COBISS: 1.01 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 al-ways 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 dis-solution 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 mag-netization (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. Colorado oDenver El Pasov County Cave, of the Winds s-rs^—Colorado Springs Manitou Springs \25y Fig. 1: Location of study area. FIELD AND LABORATORy PROCEDURES 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-per-formance liquid chromatograph (HPLC) at the Institute of Arctic and Alpine Research (University of Colorado, Boulder). 158 TIME in KARST – 2007 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 col-lected 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 inter-vals ranging from 3.0 to 10.0 cm. Te samples were ori-ented by means of a Brunton compass. Te core barrel and all pieces of drill rod that at-tached 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 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). N38"3 N38"5 (EARLY PLEISTOCENE) (CRETACEOUS) TRIASSIC, N FOUNTAIN FORMATION (PENNSYLVANIAN) (PRECAMBIAN) W 104W (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 Magnetiza-tion) 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 demag-netized at felds up to 30 mT. All remanence measure-ments were made on a Schonstedt SSM 1A spinner magnetometer with a sensitivity of 1x10-4 A/m. Repeat mea-surements 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 Devo-nian 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 de-posited 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 fold-ing 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 Qp Q es (LATE Qb Qlo Qs Qv Qrf n Kpl KPr Pf MCr Ypp Xgnb or amino acid 4 MILES 4 KILOMETERS FRED G. LUISZER Figure 3. Map Of Cave Of The Winds, Manitou Springs, Colorado show-ing locations of samplings sites. Modified from Paul Burger, 1996 Snider Hall| Cliffhanger Entrance Manitou Grand Cavern Entrance^ (Sealed) 40 80 Feet ' Passage below main cave (in red). I Passage above main "¦" cave (in red). the local hydraulic head. Te erosion of some of the im-pervious 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 re-direction 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 dissolu-tion at Cave of the winds is prob-ably 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 chro-nology. 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 relation-ship of the Nussbaum Alluvium to the coarse sediments in the cave deciphered, then an independent date can be as-signed 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 Plio-cene 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 or-ganism, the amino acids racemize, which is the natural conversion of the L-isomers into D-isomers. Eventu-ally 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 dif-ferent molecule, D-alloisoleucine. Tis reaction, simi-lar to racemization, is called epimerization (Miller and Brigham-Grette, 1989). Te rate at which this reaction takes place is a func-tion of temperature. For example, if the burial-tempera-ture 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. An-other 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 impos-sible 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 spe-cies 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 oc-curred at multiple sites could be used for the amino-acid study. Te species chosen for the Nussbaum (Black Can-yon) 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 (Loca-tions 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 ex-cluded 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 Starlight and Filmore X Black Canyon 1700 1X900 X HIGH A/I CURVE FIT Age = 1064.2y2 + 782.3y - 11.2 •Centennial -Modern AVERAGE A/I CURVE FIT Age = 1268.6y2 + 863.8y - 10.0 , LOW A/I CURVE FIT Age = 2002.4y2 + 782.0y - 4.2 500 2000 2500 1000 1500 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. Tak-ing 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 sam-ples 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 pos-sibility that the modern shells were reworked from older sediments such as the Piney Creek Alluvium. How-ever, the abundant live snails mixed with the dead snails of the same spe-cies suggests that all snail specimens were contemporaneous. Te Piney Creek Alluvium site (Fig. 2) has been mapped as Piney Creek and Post-Piney Creek (Trim-ble 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 char-coal mixed with old snails during the paleo-food or the snails were afected by a forest fre that induced anoma-lously 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 Trim-ble 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 in-ferred 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 East ( Verdos) West (Verdos) Canyon (Nussbaum) 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 163 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 0.020 0.021 0.032 0.056 0.044 0.069 0.124 0.103 0.210 0.083 0.274 0.275 0.233 0.270 0.414 0.317 0.322 0.231 0.298 0.244 0.531 0.545 0.515 0.051 0.041 0.163 0.420 0.296 0.224 0.543 0.529 0.546 0.576 0.021 0.001 Modern V AAL-5989 0.021 0.021 0.001 Centennial P AAL-5970 0.023 0.022 0.001 Centennial V AAL-5969 0.024 0.028 0.004 Manitou Cave G AAL-5993 0.042 