original scientific paper UDK 551.781(262,3 Piranski z.) STRATIGRAPHY AND SEDIMENTOLOGY OF THE PIRAN FLYSCH AREA (SLOVENIA) Jernej PAVŠIČ Ph.D., geologist, Department of geology and paleontology, University of Ljubljana, Si-1000 Ljubljana, Aškerčeva 2 dr. geol. znan., Katedra za geologijo in paleontologijo, Univerza v Ljubljani, SI-1000 Ljubljana, Aškerčeva 2 Jörn PECKMANN M,Sc. in geology, Institut für Geulogie unci Paläontologie, Georg-Aug us t' Universität, Goldschmidtstraße 3, DE-37077 Göttingen e-irtail: jpeckma @ gwdg.de mag. geologije, Institut für Geologie und Paläontologie, Georg-August. Universität, Goldschmidtstraße 3, Di~37077 Güttingen e-mail: jpeckma @ gwdg.de ABSTRACT Eocene deep-sea sediments cover an area of about 400 km2 in the Flysch Area of Piran in istria. Marlstones with Globigerina ace followed by a flysch series of more than 500 m in thickness. The flysch is devided into four units based on the occurrence of intercalated limestone turbidites. Globigerinal marlstone belongs to the combined Nannoplankton Zone NP 15/16, Flysch Units I to 4 to NP 16, of the Paleogene. Basin plain turbidites and trace fossils of the Paleodictyon subfacies (Seilacher, 1977) indicate deposition in a deep-sea environment. Individual turbidites can be traced over several kilometres. The flysch comprises marlstone beds, siliciclastic, pure carbonate, and sandy carbonate turbidites, Turbidity currents that delivered siliciclastic turbidites moved parallel to the WNW-ESE striking axis of the basin, whereas carbonate turbidites were delivered from a carbonate platform in S5IV. Key words: stratigraphy, sedimentology, Flysch, Piran, Slovenia Kljucne besede: stratigrafija, sedimentologija, flis, Piran, Slovenija INTRODUCTION cating the deepening of the basin. In this text the deep- sea sediments are emphasized. The Flysch Area of Piran borders on the Ciéarija-The biostratigraphy of the Flysch area of Piran was Plateau in the east, the Buje-Anticline in the south and investigated by Piccoli & Proto-Decima (1969) and its the Adriatic Sea in the northwest. At its eastern mar-PavSic (1981), who examined the planktonic fo­gin. Paleocene and Eocene limestones of the Cicarija-raminifers and calcareous nannoplankton respectively. Plateau are thrust southwest onto Eocene flysch. The In the autumn of 1994 we took samples of the flysch, contact of the flysch to the Paleogene and Cretaceous which was previously mapped and investigated sedi­limestones of the Buje-Anticline is flexura! due to the mentologically (Peckmann, 1995). uplift of the anticline (Pleniiar et a!,, 1969). Samples ST 1 to ST 15 were taken of the globigerinal The oldest sediments in the flysch basin are lime-marlstone to the 4th. Flysch unit (Fig, 2). We sampled stones with Nummulites and Alveolina in Ezola. They freshly broken maristones. Over 35 species of calcare­are of Middle to Upper Cuisian to Lower Lutetian age ous nannoplakton were determined. The frequency of (Pavlovec, 1985). These shallow water limestones are the poorly preserved fossils is low. In all examined overlain by marly, glauconite bearing limestones which samples both in situ and reworked fossils occur. Re­grade into globigerinal maristones and flysch, thus indi-worked nannofossils originate from the Cretaceous, Pa­ I. PAVSfC, ). PECKMANN: STRATIGRAPHY AND 5fDIMENTQ!OCY Of THE F IRAN "(23-08 [eocene and Lower Eocene strata. Especially, nannoliths of the genus Discoaster are poorly preserved, partly dis­solved and overgrown. Ail samples were examined and photographed with a Leitz Photo Microscope. They are not suitable for de­tailed studies under the SEM. Most of the field work was carried out in the map­ping area (see Pig. 1). Thickness of the described Fiysch Units varies significantly. The column shown in Fig. 2 is located in the central part of the mapping area. The Lower and the Middle Limestone Turbidite can be traced throughout most of the fiysch basin. THE CL08ICERINAL MARLSTONE The globigerinal marlstone crops out in a quarry east of Izola and in coastal cliffs west of Izola, The grey col­oured marlstone shows no bedding and breaks into