (yang, 2001). Sequence data were analyzed using the F84+Γ model. Branches at each locus were classifed into four rate groups according to their estimated rates. Te oldest known fossil representatives of major lineages within the Ostariophysi are well established in recent literature (see Briggs, 2005 and references therein), and have been used in recent studies estimating molecular-based divergence times of Otocephalan clades (Peng et al., 2006). Tese fossil representatives were used as calibration points for the AHRS divergence time analysis (Fig. 1, Tab. 2,). Fossil calibrations were accommodated as fxed ages and mapped to the basal node of the clade of interest. Given that most fossils are dated to an age range, the minimum and maximum ages of each fossil were used for divergence time estimations under separate analyses. Fossil dates were determined using the 1999 GSA Geologic Time Scale.

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tab. 1: taxonomy, gene data, and Genbank accession numbers for sequences used in Characiformes phylogeny reconstruction. Abbreviations of mitochondrial gene sequences: 16S = 16S rdNA, cytb = cytochrome b; abbreviations for nuclear gene sequences: fh = forkhead, RAG2 = recombination activating gene, sina = seven in absentia, trop = α-tropomyosin.

Anotophysi (outgroup)

Chanidae

Chanos chanos

Gonorynchidae

Gonorynchus greyi

Kneriidae

Cromeria nilotica

Parakneria cameronensis

Otophysi (ingroup)

CHARACIFORMES

16S

cytb

fkh

RAG2

sina

trop

NC004693 NC004693 NC004702 NC004702

NC007881 NC007881 NC007891 NC007891

Anostomidae Leporinus sp. Chilodontidae Chilodus punctatus Prochilodontidae Prochilodus nigricans Hemiodontidae Hemiodus gracilis Parodontidae Parodon sp. Serrasalmidae Colossoma macropomum Cynodontidae Hydrolycus pectoralis

Characidae

Acestrorhynchus sp. Aphyocheirodon sp. Astyanacinus sp.1 Astyanacinus sp.2 Astyanax bimaculatus Astyanax mexicanus (Brazil) Astyanax mexicanus (haplotype AB) Astyanax mexicanus (haplotype AL) Astyanax mexicanus (haplotype EA) Astyanax mexicanus (haplotype FA) Astyanax mexicanus (haplotype GA) Astyanax mexicanus (haplotype GB) Astyanax scabripinis Brycon hilarii

Bryconamericus diaphanus Bryconops sp. Chalceus erythrurus Chalceus macrolepidotus Cheirodon sp. Cheirodontops sp. Creagrutus sp. Exodon paradoxus Gephyrocharax sp. Hemibrycon beni Hemigrammus bleheri

AY788044 AY791416 AY817370 AY804095 AY790102 AY817252

AY787997

AY788075

AY788027

AY788065

AY788000

AY788033

AY787956 AY787966 AY787969 AY787987 AY787955

AY817325

AY790056 AY817215

AY791437 AY791405 AY791427 AY791386

AY817400 AY804120 AY790133 AY817278

AY817353 AY804084 AY790086 AY817240

AY817390 AY804110 AY790123 AY817269

AY817328 AY804061 AY790059 AY817218

AY817359 AY804088 AY790091 AY817244

AY791353 AY791363 AY791365

AY817288 AY817298 AY817301 AY817317

AY804026 AY804031 AY804033 AY804051

AY790014 AY790025 AY790028 AY790046

AY817181

AY817190 AY817209

AY817287 AY804025 AY790013 AY817180

AY177206 AY639041 AY639051 AY639075 AY639084 AY639089 AY639090

AY787967 AY787976 AY787984 AY787985 AY787990 AY787999 AY787995 AY787996 AY788001 AY788013 AY788014 AY788020 AY788017

AY791370 AY791375 AY791376 AY791379 AY791385 AY791382 AY791383

AY817299 AY817307 AY817314 AY817315 AY817320 AY817327 AY817324

AY791397 AY791398 AY791402

AY817340 AY817341 AY817346 AY817343

AY804040 AY804048 AY804049 AY804053 AY804060 AY804057 AY804058 AY804062 AY804072 AY804073 AY804079 AY804076

AY790026 AY790035 AY790043 AY790044 AY790049 AY790058 AY790054 AY790055 AY790060 AY790072 AY790073 AY790079 AY790076

AY817188 AY817198 AY817206 AY817207 AY817211 AY817217

AY817219 AY817227 AY817228 AY817234 AY817231

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16S

cytb

fkh

RAG2

sina

trop

Hemigrammus erythrozonus

Hemigrammus rodwayi

Hyphessobrycon eques

Inpaichthys kerri

Knodus sp.

Moenkhausia sanctaphilomenae

Mimagoniates lateralis

Prodontocharax sp.

Roeboides sp.

Salminus maxillosus

Triportheus angulatus

Ctenolucidae

Ctenolucius hujeta

Lebiasinidae

Nannostomus beckfordi

Crenuchidae

Characidium fasciatum

Erythrinidae

Hoplias sp.

Alestidae

Arnoldichthys spilopterus

Brycinus nurse

Phenacogrammus aurantiacus

Hepsetidae

Hepsetus odoe

Citharinidae

Citharinus citharus

Distichodontidae

Distichodus sexfasciatus

Neolebias trilineatus

AY788023 AY788034 AY788022 AY788039 AY788041 AY788054 AY788051 AY788064 AY787994 AY788080 AY788082

AY787998

AY788059

AY787992

AY788031

AY787968 AY787970 AY788066

AY788030

AY787989

AY788012 AY788063

AY817349 AY817360 AY817348 AY817365

AY791414 AY817367

AY791420 AY791426 AY791381 AY791438

AY791384

AY791380

AY791409

AY791364 AY791366 AY791428

AY791408

AY791378

AY791396 AY791425

AY817377 AY817389 AY817323 AY817405 AY817407

AY817326

AY817384

AY817322

AY817357

AY817300 AY817302 AY817391

AY817356

AY817319

AY817339 AY817388

AY804081 AY804089 AY804080 AY804093 AY804094 AY804104 AY804101 AY804109 AY804056 AY804124 AY804125

AY804059

AY804055

AY804087

AY804032 AY804034 AY804111

AY804086

AY790082 AY790092 AY790081 AY790097 AY790099 AY790112 AY790109 AY790122 AY790053 AY790137 AY790139

AY790057

AY790117

AY790051

AY817236 AY817245 AY817235 AY817248 AY817249 AY817261 AY817259

AY817214 AY817282 AY817283

AY817216

AY817265

AY817213

AY790090 AY817242

AY804071 AY804108

AY790027 AY790029 AY790124

AY790089

AY790048

AY790071 AY790121

AY817189 AY817191 AY817270

AY817241

AY817226 AY817268

CYPRINIFORMES Cobitidae Misgurnus sp. Cyprinidae Danio rerio Labeo sorex Gyrinocheilidae Gyrinocheilus sp.

SILURIFORMES Callichthyidae Corydoras rabauti Loricariidae Ancistrus sp. Bagridae Chrysichthys sp. Heptapteridae Pimelodella sp. Ictaluridae Ictalurus punctatus

AY788053

AY817379 AY804103 AY790111

AY788011 — AY817338 AY804070 AY790070 AY817225 AY788043 AY791415 AY817369 — AY790101 AY817251

AY788015 AY791399

AY804074 AY790074 AY817229

NC004698      NC004698

AY787958       AY791354 AY817290

AY787957       AY791355

AY787953       AY791351 AY817285

AY788040       AY791413 AY817366

AY790016       AY817183

AY790017       AY817193

AY790011       AY817178 AY790098

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Fig. 1: Characiform divergence time chronogram estimated using a representative topology chosen from the set of 867 most parsimonious trees. White branches indicate branches where less than 75% of the most parsimonious trees were topologically congruent. Te grey box indicates the clade of Astyanax mexicanus sequences. Fossil calibration nodes are numbered and correspond to tab. 2. Te major geologic periods are mapped onto the phylogeny.

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tab. 2: taxonomy and ages of fossils used as calibrations for divergence time estimation. Node # refers to Fig. 1.

Taxonomy

Reference

Geologic age (MYA)

Node #

Otophysi

Characiformes

Gayet, 1982

Late Cretaceous (65-99)

1

Cypriniformes

Catostomidae

Cavender, 1986

Paleocene (54.8-65)

4

Siluriformes

Gayet & Meunier, 2003

late Campanian-early Maastrichtian (68.2-77.4)

3

Corydoras

Cockerell, 1925

Late Palaeocene (61-65)

2

RESULTS

Population-level divergence time estimations. Estimates of the mean divergence times were not signifcantly different between strict and relaxed clock and population growth models and calibration methods of the substitution rate, but confdence intervals under the fxed substitution rate approach were narrower, as expected. Hence only the time estimates under the strict clock model, constant population size and minimum and maximum mean substitution rates for both genes are provided. Comparing the cytb and ND2 estimates of divergence times for the A. mexicanus A and B lineages show several features. First, the estimated ranges of divergence for cave hap-lotypes within each lineage were similar between genes (cytb and ND2) and lineages (A and B), placing the divergence among hypogean populations between 0.141-0.885 Ma for lineage A, and 0.084-0.575 Ma for lineage B (Tab. 3). when comparing the estimates among genes within a lineage, however, the divergence times of hypo-gean and epigean haplotypes are diferent, with cytb estimates providing generally older estimates.

Species-level divergence time estimation. Using the maximum parsimony ratchet, the selected Characidae,

Characiform, and Otophysi sequences generated 867 trees of score 11758. Te 50% majority rule consensus of these trees was similar to the published research that generated the data (Calcagnotto et al., 2005). Because a fully resolved tree with branch lengths is required for AHRS divergence time estimation and because very few branches in the consensus tree collapsed (e.g. were in confict), a random tree from the set of 867 was used (Fig. 1). Te A. mexicanus sequences included in the analysis clustered with other Characidae species, although were not monophyletic with other Astyanax species (A. bi-maculatus and A. scabripinnis). Te divergence time estimates for the representative A. mexicanus cave fsh populations generated using this phylogeny with Oto-physi fossil calibrations agreed well with the estimates of hypogean haplotype divergence from cytb and ND2 using substitution rates (Tab. 3). However, the estimates of cave versus surface population divergence times based on fossil calibrations were in better agreement with ND2 than with cytb estimates. Tis is particularly interesting, as the only gene included in this dataset for A. mexica-nus was cytb.

tab. 3: Comparison of divergence time estimates using substitution rates and molecular clock methods for cytochrome b (cytb) and NAdh dehydrogenase 2 (Nd2) mitochondrial genes, and for molecular methods incorporating fossil dates as calibrations.

Substitution Rates

Fossil Calibration

Cytb

ND2

Min – Max (Ma)

Min – Max (Ma)

Min – Max (Ma)

Lineage A

cave

0.261 - 0.885

0.141 - 0.331

0.2-0.3

cave vs. surface

0.588 - 2.00

0.256 - 0.599

0.4-0.5

Lineage B

cave

0.169 - 0.575

0.084 - 0.196

0.1-0.1

cave vs. surface

1.524 - 5.181

0.877 - 2.055

1.7-2.2

Lineage A vs. Lineage B

1.741 - 5.922

1.053 - 2.472

1.7-2.2

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DISCUSSION

Previous molecular studies of A. mexicanus phylogeog-raphy indicate that at least two independent invasions of surface Astyanax have occurred (Dowling et al., 2002a; Strecker et al., 2003, 2004). Our estimates of divergence time from two diferent methods and three diferent datasets are in general agreement about the divergence times among the cave haplotypes in each lineage (Tab. 3). Tese estimates place cave haplotype divergence times in the Pleistocene, when it is suggested that climatic cooling of surface waters led to the extinction of Astyanax in North America (Strecker et al., 2004). In particular, our data show an interesting pattern for lineage B haplotypes, which are proposed to be the older of the two lineages. Te recent divergence times estimated for lineage B hap-lotypes (0.084-0.575 Ma) supports the hypothesis that afer the initial colonization event, subterranean routes of colonization were associated with fuctuating ground-water levels in the Pleistocene (Strecker et al., 2004). Te fact that estimated times of within lineage divergence were similar also suggests that the divergence of subterranean haplotypes in both lineages were infuenced by the same processes.

In order to determine the evolutionary age of the subterranean lineage, and therefore estimate the time required for evolution of the troglomorphic form, the divergence of the hypogean haplotypes from epigean populations is needed. However, the estimates from our three datasets did not agree, with cytb molecular clock methods estimating older divergence times than either ND2 or fossil calibrated estimates. Some of the discrepancy is due to the fact that diferent sets of surface populations were sampled in each study (Dowling et al., 2002a; Strecker et al., 2004). For example, the most closely related surface population in the cytb study were from Belize (Strecker et al., 2004) while there were no closely related surface populations to lineage B haplotypes in the ND2 study (Dowling et al., 2002a). However, this makes the older cytb estimates even more notable because lineage B haplotypes have no evidence of introgressive hybridization with surface populations. If we consider just lineage B hypogean divergence from surface ancestors as an estimate of subterranean evolution, the estimated time for acquisition of the troglomorphic form is 0.877-2.055 Ma (quaternary – Tertiary boundary) based on ND2 and fossil calibrations, while it is 1.524-5.181 Ma (Pliocene) based on cytb.

