1. INTRODUCTION At Podsused near Zagreb, in an abandoned surface excavation of cement marls, near Kostanjek (Fig. 1) an 83 m thick lithostratigraphical column was investigated comprising layers of Sarmatian and Pannonian age. Five lithofacies units (A, AB, B, C, D) were sepa- rated on the basis of their structural-petrographic char- acteristics. From layers with greater concentrations of fossils, a rich community of molluscs, foraminifera and ostracods was sampled, from which three basic biofa- cies were distinguished and the sediment age was defined. In summary, 23 gastropod species (21 of Pan- nonian and 2 of Sarmatian age) and 27 bivalve species The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek - Medvednica Mt., Croatia Davor VRSALJKO (24 of Pannonian and 3 of Sarmatian age) were deter- mined. Within the mollusc association various forms were detected: from facies and zonal to transitional and endemic species, as well as species with opportune and equilibrium characteristics. Without discussing the chronostratigraphic division of the younger Miocene layers, the interpretation of the Sarmatian stage was accepted according to SENE© & PAPP (1974), and the Pannonian (Table 1) partially according to PAPP (1951, 1953) and STEVANOVI∆ (1957, 1985), and mostly according to the division of Croatian geologists, used for the “Basic Geological Maps” (©IKI∆ et al., 1978, 1979). In the middle of the Sarmatian (Bessarabian), the western areas of Paratethys were being separated by a natural barrier i.e. the Carpathian arch, from eastern Back-Carpathian parts, and a distinct sedimentary envi- ronment called the Pannonian basin, was being formed (STEVANOVI∆, 1985). As the marine cycle of sedi- mentation continued into the eastern parts (Sarmatian sensu lato, according to Barbot de Marny) in the Pan- nonian basin, a considerable desalinization of the water occurred, under which regime, layers with separate lithological and faunistic content were being formed. These layers are defined as a separate stage, the Pan- nonian. The Early Pannonian substage approximately corresponds to the period of the upper part of the Mid- dle and Late Sarmatian (sensu lato), while the Late Pan- nonian substage is equivalent to the Meotian stage of eastern areas (STEVANOVI∆, 1985). Among the numerous authors who wrote about the biostratigraphy of the Pannonian strata, Papp’s research is significant. Thus, PAPP (1951, 1953) divided the Pannonian layers on the basis of molluscs into several biozones: A) gravel and sand with R e p l i d a c n a, B) sand with Melanopsis impressa and Congeria ornithopsis , C) sand with M. fossilis and C. partschi , D) sand and grav- el with M. vindobonense and M. fossilis constricta, and E) clay with M. vindobonense and C. subglobosae. Papp places biozones A, B, C and D to the “Lower-congerian layers”, where zone A is similar to the Sarmatian series (A/B), and zone E represents the “Middle-congerian layers” (Table 2). Later, PAPP (1956) studied marls and gravels around Podsused and correlated them to the similar layers of the Vienna basin. The high content of a coarse-grained component in the Vienna basin layers determined the boundary facies in which river molluscs G EOL. CR OA T. 52/1 9 - 27 10 Figs. 6 Tabs. ZAGREB 1999 Key words: Mollusca, C a r d i i d a e , L y m n o c a r d i i d a e, Phylogenetic series, Biozone, Pannonian, Pannonian basin, Medvednica Mt., Croatia. Institute of Geology, Sachsova 2, P.O.Box 268, HR-10000 Zagreb, Croatia. Abstract On the south-western slope of Medvednica Mt., an 83 m thick geological column Kostanjek-1, composed of strata representing the Sarmatian and Pannonian stages, was investigated in detail. Facies analysis allowed separation of five lithofacies units (A, AB, B, C and D) and the sedimentary mechanisms for particular successions were defined. A rich community of fossil molluscs (50 species) and ostra- cods (42 species) was sampled and determined. From these fossil determinations, the sediment age was defined, and biofacies analysis allowed the determination of three basic palaeobiocenosis types: 1) a community from Sarmatian brackish lagoons, 2) a community from an Early Pannonian littoral lake, and 3) a lake basin community in the Late Pannonian. The main “record” of the salinity crisis (drop) at the Sarmatian-Pannonian boundary influences in a selective way the majority of organisms, and is shown best in the evolutionary form changes of cardid bivalves, for which phylogenetic series were made. On the basis of dominant and characteristic forms in the entire associ- ation of Pannonian molluscs five biozones were separated: I) Lymno - cardium praeponticum acrozone, II) Radix croatica - L y m n o c a r d i u m plicataeformis - Gyraulus praeponticus cenozone, III) Neodelminiella venusta - Lymnocardium cekusi cenozone, IV) Congeria banatica - Lymnocardium gorjanovici - Gyraulus tenuistriatus cenozone and V) Congeria czjzeki - Lymnocardium winkleri - Gyraulus tenuistriatus cenozone. Many ostracod forms supply and test the stratigraphic val- ue of molluscs and support zonality of Pannonian layers. 10 Geologia Croatica 52/1 lived, while at the same time in the more distant area around Medvednica Mt. a lacustrine sedimentary regi- me was established, and therefore, according to their faunistic content, these sediments can be compared, but with reservations (VRSALJKO et al., 1995). With his studies of the central parts of the Pannon- ian basin, STEVANOVI∆ (1985), completed previous divisions of the Pannonian layers, differentiating basin, transitional and littoral facies (Table 2), with their asso- ciated molluscan communities. This allowed further division of this stage into two substages: the Lower Pannonian (Slavonian: Early and Late) and the Upper Pannonian (Serbian). In the areas of the Pannonian basin the layers are also zoned on the basis of their characteristic ostracod communities. The works of POKORNY (1946) and SOKA» (1972, 1985) in this area are prominent. These authors, with small differences, both divide the Pannon- ian basin (Table 1) into the following biozones: α-zone with Hemicitherya hungarica and Miliamina subvelati - na, and the β-Erpetocypris abscisa zone (Early Panno- nian), and finally the γ -Cyprideis pannonica and δ - Erpetocypris recta zones (Late Pannonian). As the location of the study area (Fig. 1) is palaeo- geographically approximately half way between sites described by Papp and StevanoviÊ, both results will be Fig. 1 Geographical loca- tion of the Kostanjek- 1 column. used for comparison. Accepting earlier stratigraphic division of the Pannonian stage into substages (Early and Late), the results of Croatian geologists will be mostly used here (JENKO, 1944; OÆEGOVI∆, 1944; KRANJEC et al., 1973; ©IKI∆ et al., 1978, 1979). 11Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... Table 1 A stratigraphic correlation scheme for the younger Miocene layers (compilation after SENE© & PAPP, 1974; STEININGER et al., 1985; NAGYMAROSY & MÜLLER, 1988). ! i I • I • • < • • < • • • • < • < • , , • • < , , , • • • • ~ --­~-- • " • I < • < • • < • ! i I : I !i • ! • • • • , • • , • , 12 Geologia Croatica 52/1 Table 2 Biostratigraphic correla- tion of the Pannonian strata of central and western Parate- thys. ~~ iil: ~ , :~ j .i ~ , ~ f · i \ I -: !: . ~ ~ ~ . ~ t~ir~ ~ .. i la~ ~ ,~ , , '!'j . , ;."':!. 'U~'I:l I;J !;.:i ~ ~ . • Ii:! -4l ' , :, II jl jl ~ '~I--~---t--I ~lIm'd.Jllil'il:ni (ilBbt ~1IIIII0l mJ4) n ~ .t<: !l 1 ' 'qj :::O'~ ''i' ~ ._......... .._ ...... _ .... _ ...... _............. . ... _ ......... _ ......... _...... . .......... ~ ...... -............ -............ - .. . ~ ~ i H- H~} n .l ''IOf' !J'oo .,....; ; :i ~ ':Ii ~~ ~ . ...... ~ . ........., 'it \ \. ~ ' ~ ~~~ ~l.: ~~ ~j .. _ ...... _ .... _ ...... _............. . ... _ ......... _ ......... _ ................... 1 ...... _ ............ _ ............ _ .. . 'I.l. [~ I ·~ '!tU1 ~"'fAm5') N:\"ISWlfOAON: N\f1i8li!IB . ili1, 1 :;j,iJ; r(j'1 (ml'~ ~'O\I\"nS ~ :;] 13Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... 2. MATERIAL AND METHODS Samples were taken in succession from sand and marls of the Sarmatian and Pannonian layers for palae- ontological, sedimentological, petrographical and geo- chemical analyses. Using the method of “directed dot- ted sample” a rich community of fossil molluscs (50 species, Table 5) and ostracods (42 species, Table 6) was collected from the Kostanjek-1 geological column. For definition of the structural-petrographic complex of certain layers, particle analyses of the light and heavy fractions, and measurements of granulometry, spherici- ty and grain roundness were used. Calcimetry, chemical and trace element analyses provided geochemical data. Due to the large number of determined morphotypes (Table 5) detailed descriptions and synonyms were avoided - only the current systematic terminology has being used. After determination of the mollusc commu- nity, biofacies analyses (Figs. 4-6) of individual palaeo- biocenoses and biostratigraphic zoning of the Pannon- ian layers was undertaken (Fig. 2). 3. DESCRIPTION AND INTERPRETATION OF THE KOSTANJEK-1 GEOLOGICAL COLUMN 3.1. LITHOFACIES Five lithofacies units were separated in the succes- sion (Fig. 2): A) laminated silty marl , AB) l a m i n a t e d and layered marl and clay , B) layered clayey limestone and marl with sand layers , C) cross laminated gravel with sand lenses, and D) massive marl with clay layers. The laminated silty marls (A) comprise the basal lithofacies of the column, and are 1 m thick. The bou- ndary with lithofacies AB is conformable and interfin- gered, marked by a 10 cm band of clay. The succession consists of rhythmical changes of very thin laminae ( 0 .1-0.5 mm): dark laminae with a greater concentra- tion of organic matter being alternated with light lami- nae with a greater proportion of carbonate minerals. The average carbonate content is 40-50 %, and the con- centration of strontium ( 700 ppm) and manganese ( 1500 ppm) is relatively constant (Tables 3 and 4). The most frequent fossil material includes fish verte- brae and scales, ostracods, foraminifera and macroflora casts, and small gastropods and bivalves (Fig. 4). The laminated marls were deposited in a relatively deep, calm and protected environment, where sedimen- tation was taking place from suspended flow under a regime of constant climate change (Fig. 7). The proba- ble cause of the poor fossil content is the low level of aeration (BOTTJER & SAVRDA, 1990). Rare, small ervilia, ostracods and foraminifera of the M i l i o l i d a e group define the Sarmatian age and brackish character of the sedimentary environment. The laminated and layered marls and clay ( A B ) conformably overlie lithofacies A, and pass continuous- ly into platy limestone (B). This lithofacies is approxi- mately 3 m in thickness. The marls are more silty and contain 70 -80 % of the carbonate component, while clays are rich in organic detritus, granules of pyrite and limonite, and have a low carbonate content. Laminae are 0.2-0.5 cm thick and layers are 5-10 cm in thick- ness. Macrofauna remains are rare and frequently include fish fragments, while fossil grasses and conti- nental flora also occur. Small, deformed bivalve forms of the Lymnocardinae subfamily, and small pond gas- tropods are the most frequent molluscs. Large ostracods of the Amplocyprisgroup also occur. The succession retains the structural complex of the Sarmatian layers, but with a new type (oligohaline - Fig. 3) of fossil community in the Early Pannonian sub- stage, which shows the constant desalinization and shallowing of the environment (VRSALJKO, 1997). The cause of shallowing is most probably aggradational infilling of the Sarmatian lagoon and/or lifting of the sedimentary area. Disappearance of old inhabitants and their replacement by new faunistic elements is the result of the alterted water chemistry, which was close- ly related to regional events (SENE© & PAPP, 1974). Layered clay-limestone and marls with sand layers (B) overlie the transitional sediments (AB) in the suc- cession. The lower boundary is conformable while the upper contact has been eroded by deposition of lithofa- cies C. The total thickness is 31 m. Six large cycles are observed in the succession with the fining-upwards trends. Layered clay-limestone in the lower part of the cycle, passes gradually upwards into silty marl with poorly visible lamination and sand layers of variable thickness. The cycles are 2 - 7 m thick with a higher concentration of marl, while the sand layers (lenses) are 0 .5- 5.0 cm thick. The limestone layers have a higher concentration of carbonate ( 95%), and marls have more siliciclastic component. The sands are loosely consolidated and poorly sorted with well-rounded gra- ins up to 0.5 mm (exceptionally up to 0.5 cm) in diame- ter and in parts exhibit planar cross lamination. The light mineral fraction