po­lygonal pieces, in places where globigerinal marlstones are replaced by fiysch, some thin siltstone beds occur. In the quarry of the old brickwork east of izola we took the sample ST 10, southwest of Izola we sampled ST 9. in these samples we determined 24 species of cal­careous nannoplankton (Fig. 4). Among these, only the following species are important for stratigraphy; Nannotetrina cristata (Martini) Dictyococcites bisectus (Hay, Mohler et Wade) Reticulofenestra dictyoda (Deflandre) Discoaster nodifer (Bramlette et Riedel) Discoaster saipanensis Bramlette et Riedei These species, to the exclusion of Discoaster nodifer, have already been reported in PavSiC (1981). This nan­nofossil is very rare and poorly preserved. Reticulofenes­tra dictyoda is common. Because of its poor preserva­tion, it is hardly possible to discriminate it from Reticu­lofenestra piacomorpba. According to the determined species we conclude that the globigerinal marlstone belongs to the combined biozone NP15/16. Stratigraphies! distribution of Discoaster nodifer ranges from NP 1S to NP 17, with its first permanent oc­currence in biozone NP 17 (Perch-Nielsen, 1985). Pro-to-Decima et al. (1975) state that D. nodifer appeared at the end of biozone NP 15. THE FLYSCH UNITS Common features of the Fiysch Units All Fiysch Units consist of interbedded sandstones and marlstones. The ratio of marlstone to sandstone bed thickness changes as does the average thickness of the beds, whereas litbology and sedimentary structures do not change significantly throughout the sediment col­umn. The sandstone beds are siliciclastic turbidites. Most marlstone beds were partly deposited by turbidity currents, but most of their material was deposited by background sedimentation in a hemipelagic setting, in­ dividual beds can be traced over great distances. Detrital components of the sandstones are quartz and carbonate at about equal frequency, with slight variations. Glauconite grains are frequent and are smaller on the average than quartz grains. Felspars and micas are rare. The most common heavy minerals are pyrite and garnets. The matrix of the well sorted sand­stones is carbonatic. No visible porosity has been pre­served. Occasional joints are filled with coarse carbon­ate cements. The unweathered sandstone is grey, weathered brownish, indicating the oxidation of the originally reduced iron. The siliciclastic turbidite beds are usually graded, with sharp bases and occasional flute casts. Amalgama­tion can be found, cross bedding and other sedimentary structures are rare. Only beds that are some decimetres thick show cross bedding and lamination. Dewatering structures are common in thicker beds. Convolute bed­ding is often asymmetrical, indicating a depositional slope (see Discussion). Dish structures are rare. A fineafion parallel to the axis of the basin due to compressional stress is developed on the lower bedding planes of many sandstone beds, Plant debris are frequent especially in the lower part of the 1st. Fiysch Unit (Plate 1, Fig. 1). Some siliciclastic turbidites have layers of plant debris at the bases and at the tops. These layers are continuous in outcrop. The plant debris, which contain many wood fragments, are tenigenic. Most common trace fossil is Taphreheiminthopsis of the Scolicia Typ. These fossils are preserved on the lower bedding plane of siliciclastic turbidites and in marlstone beds. The winding burrows with two parallel sediment strings are about 4 cm in diameter. The Scolicia Typ was attributed to gastropods (Seiiacher, 1962) and to echi­noids (Smith & Crimes, 1983). The Taphreheiminthopsis burrows are preserved as postdepositional and pre de­positional traces (in sense of Seiiacher, 1962). Postde­positional traces are exposed on lower bedding planes of siliciclastic turbidites and in marlstones. They are pre­served in three-dimensional shape in cross section. Be­low thin and thick bedded sandstones trace fossils occur as casts of preexisting burrows filled by the sediment of the turbidity current (positive hypo-relief in sense of Seiiacher, 1964). In cross section only the lower