Although the estimates of divergence times among the three diferent datasets did not agree, comparison of estimates between the lineages show that lineage A diverged from surface ancestors more recently than lineage B (Tab. 3). Tis more recent divergence from

epigean populations is congruent with previous hypotheses, that either lineage A populations represent a more recent subterranean invasion, or that they are an older invasion masked by more recent mitochondrial intro-gressive hybridization with surface forms (Dowling et al., 2002a). In the few studies that have looked at other markers (allozymes, microsatellites, and RAPDs), it has been suggested that at least Chica and Pachón populations are the result of surface introgression (Avise & Se-lander, 1972; Espinasa & Borowsky, 2001; Strecker et al., 2003). Furthermore, based on the degree of variability in troglomorphic features of each lineage A population, it has been suggested that diferent populations represent diferent degrees and patterns of surface introgression. In order to more accurately determine both the patterns of introgression in the lineage A populations, as well as the underlying relationships of the cave populations to each other in order to estimate subterranean evolutionary times, studies investigating more types of markers are needed.

Previous research of A. mexicanus populations throughout Mexico (including cavefsh lineages A and B) estimated haplotype divergences to range from 1.8 – 4.5 Ma (Strecker et al., 2004). Our estimates suggest that divergence times among cave haplotypes and between lineage A cave and epigean haplotypes are much younger than this; however, hypogean divergences from surface ancestors in lineage B are concordant with these older dates.

Te evolutionary history of cave adaptation in A. mexicanus is complex. Based on mitochondrial molecular clock estimates, our estimates of divergence times are congruent with previous hypotheses by showing lineage B to be a phylogenetically older subterranean lineage, with more recent divergence among subterranean systems. However, this study also provides quantitative dates for these events. Lineage A populations are estimated to be younger; however, these dates only represent mito-chondrial lineages. Several of the populations in lineage A have been shown to be introgressed with surface forms (Chica, Pachón, and Subterraneo). To our knowledge, the hypothesis of surface introgression has not been investigated in the remaining lineage A populations (Molino, Pichijumo, and yerbaniz). Understanding the patterns of introgression in all of the lineage A populations, and estimating the actual subterranean evolutionary time, requires investigating additional nuclear markers.

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HOw LONG DOES EVOLUTION OF THE TROGLOMORPHIC FORM TAKE? ESTIMATING DIVERGENCE TIMES ...

CONCLUSIONS

Features including colonization routes (stream capture) and the existence of both epigean and cave-adapted hy-pogean populations make A. mexicanus an attractive system for investigating the subterranean evolutionary time necessary for acquisition of the troglomorphic form. If it is possible to estimate the divergence time of closely related cave versus surface populations, we can estimate the age of subterranean occupancy. Tis same divergence time also has relevancy to geologic processes in the karst system by providing a rough estimate of the age of subterranean stream capture in particular regions. Based on published sequence data, we have estimated divergence times for three events in the evolutionary history of troglomorphic A. mexicanus populations. First, divergence times among cave haplotypes in both lineages occurred in the Pleistocene, possibly correlating with fuctuating water levels allowing the colonization,

and subsequent isolation of, new subterranean habitats. Second, in lineage A, A. mexicanus cave populations experienced introgressive hybridization events with surface populations recently. Finally, using divergence times of lineage B from surface populations as an estimate, the acquisition of the troglomorphic form in A. mexicanus is younger than 2.2 (fossil calibration) – 5.2 (cytb) Ma (Pliocene). Given that there are at least 30 caves known to contain populations of A. mexicanus (Espinasa et al., 2001; Mitchell et al., 1977), the number of independent invasions and instances of introgressive hybridization may be even higher than currently understood. In order to fully understand the number of independent invasions, the history of introgression with surface populations, and the divergence times of cave and surface populations, a broader survey of cave fsh populations and of both nuclear and mitochondrial markers is needed.

LITERATURE CITED

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yang, Z., 2001: PAML: Phylogenetic Analysis by Maximum Likelihood. University College London, London.

yang, Z., 2004: A heuristic rate smoothing procedure for maximum likelihood estimation of species divergence times. -Acta Zoologica Sinica, 50, 645-656.

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COBISS: 1.01

AGE ESTIMATES FOR SOME SUBTERRANEAN TAxA AND LINEAGES IN THE DINARIC KARST

OCENE STAROSTI ZA NEKATERE PODZEMELJSKE TAKSONE IN ŽIVALSKE LINIJE NA DINARSKEM KRASU

Peter TRONTELJ1, Špela GORIČKI1, Slavko POLAK2, Rudi VEROVNIK1, Valerija ZAKŠEK1 & Boris SKET1

Abstract                                 UDC 575.8:551.442(234.422.1)

591.542(234.422.1)

Peter Trontelj, Špela Gorički, Slavko Polak, Rudi Verovnik, Valerija Zakšek & Boris Sket: Age estimates for some subterranean taxa and lineages in the Dinaric Karst

Using a comparative phylogeographic approach and diferent independent molecular clocks we propose a timescale for the evolution of troglobionts in the Dinaric Karst that is relatively consistent over a wide taxonomic range. Keystone events seem to belong to two age classes. (1) Major splits within holodinaric taxa are from the mid-Miocene. Tey present the potential upper limit for the age of cave invasions. (2) Regional diferentia-tion, including speciation, which can at least in part be associated with a subterranean phase, took place from early Pliocene to mid-Pleistocene. we suggest two to fve million years as the time when most of the analyzed lineages started invading the Dinaric Karst underground.

Key words: subterranean, molecular clock, molecular phylog-eny, phylogeography, Dinaric Karst.

Izvleček                                 UDK 575.8:551.442(234.422.1)

591.542(234.422.1)

Peter Trontelj, Špela Gorički, Slavko Polak, Rudi Verovnik, Valerija Zakšek & Boris Sket: Ocene starosti za nekatere podzemeljske taksone in živalske linije na Dinarskem krasu

Z uporabo primerjalnega flogeografskega pristopa in neodvisnih molekularnih ur smo predlagali časovni potek evolucije troglobiontov Dinarskega krasa, ki velja za sorazmerno veliko število taksonov. Zdi se, da ključni dogodki pripadajo dvema obdobjema. (1) Glavne razdelitve znotraj holodinarskih tak-sonov so iz obdobje srednjega miocena. Predstavljajo zgornji potencialni časovni limit za naselitev jam. (2) Regionalna diferenciacija, vključno s speciacijo, ki je lahko vsaj deloma povezana s podzemeljsko fazo, naj bi se zgodila med zgodnjim in srednjim pleistocenom. Ocenjujemo, da se je začela invazija večine proučevanih živalskih linij v podzemlje Dinarskega krasa v obdobju med dvema in petimi milijoni let. Ključne besede: podzemlje, molekularna ura, molekularna flogenija, flogeografja, Dinarski kras.

INTRODUCTION

Te use of new molecular and systematic techniques using allozymes and DNA sequences has enabled us to see a new picture of the evolution and diversity of subterranean fauna (e.g. Avise & Selander 1972; Sbordoni et al., 2000; Caccone & Sbordoni 2001; Leys et al., 2003; Verovnik et al., 2004; Gorički & Trontelj 2006; Lefébure et al., 2006; Zakšek et al., 2007). Molecular clock ap-

proaches should, at least in theory, enable us to date, to verify or to falsify previous hypotheses about the age of subterranean species. To be exact, it is usually not the age of a lineage or a taxon itself that is of special interest or under dispute, but the time since it has attained its subterranean nature, making it even more challenging. Hypotheses and models explaining cave invasions

1 Oddelek za biologijo, Biotehniška fakulteta, Univerza v Ljubljani, Večna pot 111, 1000 Ljubljana, Slovenia, fax: +386 1 2573390, e-mail: peter.trontelj@bf.uni-lj.si

2 Notranjski muzej Postojna, Ljubljanska 10, 6230 Postojna, Slovenia.

Received/Prejeto: 30.01.2007

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PETER TRONTELJ, ŠPELA GORIČKI, SLAVKO POLAK, RUDI VEROVNIK, VALERIJA ZAKŠEK & BORIS SKET

and speciation in caves are well-elaborated (e.g. Rouch & Danielopol 1987; Holsinger 2000; Trajano 2005) and should thus ofer good grounds for the timing of such events and for testing their correlation with geographical, geological and hydrographical counterparts. For example, Leys et al., (2003) have shown that all evolutionary transitions to subterranean life in Australian dytiscids took place during the Late Miocene and Early Pliocene as a result of aridifcation. However, reliable data on the age of these events is surprisingly scarce. when such data are available, the accuracy is ofen below that of molecular clock rates. In fact, the use of molecular dating methods itself has introduced considerable uncertainty about how old subterranean species might be. while the youngest estimation, based on “classical” biological reasoning, is no more than 10,000 years (Sket 1997), the upper limit for the divergence of two subterranean sister species has been pushed to an incredible 110,000,000 years (Buhay & Crandall 2005).

Boutin and Coineau (2000) have argued that dating of cladogenetic events by a molecular clock is particular-

Te presented data were taken from several phylogeo-graphic studies of subterranean animals in the Dinaric Karst, including the ubiquitous aquatic isopod Asellus aquaticus Linne (Verovnik et al., 2004, 2005), the cave salamander Proteus anguinus Laurenti (Gorički 2006, Gorički & Trontelj 2006), and the cave shrimp troglo-caris s. lato (Zakšek et al., 2007). Further, we included unpublished sequences from studies that are in progress, including leptodirine cave beetles and aquatic sphaero-matid isopods from the genus monolistra. Te age estimations for the last two groups should be regarded as preliminary because in-depth analyses of phylogenetic relationships and corroboration by further loci are still under way. we were only interested in a small number of well-supported splits and therefore used straightfor-

Te split between major geographically defned lineages Te geographical distribution of troglobiotic (including stygobiotic) sister taxa can be used to infer independent cave invasions. For example, if the present-day ranges of two troglobionts are separated by large areas of non-karstic terrain without hypogean habitat, we can

ly useful in the case when the dates are corroborated by other methods. Since the obvious problem of the Dinaric Karst area is that reliable dating for clearly defned vicari-ant events or the age of available subterranean habitat is lacking, it has been impossible to corroborate molecular clock divergence by independent data. In this case a comparative phylogeographic approach might provide the means for an independent validation of age estimates. Comparative phylogeography seeks, as does historical biogeography, concordant geographical patterns of codistributed lineages (e.g. Arbogast & Kenagy 2001). Te evolution of codistributed phylogeographic groups of diferent taxa is likely to have been driven by the same historical factors, like vicariant events or climatic shifs.

In this contribution we (1) identify common phylo-geographic patterns among those troglobiotic taxa from the Dinaric Karst for which such data are available, and (2) estimate the timeframe of the corresponding cladoge-netic events using a global molecular clock approach.

ward minimum evolution searches with bootstrapping as implemented in MEGA (Kumar et al., 2004). Divergence time estimates are based on available clock-rate data for groups that are as closely related as possible (Caccone & Sbordoni [2001] for leptodirines, Ketmaier et al., [2003] for Asellus aquaticus, and Sturmbauer et al., [1996] and Schubart et al., [1998] for monolistra). To assure compatibility between molecular divergences we used the same models as were used in the original works describing the rates (Tamura-Nei distances with a gamma distributed rate variation among sites). where more than one hap-lotype per population or lineage was analyzed we used net between group distances to correct for ancestral in-traspecifc diversity.

postulate an epigean last common ancestor. Examples of that kind can be found in the shrimp genus troglo-caris, with the hercegovinensis lineage inhabiting Trans-caucasian and SE parts of the Dinaric Karst where it is sympatric with the SE populations of the Anophthalmus lineage (Zakšek et al., 2007). Teir split estimated at 6–11

MATERIAL AND METHODS

RESULTS

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Myr ago is the oldest, although unlikely, possible time of cave invasion. Te youngest split that could be reliably inferred from the phylogenetic tree and probably still occurred in surface waters, was the one between the Bosnian lineage and other “Anophthalmus” lineages. Because the karst area in Bosanska Krajina, to which the Bosnian clade is restricted, is so remote and isolated from the rest of the Dinaric populations, it is reasonable to assume that an underground connection between them could never have existed. Te estimated time of this split, 3.7–5.3Myr ago, is hence the oldest possible age at which troglocaris anophthalmus might have invaded the Dinaric Karst underground (Tab. 1).

For the cave salamander Proteus anguinus, exhibiting a distribution pattern similar to that of troglocaris, the corresponding age of the Bosanska Krajina lineage was estimated at 4.4–5.4 Myr (Gorički 2006). However, older lineages exist that, theorethically, might have invaded caves even as early as 8.8–16 Myr ago (see also Fig. 1).

Another troglobiotic group restricted to the Dinaric Karst area and having a non-troglomorphic sister group is the Dinaric clade of Asellus aquaticus (see Verovnik et al., 2005). Te time of this split, and hence the maximum possible age of cave invasion is 3.8–4.8 Myr.

TIMING OF MORPHOLOGICAL CHANGES

where possible, we tried to combine the biology (e.g. degree of troglomorphism, lack of gene fow) of taxa with corresponding data on paleogeography and paleo-hydrography to infer speculative scenarios on how and when lineages might have switched to subterranean life and evolved troglomorphic traits. For example, we have some indication about how long at most it takes a salamander population to become troglomorphic. Since the subspecies P. a. parkelj Sket et Arntzen has retained its ancestral, non-troglomorphic characteristics, it is reasonable to conclude that its sister lineage must have evolved

troglomorphoses independently from other, less related troglomorphic lineages (Sket & Arntzen 1994; Gorički & Trontelj 2006; see Fig. 1). Te split between the non-troglomorphic lineage and its last troglomorphic sister lineage was estimated at 0.5–0.6 Myr based on mitochon-drial rDNA sequences, 1.1–2.4 Myr based on the mtDNA control region (Gorički 2006), and at 1.1–4.5 Myr by an allozyme clock (Sket & Arntzen 1994).