contains quartz (35 %), feldspate ( 20 %), rock fragments (40 %) and calcite (5 %). The heavy fraction most frequently contains limonite and magnetite (15 %), dolomite (15 %), epidote (6 %) and tourmaline (3 %). The manganese content is constant ( 300 ppm), while the strontium content noticably decreases upwards, from 3,320 -710 ppm. The fossil material contains a mollusc and ostracod community representing small number of specimens of many speci- es, together with a similar distribution of fish remains, fossil grasses, continental macroflora and frequent bio- turbation (Fig. 5). Mollusc shells are poorly preserved because of their original aragonite composition, and the most frequent samples are pulmonate gastropods and small limnocardids. Deposition of the limestone occurred during periods of low input of terrigenous particles, in contrast to the silty marls deposited from suspension during periods of 14 Geologia Croatica 52/1 greater siliciclastic input from the continental hinter- land (Fig. 8). ALLEN & COLLINSON (1986) reported similar results, in their research of the modern Little- field Lake (Michigan, USA). The origin of sand layers relates to periods of the stronger influence of fluvial processes. The rhythmic sedimentation shows the per- manent relationships between subsidence, eustatic pro- cesses and the transport of material from a denuded area. A broad photic zone and global temperature de- crease in the Early Pannonian (STEVANOVI∆, 1985) caused increased production of O2 and CO2, which resu- lted in favourable conditions for the comparatively rap- id settlement of “new” organisms adapting to oligoha- line waters. A high concentration of strontium is more likely to be explained by the increased portion of arago- nite which is linked to, and probably resulted from the dissolution of mollusc shells, rather than by the incre- ased salinity, as shown by KRANZ (1976) in Triassic carbonates. Fig. 2 The schematic representation of the Kostanjek-1 succession. 15Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... The cross layered gravel with sand lenses (C) com- prises three horizons approximately 2 m, 0.3 m and 8 m thick from the base to the top of the lithofacies. The lower boundary is distinctly erosional, while the upper boundary with lithofacies D is gradational. This gravel is polymict, clast-supported, trough cross-layered and normally graded. Grain-size is commonly around 3 cm, exceptionally up to 15 cm. Grains are semi-rounded and well sorted, and marly clasts of larger dimensions are frequent. The content of the light and heavy fractions shows great similarity with the sands of previous facies. Well-rounded fragments of mollusc shells (melanop- sids, congeria, cardids), occur together with algae and foraminifera that are reworked. On the basis of super- positional relationships and autochtonous molluscan community in underlying and overlying deposits of lithofacies D (Congeria banatica etc.) the sediment age is defined as Late Pannonian. The chaotic appearance of the sediment and fre- quent large marl clasts indicate on the effects of sedi- Table 3 Major element composition of the marl and sand (*) samples. Fig. 3 A diagram representation of salinity and species diversity (from HUDSON, 1990). 16 Geologia Croatica 52/1 ment slumping. The overlying mixed fossil community represents the allochthonous element in the given lacus- trine ambient (VRSALJKO et al., 1995). The lens- shaped gravel bodies, structure of trough cross-bedding and gradual upward decrease in grain-size indicates a probably fluvial sedimentary origin (?fan delta). Con- sidering the size and poor roundness and sorting of the clasts, the relative proximity of the source area (e.g. Medvednica Mt.) can be assumed. Considerable tecton- ic movements at the end of the Early Pannonian in the broad area of the Pannonian basin (©IKI∆ et al., 1979), were probably the trigger for the formation of these sediments, which resulted in the deepening of the lacus- trine palaeoecosystem. This also increased the fluvial input of terrigenous material into the area. Massive marls with clay layers ( D ) complete the succession continuously overlying the gravel of lithofa- cies C. This lithofacies is distinguished by the compact- ness of the marl layers which are more strongly biotur- bated and rarely contain cm-thick clay layers. The car- bonate content is constant ( 65%). There is a rich com- munity of deep-water lacustrine bivalves and numerous ostracod forms, which together show that the sediments belong to the Late Pannonian substage (Fig. 6). The marls and clay were deposited slowly from sus- pension in the deeper, more distal parts of the lake (Fig. 9). Primary sedimentary structures are poorly preserved due to the increased destructive activity of a benthic infauna. 3.2. BIOFACIES In view of other biotic and abiotic ecological factors which were prevalent during the life of the organisms and which were important parameters in environmental determination (DODD & STANTON, 1990), previous- ly defined sedimentary models (Figs. 7-9) were applied to the fossil community. Therefore, one basic biofacies unit was separated for sediments of the Sarmatian stage, and two biofacies units for the younger, Pannonian stage. Biofacies 1 is a fossil community of brackish lago - ons (Fig. 4). A sparse molluscs, ostracods and foramini- fera existed in the community in thin-laminated marls and clay of the Sarmatian age. The most common are molluscs Ervilia and Cardium, ostracods from the Auri - la and L o x o c o n c h a genera, and foraminifera from t h e M i l i o l i d a e and E l p h i d i u m groups. The remains of fish, macroflora and radiolarians are also common. Seasonal surface suspension flows stratified the water column, weak vertical circulation and thermal stratification being formed due to differences in water density, which influenced the organic production and distribution of the biomass (DODD & STANTON, 1990). A warmer surface layer was created, aerated and of decreased salinity with increased concentrations of zoo- and phytoplankton. The colder, deeper layer was of increased salinity supporting benthic organisms which have anaerobic respiratory characteristics (simi- lar to the modern environment in the Black Sea). The degree of fossilization of skeletal parts and frequent Table 4 Trace element composi- tion of the marl samples. 17Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... globules of authigenic pyrite, limited by the organic carbon concentration, dissolved phosphate and terrige- nous Fe-minerals, illustrate a more reduced aquatic environment (ALLISON, 1990). The sparsity of certain biogenic structures and preservation of primary lamina- tion (BOTTJER & SAVRDA, 1990), also indicate deposition in relatively deeper environment. Under the deep-water anoxic conditions in which clay and marl are layered, the calcitisation of aragonitic shells ceases due to the increased concentrations of organic matter, which increased the conservation of organism skeletons (BRETT & SPEYER, 1990). Biofacies 2 is composed of a littoral lacustrine c o m m u n i t y (Fig. 5). The marls and limestones of the Lower Pannonian contain a specific, endemic associa- tion of molluscs and ostracods. Endemism which devel - oped in certain groups of organisms occured due to the spatial isolation of the Pannonian basin (STEVANO- VI∆, 1985) from other parts of Paratethys during the Pannonian. Shallow carbonates of the Lower Pannonian supported an ostracod community which has numerous species, dominated by the Hungarocypris , Amplocypris, L o x o c o n c h a and C a n d o n a genera (Table 6). Within the mollusc community, the most numerous and most fre- quent are pulmonate gastropods of Radix and G y r a u l u s genera and in smaller proportions representatives of L y m n o c a r d i u m, M i c r o m e l a n i a , V a l v a t a and O r y g o c e - r a s (Table 5). Bivalves of the L y m n o c a r d i u m g e n u s here represent the derived forms from their older cardid ancestors (GORJANOVI∆-KRAMBERGER, 1890), that survived the salinity crisis at the end of the Sarmat- ian. Limonitised imprints of a continental flora, swamp grass and fish skeletons are also common, while gas- tropods and foraminifera rarely occur in sands. Aeration of the shallow water column is the cause of the increased pH (PIRSON, 1985) and greater con- centration of dissolved gasses which participate in the formation of carbonate mud. The rich community of swamp grass supported an epibenthos herbivorous gas- tropod and ostracod community. The use of dissolved aragonite for the skeletal formation of most molluscs was closely connected with its increased content in this shallow water area. A considerable presence of lacus- trine gastropods which breathe with their lungs presup- poses constant vertical (?daily) migration of these organisms. In some shells growths shaped like hollow needles have been noticed on their ribs, and were prob- ably used for temperature regulation. Formation of sec- ondary ribs in some shells (Lymnocardium plicataefor - mis and L. praeponticum) was connected with the extra strengthening of otherwise small and thin shells. Biofacies 3 represents a fossil community of a lacustrine basin (Fig. 6). Sediments of this biofacies are represented by marls of a comparatively deeper lake. On many levels within these sediments lensoid gravel-sand bodies of fluvial origin occur. Marls con- tain a rich autochthonous community of fossil molluscs, in which bivalves of the C o n g e r i a and L y m n o c a r d i u m Fig. 4 The brackish Sarmatian lagoon com- munity. Legend: a) Ervilia dissita ; b) Modiolus incrassatus ; c) Musculus sar - m a t i c u s; d) G i b b u l a sp.; e) H y d r o b i a sp.; f) Cardium vindobonense; g) M a c - tra vitaliana ; h) i c h n o f o s s i l s; i ) f i s h; j ) macrophyta; k) grasses; l) ostracoda; m) foraminifera; n) radiolaria. 18 Geologia Croatica 52/1 (sensu lato) genera dominate, and gastropods of the genera V a l e n c i e n n i u s, G y r a u l u s and R a d i x are present in smaller numbers (Table 5). An abundant ostracod population contains different genera, of which in the lower parts of the column the most frequent were C a n - d o n a, C y p r i a , H e m i c y t h e r i a and C y p r i d e i s, while close to the top of the column “new” representatives of the C a n d o n a subgenus were found (Table 6). The marls were almost completely reworked by extensive biotur- bation of various orientations, and often contain the Fig. 6 The lacustrine basin community of the Late Pannonian. Legend: a) C o n g e - ria banatica ; b) Congeria czjzeki; c) Va - l e n c i e n n i u s sp.; d) Limnocardium wink - l e r i ; e) Limnocardium gorjanovici; f) L i m n o c a r d i um c e k u s i; g) Paradacna syr - m i e n s e; h) Pisidium sp.; i) i c h n o f o s s i l s ; j ) watered grasses; k) fish; l) ostracoda; m) Melanopsidae; n) foraminifera. Fig. 5 The littoral lacustrine community of the Early Pannonian. Legend: a) R a d i x c r o a t i c a ; b) Gyraulus praeponticus ; c) Micromelania striata ; d) V a l v a t a sp.; e) Hydrobia sp.; f) Orygoceras laevis ; g) Limnocardium praeponticum; h) w a t e- red grasses; i)algae (?Chara ); j) fish; k) insecta; l) ostracoda; m) ichnofossils; n) continental macroflora. 19Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... imprints of fish scales, continental macroflora and limonitised fossil grass. In the gravel lenses there is a mixed type of alloch- thonous fossil community. The large, freshwater gas- tropods (BRUSINA, 1897; PAPP, 1956) of the Melano - p s i d a e are numerous (Table 5), and are dispersed as bioclasts in sand. Apart from gastropods there are also individual examples of bivalves with thick shell mem- branes (Congeria partschi , C. ornithopsis ), as well as E r v i l i a, M a c t r a and O s t r e a , which are reworked from earlier Sarmatian and Badenian layers. Algae (?L i t h o - t h a m n i u m) and foraminifera from older levels are also common in the sandy matrix. This resedimented fossil community does not have particular stratigraphic value, as in the Vienna basin (PAPP, 1953), but defines depo- sitional processes. The aforementioned process of the deepening of the depositional system at the end of the Early Pannonian is here represented by the changed style of sedimentation, as well as by evolutionary changes of the pulmonate gastropods (MOSS, 1944) and limnocardids (Fig. 10). The mollusc community (Table 5) and numerous ostra- cod species (Table 6) determine the high degree of adaptive radiation (adjustments and expansion) in new ecological environments. At the same time, the area of grass communities is decreased, and organisms adapt to a comparatively deeper, calcite-clay mud substrate. A highly oxygenated area is confirmed by the occurrence of imprints of water grasses, which need light for pho- tosynthesis. The