side of the burrow has been preserved. The predepositional trace fossils Taphreheiminthopsis are much more com­mon than postdepositional traces. The regular nets of Paleociictyon are made of hexago­nal meshes and vertical outlets. Preferentially, the net is preserved (Uchman, 1995). Paleodictyon is exposed on the lower bedding planes of sandstone beds, The dia­meter of a single hexagon varies between 0,2 and 7 cm (Pavlovec, 1980). in the Fiysch Basin of Pi ran the hexa­ J. PAVStČ, t. PECKMANN: STRATIGRAPHY AN D SED1MENTOI.OCY OF THE PIRAN ..., 123-139 Fig. 1: Flysch Area of Piran; geological margins after Pleničar et al. (1969). Si. 1: Piransko fliSno območje; geološke meje po Pleničar ju in sodelavcih (1969). gons are elongated parallel to the axis of the basin {see Discussion). Paleodictyon is exclusively predepositional, The sharply bounded burrows of Granulans are in­tersecting flute casts, providing clear evidence for the postdepositional nature of Granularia. In the 1st Flysch Unit a single specimen of Glockeria afata (Seilacher, 1977) was found. The trace has a di­ameter of 40 cm. Several burrows, 1 cm in diameter, are directed from one centre to the periphery. Zoophycos was found as a single Specimen in the 2nd Flysch Unit. It is a three-dimensional spreite structure with helicoidal elements (Ekdale, 1977; Uchman, 1995). The 1 s t Flysch Unit The 1 st Flysch Unit is 175 m thick. It consists of marl-stone and sandstone beds and some intercalated sandy carbonate turbidites. In the basal part of the 1st Flysch Unit the ratio of marlstone to sandstone bed thickness is much higher east rather than west of izola (Fig, 3, Sections a and b). East of Izola most marlstone beds range in thick­ness from 16 to 64 cm, while west of Izola most marlstone beds range from 4 to 32 cm. In the intermediate part of the Unit sandstone beds are reduced in bed thickness (Fig. 3, Section c). There the ratio of marlstone to sandstone of 6:1 is higher than anywhere else in the flysch. Samples ST 5, ST 6, ST 8 and ST 11 come from the lower part of the 1st Flysch Unit. We found 27 species of calcareous nannoplankton including the following species, significant for biostratigraphy: Discoaster nodifer (B ram fette et Riedel) Discoaster saipanensis (Bramlefte et Riedel) Reticulofenestra umbilica (Levin) Cribrocentrum coenurum (Reinhardt) Dictyococcites bisectus (Hay, Möhler et Wade) J. PAVÍlC, j, PECKMANN: STRATIGRAPHY AMD SEDIMENTO LOG Y O F THE !'IRAN .... 123-13 8 Samples m Surface o! Recent erozion ST 13 65 4 th. Fiyscb Unit 0,7 Upper Limestone Turbidile ST 15 75 3 id. Fiyscb Unit ST 12 3.5 Middi© Limestone Turbidile 170 2 nd. Fiysch Unit ST4/ST14 ST1 ST2 ST3 Lower Limestone Turbidile - sct4 175 1 s!. Fiysch Unit sct3 ST7 (-sd 50 ' 2 ST5/ST6 ST8/ST11 Globigerlnai Marlstone ST9/ST10 [exposed) V/MM 16,5 Fig. 2: Stratigraphic column of the fiysch in the central part of the mapping area including the sandy carbonate turbidites set 1 to set 4. SI. 2: Stratigrafski stolpec fliša v osrednjem delu kartiranega območja, vključno s karbonatnim turbiditom (profil 1 do profil 4), With the beginning of fiysch sedimentation Reticu­lofenestra umbilica, Reticulofenestra dictyoda and Cri­brocentrum coenurum appear. R. umbilica and C. coenurum have a similar stratigraphies! range from NP16 to NP 23 (Perch-Nielsen, 1985). Because oí their poor state, it is very difficult to distinguish these two species. The first occurrence of Dictyococcites bisectus is controversiaÍ, According to Perch-Nielsen (1985) D. bi­sectus appears at the base of NP 17 (p. 504) or at the biozone NP 16 (p. 431). Proto-Decima et al. (1975) state that it first occurred in biozone NP 16. In the samples of the younger roarlstones of the 1st Fiysch Unit ST 7, ST 3, ST 2 and ST 1 we found 21 spe­cies of calcareous nannoplankton (Fig, 4). All these nannofossiis are characteristic of biozone NP 16. The 2nd Fiysch Unit The 2nd Fiysch Unit is 170 m thick in the centre of the mapping area and slightly less in the southeast, Marlstone beds are reduced in thickness in comparison to the 1st Fiysch Unit (Fig. 10, Section d). The 1.3:1 ratio