Asellus aquaticus has evolved several separate subterranean and troglomorphic populations. One of them, from the subterranean Reka River below the Kras/Carso Plateau, is genetically completely isolated from epigean populations at the Reka resurgence while there are no epi-gean populations in the Reka before the sink (Verovnik et al., 2003, 2004, 2005; Fig. 2). Further, it has no mtDNA

tab. 1. Estimated time (in million years) of some keystone events in the evolution of troglobionts in the dinaric Karst.

Taxon

Age of

holodinaric

group

Age of

merodinaric

group

Mid-Dinaric split

Northwest split

Troglocaris (Dinaric and Caucasian lineages)1

7.9-15.1

n.a.

n.a.

n.a.

Troglocaris anophthalmus agg.1

n.a.

3.7-5.3

1.3-2.3

1.5-2.1

Troglocaris hercegovinensis agg.1

n.a.

3.8-4.8

n.a.

n.a.

Proteus anguinus2

8.8-16.0

n.a.

8.8-16.0

4.2-5.2

Asellus aquaticus (Dinaric clade)3

n.a.

3.8-4.8

n.a.

0.8-1.2

Microlistra4

n.a.

1.1-2.3

n.a.

n.a.

Pseudomonolistra hercegoviniensis4

n.a.

0.3-1.0

n.a.

n.a.

Monolistra caeca4

n.a.

1.8-3.7

n.a.

n.a.

Leptodirus hochenwartii hochenwartii

et L. h. reticulatus5

n.a.

1.9-2.0

n.a.

n.a.

1Using COI clock for shrimps (see Knowlton & Weigt 1998; zakšek et al., 2007)

2Using 12S and 16S rdNA clock for Newts (see Cacconesee et al., 1997; Gorički 2006)

3Using COI clock for subterranean Asellota (see Ketmaier et al., 2003; verovnik et al 2005)

4Using 16S r-RNA clock for fddler crabs (Sturmbauer et al 1996) and land crabs (Schubart et all 1998)

5Using COI clock for subterranean leptodirine beetles (Caccone & Sbordoni 2001)

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Fig. 1: A simplifed view of the phylogenetic relationships obetween troglomorphic and non-troglomorphic Proteus anguinus populations (from Gorički and trontelj 2006). Postulating a non-troglomorphic ancestor and unidirectional evolution toward troglomorphism, we can take the split between the black subspecies (non-troglomorphic) and its unpigmented sister lineage to estimate the maximal time (t1) needed for a salamander lineage to evolve the entire array of cave-related traits known in this taxon. If one accepts the notion of multiple independent cave invasions for Proteus, than t2 is the potentially oldest time since it has become subterranean.

and nuclear rDNA haplotypes in common with hypoge-an populations from the Ljubljanica River drainage with which the Reka drainage has been connected many times during the Pleistocene and occasionally even nowadays (Habič 1989). It is thus reasonable to assume that the ancestor of the subterranean Reka River population invaded hypogean waters and became cave-adapted before any secondary contact could occur. Te estimated age of the Reka River lineage is 3.1–4.1 Myr (Verovnik et al., 2004), making it a pre-Pleistocene troglobiotic relict (Verovnik et al., 2004).

monolistra, a troglobiotic group of freshawater sphaeromatid isopods, shows a high taxonomic and morphological diversity restricted to the Dinaric Karst and parts of the Southern Calcareous Alps. According to our preliminary results of a molecular phylogenetic analysis based on nuclear and mitochondrial DNA sequences, there are at least three well-supported monophyla. Tese are the subgenus m. (microlistra), m. (monolistra) caeca Gerstaecker, and the polytypic m. (Pseudomonolistra) hercegoviniensis Absolon. Several lines of evidence suggest that the common ancestors of each of these groups invaded cave waters polytopically (Sket 1986, 1994). while we remain ignorant about when and how ofen ancestral monolistra lineages invaded subterranean waters, we can expect that the radiation of at least some of the three groups took place in the underground. Teir ages

VALERIJA ZAKŠEK & BORIS SKET

Fig. 2: Te case of troglomorphic and non-troglomorphic lineages of Asellus aquaticus in the dinaric Karst, highly simplifed (from verovnik et al 2004, 2005). Te Reka and the Ljubljanica (Ljub) basin lineages have independently invaded subterranean waters and thus constitute separate taxa, although traditionally assigned to the same subspecies, A. a. cavernicolus. Te subterranean Reka River population presents the oldest stygobiotic lineage of Asellus aquaticus. because it is genetically completely distinct, it must have escaped interbreeding during various times of hydrological contact with surface populations. We therefore believe that it became a specialized stygobiont soon afer the split at time t1. Te Ljub lineage from the subterranean Ljubljanica River, although morphologically distinct, is still sharing mtdNA haplotypes with surface populations and thus represents a younger invasion. Eur and din denote various epigean European and dinaric lineages, respectively.

(maximally 0.4–3.7 Myr) give us an idea for how long some monolistra lineages have been dwelling in the Di-naric Karst underground.

Leptodirus hochenwartii Schmidt, a highly troglo-morphic leptodirine cave beetle, is the only terrestrial Dinaric troglobiont with available molecular dating. Using a leptodirine COI clock calibration by Caccone and Sbordoni (2001) we estimated the age of the Leptodirus lineage by dating the split with Astagobius angustatus Schmidt, its slightly less troglomorphic sister lineage. Te estimated time of this split (8.7–9.8 Myr ago) is the oldest possible age at which the extremely specialized morphology of Leptodirus could have started evolving. Moreover, taking into account recent unpublished phy-logenetic fndings based on nuclear and mitochondrial gene sequences, the traditional subspecies of Leptodirus in fact represent distinct lineages with divergences well in the range of between species comparisons. Tese lineages all share the same constructive apomorphic troglomor-phic characters, and it seems probable these troglomor-phies have already existed at least at the time of their last common ancestor. Te time of divergence between basal Leptodirus lineages hence represents the youngest possible age at which Leptodirus has evolved its full array

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of troglomorphic characters. Based on a yet incomplete taxonomic sample (L. h. hochenwartii Schmidt and L. h. reticulatus J. Müller) we tentatively dated it at 1.9–2.0 Mya.

TIMING OF PALEOHyDROGRAPHIC CHANGES

For some stygobiotic taxa with a broader Dinaric range, we identifed two concordant geographic patterns possibly pointing to common underlying historical events, like changes in hydrographic connections. Tese vicari-ant patterns include (1) a split between a northwestern and southeastern Dinaric clade (mid-Dinaric split), and (2) a younger subdivision of the northwestern clade (or of a part thereof) into a western and eastern Slovenian lineage (Tab. 1).

It has been stated that some stygobiotic species inhabit areas that are hydrographically fragmented. Te

Before we reach any conclusions we would like to note that dating of keystone events in the evolution of subterranean life, as well as anywhere else in evolution (e.g. Graur & Martin 2004), remains a highly speculative enterprise. Of central concern should be the fact that we are relying on a more or less global clock within certain taxonomic boundaries. Tese clocks usually rely on single calibration points (e.g. the separation of the Sardinia-Corsica microplate from the Iberian Peninsula; Ketmaier et al., 2003) and have mostly not been tested against independent geological events.

Further, all our timings assume linear accumulation of substitutions over time, i.e. the existence of a valid molecular clock. Although we can be quite sure that this assumption is violated to a certain extent, we can mitigate the problem by excluding those taxa from the analysis that violate the linearity assumption most. More sophisticated and realistically modeled approaches use a relaxed clock allowing for diferent local rates on diferent branches of the tree (e.g. Sanderson 2002). However, with single calibration points only, such approaches yield quite hopeless and certainly unrealistic intervals. For example, the age of the deepest split in the Niphargus virei (subterranean amphipod from France) complex was estimated at 14–19 Myr using a global Stenasellus clock, whereas the relaxed clock estimate was 22–71 Myr (Lefébure et al., 2006).

Tird, it should be noted that even with the aid of molecular phylogenetic tools the timing is still susceptible to incorrect estimations of relationships and incomplete taxonomic coverage. For example, the timing of the

most parsimonious explanation of such distributions is that their ranges were hydrographically interconnected in the past. Tis may as well include the surface paleohy-drography that was heavily fragmented by karstifcation. Te (polytopic) immigration underground could thus have proceeded simultaneously with the separation of ancestral populations. we can illustrate this scenario by the case of some monolistra lineages, namely of the subgenus microlistra and of the species m. (m.) caeca. Some ten microlistra spp. are perfectly allopatric in distribution, mainly bound to actual watersheds. Another group, m. caeca, inhabits at least three watersheds, in which four named subspecies have evolved. According to a 16S rDNA molecular clock (Sturmbauer et al., 1996, Schubart et al., 1998), the system began to fragment about three million years ago.

origin of the highly troglomorphic morphologies in Lep-todirus depends on the most basal split in the taxon. By not having included all known subspecies, we are facing the risk that some other subspecies might have branched of earlier than the studied ones.

One potentially useful way to improve our informal confdence in the timing of evolutionary events in subterranean animals is to look for phylogeographic correspondence of timings derived from independent taxa with independent molecular clocks. At the present stage of most of our analyses such comparisons can only be preliminary. we can nevertheless notice that specifc groups of events belong to diferent age classes, most markedly the gap between the age of holodinaric troglobionts and those with narrower distributions within the Dinaric Karst (Tab. 1). Te recent lineages of Proteus and troglocaris probably both originate from the Miocene Dinaride Lake System (Krstić et al., 2003), and the age of both taxa refects their diferentiation long before they invaded the hypogean environment (Sket 1997; Gorički 2006; Zakšek et al., 2007). Regional diferentiation, including speciation, which can at least in part be associated with a subterranean phase, appears to be much younger, ranging from Pliocene to mid-Pleistocene. Based on these estimates plus the estimated age of the Reka River lineage of Asellus aquaticus (see above) we, tentatively, suggest two to fve million years as the time when most of the analyzed lineages started invading the Dinaric Karst underground.

Te mid-Dinaric split of Proteus and troglocaris anopthalmus does not seem to originate from the same

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vicariant event as the latter was estimated to be younger by an order of magnitude. Another commonality of the phylogeographic pattern, the division between a western and an eastern clade in the Slovenian Dinaric Karst, might have a common hydrogeological cause in two sty-gobiotic crustaceans (A. aquaticus and t. anophthalmus) somewhere in the middle of the Pleistocene. In Proteus, however, the same split appears to be substantially older. In the Dinaric Karst we were, so far, unable to fnd reliable time estimates for paleogeographic events to calibrate local molecular clocks in diferent lineages. Con-

versely, the timing of phylogenetic events can serve, inasmuch as we rely on global molecular clocks, to estimate the date of geographical, hydrographical, and geological changes (Sket 2002). Te comparative phylogeographic approach and the use of diferent independent molecular clocks have enabled us for the frst time to propose a tim-escale for the evolution of troglobionts that is relatively consistent over a wide taxonomic range. Tis timescale is a preliminary one, though. we expect it to change with the inclusion of further taxa, the study of more genes and the use of more accurate molecular dating approaches.

ACKNOwLEDGMENTS

we are indebted to many friends and colleagues who      several research projects funded by the Slovenian Re-helped us with the acquisition of biological samples and      search Agency, and of the contract n° EVK2-CT-2001-accompanied us during feld work. we thank Gregor      00121- PASCALIS of the Fifh Research and Technologi-Bračko and Jožica Murko-Bulič for their indispensable      cal Development Framework Program supported by the assistance in the lab. Te presented work is the result of      European Community

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IZZIV OCENJEVANJA STAROSTI PODZEMELJSKIH ŽIVALSKIH

LINIJ: PRIMERI IZ BRAZILIJE

Eleonora TRAJANO1

Abstract                                               UDC 551.44:597(81)

591.542(81)

Eleonora Trajano: Te challenge of estimating the age of subterranean lineages: examples from Brazil

Te applicability and efectiveness of diferent kinds of evidence used to estimate the age of lineages – morphological, molecular, phylogenetic, biogeographical, geological – are discussed. Examples from the Brazilian subterranean fauna are presented, using mainly fshes, one of the best studied groups, as a model. Only three taxa including troglobites are object of molecular studies, all in progress. Terefore, molecular clocks cannot be applied yet, and indirect evidence is used. Few phylogenies are available, e.g. for the catfsh families Heptapteridae and Tricho-mycteridae. Teoretically, basal troglobitic clades are older than apical ones, but the possible existence of extinct epigean taxa belonging to such clades hampers the comparison. As well, the limitations of the use degrees of troglomorphism to estimate phylogenetic ages are analyzed with focus on the complexity of the mechanisms underlying morphological diferentiation. Paleoclimatic reconstructions based on dating of speleothems from caves in northeastern and southeastern Brazil are available, but limited up to the last 200,000 years, thus useful for relatively recent lineages. Topographic isolation, probable for some fsh groups from Central Brazil, is also within the time range of 105 years. Older dated events (in the order of 106 years or more) that may represent vicariant events afecting aquatic lineages with subterranean derivatives are related to the establishment of the modern South American main river basins. In view of the paucity of data useful for estimating the age of Brazilian troglobitic lineages, combined evidence, including morphology, systematics and biogeography, seems to be the best approach at the moment.

Key words: evolution of troglobites, degree of troglomorphism, Brazil, subterranean fshes, diferentiation rates.

