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Karpatian and Badenian transgression in Croatian part of the pannonian Basin System (biostratigraphy and palaeoenvironments)

The opening of the Pannonian Basin System during the early Miocene is a result of the intense extensional tectonics between the Alps, Carpathians and Dinarides. Miocene sediments in Northern and Central Croatia were deposited in several basins in the southwest part of the Central Paratethys. The detailed biostratigraphic, petrographic and well logs analyses were conducted on rock material from exploration wells in the Sava Depression in order to define five marine transgressions from the late Karpatian to Sarmatian and compared with global 3rd order sequences after Haq et al., 1988. The oldest Miocene sediments (Ottnangian to lower Karpatian) discontinuously overlie Palaeozoic and Mesozoic basement rocks and consist of conglomerates, sandstones and marls which were deposited in fluvial to lacustrine environments. First marine transgression (corresponds to the TB 2.2, 3rd order sequence) is recorded in wells situated in the central parts along the Sava Depression. Sediments consist of dark silty marls with planktonic foraminifera which indicate late Karpatian – Globigerinoides bisphaericus Zone. Lowest occurrence (LO) of the Praeorbulina sicana marks Karpatian/Badenian boundary. Lower Badenian (TB 2.3, 3rd order sequence) mainly presented by fossiliferous marls, contains highly diverse planktonic foraminiferal assemblages which indicate open sea environment, warm to subtropical climate, well stratified water column and excellent connection with Mediterranean bioprovinces. LO of Orbulina suturalis indicates early/middle Badenian boundary (approximately the beginning of TB 2.4, 3rd order sequence). Planktonic foraminiferal assemblages of the middle Badenian are dominated by Praeorbulina and Orbulina species. The beginning of the late Badenian was characterized by significant decrease of the sea level when the most deep water marine niche were replaced by reef and perireef environments with corallinacean-bryozoans associations. However, during late Badenian smaller scale transgressive cycle was recorded (TB 2.5, 3rd order sequence) when in deeper parts of the basin planktonic association dominated by Orbulina and Globigerina, with rare occurrence of Velapertina indigena, existed. The Badenian/Sarmatian boundary (BSEE) is characterized by the extinction of almost all planktonic species and marine reef organisms due to closing of the marine gateway towards Mediterranean bioprovinces and imply major paleoenvironmental changes. In Sarmatian sediments (TB 2.6, 3rd order sequence) benthic foraminiferal assemblages with Elphidium, Ammonia and Anomalinoides dominated.

planktonic foraminifera, karpatian, Badenian, transgression, Pannonian Basin

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