between marlstone and sandstone is at its lowest value in the whole fiysch succession. Amaigamated sandstone beds are freq­uent. Assuming a constant sedimentation rate for the hem i­peiagic marts, siliciclastic turbidites are more frequent in time compared with the 1 st Fiysch Unit (see Discuss ion). The 3rd Fiysch Unit The thickness of the 3rd Fiysch Unit is reduced from 90 m near Piran to 50 m in the southeast of the mapping area. The Unit has a similar ratio of marlstone to sand­stone bed thickness as the 2nd Fiysch Unit, Sample ST 12 is of the marlstone cap of the Middle Limestone Turbidite. In sample ST 15 we determined 14 species of calcareous nannoplankton, including the fol­lowing species: I. PAVSiC, J. PECKMANN: STRATIGRAPHY AN D SED1MENTOLOGY O f THE PIRAN .... Î23-13B Cribrocentrum reticulatum (Gartner et Smith) Dictyococcites bisectus (Hay, Mohler et Wade) Reticuiofenestra umbilica (Levin) Discoaster saipanensis Bramiette et Riedel Discoaster nodifer {Bramiette et Riedel) According to the frequent occurrence of Cribrocen­ trum reticulatum, this unit belongs to the upper part of biozone NP 16 or to biozone NP 17. Clear evidence of the affiliation to NP 17 is missing. The 4th Flysch Unit The 4th Flysch Unit forms the tops of the highest hills in the mapping area. Younger sediments are eroded. Today 85 m of the 4th. Flysch Unit are exposed. In the western part of the Flysch Area there is only one small outcrop in this Unit (Fig, .3, Section e). The ratio of maristone to sandstone is 2:1. Sample ST 13 contains the same stratigraphically relevant nannofossils as the 3rd Flysch Unit: Cribrocentrum reticulatum (Gartner et Smith) Dictyococcites biesctus (Hay, Mohler et Wade) Reticulofenestra umbilica (Levin) Discoaster saipanensis Bramiette et Riedel Discoaster nodi fer (Bramiette et Riedel) We assigned it to the upper part of biozone NP 16. SAND Y CARBONAT E TURBIDITES Sandy carbonate turbidites differ from siliciclastic and pure limestone turbidites. This type of turbidite oc­curs in the 1st. Flysch Unit, but. it is missing in the other Units. The four sandy carbonate turbidites (sct1-sct4) are prominent beds, wich are more resistent to weathering than siliciclastic turbidites. The bed set! consists of carbonate detritus and a mi­nor portion of quartz detritus. It is 33 cm thick. Com­pounds are not rounded and very well sorted. sct1 has no maristone cap in contrast to sct3 and sct4. From base to top a graded zone is followed by lamination, cross bedding and finally by a structureless zone. Bed sct2 is 50 cm thick, it is one bed deposited by three turbidity currents. This is documented by thin maristone interbeds. The quartz content is higher com­pared to sct1. The layer sct3 has a 81 cm thick sandy limestone bed and a maristone cap of 34 cm. The hemipeiagic marl-stones differ from the marlstones sedimentated by a turbi­dity current of the sandy carbonate type, The turbidite marlstones are much harder, brighter and have a higher carbonate content. They break into polygonal pieces and show no bedding planes. The sandy limestone bed is 81 cm thick. It is divided vertically in three zones: laminated base, cross bedded center and laminated top. The 12 cm thick limestone bed of sct4 is capped by 40 cm maristone (Plate 2, Fig 3). The limestone bed consists mainly of detrital carbonate. Quartz grains are enriched in layers. Glaukonite grains are frequent. Components are not rounded. Sorting is good, no po­rosity is visible. LIMESTONE TURBIDITES Limestone Turbidites are most spectacular beds irt the Flysch Basin of Piran. In coastal cliffs, the Lower and the Middle Limestone Turbidite are well detectable from great distance. The Lower Limestone Turbidite The Lower Limestone Turbidite consists of a lime­stone bed and a maristone cap, Its maximal thickness is exposed in coastal cliffs, where the limestone bed is 3,58 to 3,75 m and the maristone cap 4,05 m thick. South of the mapping area the thickness of the limestone bed is reduced to 1.7 m. Limestone is made of various biogenic detritus. Fo­raminifera of the genera Nummulites and Discocyciina and the coralline red