Izvleček                                                UDK 551.44:597(81)

591.542(81)

Eleonora Trajano: Izziv ocenjevanja starosti podzemeljskih živalskih linij: primeri iz Brazilije

V prispevku je opisana uporabnost in učinkovitost različnih pristopov za ocenjevanje starosti živalskih linij s pomočjo morfologije, molekularne flogenije, biogeografje in geologije. Predstavljeni so primeri podzemeljske favne iz Brazilije, predvsem rib kot najbolj raziskane skupine. Molekularno-biološke raziskave, ki vključujejo tudi troglobionte, opravljamo na zgolj treh taksonih. Molekularne ure zaenkrat še ne moreme uporabiti, vendar zgolj posredne dokaze. Na voljo imamo le nekaj flogenetskih podatkov, npr. za morske zmaje iz družin Hep-tapteridae in Trichomycteridae. Teoretično so bazalni troglo-bitski kladi starejši od apikalnih, čeprav verjeten obstoj, sicer izumrlega epigejičnega taksona, ki pripada takim kladom, ovira primerjavo. Omejitve uporabe troglomorfzma za ocenjevanje flogenetske starosti smo analizirali s poudarkom na kompleksnosti mehanizmov, ki so osnova morfološkemu razločevanju. Razpoložljiva paleoklimatska rekonstrukcija, ki temelji na dat-iranju kapnikov iz jam severovzhodne in jugovzhodne Brazilije, je omejena na zadnjih 200.000 let in je kot taka uporabna le za relativno recentne linije. Topografska izolacija, ki verjetno velja za nekaj skupin rib iz osrednje Brazilije, spada v časovno obdobje 105 let. Starejši datirani dogodki (obdobje 106 let ali več), ki naj bi predstavljali vikariantske dogodke in ki so pomembni za vodne linije podzemeljskih sorodnikov, so povezane z razvojem današnjih glavnih južnoameriških porečij. Trenutno je, zaradi maloštevilnih podatkov, najboljša metoda za ocenjevanje starosti brazilskih troglobitskih linij kombinacija pristopov, ki vključujejo morfologijo, sistematiko in biogeografjo. Ključne besede: evolucija troglobiontov, speleobiologija, stopnja troglomorfzma, Brazilija, podzemeljske ribe, razločevalno razmerje.

1 Departamento de Zoologia, Instituto de Biociências da Universidade de São Paulo, São Paulo, BRASIL; e-mail: etrajano@usp.br Received/Prejeto: 06.12.2006

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ELEONORA TRAJANO

INTRODUCTION

Te problem of estimating ages for subterranean or any other lineages starts with the very defnition of age, whether the time since the isolation from the immediate sister-group (age of the cladogenetic event) or the beginning of diferentiation, either the genetic or the morphological one (see Boutin & Coineau, 2000, for a discussion about the concept of phylogenetic ages). Diferent kinds of evidence have been used to establish ages of lineages, but their applicability depends on the aspect of age considered. Molecular studies may provide ages of genetic diferentiation, independently of morphological change. Dating of potential geological isolation events, such as periods of climatic stress and large scale geological changes, may be used to infer the time in isolation. Inferences about relative times of isolation or diferentiation also come out from comparative morphological studies within a phylogenetic and biogeographic framework. Ideally, all evidence should be combined to produce coherent hypotheses about the evolution of subterranean lineages in the temporal scale.

In Brazil, robust molecular studies encompassing exclusively subterranean (troglobitic) taxa started very recently and focus on a few fsh groups with very specialized troglomorphic derivatives. Basically three groups are under study with focus on populations or species: the phreatobitic characiform Stygicthys typhlops, from a karst area in eastern Brazil (studied by F. P. L. Marques & C. R. Moreira); the Amazonian catfsh genus Phreatobius, with phreatobic species collected in wells situated in alluvial plains (studied by J. Muriel Cunha); and the hep-tapterid subterranean catfsh from Chapada Diamantina, northeastern Brazil, belonging to the genus Rhamdiopsis (F.A.Bockmann, pers. comm.), previously cited as a “new genus” (studied by R. Borowsky & M. E. Bichuette). Few phylogenetic studies with biogeographic analyses of larger groups including Brazilian troglobites are available.

Studies aiming to establish the ages of paleoclimatic fuctuations based on speleothem dating are also recent in Brazil, but are progressing quickly. Important climatic

changes have been recorded in diferent karst areas, from the presently semiarid northeast to wet areas in the subtropical southeast. However, these studies are restricted to the late quaternary, imposing limits to its application to the problem of establishing ages for subterranean lineages because many of these lineages probably have a more ancient origin. Older geological events, such as the Miocene – Plio-Pleistocene important changes that produced the modern Amazon River system, are useful to estimate the age of some Brazilian lineages.

Classically, the degree of troglomorphism, basically the reduction of eyes and pigmentation, has been used as a measure of the phylogenetic age for troglobitic animals (Poulson, 1963; wilkens, 1973, 1982; Langecker, 2000). In spite of the many restrictions to its generalized application (see below), the degree of morphological specialization may, in certain cases, provide relative ages of isolation in the subterranean environment, being a supplement to molecular and geological evidence.

In the phylogenetic context, a lineage is a branch which departs from one node to another (hypothetical “ancestor”), from a node to a terminal, or an “ancestral” branch plus all the derived terminals, including extinct taxa (which remain unnoticed unless a fossil is known). Te present discussion deals lineages including terminals. It must be noted that the ever present possibility of extinction of epigean terminals in a lineage leading to a troglobitic taxon is a source of bias that may produce overestimations of its time of isolation in the subterranean environment.

Among Brazilian subterranean taxa, fshes are by far the best studied group with focus on the currently discussed aspects. Tus, I took basically examples from these animals. For the sake of simplicity, I use herein the term “subterranean” as synonym of “troglobitic” (exclusively subterranean) species, to the exclusion of the equally subterranean, although not exclusively, troglophilic and trogloxenic populations.

DEGREE OF TROGLOMORPHISM AND PHyLOGENETIC AGE:

Te use of the degree of troglomorphism to infer relative phylogenetic ages is based on the assumption that the rates of morphological diferentiation are fairly constant among subterranean taxa, at least those regarding eyes and pigmentation, which tend to be lost along the isolation in subterranean habitats. To accept this notion, it is

necessary to assume that the mechanisms of reduction are the same for each of these characters and that their reduction progress in parallel. However, there is strong evidence in contrary.

Te occurrence of diferent mosaics of character states in closely related taxa suggests diferent mecha-

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nisms acting at diferent rates in each population. An illustrative example is provided by the armored catfshes, Ancistrus cryptophthalmus, from Central Brazil: in the large population found in Angélica Cave, pigmentation is more reduced but eyes are less reduced than in the much smaller population from Passa Três Caves (Reis et al., 2006). A study based on geometric morphomet-rics showed that the four known populations also difer in general body shape, with a mosaic in the deformation axes, indicating divergence probably due (at least partially) to topographic isolation (Reis et al., op. cit.). Other mosaics are also observed among related heptapterids – among the Rhamdiini, Pimelodella kronei presents eyes more reduced than Rhamdia enfurnada, the opposite being observed for melanic pigmentation.

Such mosaics may encompass a larger number of characters, including behavioral and physiological ones. Tis is the case with the troglobitic amblyopsids, traditionally ranked in order of increasing degree of reduction of eyes and pigmentation as: typhlichthys subterraneus < Amblyopsis spelaea < A. rosae (Poulson, 1963). Nevertheless, A. spelaea presents more specialized life history traits and feeding behavior, while A. rosae is more derived as regards to agonistic behavior and metabolic rates (both subject to reduction); the otherwise less derived typhlichthys subterraneus is intermediate in relation to agonistic behavior and metabolic rates (Poulson, 1963; Bechler, 1983). Distinct selective pressures are likely to explain such mosaics. For this reason, attempts to rank species like these according to their degree of “adaptation” or specialization to the cave life are unconvincing.

In fact, the reduction of melanic pigmentation in subterranean fshes results from diferent, independent mechanisms, which may superpose. Morphological mechanisms afect the size and number of melanocytes, whereas physiological ones afect the ability to synthesize melanin. Apparently, this ability may be lost due to diferent mutations afecting at least distinct two steps in the synthesis of eumelanin, one upstream and the other downstream the synthesis of DOPA: the frst corresponds to completely depigmented fsh which respond to the administration of L-DOPA by synthesizing melanin, referred as DOPA(+) by Trajano & Pinna (1996) and tyrosinase-positive by Jefery (2006); the second correspond to depigmented fsh which to not respond to L-DOPA (DOPA(-) albinos; Trajano & Pinna, op. cit.). Among Brazilian completely depigmented subterranean fshes, Stygichthys typhlops, the new Rhamdiopsis from Chapada Diamantina and the armored catfsh, Ancistrus formoso are DOPA(+), the heptapterid “taunayia” sp. (actually a Rhamdiopsis – F.A. Bockmann, pers. comm.) is DOPA(-) (M.A. Visconti and V. Felice, pers. comm.), and one third of the population of the trichomycterid

trichomycterus itacarambiensis is DOPA(-), whereas the remaining two thirds have functional melanophores reduced in density.

Te morphological mechanism is based on an additive polygenic system (wilkens, 1988), resulting in a continuous variation in the frst evolutionary steps and progressing towards complete depigmentation throughout the population at slower rates than that caused by the loss of the ability to synthesize melanin, which is based on monogenic systems (wilkens, 1988). For instance, it has been demonstrated that albinism in diferent populations of Mexican Astyanax is caused by independent mutations in the same gene, Oca2 (Protas et al., 2005). Terefore, very pale but still pigmented fsh species, with scattered micromelanophores (such as the trichomycter-us undescribed species respectively from Bodoquena and from Serra do Ramalho karst areas, and the Ituglanis spp. from São Domingos karst areas) may be younger than any of those DOPA(+) “albinos”. Tus, the use of troglo-morphic pigmentation as a measure of relative age should be restricted to related taxa retaining melanin (i.e., to the exclusion of DOPA albinos), where the degree of paleness is due to mutations in the additive polygenic system underlying the morphological, gradual mechanism.

Regression of eyes is also due to complex genetic systems. In the blind Mexican tetra characins, genus As-tyanax, it has been shown that regression is caused by the inactivation of several genes that take part in the developmental control, and that growth factors acting at a lower level of this control appear to be involved in the degeneration of the eyes (Langecker, 2000). Clearly, studies on a much large sample of troglobitic species are needed before any inference about diferentiation rates can be made.

Two other factors infuence the rates of divergence: population sizes and life cycle strategies. Small populations tend to diferentiate faster due to phenomena as genetic drif. Population sizes are highly infuenced by ecological factors such as nutrient availability and the extent of habitats suitable for colonization. It is noteworthy that energy is higher in streams (higher carrying capacity), but phreatic habitats occupy larger areas and volumes. Because there is no taxonomic correlation with these factors, related species may difer in population sizes (for instance, populations respectively with 20,000 and 1,000 individuals were estimated for A. cryptophthalmus in An-gélica and in Passa Três caves – Trajano, 2001a), thus in divergence rates. As well, nutrient availability may also be “perceived” diferently even by taxonomically related species, depending on the efciency of energy use. Such efciency may be improved along the adaptation to the subterranean life, allowing for increase in population sizes, then in lowered diferentiation rates.

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K-selected life strategies imply lower diferentia-tion rates due to delayed ages for frst maturation and low reproductive rates (few individuals reproducing at given times), which work on opposite directions: delayed frst maturation implies slow divergence rates (longer reproductive generations), whereas low reproductive rates result in lowered efective populations, which would accelerate divergence rates..

Dating of paleoclimatic events based on growth phases of speleothems and similar deposits may be applied to subterranean lineages within the framework of the paleocli-matic model (Barr, 1968; wilkens et al., 2000). However, its cyclical nature imposes serious limitations because, without biological data (molecular, morphological, phy-logenetic), it is not possible to establish in which phase the isolation frst took place. As a matter of fact, isolation with diferentiation may occur along several subsequent unfavorable phases intercalated with coalition phases, thus what really counts to produce genetic and/or morphological divergence is the sum of isolation periods (Trajano, 1995), and not simply the time since the frst isolation event.

For instance, in northeastern Brazil there were nine dry phases (no speleothem growth) in the last 210,000 years, intercalated with short wet phases lasting from several hundreds to a few thousand years each. Overall, these periods of speleothem growth occupied only 8% of the studied period, i.e., around 20,000 years in contrast with 190,000 years with dry conditions, like the one prevalent nowadays in the region (wang et al., 2004). Hence, at least in the late Pleistocene, there was a much extended period of isolation for the hypogean fauna in northeastern Brazil – for lineages already established in subterranean habitats, from 190,000 to 210,000 years, depending on the occurrence or not of introgression with epigean relatives during the wet periods. As a matter of fact, several of the most highly specialized Brazilian tro-globites have been found in this region (e.g., Rhamdiopsis catfshes, Spelaeogammarus amphipods, Pongicarcinia xi-phidophorum isopods, Coarazuphium beetles), as well as the only Brazilian troglobitic scorpions, cockroaches and Ctenid spiders.