water grass grew distintly high and also stabilized the bottom, and herbivorous organisms fed on them. Mollusc skeletons are mainly well pre- served, although they had a fragile structure as a result of their predominant calcitic composition and insignifi- cant postmortal erosion. Small pyrite granules frequntly occur in marls, which may indicate a more reducing environment (ALLISON, 1990). However, these condi- tions were most probably present only close to the bot- tom. Faunistic diversity with the dominant C o n g e r i a and L y m n o c a r d i u m genera in the upper parts of this facies might suggest slightly increased salinity to meso- haline (Fig. 10) by the end of the Pannonian, and this is supported by the occurrence of new bivalve genera (D i d a c n a , P a r a d a c n a , C a l a d a c n a ) and ostracod subge- nera (L i n e o c y p r i s, T y p h l o c y p r e l l a, S i n e g u b i e l l a). Con- gerian forms belong to the Modioliformes and Subglo- bosae groups, which live attached by a byssus to a soft substrate (ANDRUSOV, 1923) and are good indicators of calm and brackish water. 3.3. RECONSTRUCTION OF LAYERED MECHANISMS The Sarmatian clay and marls (Facies A) were deposited in comparatively deeper and more protected, semi-closed areas (lagoons, estuaries). The insufficien- cy of considerable fluvial flows and smaller amounts of planktonic foraminifera indicate the isolation of the depositional system. The depth of the depositional sys- tem is determined by the high content of reductive lay- ered components (pyrite, manganese, phosphate), low biogenic content and degree of skeletal fossilization and by the preservation of primary mm-lamination and the low granulometric composition (DODD & STANTON, 1990). Facies A sediments (“varvite”) were deposited from surface suspension flows and with frequent sea- sonal climate changes (Fig. 7) by changing the thermal gradient (thermocline) of a stratified water column. Light laminae were formed during periods of lower atmospheric temperatures, when the inflow of terrige- nous material was decreased, while dark laminae were deposited during the increased inflow of siliciclastic and organic terrigenous material. A similar example was described by BOTTJER & SAVRDA (1990). Con- stant turbidity of the surface level and bottom currents, together with the probable vertical stratification of water salinity, had a selective influence on organic pro- duction (similar to the modern situation in Black Sea). Characteristics of Sarmatian depositional system continued to the Early Pannonian as indicated by con- tinuous sedimentation. This is expressed by deposition of the “transitional layers” of facies AB, characterized by structural-petrographic properties of the older, un- derlying deposits. The fossil association of small, degenerated cardids and pulmonate gastropods indicate partial “life discontinuity” towards the older deposits, as the consequence of shallowing, restriction and desalinization of the marine environment (VRSALJKO, 1997). Limestone and marls of facies B were deposited in a shallow, “lake-pond” palaeoenvironment (Fig. 8), with- out considerable influence of a land area. Limestone beds were layered in the shallow littoral zone, and marls deposited from suspension were layered in slight- ly deeper lake areas (sublittoral), by combined physico- chemical and biogenic processes. The basic model for the interpretation of the formation of these layers is a study by ALLEN & COLLINSON (1986). Periodic and comparatively poor inflow of terrigenous material is indicated by cm-thick interlayers of fine-grained sand, which have the form of bands or lenses, with planar cross-lamination (?ripple marks). The discovery of nu- merous “Seegrasswissenfauna” (pulmonate gastropods, small limnocardids and ostracods), which live on water grasses (“fossil reed” - KRANJEC et al., 1973) as epi- bionts, determine the high degree of aeration and desa- linization of the lacustrine area. Frequent limonite gran- ules indicate the oxidizing conditions of carbonate lay- ering (ALLISON, 1990). The gravels (C) and marls (D) were sedimented in a comparatively deeper palaeolacustrine environment (Fig. 9). Tectonic activity at the end of the Early Pan- nonian has been determined by boundary faults with considerable vertical movements in two directions (©IKI∆ et al., 1979). Coarse clastic sediments were transported from higher land areas to the depositional system by rivers and torrents, most probably forming a fan delta. In the upper half of the Kostanjek-1 column, 20 Geologia Croatica 52/1 where the marl layers are dominant, three levels with gravel and sand were separated, so the instability, i.e. the occasional occurrence of significant rivers flows can be postulated. The discovery of a new limnocardid community and ostracods in the youngest part of the layers indicate the possible reestablishment of connec- tions between these areas and the Paratethys area, as is proved by STEVANOVI∆ (1985). 3.4. EVOLUTIONARY SERIES OF THE CARDIIDAE FAMILY Within the vertical sediment succession, lithological changes as well as faunistic changes have been detect- ed, from the Sarmatian up to the Late Pannonian. Com- bined, sedimentological and palaeontological analysis allowed the definition of the formation, trends and char- acteristics of the layers. During the evolution of the depositional system (Figs. 7-9) the permanent desalin- ization of the water became evident, particularly as shown by the Cardiidae group of molluscs. At the end of Badenian only some groups of organ- isms (SENE© & PAPP, 1974) survived the salinity cri- sis, while certain cardid species “continued” into the Sarmatian with considerable evolutionary changes. The change from mesohaline to polihaline conditions result- ed in the cardid bivalves developing smaller and thinner shells with the reduction of teeth-hook apparatus. In the newly formed brackish Sarmatian environment, a car- did form can be found, which has been defined by some authors as a separate C e r a s t o d e r m a subgenus (KOJU- MDGIEVA, 1969), and by others as a C a r d i u m g e n u s (GORJANOVI∆-KRAMBERGER, 1890). Here, the results from the later, more current study have been adapted. The continuous salinity drop, which overlaps in the western and central Paratethys areas with the period of the formation of the Pannonian basin (lower part of the Middle Sarmatian), and its isolation from the eastern parts (STEVANOVI∆, 1985), resulted in an evolution- ary surge in the cardid group. For the majority of spe- Fig. 8 Idealized deposi- tional model for sedi- mentation of the Low- er Pannonian carbo- nates. Fig. 9 Idealized deposi- tional scenario allow- ing simultaneous dep- osition of coarse fluvi- al clastics and deep- water Upper Pannon- ian marls. Fig. 7 Idealized deposi- tional model for sedi- mentation of the Sar- matian clays. 21Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... cies of Sarmatian cardids the salinity drop has a disas- trous influence. Only a few species evolved and ada- pted to the new conditions. Evolutionary changes are expressed by their smaller dimensions, longer and thin- ner shells, the increased number and occurrence of sec- ondary ribs, almost entire reduction of cardinal teeth hooks, and probably altered skeleton mineralization. Recently most authors separate and determine these Pannonian forms as a separate L y m n o c a r d i u m g e n u s (STEVANOVI∆, 1957), which is also accepted in this paper. Spatial isolation of the Pannonian basin was the cause of the occurrence of the variability and endemism in many species. The multiple mutations provide evolu- tionary material for the occurrence of new limnocardid species in a comparatively short period of time. The formation of new species of the L y m n o c a r d i i n a e s u b- family at the end of Pannonian (P a r a d a c n a , D i d a c n a , C a l a d a c n a ) marks the evolutionary maximum of this group. This maximum may have two interpretations: 1) the settlement (expansion) of “finished species” from the eastern parts (Dacian and Euxinian basin), due to a reestablished connection with the unique Paratethys area (STEVANOVI∆, 1985), and/or 2) a mixture of newly settled “immature eastern species” with domicili- ary forms, and comparatively accelerated evolutionary change up to the level of creation of new genera, which is more probable. Starting from the fact that all Pannonian limnocar- dids (sensu lato ) are evolutionary derived from the Sar- matian cardids (sensu lato), using morphological-func- tional scale analysis, and following the constructive morphological diagnostic characteristics (BASCH, 1990), their phylogenetic series were defined (Fig. 10). Phylogenetic relationships were produced according to the models of KOLESNIKOV (1948) and KOJUM- DGIEVA (1969), who divided the cardid group into four basic groups: Obsoletiformes, Inaequicostates, Protractiformes and Plicataeformes. The Plicataeformes group is the most poorly repre- sented in the Pannonian strata of the Kostanjek-1 col- umn. Not until the Lower Pannonian sediments is the Lymnocardium plicataeformis species found, which is probabaly an evolutionary descendant of the Sarmatian Cardium (C e r a s t o d e r m a ) l a t i s u l c u m form. The new species is quite variable as indicated by the changeable number of ribs (13-15), that are sometimes decorated with pierce marks, and by the occurrence of weaker secondary ribs (3-4) in some samples. The Protractiformes group has two representatives in the Pannonian layers: Lymnocardium spinosum which can be most frequently found in the zone of tran- Fig. 10 The phylogeny of the Cardiidae family (according to basal diagnostic elements: number and type of ribs), and span of species occur- rences in the sedimentary succession of the Sarmatian and Pannonian. 2 2 G eo lo g ia C ro at ic a 5 2 /1 I 23Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... sitional layers (Lower - Upper Pannonian) and L y m n o - cardium gorjanovici which has been found in the upper part of the Upper Pannonian marls. The former is an indirect descendant (between the original form and L . s p i n o s u m a transitional form should be defined) from the Sarmatian Cardium (C e r . ) l i t h o p o d o l i c u m s p e c i e s , and differs from it by the considerably increased num- ber of ribs, and significantly smaller shell size and finally by strengthening of the back hook edge with small pierce marks. The latter L. g o r j a n o v i c i form is once again larger and distinguished by the occurrence of various rib types, from pointed to rounded. In the Inaequicostates group, the Early Pannonian Lymnocardium praeponticum developed from the origi- nal Sarmatian Cardium (C e r . ) g l e i c h e n b e r g e n s e f o r m , keeping the basic shell characteristics. Later forms: Caladacna ornata and Paradacna syrmiense occured in the Late Pannonian along with significant changes in the number and type of ribs, and greater elongation. Lymnocardium robici with apparent variability (chan- gable relations between rib width and interribs parts) might be the transitional form among the majority of Pannonian limnocardids (sensu lato). The most represented group is the Obsoletiformes, in which the evolutionary changes from the original Sarmatian cardids to the Pannonian limnocardids, can be clearly followed. Earlier Pannonian forms (L y m n o - cardium obsoletum protractum , L. fatioi and L. promul - t i s t r i a t u m ) originated directly from older brackish forms (GORJANOVI∆-KRAMBERGER, 1890), with insignificant morphometric differences. It is possible that L. cekusi, which generally appears in the middle of the sedimentary column, is the transitional form to the Late Pannonian Didacna deserta and L. winkleri forms. GORJANOVI∆-KRAMBERGER (1890) was the first to define the L. c e k u s i species in the lowest parts of Pannonian marls of VrapËe. However the author was not aware of the biostratigraphic condensation phenom- enon, which necessitates revision of the stratigraphic position of this species (VRSALJKO, 1997). The evaluation of the comparative significance of every limnocardid species throughout geological histo- ry cannot be completely understood without study of the adaptive (natural selection) and morphogenetic (growth processes) factors, which is not complete in this case. However, on the basis of the established development series, and some specific mollusc index fosssils, it is possible to suggest biostratigraphic zoning in the sediments of the Pannonian basin, which should be completed and tested by future research. 