algae Lithotbamnium are the most frequent components. Nummulites refer to the species Nummulites millecaput after Pavlovec (1963). in Lime­stone Turbidites the microspheric forms dominate, Fo­raminifera of the genus Gypsina, cbeilostomate bryo­zons, the red algae Mesopbyllum, fragments of brachi­opod shells and echinoids and small snail conchs were found in Limestone Turbidites, too. Clasts make about 10% of the rock volume. Partly they show a high diage­netic grade. The upper part of the limestone bed, where miliolid foraminifera dominate, contains small fragments of Nummulites and Discocyciina. The Lower Limestone Turbidite has no matrix and no visible porosity. Pressure solution is very intense. Sty­lolites are "circumidenic" and their form is "peaked low amplitude" to "irregular" (after Logan & Semeniuk, 1976). The intensity of pressure solution increases with grain size. Cements are developed in proloculi and partly in the median chambers layer of Nummulites. The cavities are filled with blocky spar and partly with ferroan calcite. Fringing cements are rare. In proloculi geopetal cements and micrites can be found. The geopetals show different orientations and indicate a filling of the cavities before resedimentation. Most of the limestone bed of the Lower Limestone Turbidite is rudstone, while its uppermost part is grainstone. Sorting in horizontal section is good and increases upwards. The components consist of calcite. Glauconite grains are quite frequent, too. Maristone chips, eroded hemipeiagic marls, can'be found in the lower part of the bed. j, PAVŠIČ, j. PECKMANN: STRATIGRAPHY AN D SEDÎ MENTOIOCY OF THE PIRAN ..., 123-738 Fig. 3: Frequency distribution of bed thickness; Section a: 7st Flysch Unit (basal) east of Izola, Section b: 1st Flyscb Unit (basal) west of Izola, Section c: 1st Flysch Unit (intermediate), Section d: 2nd Flysch Unit, Section c: 4th Flysch Unit. Si. 3: Frekvenčna porazdelitev debeline plasti; profil a: prva Hišna enota (bazalni del) vzhodno od Izole, profil b: prva flišna enota (bazalni del) zahodno od Izole, profil c: prva flišna enota (vmesni del), sekcija d: druga flišna enota, profil c: četrta flišna enota. I. PAVSLT J. I'ECKMANNIITKATIORAI'HY AN D SEDIMENTOLOCY OF THF PIRAN ..., 123-1 J ? Species / Samples --» ST/ 9 1 10 11 8 5 6 7 3 2 1 4 [ 14 12 15 13 Coccolithus pelagicus + + + + + + + + -t- + + + + + -f Cyclicargolithus floridanus + | + + + + + + + + + "^T j + + 4 Discoaster bisectus + + + + + + + + + + + + Fasciculithus tympan iform is + + + + + + + + + + Ericsonia tormosa + + + + + + + + + + + + + + + Braarudosphaera bigeiowi + + + + + + + + + Chiasmolithus grandis + + + + + + + + 4 Discoaster barbaciiensis + + + + + + + + Ericsonia cava + + + + + + + + + + 4 + Discoaster lodoensis + + Discoaster deflandrei + + + + + + + Discoaster binodosus + + + + + + + + + Coccolithus eopelagicus + + + + + + Tboracosphaera sp. + + Transversopontis pulcheroicles + + Pontosphaera plana + + + + + + + + + Helicosphaera seminulum + + + + Lanfernithus minutus + + + + + + + + + + SphenoHthus radians a. + + + + + + + Sphenolithus obtusus + + Cribrocentrum coenurum + + + + + + Prinsius bisuicus + + + + Pemma roiimdum + Cribrocentrum reticulatum + + + + Transversopontis obliquipos + Zvgrhabiithus bijugatus + + + + + + + + + + + + + Nannotetrina cristata + + Discoaster germa ni eus + Heliolithus kleinpellii + Reticulofenestra umbiîica + + + + + + + + + + + + Reticulofenestra dictyocla + + + + + 4 + + + + + + + Dictyococcites scrippsae + + + Discoaster distinctus + •f + 4- Discoaster nodifer + + + + + + + Discoaster saipanensis + + + + + + + Micrantholithus sp. + Toweius enitnens + Discoaster elegans + + Discoaster keupperi + Discoaster aster + Discoaster diastypus + Reticulofenestra hampclenensis + Toweius callosus + Helicosphaaera lophota + Neococcolithes dubius + Fig. 4: Distribution of calcareous nannoplankton in the samples of Piran Flysch Area. $1. 