On the other hand, climatic changes were not as dominant in the subtropical southeast Brazil and dry phases were shorter, at least for the last 116,200 years (Cruz-Jr. et al., 2005). Terefore, total time of isolation in subterranean habitats during the late Pleistocene was shorter in SE than in NE Brazil. Hypothetically, a pop-

In conclusion, there is a complex balance between diferent genetic, ecological and biological factors, which may act in diferent directions to produce the actual divergence rates. Such rates may difer among related taxa, and even among diferent characters. Terefore, the degree of troglomorphism as a measure of age of subterranean lineages should be used with extreme caution.

ulation that became frst isolated at a given time in the northeast would be much more diferentiated, both genetically and morphologically, than another population frst isolated at the same time in the southeast. If one considers “age” as the time of the frst isolation, these two lineages have the same age; if “age” is the total time in isolation, then the frst one is older. It is clear that, in a cyclical model, the degree of genetic diferentiation do not provide a good evidence of age without a precise determination of the duration of each phase.

Geological and geographical events over larger temporal scales may provide more robust evidence. Te genus Phreatobius is distributed around the Amazon basin, in tributary basins from both margins of the Amazon River. Te frst described species, P. cisternarum, lives underground in the alluvial fan around the Amazon delta, being collected in shallow hand-dug wells. Much latter, in the 1990´s, other species were found deeply buried in submerged litter banks in shallow “igarapés” (small tributaries) along the lef margin of the Negro and Amazon rivers. More recently, a second phreatobic species was discovered in wells in the State of Rondônia, Rio Madeira basin, in the right margin of the Amazon drainage (J. Muriel-Cunha & J. Zuanon, pers. comm..; description in progress by J. Muriel-Cunha & M. de Pinna). Tis wide, peripheral distribution of the Phreatobius genus around the Amazon basin may be explained by an origin between the late Miocene and the late Pliocene (~2.5 Ma), when a gigantic lake, or a series of interconnected mega-lakes occasionally united to cover most or all of lowland Amazonia to a shallow depth (Campbell et al., 2006). In fact, Phreatobius cat-fshes are adapted to shallow, hypoxic conditions, with dark pink to red skin indicating cutaneous breathing; since all known species exhibit this conspicuous trait, this is probably an ancestral condition for the genus. I suggest that the fragmentation of the lacustrine habitat during the late Pliocene, leading to the establishment of the modern Amazon River drainage system, may have been an isolation event for the ancestors of the extant

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species. Nevertheless, an older origin for cannot be ruled out.

On the other hand, P. cisternarum has been found not only north and south of the Amazon River mouth but also in the large Marajó Island in between, with no unequivocal morphological diferentiation so far detected between these localities (Muriel-Cunha & Pinna, 2005). Tese populations were isolated during the formation of the Amazon delta, ~2.5 Ma ago, suggesting a high evolutionary stability, at least at the morphological level, possibly due to the environmental stability of the subterranean habitat.

Te disjunct distribution also points to a very ancient origin for the Calabozoidea isopods. So far, this taxon is composed exclusively by three extant phreatobic species, one from the Orinoco basin, in Venezuela (Calabozoa pellucida), e two from Brazil, respectively from the São Francisco (Pongycarcinia xiphidiourus) and the Paraguay (undescribed species) river basins. Te only connection between these regions is through the Amazon basin, and I speculate that the ancestors may have dispersed during

In order to be minimally reliable and useful, molecular clocks must be based on well corroborated phylogenies with at least one node correlated to geographic or geological isolation events of known age. In cyclical models, such correlation is hampered when cycles are relatively short and repetitive, as is the case with the paleoclimatic fuctuations in the late Pleistocene in Brazil, adding a great deal of uncertainty to the molecular clock. Marine transgressions, which have been used to establish dates for vicariant events in epigean Brazilian taxa such as freshwater fshes, are of no use for subterranean lineages because almost all karst areas in Brazil are above the maximum sea levels. In any case, the conclusion of the molecular studies on Phreatobius spp., S. typhlops and Rhamdiopsis sp. from Chapada Diamantina will certainly open new interesting avenues in this feld.

As already mentioned, few phylogenetic studies of groups including Brazilian troglobites are available, most at the genus level and incomplete in terms of taxa encompassed. Among fshes, the heptapterid catfshes were object of a phylogenetic study, but the cave species were not included (Bockmann, 1998). Phylogenetic and molecular studies on heptapterids are in progress, but the position of the Phreatobius genus and of the troglobitic Rhamdi-opsis species within this genus are still unclear. Recently analyzed morphological data indicate that, within the genus Rhamdiopsis, “taunayia” sp. is basal whereas the species from Chapada Diamantina have a more apical posi-

or prior to the formation of the huge Lago Amazonas. Actually, the São Francisco lineage would be older, at least 5 Ma, which is the estimated age of separation of this basin based on studies of the biogeographical patterns in Brazilian freshwater fshes (Hubert & Renno, 2006). Messana et al., (2002) argue for a close relationship between the Calabozoidea and the Oniscoidea isopods, thus both lineages have the same phylogenetic age, which goes back to the Jurassic-Cretaceous (gondwanic origin – L. A. Souza, pers. comm.). A phylogenetic study, that could add more light to this interesting problem, is waiting for the collection of additional specimens, what is proving to be very difcult in spite of the eforts of biologists and cave divers. Apparently these animals are very rare and/ or live mainly in inaccessible, deep phreatic habitats.

Geomorphological events as alluvial erosion producing waterfalls that split populations (topographical isolation), once dated, also provide data useful to estimate the age of lineages such as the diferent populations of the armored catfsh, A. cryptophthalmus.

tion in the phylogeny (F. A. Bockmann, pers. comm.). Tese two species independently adapted to the same kind of habitat, the upper phreatic zone connected to the surface through caves (Trajano, 2001b), having developed advanced characters states related to the hypogean life, including miniaturization. “taunayia” sp., however, is even more specialized, presenting a hypertrophied lateral line system in the head, with behavioral evidence of enhanced mechano-sensory sensitivity. Tis, associated with its putative basal position in the Rhamdiopsis phy-logeny, points to an older age for the lineage to which the troglobitic “taunyaia” sp. belongs, much anterior to the late Pleistocene.

Te phylogeny of the catfsh family Trichomycteri-dae was also studied (wosiack, 2002), but only one among 10+ troglobitic species presently known, trichomycterus itacarambiensis, was included. It is an apical taxa in the phylogeny, indicating a relatively recent origin. A recent derivation of t. itacarambiensis from an epigean ancestor from the Upper São Francisco River basin is consistent with the morphological variation observed in eyes and pigmentation and also with the notion of a quick fxation of genes for albinism, since one third of the population is made of albinos. However, in the absence of a correlation between some node and dated geographic or geological isolation events, it is not possible to estimate an absolute age, even approximate, for this cave lineage.

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COMBINED EVIDENCE:

For extremes in the inter-taxa variation, the troglomor-phism degree may provide good evidence of relative ages. For instance, it is reasonable to suppose that fshes with slightly reduced eyes and pigmentation such as the heptapterids Rhamdiopsis sp. from Cordisburgo (eastern Brazil) and Pimelodella spelaea, from São Domingos (Central Brazil), are younger than the highly troglomor-phic Rhamdiopsis sp. from Chapada Diamantina and “taunaya” sp., from Campo Formoso. Te two former species probably have been isolated topographically because they inhabit streams several meters above the base level, and an isolation period in the order of 105 years (estimated time for the erosional processes lead to the current landscape – A. Auler, pers. comm..) may be estimated. Te two latter species inhabit presently semiarid karst areas in northeastern Brazil subject to extended periods of isolation at least during the last 210,000 years, but they probably became isolated well before. Tus, an estimate in the order of 105-106 years seems reasonable.

A molecular study focusing on the hypervariable Region I of MtDNA did not fnd any evidence of divergence between the cave populations of Ancistrus cryptophthalmus (Moller & Parzefall, 2001). However, geometric morphometric analyses showed a clear, statistically signifcant diference between these populations, but with some superposition with the epigean closest relatives (Reis et al., 2006). Taken together, these data indicate a recent isolation of the cave populations from the epigean ones and also from each other, in the order of 104 -105 years.

Preliminary molecular studies on Ituglanis species from São Domingos karst area are consistent with the observed morphological diferences (Bichuette et al., 2001) justifying the recognition of four species, each one in a separate microbasin that runs parallel westwards (Bichuette & Trajano, 2004). Tese catfshes are sym-patric with the morphologically less specialized A. cryp-

tophthalmus, P. spelaea and Eigenmannia vicentespelaea (Gymnotiformes), making São Domingos karst area a world hotspot of biodiversity for subterranean fshes. All the Ituglanis catfshes have eyes more reduced and are paler than the other species, presenting scattered mela-nophores, i.e., they are not DOPA albinos. Tree among these Ituglanis species occupy a very specialized habitat, with adaptations to the phreatic environment that include miniaturization. Moreover, I. epikarsticus, and probably also I. bambui and I. ramiroi (Trajano & Bichuette, unpubl. data), live and disperse through the epikarst, whereas the other species are typical stream-dwellers, like their epigean relatives. In spite of intensive collecting eforts, no epigean Ituglanis catfsh was found in São Domingos (the same is true for Pimelodella; Bichuette & Trajano, 2003). Taken together, these evidences indicate a longer time in isolation for the Ituglanis catfshes. In conclusion, the rich troglobitic ichthyofauna from São Domingos seems to be the result of anachronous isolation events, including both the extinction of epigean relatives due to unknown factors (for Ituglanis and Pimelodella) and topographic isolation (for Ituglanis spp. and also A. cryptophthalmus).

Anachronous isolation, possibly in association with diferent divergence rates, may also explain the disparity in troglomorphic degree observed for the subterranean fauna from the Upper Ribeira Valley karst area, SE Brazil. Tis fauna includes very specialized species, such as the pseudoscorpion Spelaeobochica muchmorei and the decapod Aegla microphthalma, to moderately troglomorphic species, such as the opilionid Pachylospeleus strinatii, the carabid beetle Schizogenius ocellatus and the catfsh Pimelodella kronei. within the framework of the paleo-climatic model, in view of the short isolation periods (= dry phases) during the late Pleistocene (see above) it is probable that all these species became frst isolated in caves before this period.

ACKNOwLEDGEMENTS

I am grateful to Augusto Auler, Fernando P. L. Marques and Janice Muriel Cunha for the discussion of ideas and criticisms, and to Richard Borowsky for the critical reading and revision of the English style of an early version of the manuscript. Many data were gathered during stud-

ies sponsored by the Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (grant n. 03/00794-5, among others). Te author studies are also supported by the CNPq (fellowship and grant n. 302174/2004-4).

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REFERENCES:

Bechler, D. L., 1983: Te evolution of agonistic behavior in amblyopsid fshes. Behavioral Ecology and Socio-biology, 12, 35-42, Heidelberg.

Bichuette, M. E., Garz, A. & D. Möller., 2001: Preiminary study on cave-dwelling catfshes, Ituglanis sp., from Goiás, Brazil, p. 22. In: E. Trajano. & R. Pinto-da-Rocha (eds.). xV International Symposium of Bio-speleology, Société Internationale de Biospéologie, São Paulo.

Bichuette, M. E. & E. Trajano., 2003: Epigean and subterranean ichthyofauna from São Domingos karst area, Upper Tocantins river basin, Central Brazil. Journal of Fish Biology, 63, 1100-1121, London.

Bichuette, M. E. & E. Trajano., 2004: Tree new subterranean species of Ituglanis from Central Brazil (Siluri-formes: Trichomycteridae). Ichthyological Explorations of Freshwaters, 15, 3, 243-256, München.

Bockmann, F. A., 1998: Análise flogenética da família heptapteridae (teleostei, Ostariophysi, Siluriformes) e redefnição de seus gêneros. - PhD Tesis, Universi-dade de São Paulo, São Paulo, 589 p.

Boutin, C. & N. Coineau., 2000: Evolutionary rates and phylogenetic age in some stygobiontic species, p. 433-451. In: wilkens, H., Culver, D.C. & w.F. Humphreys (eds.). Ecosystems of the world 30. Subterranean Ecosystems (eds.). Elsevier, Amsterdan.

Campbell Jr., K. E., Frailey, C. D. & L. Romero-Pittman., 2006. Te Pan-Amazonian Ucayali Peneplain, late Neogene sedimentation in Amazonia, and the birth of the modern River system. Palaeogeography, Pa-laeoclimatology, Palaeoecology, 239, 166-219, Am-sterdan.

Cruz Jr., F. w. , Burns, S. J., Karmann, I., Sharp, w. D., Vuille, M., Cardoso, A. O., Ferrari, J. A., Dias, P. L. S. & O. Viana Jr., 2005: Insolation-friven changes in atmospheric circulation over the past 116,000 years in subtropical Brazil. Nature, 434, 63-66, London.

Hubert, N. & J.-F. Renno., 2006: Historical biogeogra-phy of South American freshwater fshes. Journal of Biogeography, p. 1-23 [www.blackwellpublishing. com/jbi]

Jefery, w. R., 2006: Convergence of pigment regression in cave animals: developmental, biochemical, and genetic progress toward understanding evolution of the colorless phenotype., p. 38. In: Moldovan, O. T. (ed.). xVIIIth International Symposium of Biospel-eology – 100 years of Biospeleology, Cluj-Napoca, SIBIOS – Société Internationale de Biospéologie.

Langecker, T.G., 2000: Te efects of continuous darkness on cave ecology and and cavernicolous evolution, p. 135-157. In: wilkens, H., Culver, D.C. & w.F. Humphreys (eds.). Ecosystems of the world 30. Subterranean Ecosystems (Eds.). Elsevier, Amsterdan.

Messana, G., Baratti, M. & D. Benvenuti., 2002: Pongy-carcinia xiphidiourus n. gen. n. sp., a new Brazilian Calabozoidae (Crustacea Isopoda). Tropical Zoology, 15, 243-252, Firenze.