3.5. BIOZONES Accepting earlier research, especially PAPP (1951, 1953, 1956) and STEVANOVI∆ (1951, 1953, 1957, 1985), on the stratigraphy of Pannonian basin, new solutions are proposed here (Fig. 2, Tables 2 and 5). In the Kostanjek-1 geological column (Fig. 2), rare samples of Ervilia dissita and Cardium (Cerastoderma ) v i n d o b o n e n s e with a rare accessory foraminiferal com- munity of Miliolidae and Elphidium group occur within the laminites (facies A), which collectively indicates zone “d” (SENE© & PAPP, 1974), i.e. N15 zone, which is of the Late Sarmatian age (sensu stricto). Lower Pannonian marls and clays of facies AB con- tain ostracod samples, which represent an overture for the later explosion and divergence of species (HAJEK- TADESSE, pers. comm.). In this lowest part of the Pan- nonian there are also examples of small limnocardids. Previous analysis of individual, characteristic mol- lusc species, resulted in the Pannonian layers of broader areas (KRANJEC et al., 1973; ©IKI∆ et al., 1978, 1979) being divided into two acrozones (lower R a d i x c r o a t i c a and the upper Congeria banatica ), which are inadequate. Treating the entire fossil mollusc communi- ty by the method of characteristic associations (unique- ness of identical community) produced more detailed results. Therefore, in the entire Pannonian succession of the Kostanjek-1 column three zones and two subzones can be separated (Table 2, Fig. 2): Subzone I (0-3 m thick): “poor zone of transitional layers” - Lymnocardium praeponticum acrozone. Fine- laminated clay and marl with rare samples of L. prae - p o n t i c u m and small gastropods of H y d r o b i a and the V a l v a t a group. The lowest part of the Early Pannonian substage. Zone II (3-27 m thick): Cenozone Radix croatica - Lymnocardium plicataeformis - Gyraulus praeponticus . Layered limestone and marl with frequent and numer- ous gastropods. Examples of Radix croatica , R. exten - s a, Gyraulus praeponticus , G. dubius and others, and bivalves of Lymnocardium plicataeformis, L. c f . p r o - multistriatum, L. praeponticum , L. obsoletum, Congeria sp. ?nov. and other accessory forms, which entirely rep- resent the Early Pannonian. Subzone III (27-35 m thick): “transitional layers” - Neodelminiella venusta - Lymnocardium cekusi C e n o- zone. Silty marl with rare gastropod community includ- ing Neodelminiella venusta, Radix kobelti, G y r a u l u s d u b i u s, Undulotheca halavatsi and others. Also bival- ves of Lymnocardium cekusi, L. spinosum, L. cf. robici, ?Cerastoderma protracta , and other transitional spe- cies, determined (conditionally) as the Middle Pannon- ian. Zone IV (35-65 m thick): Congeria banatica - Lym - nocardium gorjanovici - Gyraulus tenuistriatus C e n o- zone. Massive marl with abundant bivalve community: Congeria banatica , C. m a r t o n f i i, C. z a h a l k a i, L y m n o - Table 5 List of molluscs from the Kostanjek-1 column. 24 Geologia Croatica 52/1 Table 6 List of ostracods from the Kostanjek-1 column. cardium gorjanovici , L. cekusi, L. spinosum, Caladacna o r n a t a and others. Gastropods Gyraulus tenuistriatus , Orygoceras laevis , Micromelania striata and other less important fossils also occur. Lower and central part of the Late Pannonian substage. • 70 ... , ' 25Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... Zone V (65-83 m thick): Congeria czjzeki - Lymno - cardium winkleri - Gyraulus tenuistriatus C e n o z o n e . Massive marl and clay with evolved bivalve community including Congeria czjzeki, C. banatica , Lymnocardium w i n k l e r i, L. cf. r o b i c i , Paradacna syrmiense , D i d a c n a d e s e r t a , P i s i d i u m sp. Also contains gastropods O r y g o - ceras c f . b r u s i n a i , Velutinopsis c f . p a n c i c i , G y r a u l u s t e n u i s t r i a t u s and others. Uppermost part of the Late Pannonian substage. Due to the specific development and comparatively narrow regional spreading of “so-called Croatica lay- ers” (JENKO, 1944), this locality in Podsused, among other possibilities, should serve as the stratotype for correlation in the western and central parts of the Pan- nonian basin (HOLLAND, 1990). 4. CONCLUSIONS 1) In the study area the formation of the Pannonian basin as a separate palaeogeographic province, whi- ch partly overlaps with the isolation of the western and central Paratethys from the eastern parts during the Middle Sarmatian (sensu lato), is expressed in the layering of fluvial-lacustrine Pannonian sedi- ments with a unique endemic mollusc and ostracod fauna which have oligohaline characteristics. 2) The end of the Sarmatian (sensu stricto) sedimenta- tion cycle in the study area is manifested as a conti- nuity of sedimentation into the Pannonian, due to the significant desalinization of the water. 3) The salinity drop at the Sarmatian-Pannonian boun- dary is manifested by the disappearance of most Sarmatian organisms (especially gastropods and foraminifera), and the occurrence of new Pannonian mollusc and ostracod forms. It can be best followed through the evolutionary changes of the C a r d i i d a e family. 4) Altered water chemistry in the Pannonian is reflect- ed by changes in the style of sedimentation, and can be followed through geochemical parameters such as carbonate content and content of trace elements (especially strontium and manganese). 5) The great variability and weak diversity of taxo- nomic structures of organisms in the Early Pannon- ian substage is the consequence of basin isolation, and is manifested by the endemism of most fossil groups. 6) Gravel lenses of fluvial origin (fan delta system), situated in the Upper Pannonian deep-water marls, are the result of synsedimentary tectonics, which reflected regional tectonic movements. 7) Taxonomic diversity of the fossil community of the Late Pannonian is the consequence of optimum env- ironmental conditions, and relates to the evolution- ary maximum of most lacustrine organisms, and was probably the consequence of the introduction of new species from the Back-Carpathian area. 8) Layering of the Sarmatian laminites in reduced con- ditions with high contents of manganese and pyrite (comparable with the recent situation in the Black Sea), together with high periodic organic produc- tion, could indicate their potential as source rocks. 9) Phylogenetic analysis of the C a r d i i d a e family sho- uld be complememented with the analysis of adap- tive and morphogenetic factors, to improve the qua- litative estimation of their evolutionary and strati- graphic significance. Acknowledgements This study resulted from a project “Facies and phys- ical characters of Neogene carbonate sediments”, which was conducted under the supervision of Mato PIKIJA to whom I am sincerely thankful for his valuable instru- ction and professional advice. I thank my colleagues for numerous analytical data, especialy specialists from the Institute of Geology: Valentina HAJEK-TADESSE for the definition of numerous ostracod forms, Slobodan MIKO for trace elements analyses, Vlasta JURI©I∆- MITROVI∆ for major elements analyses, and Æeljka GLOVACKI-JERNEJ for petrographic analyses. I wish to thank Miroslav KLADNI»KI who prepared figures and tables. 