4: Razporeditev ka Icitnega nanoplanktona v vzorcih piranskega ffišnega območja. f. PAVŽiČ, j, PECKMANN: STRATtCRAPHy AN D SEDIMENTOI.OGT Of THE PI RAN 123-138 Inverse grading of the basal part changes into normal Plate 3 - Tabla 3 grading. Foraminifera and other planar elements are im­ bricated. Near the top of the bed a zone of basal inverse grading overlies a laminated zone. The amalgamated limestone bed was deposited by two turbidity currents. The second current followed directly after the first one, The marlstone cap was deposited from the tails of the turbidity currents, it is harder and brighter than the hemipelagic marlstones, shows no bedding and breaks into polygonal pieces. Samples ST 4 and ST 14 are of the marlstone cap of the Lower Limestone Turbidite. They contain the follow­ing relevant nannoflora: Discoaster noclifer (8ramlette et Riede!) Discoaster saipanensis Bramlette et Riedel Reticulofenestra umbilica (Levin) Cribrocentrum coenurum (Reinhardt) Cribrocentrum reticulatum (Gartner et Smith) Of special interest is Cribocentrum reticulatum, Perch-Nielsen (1985) attributes its first occurence to the upper part of biozone NP 16 before the first constant oc­currence of Discoaster noclifer and also before the occur­rence of Reticulofenestra umbilica. We assigned the Lower Limestone Turbidite to the upper part of biozone NP 1 6. PLATES -TABLE Plate 1 - Tabla 1 Fig. 1: Plant debris on the lower bedding plane of a thick bedded siliciclastic turbidite; 1st Flysch Unit. Fig. 2: Taphrehelminthopsis on the lower bedding plane of a siliciclastic turbidite. Si. 1: Ostanki rastlin na spodnji strani plasti debelo plastnatega silikoklastičnega turbidita. Prva flišna enofa. SI. 2: Taphrehelminthopsis na spodnji strani plasti kre­silikoklastičnega turbiditnega peščenjaka. Plate 2 - Tabla 2 Fig. 1: Middle Limestone Turbidite separating 2nd and 3rd Flysch Units. Fig. 2: 1st. Flysch Unit, intcrbvdding of sandstones and marlstones. Fig. 3: Sandy carbonate turbidite set 4. SI. 1: Apnenčev turbidit, ki loči drugo in tretjo ftišno enoto. SI. 2: Prva flišna enota; menjavanje peščenjaka in laporja. SI. 3: Peščen karbonatni turbidit, profil 4. Fig. (SI.) I, 2 Discoaster nodifer (Bramlette et Riedel), ST/6 3 D. nodifer (Bramlette et Riedel), ST/12 4 D. nodifer (Bramlette et Riedel), ST/13 5 Discoaster keupperi Stradner, ST/7 6, 7 Discoaster saipanensis Bramlette et Riedel, ST/12 8 Discoaster germ a ni eus Martini, ST/12 9 Discoaster aster Bramlette et Riedel, ST/2 10, 12 Discoaster binodosus, Martini ST/6 13 Discoaster diastypus Bramlette et Sullivan, ST/6 14 Discoaster elegans Bramlette et Sullivan, ST/12 15, 16 Heiiolithus kleinpellii Sullivan, ST/7 All under ordinary light. All 2000 X enlarged. Vse pod presevno svetlobo, 2000-kratna povečava. Plate 4 - Tabla 4 Fig. (SI.) 1-6 Reticulofenestra umbilica (Levin), 1, 3, 4, 5 ST/2, 2 ST/7, 6 ST/17 7-9 Dictyococcites bisectus (Hay, Mobler et Wade), 7,8 ST/13, 9 ST/17 10 Reticulofenestra hampdenensis Edwards, ST/13 11 Toweius callosus Perch-Nielsen, ST/13 12 Cyclicargolithus floridanus (Roth et Hay), ST/6 13 Sphenolithus radians Deflandre, ST/11 14 Ericsonia formosa (Kamptner), ST/2 15 Helicosphaera lophota Bramlette et Sullivan, ST/12 Fig. 4. under ordinary light All others between crossed nicols. All 2000 X enlarged. SI. 4. pod presevno svetlobo. Druge pod navzkrižnimi nikoli, vse 2000-kratna povečava. Plate 5 - Tabla 5 Fig. (SI.) 1-3 Chiasmolithus grandis (Bramlette et Riedel), 1,3 ST/11, 2 ST/6 4, 7, 8 Coc eolith us pelagicus (Wallich), 4 ST/12, 7 ST/3, 8 ST/11 5, 6 Cribrocentrum reticulatum (Gartner et Smith), 5 ST/14, 6 ST/12 9 Braarudosphaera bigelowi (Gran et Braarud), ST/15 10, 11 Pontosphaera plana (Bramlette et Sullivan) 10 ST/11, 11 ST/9 12 Neococcolithes dubius (Deflandre), ST/12 13, 14 Neotetrina sp., ST/6 15 Zygrhablithus bijugatus (Deflnadre), ST/9 16 Lanternithus minutus Stradner, ST/2 Fig. 3, 8, 11, 12, 13 under ordinary light. All others between crossed nicols. All 2000 enlarged. Slike 3, 8, 11, 12 in 13 pod presevno svetlobo, druge pod navzkrižn i m i nikoli. Vse 2000-krat povečano. ANNALES 9/'% I. f'AVéíC, f. reCKMANN: STRATIGRAPHY ANO SEDIMCNTOLOGY OF TU t' t>IRAN~7 m Plate 1 - Tabla 1 131 ANNALES 9/'96 ANNALE S 9/'9 6 PECKMANN: STRATiGRAPHY AN D SFBIMfNTCXOGY OF THE PJR.AN ). !