Muriel-Cunha, J. & M. de Pinna., 2005: New data on cistern catfsh, Phreatobius cisternarum, from subterranean waters at the mouth of the Amazon River (Siluriformes, Incertae Sedis). Papéis avulses de Zoologia, 45, 26, 327-339, São Paulo.

Moller, D. & J. Parzefall., 2001: Single or multiple origin of the subterranean catfsh Ancistrus cryptophthal-mus. what we can learn from molecular data, p. 38. In: Trajano, E. & R. Pinto-da-Rocha (eds.). xV International Symposium of Biospeleology, Société Internationale de Biospéologie, São Paulo.

Poulson, T. L., 1963: Cave adaptation in Amblyopsid fshes. American Midland Naturalist, 70, 2, 257-290, Notre Dame.

Protas, M. E., Hersey, C., Kochanek, D., Zhou, y., wilkens, H., Jefery, w. R., Zon, L. I. Borowsky, R. & C. J. Tabin., 2005: Genetic analysis of cavefsh reveals molecular convergence in the evolution of albinism. Nature Genetics, Advance Online Publication, Letters, p. 1-5 [published online 11 December 2005]

Reis, R. E., Trajano, E. & E. Hingst-Zaher., 2006: Shape variation in surface and cave populations of the armoured catfsh Ancistrus (Siluriformes: Lori-cariidae) from the São Domingos karst area, Upper Tocantins River, Brazil. Journal of Fish Biology, 68, 414-429, London.

Trajano, E., 1995: Evolution of tropical troglobites: Applicability of the model of quaternary climatic fuc-tuations. Mémoires de Biospéologie, 22, 203-209, Moulis.

Trajano, E., 2001: Habitat and population data of tro-globitic armoured cave catfshes, Ancistrus cryp-tophthalmus Reis 1987, from Central Brazil (Silu-riformes: Loricariidae). Environmental Biology of Fishes, 62, 1-3, 195-200, Dordrecht.

Trajano, E., 2001: Ecology of subterranean fshes: an overview. Environmental Biology of Fishes, 62, 1-3, 133-160, Dordrecht.

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Trajano, E. & M.C.C. Pinna., 1996: A new cave species of trichomycterus from eastern Brazil (Siluriformes, Trichomycteridae). Revue française d’Aquariologie, 23, 3-4, 85-90, Nancy.

wang, x., Auler, A. S., Edwards, R. L., Cheng, H., Cris-talli, P. S., Smart, P. L., Richards, D. A. & C.-C. Shen., 2004: wet periods in northeastern Brazil over the past 210 kyr linked to distant climate anomalies. Nature, 432, 740-743, London.

wilkens, H., 1973: Ancienneté phylogénetique et degrees de reduction chez les animaux cavernicoles. Annales de Spéléologie, 28, 2, 327-330, Paris.

wilkens, H., 1982: Regressive evolution and phylogenetic age: the history of colonization of freshwaters of yucatan by fsh and Crustacea. Texas Memorial Museum Bulletin, 28, 237-243.

wilkens, H., 1988: Evolution and genetics of epigean and cave Astyanax fasciatus (Characidae, Pisces). Evolutionary Biology, 23, 271-367, New york.

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PATTERN AND PROCESS: EVOLUTION OF TROGLOMORPHy

IN THE CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I

– PRELIMINARy OBSERVATIONS (INSECTA: HEMIPTERA:

FULGOROMORPHA: CIxIIDAE)

VZOREC IN PROCES: EVOLUCIJA TROGLOMORFNOSTI

PRI JAMSKIH MREŽEKRILNIH ŠKRŽATKIH IZ AVSTRALIJE

IN HAVAJEV – PRELIMINARNE UGOTOVITVE (INSECTA:

HEMIPTERA: FULGOROMORPHA: CIxIIDAE)

Andreas wESSEL1, Petra ERBE1,2 & Hannelore HOCH1

Abstract                                          UDC 591.542(94+739,9)

Andreas Wessel, Petra Erbe & Hannelore Hoch: Pattern and process: Evolution of troglomorphy in the cave-planthoppers of Australia and Hawai’i ‒ Preliminary observations (Insecta: Hemiptera: Fulgoromorpha: Cixiidae)

Te evolution of troglobites comprises three distinct problems: cave colonization by an epigean ancestor, the evolution of tro-glomorphies, and intra-cave speciation. Te study of cave-dwelling planthoppers has contributed much to our understanding of troglobite evolution and provides useful model systems to test various aspects of the theoretic framework developed in recent years. Most promising in this respect are taxa with several closely related but independently evolved troglobiontic lineages, such as on the Canary Islands, in queensland/Australia and on the Hawaiian Archipelago. Closely related species ofen occur in caves with comparable ecological parameters yet difer in their age. Here we use comparative age estimates for Australian and Hawaiian cave cixiids to assess the dynamics of reductive evolutionary trends (evolution of troglomorphy) in these taxa and cave planthoppers in general. we show that the degree of troglomorphy is not correlated with the age of cave lineages. Morphological alteration may not be used to draw conclusions about the phylogenetic age of cave organisms, and hypotheses based on such assumptions should be tested in light of these fndings.

Key words: adaptive shif, cave adaptation, climatic relict, founder efect, reductive evolutionary trends, troglobites, tro-glomorphies.

Izvleček                                           UDK 591.542(94+739,9)

Andreas Wessel, Petra Erbe & Hannelore Hoch: Vzorec in proces: Evolucija troglomorfnosti pri jamskih mrežekrilnih škržatkih iz Avstralije in Havajev Preliminarne ugotovitve (Insecta: Hemiptera: Fulgoromorpha: Cixiidae)

Evolucija troglobiontov zajema tri značilne korake: kolonizacija jame s površinskim prednikom, razvoj troglomorfnosti ter podzemeljska speciacija. Študija podzemeljskih mrežekrilnih škržatkov je prispevala veliko k našemu razumevanju evolucije troglobiontov in hkrati predstavlja uporaben modelni sistem za testiranje različnih teoretičnih pristopov, ki so bili razviti v zadnjih letih. V tem pogledu so najobetavnejši tisti taksoni, ki so si sicer sorodni, toda pripadajo evolucijsko neodvisnim troglobiontskimi linijami, kot so npr. tisti na Kanarskih otokih, v državi queensland (Avstralija) in na havajskem arhipelagu. Bližje sorodne vrste se v jamah pogosto pojavijo v primerljivih ekoloških pogojih, vendar se razlikujejo v starosti. Za ugotavljanje dinamike trendov redukcijske evolucije (evolucija tro-glomorfzmov) teh taksonov in jamskih škržatkov na splošno, smo v prispevku uporabili ocene primerjalnih starosti za avstralske in havajske jamske škržatke. Ugotavljamo, da stopnja troglomorfnosti ni v korelaciji s starostjo jamskih linij. Zgolj morfološke spremembe pri organizmih se ne bi smele uporabljati za prikazovanje flogenetske starosti jamskih organizmov. Hipoteze, ki temeljijo na takšnih predpostavkah, bi morale biti preverejene v luči pričujočih ugotovitev.

Ključne besede: prilagoditveni premik, prilagoditve na podzemlje, klimatski relikt, učinek osnovatelja, redukcijski evolucijski trendi, troglobiti, troglomorfzmi.

1 Museum für Naturkunde der Humboldt-Universität zu Berlin, Biosystematics Research Group, Invalidenstrasse 43, D-10115 Berlin, Germany; e-mail: andreas.wessel@museum.hu-berlin.de

2 Chiang Mai University, Te Uplands Program, Faculty of Agriculture, Chiang Mai, Tailand

Received/Prejeto: 30.01.2007

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ANDREAS wESSEL, PETRA ERBE & HANNELORE HOCH

INTRODUCTION

Te origin of troglobites has fascinated evolutionary biologists since Darwin remarked on their curious and strong modifcation (1859: 177-178). He did not provide a ‘Darwinistic’ explanation for their evolution1, however, this was subsequently supplied by August weismann (1886)2.

Troglobite evolution, i.e. the process leading to diferent, sometimes closely related species, which are highly adapted to life in subterranean spaces, comprises three somewhat independent phenomena and problems: (i) initial cladogenesis of a cave species, or the origin of a cave-dwelling bio-species from an epigean ancestor, which is basically the problem of isolation or rather (spatial) separation of a cave population from its epigean relatives; (ii) subsequent anagenetic transformation, which comprises the dynamics and driving forces of cave adaptation, the ofen so-called regressive evolution or reductive evolutionary trend, and, in some cases, (iii) subterranean (intra-cave) radiation.

RELICTS OR ExPLORERS?

A widely accepted concept aiming to explain the specia-tion event giving rise to a cave-dwelling and reproduc-tively isolated bio-species, was developed by Tomas Barr in the 1960s, commonly known as the Climatic Relict Hypothesis (CRH):

“A s it is difcult to imagine that eyes, though useless, could be in any way injurious to animals living in darkness, I attribute their loss wholly to disuse.” (Darwin 1859: 177)

„As soon as such a cave immigrant has developed the ability to obtain food without the help of eyes a reduction of the eyes must commence, since as soon as the same are no longer neces-sary for the animals’ existence, they are not infuenced anymore by natural selection, because now it does not matter whether the eyes are a little worse or a little better. Now, no more selec-tion will take place between individuals with better and those with worse eyes, but both will have an equal chance to be preserved and reproduce. Individuals with better and those with worse eyes will cross from now on, and the result can only be a general degradation of the eyes. Pos-sibly this is helped by the circumstance that smaller and stunted eyes can even present an ad-vantage, since this allows other organs such as sensory and olfactory organs, which are more important for the animal now, to develop more strongly. Even without such efect, though, the lack of natural selection maintaining the eye’s high level of organization will necessarily lead to its degradation, slowly or even very slowly, especially at the beginning of this process, but in-exorably.” (Translated from the German; weismann 1886: 16-17)

“Troglobites have evolved from colonies of troglo-philes which became isolated in caves through extinction of surface populations of the troglophiles” (Barr 1968: 96).

According to Barr, the evolution of troglobites is a two-step process: at frst, it involves a preliminary, tro-glophilic stage without apparent troglomorphies or a disruption of genefow between cave-dwelling and epigean populations. Following this initial cave colonization, the cave-dwellers become geographically separated, and thus genetically isolated, due to the extinction of parental epi-gean populations (supposedly caused by climatic change), at least in the region of the cave. Over time, reproductive isolation will inevitably follow as a side efect of genetic change by drif and natural selection (Barr 1968). Support and evidence for this concept was gained from the observed relict distribution of most troglobites known at that time, which were almost exclusively confned to temperate regions. Glaciation during the ice ages was suggested as the most important factor for the change of surface conditions (Barr 1968, Sbordoni 1982, Barr & Holsinger 1985).

Tis hypothesis remained without alternatives until the early 1970s, when Francis G. Howarth discovered the Hawaiian cave ecosystems (Howarth 1972). Te lava tubes host, among other taxa, highly troglomorphic plan-thoppers that are parapatrically distributed with respect to their close epigean relatives, which are still extant, i.e. they are non-relictual troglobites. Consequently, How-arth (1981, 1986, 1987) formulated the Adaptive Shif Hypothesis (ASH):

“[...] potential food resource provides the driving force for the [...] evolution of cave species. Troglomor-phic populations [...] evolve from pre-adapted habitual accidentals which [...] establish temporary populations in marginal underground habitats. Once an adaptive shif occurs, allowing a reproducing population to establish itself underground, then it is both the efects of strong new selection pressures and the release from previously strong selection pressures that bring about [...] troglo-morphy” (Howarth 1986: 155).

while the exploitation of a large new habitat with new food resources may be the driving force in the evolution of troglobites according to the ASH, a major challenge for survival underground is probably the ability to locate mates and reproduce in the dark. A change in mating behaviour might thus have been the most important adaptive shif necessary for a successful colonization of caves, and would almost inevitably lead to reproductive isolation of the incipient cavernicolous species. Te Hawaiian cave planthoppers provide a striking example for

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PATTERN AND PROCESS: EVOLUTION OF TROGLOMORPHy IN THE CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I

this process, and consequently played a pivotal role in the formation of the Adaptive Shif Hypothesis (Howarth 1986, Howarth & Hoch 2005).

A principal acceptance of the ASH does not necessarily invalidate the CRH, especially not in cases where the preconditions for the CRH are met, i.e. cave taxa displaying a relict distribution. However, a relict distribution observed today is not sufcient evidence to unconditionally accept the CRH, given the alternative present in the ASH 3. Te predictions arising from both hypotheses must be tested for every single system. For the CRH, we expect the closest epigean relatives at least to be allopatrically distributed compared to the cave species, while the ASH predicts a parapatric distribution of cave and epigean species, which are necessarily sistergroups (adelphotaxa). Conclusive evidence for a decision between both hypotheses may be gained from a well-founded phylogeny in conjunction with a sound knowledge of the geographic distribution of both cave and epigean taxa. Te last requirement is ofen problematic, though, as the sampling of epigean relatives for some cave species is frequently insufcient. For some groups no epigean relatives are known at all, and it is only through intensive, directed search eforts that this obstacle may be overcome (see e.g. Stone 2004).