5. REFERENCES ALLEN, P.A. & COLLINSON, J.D. (1986): Lakes.- In: READING, H.G. (ed.): Sedimentary Environments and Facies. 2nd ed., Blackwell Sci. Publ., 69-73, Oxford. ALLISON, P.A. (1990): Nodules and platenkalks.- In: BRIGGS, D.E.G. & CROWTHER, P.R. (eds.): Pal- aeobiology. Blackwell Sci. Publ., 250-253, Oxford. ANDRUSOV, N. (1917): PontiËeskij jarus.- Geol. Ros- sii, 42/2, 1-41, Petrograd. ANDRUSOV, N. (1923): Apseronskij jarus.- Mem. Col. Geol., 110, 1-206, St. Petersburg. BASCH, O. (1990): Cardiidae (Mollusca, Lamellibran- chiata) pontskog kata u Hrvatskoj.- Paleont. Jugosl., 39, 1-158, Zagreb. BOTTJER, D.J. & SAVRDA, C.E. (1990): Oxygen lev- els from biofacies and trace fossils.- In: BRIGGS, D.E.G. & CROWTHER, P.R. (eds.): Palaeobiology. Blackwell Sci. Publ., 408-410, Oxford. BRETT, C.E. & SPEYER, S.E. (1990): Taphofacies.- In: BRIGGS, D.E.G. & CROWTHER, P.R. (eds.): Palaeobiology. Blackwell Sci. Publ., 258-263, Ox- ford. 26 Geologia Croatica 52/1 BRUSINA, S. (1897): Gragja za neogensku malakolo- πku faunu Dalmacije, Hrvatske i Slavonije uz neke vrste iz Bosne i Hercegovine i Srbije.- Rad Jugosl. akad. znan. i umjet., 18, 1-43, Zagreb. DODD, J.R. & STANTON, R.J. (1990): Palaeoecology, concepts and aplications.- A Wiley-Intersc. Publ., New York, 502 p. GORJANOVI∆-KRAMBERGER, D. (1890): Die Prä- pontischen bildungen des Agramer gebirges.- Glas- nik Hrv. narav. druπtva, 5, 151-164, Zagreb. HOLLAND, C.H. (1990): Biostratigraphic units and the stratotype - golden spike concept.- In: BRIGGS, D.E.G. & CROETHER, P.R. (eds.): Palaeobiology. Blackwell Sci. Publ., 461-465, Oxford. HUDSON, J.D. (1990): Salinity from faunal analysis and geochemistry.- In: BRIGGS, D.E.G. & CROW- THER, P.R. (eds.): Palaeobiology. Blackwell Sci. Publ., 406-408, Oxford. JENKO, K. (1944): Stratigrafski i tektonski snoπaj Plio- cena juænog poboËja Poæeπke gore i Kasonja brda.- Vjestnik Hrv. dræav. geol. zavoda i Hrv. dræav. geol. muzeja, 2/3, 89-159, Zagreb. KOJUMDGIEVA, E. (1969): Fossilite na Blgaria - Sar- mat.- Blg. Akad. Nauk., 8, 1-133, Sofia. KOLESNIKOV, W.P. (1948): Die sarmatische Stufe.- Die Strat. der SSSR, 12, 1-242, Moskva. KRANJEC, V., HERNITZ, Z. & PRELOGOVI∆, E. (1973): Prilog poznavanju mlaih tercijarnih nasla- ga Medvednice (SZ Hrvatska).- Geol. vjesnik, 25, 65-99. KRANZ, J.R. (1976): Strontium - ein Fazies-Diage- nese-Indikator im Oberen Wettersteinkalk (Mittel- Trias) der Ostalpen.- Geol. Rdsch., 65, 593-615, Stuttgart. MOOS, A. (1944): Neue Funde von Limnaeiden, ins- besondere von Valenciennesiden in Pannon Kroat- iens.- Vjestnik Hrv. dræav. geol. zavoda i Hrv. dræ- av. geol. muzeja, 2/3, 341-391, Zagreb. NAGYMAROSY, A. & MÜLLER, P. (1988): Some aspects of Neogene biostratigraphy in the Pannonian basin.- In: ROYDEN, L.H. & HORVATH, F. (eds.): The Pannonian Basin, a Study in Basin Evolution. Amer. Assoc. Petr. Geol., Mem. Spec., 45, 69-77, Budapest and Tulsa. OÆEGOVI∆, F. (1944): Prilog geologiji mlaeg terci- jara na temelju podataka iz novijih buπotina u Hrvatskoj.- Vjestnik Hrv. dræav. geol. zavoda i Hrv. dræav. geol. muzeja, 2/3, 391-473, Zagreb. PAPP, A. (1951): Das Pannonian des Wiener Beckens.- Mitt. Geol. Ges., 39-41, 99-193, Wien. PAPP, A. (1953): Die Molluskenfauna des Pannon im Wiener Becken.- Mitt. Geol. Ges., 44, 85-222, Wien. PAPP, A. (1956): Paläontologische beobachtungen im Pannon von Podsused bei Zagreb (Kroatien).- Geol. vjesnik, 8-9, 67-81. PIRSON, J.S. (1985): Geologic well-log analysis.- Gulf Publ. Comp., Houston, 71 p. POKORNY, V. (1946): Microstratigraphie pannonu mezi Hodonienem a Mikulcicemi.- Razpravi ceske akad. ved., 54, 23-41, Praha. SENE©, J. & PAPP, A. (1974): Grundzuge der Entwic- klung der Fauna und die Biozonen im Sarmatien s. str. der Zentralen Paratethys.- In: BRESTENSKA, E. (ed.): Chronostratigraphie und Neostratotypen - Sarmatien. Verlag Slowak. Akad. Wiss, 4, 41-44, Bratislava. SOKA», A. (1972): Panonska i pontska fauna ostrako- da ZagrebaËke gore.- Paleont. jugosl., 11, 1-140, Zagreb. SOKA», A. (1985): Das Pannonien in Kroatien.- In: PAPP, A., JAMBOR, A. & STEININGER, F.F. (eds.): Chronostratigraphie und Neostratotypen - Pannonien. Ung. Geol. Anst., 89-95, Budapest. STEININGER, F.F., RABEDER, G. & ROEGL, F. (1985): Land mammal distribution in the Mediter- ranean Neogene: A consequence of geokinematic and climatic events.- In: STANLEY & WEZEL (eds.): Geological Evolution of the Mediterranean Basin. Springer-Verlag, 559-571, New York. STEVANOVI∆, P. (1951): Donji pliocen Srbije i suse- dnih oblasti.- Srb. akad. nauka i umet., 187, 1-286, Beograd. STEVANOVI∆, P. (1953): Nomenklatura tercijarnih slojeva, u prvom redu domaÊih neogenih terena.- I. savjet. geol. FNRJ u Zagrebu, Hrv. geol. druπtvo, 121-143, Zagreb. STEVANOVI∆, P. (1957): Pannon und Pont im nord- lichen Bosnien - bedeutung ihrer studien für die lös- ung der faziesprobleme und horizontierung der Con- gerienschichten im Pannonischen becken.- II. kon- gres geol. Jugosl., 155-176, Sarajevo. STEVANOVI∆, P. (1985): Diskussion der unterstufen Slavonien und Serbien.- In: PAPP, A., JAMBOR, A. & STEININGER, F.F. (eds.): Chronostratigra- phie und Neostratotypen - Pannonien. Ung. Geol. Anst., 82-85, Budapest. ©IKI∆, K., BASCH, O. & ©IMUNI∆, A. (1978): Osno- vna geoloπka karta SFRJ 1:100000. List Zagreb L33-80.- Geol. zavod Zagreb (1972), Savez. geol. zavod Beograd. ©IKI∆, K., BASCH, O. & ©IMUNI∆, A. (1979): Osno- vna geoloπka karta SFRJ 1:100000. TumaË za list Zagreb L33-80 (Geology of Zagreb sheet).- Geol. zavod Zagreb (1972), Savez. geol. zavod Beograd, 81 p. 27Vrsaljko: The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek... VRSALJKO, D., PIKIJA, M., ©IKI∆, K. & GLOVAC- KI-JERNEJ, Æ. (1995): Sarmatske i panonske nasla- ge u tupinolomu Kostanjek.- In: ©IKI∆, K. (ed.): Geoloπki vodiË Medvednice, 56-60, Zagreb. VRSALJKO, D. (1997): Stratigrafija naslaga panona jugozapadnog dijela Medvednice.- Unpublished M.Sc. Thesis, University of Zagreb, 80 p. Manuscript received December 4, 1998. Revised manuscript accepted May 28, 1999. 28 Geologia Croatica 52/1