The Pannonian Palaeoecology and Biostratigraphy of Molluscs from Kostanjek - Medvednica Mt., Croatia

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 ostracods (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 association of Pannonian molluscs five biozones were separated: I) Lymnocardium praeponticum acrozone, II) Radix croatica - Lymnocardium 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 value of molluscs and support zonality of Pannonian layers

New Congerian Species and Their Similarity with Congeria banatica from the Pannonian Sediments in Northern Croatia

Congeria baschi n.sp. and Congeria susedana n.sp. are two new species from the Pannonian sediments of the Medvednica Mts. (NW Croatia). C. baschi n.sp. was found in the Lower Pannonian limestones, and C. susedana n.sp. was collected from the Upper Pannonian marls. Relationships with the affiliated taxa enable reconstruction of a phyletic lineage beginning with Congeria soceni JEKELIUS, through C. baschi n.sp. to Congeria banatica HÖRNES. C. banatica is the ancestor of two branches, leading to C. susedana n.sp. and C. vugroveci SREMAC, respectively. Dreissenomya digitifera (ANDRUSOV) is the probable descendant of C. vugroveci. The accompanying assemblages of fossil molluscs and ostracods from the same horizons facilitate the precise stratigraphic and palaeoenvironmental positioning of the new taxa

Stratigraphy and Palaeogeography of Miocene Deposits from the Marginal Area of Zumberak Mt. and the Samoborsko Gorje Mts. (Northwestern Croatia)

Miocene sediments rimming the Palaeozoic–Mesozoic–Palaeogene rocks, form Zumberak Mt. and the Samoborsko Gorje Mts. Spatial analysis of the setting and development of the surface Miocene stratigraphy, at the marginal areas of the Zumberak and Samoborsko Gorje Mts., allows four palaeogeographic areas to be distinguished: Zumberak, Plesivica–Sveta Jana, Samobor–Sveta Nedelja and Grdanjci. In the Miocene deposits (totaling 350 m), within the area of Zumberak, coarse-grained clastics from deltaic deposits of Pannonian age prevail. Here only, 50 m of sediments of Pliocene–Pleistocene age overlie the Miocene deposits whereas Mesozoic carbonates represent the basement. The Plesivica–Sveta Jana area is characterized by a 600 m sequence of Miocene deposits, mainly overlying Triassic dolomites, where finely-grained layers of marls and silts prevail. In this area, Miocene successions from the Badenian to the Pontian are characterized by a continuity of sedimentation with an inherited depositional environment. In the area of Samobor–Sveta Nedelja, the basement is diverse: Triassic dolomites, volcanogenic–sedimentary complex of Cretaceous age and a clastic–carbonate complex of Palaeogene age. The Miocene succession shows a regressive trend from the Badenian to the Pontian and the total thickness is estimated at 400 m. The area of Grdanjci differs considerably from the other Miocene palaeorelief. An approximately 50 m-thick series of coarse-grained clastics with coal is distinguished, of unclear stratigraphic age (Ottnangian?). Miocene sediments of the Grdanjci area are represented by both a transgressive type of conglomerates and shallow water limestones of Badenian age, with a total thickness of about 100 m. The development of the Miocene stratigraphy of the Zumberak and Samoborsko Gorje Mts. is generally correlative with that in the other parts of the Pannonian area, though it does exhibit local variations. Comparison of the Miocene palaeorelief of Zumberak Mt. with the Samoborsko Gorje Mts., together with neighbouring areas, enabled wider correlation with other parts of northern Croatia, and the more distant Western and Central Paratethys