>AVS? C j . PECKMANN: STRATiCRAPHY AND SED1MFNIGI.OGY Of THE PIRAN .., I 23-1 38 | PAVÎtC, j. IM-tTB Plate 2 -Tabla 2 Plate 3 -Tabla 3 132 133 ANNALES 9/'% J. F'AVÎlC J. PECKMANN: STRAT1GRAPHY AND SEDtMENTOi.OCY OFTIJÉ PiRAN 123-138 Plate 4 -Tabla 4 134 ANNALES 9/'% I. PAVSC [•P LCKMANN:STRAI!GRAPHY ANDSEDIMÉNTOI.OGYORTHEPIRAN .... 123-08 Plate 5 -Tabla 5 135 J. PAVŠIČ, j, FECKMANN: STRATIGRAPHY AND 5EDIMENTOLOGYOP THE PIRAN ..., 123-1.18 The Middle Limestone Turbidite The Middle Limestone Turbidite is similar to the Lo­wer Limestone Turbidite. It is made of the same compo­nents, shows the same sedimentological features and is amalgamated, too. The maximal thickness is 1.65 m for the limestone bed and 2.03 m for the marlstone cap. The Middle Limestone Turbidite is well exposed in most parts of the basin. We estimate its rock volume at about 1 km3 . Sample ST 12 was taken of the marlstone cap of the Middle Limestone Turbidite. According to the frequent occurrence of Cribocentrum reticulatum, we believe that this layer belongs to the upper part of biozone NP 16. The Upper Limestone Turbidite The Upper Limestone Turbidite has no marlstone cap. Its thickness decreases from 1.3 m in the south to 0.4 m in the north of the mapping area. It consists of the same components as the other Limestone Turbidites, though clasts are less frequent. Pressure solution is equally inten­se (see Discussion). Grading is less obvious because of good sorting throughout the bed. The grain size is smaller in comparison to the older Limestone Turbidites, A rud­stone at the basis grades into a grainstone, As a con­sequence of its narrow grain size spectrum, the Upper Limestone Turbidite shows intense cross bedding, which is missing in other Limestone Turbidites (cf. Engel, 1974). DISCUSSION Turbidites in association with trace fossils clearly in­dicate the deep-sea environment during flysch sedi­mentation, The trace fossils belong to the Paleodictyon subfacies of the Nereites facies in sense of Seilacher (1977) or to the Zoophycos-Nereites-assoct&tion in sense of Collinson & Thompson (1989). During flysch sedimen­tation the water depth ranged of some hundred metres. Cohrbandt ei ai. (1960) suggested 700-1200 m based on the association of foraminifera and a depth of several hundred metres based on the association of ostracods. Assuming a water-depth of several hundred metres, a strong subsidence in the basin is needed to explain a succession of several hundred metres of flysch. Today more than 500 m of deep-sea sediments are exposed in vertical succession. The intense pressure solution in the Upper Lime Turbidite indicates that it was covered by a much thicker sediment-column than the 85 m that are preserved of the 4th Flysch Unit. The axis of the Eocene basin extended in WNW-LSE direction, This can be seen from the lineation on lower bedding planes of sandstone beds, from the inclination of originally vertical elements caused by sedimentary creep, from the orientation of the long axis of elongated Paleodictyon hexagons and from the asymmetry of con­volute bedding. Turbidity currents of the silicicfastic turbidites moved parallel to the axis of the basin, in the 1st. Flysch Unit from ESE to WNW. in the uppermost part of this Unit the direction was reversed, and from then on remained from WNW to ESE. With this change in current directions the ratio of marlstone to sandstone bed thicknesses de­creased. Turbidity currents of the Limestone Turbidites were directed to NNE, which is evident from the dipping of the imbrication of foraminifera and other planar ele­ments. Their source area was the rim of a carbonate platform in the SSW. CONCLUSION S Sedimentoiogy The Piran Flysch shows the characteristics of basin plain sediments in sense of Ricc.i Lucchi & Valmori (1980). It. is a regular, repetitive interbedding of hemi­peiagites with turbidites. The ratio of marlstone to sand­stone bed thickness changes irregulary from one section to another (see Fig. 3). Obvious trends like thickening- or coarsening-upward sequences are missing. Beds do not wedge out and can be traced over long distances. The turbidity currents moved