REDUCTIVE EVOLUTIONARy TRENDS

Once a population has shifed towards a permanently cav-ernicolous mode of living, the second problem of troglo-bite evolution – subsequent anagenetic transformation – arises. A basic assumption since weismann (1886) has been a correlation between the degree of troglomorphy of a taxon and its residence time in caves. Cave adaptation is accordingly described as an orthogenetic, time-dependent process, which is an overall slow, gradual adaptation towards a stage of ‘absolute troglomorphy’; see e.g. wilkens (1986), for review see Barr (1968) and Howarth

“Te evidence suggests that troglobites evolve from pre-adapted habitual visitors or accidentals in the cave rather than from well-adapted troglophiles. Te former group requires an adaptive shif in order to fully exploit the cave resources. Tis adaptive shif may lead to the evolution of a troglobitic lifestyle. well-adapted troglophiles on the other hand tend to remain opportunistic exploiters of the cave environment. Some temperate troglobites may ft the scenario of isolation by changing climates (Barr, 1968). However, many species including those in the tropics probably do not. I postulate that adaptive shifs led to the colonization of caves and evolution of troglobites, including most of those in temperate caves, but that the complex geological history of the continents including glaciations has obscured the early history and obfuscated the earlier distribution and the evolution of troglobites there.” (Howarth 1981: 540)

(1987). Traditional explanations for the mechanisms of this process includes (i) the accumulation of neutral mutations, (ii) pleiotropic efects, and (iii) natural selection for energy economy (Sket 1986, Culver 1982). Both the CRH (Barr 1968) and ASH (Howarth 1986), however, contain some notion of a founder efect: Barr with an explicit quotation of Mayr’s genetic revolution (Mayr 1954) and Howarth with reference to the Carson model of founder efects (Carson 1968, 1975).

Te process of cave adaptation is infuenced by several parameters – such as availability of food, population density, microclimate of the caves and other biotic and abiotic factors of the cave ecosystem – , which make comparisons even between closely-related species exceedingly difcult, and generalisations even more so. An excellent opportunity to test the assumption of gradual and increased troglomorphy over time may nevertheless be found in radiations of cave-dwelling planthoppers inhabiting caves of diferent age.

CAVE-ADAPTATION IN PLANTHOPPERS

Studies during the last three decades have revealed numerous cases of evolution of cave-adapted planthoppers in tropical and subtropical caves. Among the Fulgoro-morpha, 53 cave-dwelling species have been described from many parts of the world, four-ffh of them cixiids including the Australian taxa Solonaima and Undarana and the Hawai’ian Oliarus species (Hoch 1994, Hoch & wessel 2006).

Te adaptation to similar environments in cave planthoppers has led to the evolution of a very similar external morphology in diferent parts of the world and represents a striking example of parallel evolution. Te morphological modifcations of cave planthoppers are characterized by reductive evolutionary trends, as in most obligately cavernicolous animals. Te degree of adaptation to a subterranean life varies greatly, primarily depending on their habitat in the cave or soil (Fig. 1). Most conspicuous are the reduction and loss of compound eyes and ocelli, tegmina, wings and bodily pigment. It has also been suggested that apparently non-troglomor-phic characters have an increased adaptive value in the underground environment, such as e.g. the specialized spine confgurations of hind tibiae and tarsi, which may possibly enhance walking on wet or rocky surfaces (Hoch & Howarth 1989a, 1989b, Hoch 2002).

Te closest epigean relatives of cavernicolous Fulgo-romorpha species all have immature stages living close to the soil, e.g. under the dead bark of rotting logs, in leaf litter or moss, or even within the soil, feeding on roots or perhaps on fungi (Remane & Hoch 1988). Tis mode of life has been considered an ecological pre-adaptation

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ANDREAS wESSEL, PETRA ERBE & HANNELORE HOCH

Habitat

Abiotic factors

Life cycle

Morphology

epigeic (surface) habitats

unstable physical parameters

entirely epigeic / epigean

no troglomorphies

(including leaf litter)

(ambient climatic influence high)

troglophilic

(facultative soil & cave-dwellers,

may live & reproduce

underground as well as

in surface domain)

troglomorphies

hypogeic (subterranean) habitats

T

stable / constant physical parameters

(ambient climatic influence low)

of varying degrees

e.g.

.''*■ + +■+■ , ;'' soil- *\ .

[ interstitial [ • chambers )

; meso-cavernous rock stratum \

endogeic / endogean

(obligatory soil dwellers)

- reduction of eyes,

body pigmentation & wings

- decreasing cuticle sclerotization

I caves '• (deep cave zone)

troglobitic

(obligatory cavernicoles, restricted to cave environment)

- specialized sensory organs

- elongate appendages

Fig. 1: terminology of interdependence between physical parameters of the habitat and organismic adaptations (From hoch et al. 2006).

to a later switch to a permanent (adult) life underground (Hoch 2002, Howarth & Hoch 2005).

CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I

In Australia, closely related Solonaima and Undarana species have colonized old karst caves as well as younger lava tube systems. Te four epigean Undarana species occur in the (rain)forest at the south of queensland’s east coast, while the two cave-dwelling species (U. rosella, Bayliss & Pinwills cave, Undara lava tube; U. collina, Collins cave) inhabit the lava caves of the McBride Formation in the dry grasslands westward of the Great Dividing Range (Hoch & Howarth 1989a). Te epigean Solonaima species can be found all along the east coast (rain)forest, while the cave species inhabit lava tubes within the Mc-Bride Formation, too (S. baylissa, sympatric with U. rosella), as well as karst caves of the Chillagoe Karst Towers (S. pholetor, S. stonei, S. halos, S. irvini) and Mount Mul-grave (S. sullivani) (Hoch & Howarth 1989b). Tus, epi-gean and cavernicolous species of both Australian genera show an allopatric distribution.

On the Hawaiian islands the cave-dwelling species of the endemic, monophyletic Oliarus clade represent independent cave colonizations on islands of diferent age. with about 80 described epigean taxa (species and subspecies), Oliarus is the most speciose planthopper genus on the Hawaiian islands (Zimmerman 1948, Asche 1997).

Based on morphological data, this diversity has been hypothesized to stem from a single colonization event (Asche 1997, Hoch & Howarth 1993). Te frst cave-dwelling species of the genus, Oliarus polyphemus Fennah, 1973 and Oliarus priola Fennah, 1973 (Fennah 1973) were discovered by Howarth (1972) on Hawai’i Island and Maui where they are endemic. Later, fve more troglobitic taxa were discovered on the archipelago (Hoch & Howarth 1999). Te seven cave-dwelling species owe their origin to several independent colonization events on three islands; on Molokai, one adaptive shif (O. kalaupapae); on Maui, three adaptive shifs (O. priola, O. gagnei, O. waikau); on Hawai’i Island, at least three adaptive shifs (O. polyphemus, O. lorettae, O. makaiki) (Hoch & Howarth 1999). Te closely related epigean species of all cavernicolous Oliarus taxa occur parapatrically at the surface.

Both the Australian and the Hawaiian cave species complexes exhibit diferent degrees of troglomorphy. Figure 2 shows the heads of six Australian Solonaima, one epigean (1), three facultative cavernicolous (2-4), and two obligate cavernicolous species (5,6). Figure 3 depicts the habitus of six Hawai’ian Oliarus species, one epigean relative on the lef (note the diferent scale), and fve troglobitic species. Te varying degree of eye reduction is clearly visible; two of the Hawaiian species even show a complete loss of eyes. Te same pattern is seen in wing reduction.

Te time factor is crucial for assessing the dynamics of troglobite evolution. Unfortunately, though, it is

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PATTERN AND PROCESS: EVOLUTION OF TROGLOMORPHy IN THE CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I

Fig. 2: Australian Solonaima species, heads, dorsal view. 1, S. solonaima (epigean); 2. S. sullivani; 3, S. pholetor; 4, S. stonei; 5, S. irvini; 6, S. baylissa. (From hoch & howarth 1989b).

rarely possible to obtain direct estimates of the age of the cave lineages. Rather, the maximum age of the habitat is usually employed - at least if an active colonization of caves sensu Howarth is assumed - , or even just the maximum age of the underlying geological structure. By these measures, the maximum age for the troglobitic Oliarus lineages on Hawai’i is the age of the islands: 1.8 myr for Molokai, 1.3 myr for Maui, and less than 400,000 y for Hawai’i Island.

In the case of the Australian troglobitic cave plan-thoppers, the situation is even more complex. At frst sight their distribution fts the Climatic Relict Model sensu Barr very well assuming a late Miocene desertifca-tion, i.e. replacement of the rain forest by dry savannah or grassland east of the Great Dividing Range (see Kemp 1978, Truswell 1990). while not per se refuting the relict hypothesis, we do not exclude the possibility of adaptive shifs for the Australian cave planthoppers as well. In that case, Australian cave taxa may be much older than hitherto assumed. Also, the late Miocene climatic change is not necessarily be regarded as the sole reference point for the calculation of the maximum age of the Australian cave planthoppers. what could matter instead is the availability of the caves as a suitable novel habitat.

Te limestone of the Chillagoe Tower Karst and Mitchell-Palmer Karst are presumably of Silurian origin, and the current main caves were formed by phreatic solution during the last 5-10 million years (Ford 1978, Jennings 1982, Pearson 1982). Remnant older passages and solution breccias near the tops of many towers indicate the existence of caves since the area was uplifed and the limestone was exposed in the mid-Tertiary about 20-25 million years ago (Howarth 1988).

Te much younger Undara lava fow (190,000 years old) covers portions of older fows within the McBride Formation (Atkinson et al., 1976), some of which may date back from the Pliocene, i.e. more than 2.5 million years ago (Best 1983). Te cave animals could have migrated through the mesocavernous systeme into young basalt and colonized new caves in each fow in succession.

“Te troglobitic species could be, and probably are, older than the age of their caves” (Howarth 1988).

PHyLOGENETIC AGE AND TROGLOMORPHy Against this background we here attempt to assess the problem of the dynamics of reductive evolutionary

Fig. 3: hawai’ian Oliarus species, habitus, dorsal view. 1, epigean Oliarus species (O. tamehameha); 2, O. kalaupapae; 3, O. lorettae; 4, O. gagnei; 5, O. waikau; 6. O. polyphemus. (1, from zimmermann 1948; 2-5, from hoch & howarth 1999; 6, hoch, Original).

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ANDREAS wESSEL, PETRA ERBE & HANNELORE HOCH

Fig. 4: variability of relative eye width and relative tegmina length in epigean and cave-dwelling species (O. polyphemus, O. lorettae, O. makaiki (no wing measurements), O. gagnei, O. waikau, O. kalaupapae; S. pholetor (stonei), S. irvini (halos), S. baylissa; U. collina, U. rosella).

Fig. 5: Correlation of indices for troglomorphic characters with the maximum age of inhabited cave formations (O. polyphemus, O. lorettae, O. gagnei, O. waikau, O. kalaupapae; S. pholetor (stonei), S. irvini (halos), S. baylissa; U. collina, U.

trends (troglomorphies) or regressive evolution. A ma- approach should aim at analyzing character evolution jor obstacle in this context is the poor comparability of in monophyletic groups where similar (morphological) characters across diferent taxonomic groups. A strict pre-conditions or pre-adaptations for parallel evolution

204 TIME in KARST – 2007

PATTERN AND PROCESS: EVOLUTION OF TROGLOMORPHy IN THE CAVE-PLANTHOPPERS OF AUSTRALIA AND HAwAI’I

may safely be assumed. while we are aware of these problems, we nevertheless found it useful to employ a quanti-fcation of troglomorphic characters in order to achieve at least a preliminary idea of the possible correlation between troglomorphy and lineage age. we computed two ‘troglomorphy indices’ for all Hawaiian and Australian taxa from which data were available by using two characteristic troglomorphic characters in cavernicolous plan-thoppers: the reduction of eyes and the reduction of the tegmina. Eye reduction is apparently coupled with an obvious broadening of the vertex (see Fig. 2), so the index eye diameter: vertex width gives a clear statistical signal, ranging from 2-5 in epigean species with fully developed eyes to 0 in eyeless species. For the second index relative tegmina length we computed the absolute tegmina length: mesonotum width. Values ranges from 4.6-5.5 in epigean and from 1.1 to 5.3 in facultative and obligatory cavernicolous species.

Te conspicuous diferences between epigean and cave-dwelling species are clearly refected in both indices (Fig. 4). If the data are plotted against the maximum age

Asche, M., 1997: A review of the systematics of Hawaiian planthoppers (Hemiptera: Fulgoroidea). - Pac. Sci., 51(4), 366-376, Honolulu.

Atkinson, A., Grifn, T. J. & Stephenson, P. J., 1976: A major lava tube system from Undara volcano, North queensland. - Bull. Volcanol., 39(2), 1-28, Napoli.

Barr, T. C., 1968: Cave ecology and the evolution of tro-globites. - Evol. Biol., 2, 35-102, Amsterdam.

Barr, T. C. & Holsinger, J. R., 1985: Speciation in cave faunas. - Ann. Rev. Ecol. Syst., 16, 313-337, Palo Alto.

Best, J. G., 1983: 1:250,000 geological series, explanation notes. 2nd printing. - Geological Survey of queensland, p. 36, Atherton, qld.

Carson, H. L., 1968: Te population fush and its genetic consequences. In: Lewontin, R. C., ed.: Population biology and evolution. - Syracuse University Press, 123-137, Syracuse, Ny.

Carson, H. L., 1975: Te genetics of speciation at the dip-loid level. - Am. Nat., 109, 83-92, Chicago.

of the cave species, the a priori expectation is a clear negative correlation, at least for the Hawaiian taxa: the oldest cave lineages should exhibit the highest degree of troglo-morphy. In contrast, we surprisingly found a weak (not signifcant) positive trend (Fig. 5). Te same unexpected trends are seen in the Australian planthopper species.