0.050 0.006 Manitou Cave P AAL-5992 0.039 0.041 0.002 Manitou Cave V AAL-5991 0.043 0.056 0.013 Chesnut GO AAL-5972 0.106 0.115 0.009 Chesnut V AAL-5971 0.106 0.105 0.002 Colorado City G AAL-5986 0.154 0.176 0.025 Colorado City V AAL-5985 0.076 0.080 0.004 Fillmore 1 G AAL-5976 0.279 0.277 0.003 Fillmore 1 V AAL-5975 0.298 0.287 0.012 Fillmore 2 G AAL-5988 0.239 0.236 0.003 Fillmore 2 V AAL-5987 0.283 0.277 0.007 Starlight P AAL-5768 0.423 0.419 0.004 Starlight V AAL-5767 0.276 0.296 0.017 Starlight 1 G AAL-5974 0.302 0.312 0.010 Starlight 1 V AAL-5973 0.307 0.254 0.038 Starlight 2 G AAL-5978 0.292 0.295 0.003 Starlight 2 V AAL-5977 0.246 0.245 0.001 Black Canyon P AAL-5766 0.502 0.526 0.015 Black Canyon V AAL-5765 0.545 0.544 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 func-tion (y=x2) with good results. Ap-plying 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 para-bolic 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 ap-pears to have little efect on curve ftting of relatively young snails (<100 Ka). Te generalized para-bolic function, however, was used in this study because the age of the Nussbaum Alluvium is extrapolated 3 to 4 times beyond the oldest cali-bration 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). 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 tab. 3: Uranium-thorium and 14C dates. 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 cor-relative 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 cali-brate 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), acquir-ing 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 correlat-ing 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 sec-tion 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 pos-sible 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 ex-ception 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, A------- Sniders Hall 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 A' Mummys Alcove Heavenly Hall TIME in KARST – 2007 165 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 1.0E-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 1.5 2.0 2.5 3.0 3.5- 4.5 o h» CM I Floor . Angular limestone clasts 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. White clay Normal Polarity Reversed Polarity Green Clay Limestone 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 com-paction (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 ac-quisition 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 par-ticles during compaction and especially dewatering, both of which can take place thousands to millions of years afer deposition (Verosub, 1977). A possible explana-tion of the variability of the inclination of the reversed samples is that these samples were compacted and dewatered during a normal polarity interval, overprint-ing 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 mi-cro-sampling and precision analysis would be necessary to ascertain the mechanism responsible for the dif-ference in the inclinations. Chemical remanent magne-tization (CRM) may also be a con-tributing 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 precipita-tion of iron oxides. Te underlying soil-derived clays, which have al-ready undergone prolonged oxida-tion 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 ap-parently 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. Bedrock Chert sms Red Sandstone 168 TIME in KARST – 2007 TIMING OF PASSAGE DEVELOPMENT AND SEDIMENTATION AT CAVE OF THE wINDS, MANITOU SPRINGS, COLORADO, USA South Fountain Creek 'Water table - - South A. ~2 Ma Fountain Creek Williams Canyon Creek Mixing Zone -^- — ¦ ¦ ¦ " Clay_ Mn-oxide Fe-oxide——-—~~ ^Solution debris 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 >ass B. ~1.8 Ma North Williams Canyon 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 Con-cert 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- North ergy changed the sedimenta- tion 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 deposit-ed. 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. Accord-ingly, 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. Alter-natively, 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 Manitou Cave Water table 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 re-lated 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. Cor-relation 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 perme-ability of Its crystalline rocks [M.S. Tesis]: Golden, Colorado School of Mines. Cande, S. C., and D. Kent., 1992: A new geomagnetic po-larity 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 tec-tonic implications of the Post-Laramide, Late Eo-cene 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 Pro-grams, 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 Uni-versity, 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, Uni-versity 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 geo-magnetic 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 carbon-ate 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 (Pleis-tocene) 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 archaeol-ogy: 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 Ter-tiary) 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. TIME in KARST – 2007 171