parallel to the axis of the basin. They experienced a reversal in current direction. The Piran Flysch corresponds to Type I System in sense of Mutti (1985), which develops in the proximity of an uplifting orogen at times of low seafevei, The Eo­cene was a period of global sealevel lowstand (Heller & Dickinson, 1985). The turbidites were deposited by highly efficient turbidity currents carrying their load far into the Basin (cf. Mutti, 1985). Biostratigraphy Biostratigraphers began to investigate the flysch be­tween Trieste and Piran by microfossils in 1969. The work of Piccoli & Proio-Decima (1969) deals with planktonic foraminifera in the area of Slovensko Pri mor­je. The main purpose of their paper was to determine the age of flysch sediments, in the area between Trieste and Piran they repotted four plankton b!ozones: the old­est biozone, Globorotalia aragonensis (now Moro­zovella aragonensis, P8), containing planktonic fo­raminifers near Trieste, biozone Hantkenina aragonensis (now Hantkenina nuttalli, PIG) in Milje peninsula, bio­zone Globigerapis kugleri (now Globigerinatbeka s. subconglobata, P11) between Črni Kal, Rižana and Dekani, and hiozones P11 and Globorotalia lehneri (now Morozovella lehneri, PI 2) between Koper and Pi-ran. Pavšič (1981) studied nannofossils of different strata in Slovensko Primorje. He reported biozone Discoaster iodoensis (NP 13) at Ankaran, biozone Discoaster sublodoensis from the surroundings of Dekani and bio­ t. PAVjlČ, I. PECKMANN: STRATIGRAPHY AND SEDiMENTOLOCY Of THE PIRAN ..., 123-138 zone Nanotetrina fulgens, which corresponds to the long ranging biozone NP15 - NP16, form the glohigeri­nal maIIstone in the quarry of the old brickwork at izola. According to PavâiC (1981) the flysch sequence between Izola and Piran is equivalent to biozone NP 16. Com­paring plankton and nannoplankton biozones PI 1, cor­responds to NP1 5 and P I 2 to NP16. The limestone with nummulitins and alveolinas at Izola grades into marly limestones with glauconite, which are overlain by the globigerinal marlstone. Pavlovec (1985) divided the limestone at Izola in four parts: a transition from Middle to Upper Cuisian, Upper CuLsian, Uppermost Cuisian and Lower Lutetian, corre­sponding to the biozone Nummulites gatlensis. Biozone N. galiensis corresponds to the standard nannoplankton biozone Discoaster sublodoensis (NP 14) (Kapellos & Schaub, 1973; Serra-Kiel & Hottinger, 1995). : The globigerinal marlstone belongs to the combined biozone NP 15/16. The Flysch Units 1 to 4 are assigned to NP 16 on the basis of the following species: Dis-coaster saipanensis, Reticulofenestra umbilica and Cri­bocentrum reticulatum. Cribocentrum reticulatum is characteristic for the upper part of NP! 6. In the southern parts of the Piran Flysch Basin even younger sediments crop out (PleniCar ef al., 1969). So the existence of younger flysch, belonging to NP17, could be expected. ACKNOWLEDGEMENTS Jörn Peckmann benefited from the advice and help­ful criticism of the manuscript by Prof. Dieter Metsch­ner, Göttingen. POVZETEK Eocens ki globo ko morski sedimenti piranskega flišnega območja se razprostirajo na površini okrog 400 km2. Globi­gerinskemu laporju, ki leži nad alveolinsko-numulitnim apnencem pri Izoli, sledi flišno zaporedje, debelo več kot 500 metrov. Fliš je bil razdeljen na štiri enote glede na število vmesnih apnenčevih turbiditov. Globigerinskl lapor pripada meji nanoplanktonskih biocon NP 15/16, vse druge flišne enote pa nanoplanktonski paleogenski bioconi NP 16. Bazenski turbiditi in fosilni sledovi Paleodictyon podfaciesa (Seilacher, 1977) kažejo na globokomorsko okolje. Posamezni turbiditi si lahko sledijo na več kilometrov. Fliš sestoji iz laporjev, silikoklastitov, čistih karbonatov in peščenih karbonatnih turbiditov. Turbiditni tokovi, ki so prinašali silikoklastične turbidite, so tekli v smeri ZSZ-VJV', medtem ko so karbonatni turbiditi dobivali material iz karbonatne platforme iz smeri jjZ. REFERENCES COLLINSON , J.D. & THOMPSON, D.S. (1989): Sedi­mentary structures.- Chapman and Hall, 207 p., London. 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