Our results presented here, although preliminary, do not provide any evidence for cave-adaptation as a gradual orthogenetic process. Instead, we rather postulate that founder efects indeed play an important role in the origin of cave species. A correlation of the observed trends with particular ecological parameters of the cave environment cannot be excluded based on our data, but clearly this hypothesis needs further testing, especially in respect to selection pressures exerted by the conditions in high stress environments (such as caves) (Hoch & How-arth 1989b, Howarth 1993). we can conclude with some certainty, however, that even in closely related species the degree of troglomorphy cannot be employed to infer the phylogenetic age of the cave lineages.

Culver, D. C., 1982: Cave life. Evolution and ecology. -Harvard University Press, p. 190, Cambridge, MA.

Darwin, C. R., 1859: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. - John Murray, p. 502, London.

Fennah, R. G., 1973: Te cavernicolous fauna of Hawaiian lava tubes, 4. Two new blind Oliarus (Fulgoroi-dea: Cixiidae). – Pac. Ins., 15, 181-184, Honolulu.

Ford, T. D., 1978: Chillagoe – a tower karst in decay. -Trans. Brit. Cave Res. Assoc., 5(2), 61-84, Bridge-water.

Hoch, H., 1994: Homoptera (Auchenorrhyncha, Fulgoroi-dea). In: Juberthie, C. & Decu, V. , eds.: Encyclopaedia biospeologica. tome I. - Société de Biospéologie, 313-325, Moulis-Bucarest.

ACKNOwLEDGEMENTS

we thank Dr. Tomas von Rintelen, Museum für Naturkunde der Humboldt-Universität zu Berlin, for helpful discussions and many useful suggestions.

REFERENCES

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Hoch, H., 2002: Hidden from the light of day: planthop-pers in subterranean habitats (Hemiptera: Auche-norrhyncha: Fulgoromorpha). In: Holzinger, w. & Gusenleitner, F., eds.: zikaden. Leafoppers, plan-thoppers and cicadas (Insecta: hemiptera: Auchenor-rhyncha). (Denisia 4) - Oberösterreichisches Landesmuseum, 139-146, Linz.

Hoch, H. & Howarth, F. G., 1989a: Reductive evolutionary trends in two new cavernicolous species of a new Australian cixiid genus (Homoptera Fulgoroidea). -Syst. Entomol., 14, 179-196, Oxford.

Hoch, H. & Howarth, F. G., 1989b: Six new cavernicolous cixiid planthoppers in the genus Solonaima from Australia (Homoptera Fulgoroidea). - Syst. Ento-mol., 14, 377-402, Oxford.

Hoch, H. & Howarth, F. G., 1993: Evolutionary dynamics of behavioral divergence among populations of the Hawaiian cave-dwelling planthopper Oliarus polyphemus (Homoptera: Fulgoroidea: Cixiidae). - Pac. Sci., 47, 303-318, Honolulu.

Hoch, H. & Howarth, F. G., 1999: Multiple cave invasions by species of the planthopper genus Oliarus in Hawaii (Homoptera: Fulgoroidea: Cixiidae). - Zool. J. Linn. Soc., 127, 453-475, Oxford.

Hoch, H., Asche, M., Burwell, C., Monteith, G. M. & wessel, A., 2006: Morphological alteration in response to endogean habitat and ant association in two new planthopper species from New Caledonia (Hemiptera: Auchenorrhyncha: Fulgoromorpha: Delphacidae). - J. Nat. Hist., 40(32-34), 1867-1886, London.

Hoch, H. & wessel, A., 2006: Communication by substrate-borne vibrations in cave planthoppers. In: Drosopoulos, S. & Claridge, M. F., eds.: Insect sounds and communication. Physiology, behaviour, ecology and evolution. - CRC-Taylor & Francis, 187-197, Boca Raton, London, New york.

Howarth, F. G., 1972: Cavernicoles in lava tubes on the Island of Hawaii. – Science, 175, 325-326, washington, DC.

Howarth, F. G., 1981: Non-relictual troglobites in the tropical Hawaiian caves. - Proc. 8th Int. Cong. Spe-leol., 539-541, Bowling Green.

Howarth, F. G., 1986: Te tropical cave environment and the evolution of troglobites. - Proc. 9th Cong. Int. Speleol., 2, 153-155, Barcelona.

Howarth, F. G., 1987: Te evolution of non-relictual tropical troglobites. - Int. J. Speleol., 16, 1-16, Bologna.

Howarth, F. G., 1988: Environmental ecology of North queensland Caves: why there are so many troglo-bites in Australia. - Te 17th Australian Speleological Federation Biennial Conference, TROPICON, 77-84, Lake Tinaroo, Far North queensland, Australia.

Howarth, F. G., 1993: High-stress subterranean habitats and evolutionary change in cave-inhabiting arthropods. - Amer. Nat., 142(Suppl.), 65-77, Chicago.

Howarth, F. G. & Hoch, H., 2005: Adaptive shifs. In: Culver, D. C. & white, w. B., eds.: Encyclopedia of caves.

- Elsevier Academic Press, 17-24, Amsterdam. Jennings, J. N., 1982: Karst of northeastern queensland

reconsidered. - Tower Karst, 4, 13-52, Chillagoe.

Kemp, E. M., 1978: Tertiary climatic and vegetation history of the Southeast Indian Ocean region. - Palaeo-geography, Palaeoclimatology, Palaeoecology, 24, 169-208, Amsterdam.

Mayr, E., 1954: Change of genetic environment and evolution. In: Huxley, J., Hardy, A. C. & Ford, E. B., eds.: Evolution as a process. - Allen & Unwin, 157-180, London.

Pearson, L. M., 1982: Chillagoe Karst solution and weathering. - Tower Karst, 4, 58-70, Chillagoe.

Remane, R. & Hoch, H., 1988: Cave-dwelling Fulgoroi-dea (Homoptera Auchenorrhyncha) from the Canary Islands. - J. Nat. Hist., 22, 403-412, London.

Sbordoni, V. , 1982: Advances in speciation of cave animals. In: Barigozzi, C., ed.: mechanisms of specia-tion. - Liss, 219-240, New york.

Sket, B., 1986: why all cave animals do not look alike – A discussion on adaptive value of reduction processes.

- NSS Bulletin, 47, 78-85, Huntsville. Stone, F. D., 2004: Blattodea in the genus Nocticola from

Australian cave & surface habitats. In: LaSalle, J., Patten, M. & Zalucki, M., eds.: Entomology – Strength in diversity. (xxII International Congress of Entomology, Brisbane 2004) - Austr. Entomol. Soc., S14w66 (abstract on CD-ROM), Brisbane.

Truswell, E. M., 1990: Australian rainforests: the 100 million year record. In: webb, L. J. & Kikkawa, J., eds.: Australian tropical rainforests: science, values, meanings. - CSIRO, 7-22, Melbourne.

weismann, A., 1886: Ueber den Rückschritt in der Natur. – Ber. Naturforsch. Ges. Freiburg i. Br., 2, 1-30, Freiburg/Br.

wilkens, H., 1986: Te tempo of regressive evolution: Studies of the eye reduction in stygobiont fshes and decapod crustaceans of the Gulf Coast and west Atlantic region. - Stygol., 2, 130-143, Leiden.

Zimmerman, E. C., 1948: Insects of hawaii. A manual of the insects of the hawaiian Islands, including an enumeration of the species and notes on their origin, distribution, hosts, parasites, etc. vol. 4, homoptera: Auchenorhyncha. - University of Hawaii Press, p. 268, Honolulu.

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ABSTRACTS

RULES OF CLIMATE, SOIL AND VEGETATION ON DEVELOPMENT

OF THE KARSTSySTEM

Ilona BÁRÁNy –KEVEI1

Department of Climatology and Landscape Ecology, University of Szeged, 6722. Szeged, Egyetem u. 2. POBox 653, Hungary; e-mail: keveibar@earth.geo.u-szeged.hu

In the evaluation of environmentally sensitive karst regions for nature conservation value the most useful information is supplied by the changes in the ecological conditions of the climate-soil-vegetation system. Te changes in the system determine matter and energy cycles. A change in any of the three factors involves changes in the other two and eventually in the future functioning of the whole karst system. Climate infuences the physical, chemical and biological processes of the karst system.

Air temperature, humidity, precipitation and evaporation infuence the water and matter cycles. Temperature regulates life processes of the biota. Matter transport is a function of soil, vegetation, relief and climatic parameters. Te karst regions of various nature are characterised by diferent processes. In landscape planning and management this mechanism of interactions has to be taken into consideration in every case in the future.

TIME AND KARST PROCESSES: SOME CONSIDERATIONS

Pavel BOSÁK1, 2

Institute of Geology, Academy of Science of the Czech Republic, Rozvojová 269, 165 02 Praha 6-Lysolaje; email: bosak@gli.cas.cz Karst Research Institute, ZRC SAZU, Titov trg 2, 6230 Postojna, Slovenia

Karst evolution is particularly dependent upon the time available for process evolution and on the geographical and geological conditions of the exposure of the rock. Te time scale for the development of karst features cannot be longer than that of the rocks on which they form. Te longer the time, the higher the hydraulic gradient and the larger the amount of solvent water entering the karst system, the more evolved is the karst (Tab. 1). In general, stratigraphic discontinuities, i.e. intervals of nondepo-sition (disconformities and unconformities), directly infuence the intensity and extent of karstifcation. Te higher the order of discontinuity under study, the greater will be the problems of dating processes and events. Te order of unconformities infuences the stratigraphy of the karst through the amount of time available for suba-erial processes to operate. Results of paleokarst evolution are best preserved directly beneath a cover of marine or continental sediments, i.e. under sediments, which terminated karstifcation periods or phases. Te longer the stratigraphic gap the more problematic is precise dating of the age of the paleokarst, if it cannot be chronostrati-graphically proven. Terefore, ages of paleokarsts has been associated chiefy with periods just or shortly before the termination of the stratigraphic gap. Te characteristic time scale for the development of a karst surface landform or a conduit is 10 to 100 ka.

Determining the beginning and the end of the life of a karst system is a substantial problem. In contrast to most of living systems development of a karst system can be „frozen“ and then rejuvenated several times (polycy-clic and polygenetic nature). Te principal problems may include precise defnition of the beginning of karstifca-tion (e.g. inception in speleogenesis) and the manner of preservation of the products of karstifcation. Terefore, karst and cave flls are relatively special kinds of geologic materials.

Te end of karstifcation can also be viewed from various perspectives. Te fnal end occurs at the moment when the host rock together with its karst phenomena is completely eroded/denuded (tze end of the karst cycle) or sunken into the subduction zone. In such cases, nothing remains to be dated. Karst forms of individual evolution stages (cycles) can also be destroyed by erosion, denudation and abrasion, complete flling of epikarst and covering of karst surface by impermeable sediments, without the necessity of the destruction of the whole sequence of karst rocks. Temporary and/or fnal interruption of the karstifcation process can be caused by the fossilisation of karst due to loss of its hydrological function. Such fossili-sation can be caused by metamorphism, mineralisation, marine transgressions, burial by continental deposits or volcanic products, tectonic movements, climatic change

TIME in KARST – 2007 207

ABSTRACTS

tab. 1: Evolution of selected karst features in time on the background of transgression-regression set within one hypothetical karst period related to unconformity order

FealufeJOtdef 1 2 3

4

5

UtiCOtifttffaity'

MegaurtCönfüimily SupönurtCönfünTiily

Regional Lin content hty

Parastqui&noe öüundary

■eeddmg plana'

Cam'frean mcufef*

Interregional kars-l

Local karst

Deposit kj rial karsi

General model"

Karst penod

Karst phase Type 1

Karst pnase TvwZ

Gät>k>QiCal SGHirtQ

Cralan/Platfomn - CralDri.flaHurnfi + c&nire margins

DBpoalional basin

Ttms {Mb}

XM-XÜ XÜ-X

x-o.x

O.X-fl.OX

0.OX-O.0DX

Fnsshw-Bler lEni

Protoso)

Caliche

Soil

W&Blhefing BroJile

Karren

1

Sinkhole

Cava

Cave s-yslem

HvpogenitKarsI

HYdml hernial k.

Early tarsi"

Mjilure lonjf*

BuneC ksnst"

Reju>analBd k "

Relict karsl"

Unnco^gd ia^gr

<-----------------------

Transgression

Regression

-------------------------------------------------------------------------------------------------------------■>

SJKßV!

Ja a>"

SffiH^S

+ sensu Esteban (1991); * sensu Choquette & James (1988); ** sensu Bosák et al, (1989); § sensu Mihevc (1996); weathering profile = more evolved weathering cover (like laterite, bauxite, kaoline, etc.); Hypogenic karst = deep-seated karst, interstratal karst, intras-tratal karst, subjacent karst, subrosion. a

etc. Nevertheless, in contrast to living organisms, the development of the karst system can be „frozen“ and rejuvenated even for a multiplicity of times (polycyclic and polygenetic nature of karst). Further, the dynamic nature of karst can cause redeposition and reworking of classical stratigraphic order, making the karst record unreadable and problematic for interpretation.

Known karst records for the 1st and 2nd orders of stratigraphic discontinuity cover only from 5 to 60 % of geological time (time not recorded in any correlated sediments in old platforms usually represents 40 to 90 % of time). Te shorter the time available for karstifcation,

the greater is the likelihood that karst phenomena will be preserved in the stratigraphic record. while products of short-lived karstifcation on sha