Integrated bio-magnetostratigraphy of the Badenian reference section Ugljevik in southern Pannonian Basin - implications for the Paratethys history (middle Miocene, Central Europe)

Abstract

The Central Paratethys was a large-scale Oligo-Miocene epicontinental sea located in Central and Eastern Europe. It was separated from the Mediterranean by the Alpine orogenic belt. The Paratethys progressively flooded the Pannonian back-arc basin that formed during the early to middle Miocene. Along the southern margin of the basin, the maximum extension of the Paratethys onto the flanks of the Dinarides Mountains occurred during the middle Miocene (Badenian). We have studied the most complete middle Miocene (Badenian-Sarmatian) Paratethys section located at this southern margin. It comprises a >1.5 Myr long, continuous marine depositional sequence, which is highly relevant for our understanding of the interplay between global climatic and regional geodynamic perturbations in this semi-isolated epicontinental basin. The investigated record is particularly important to assess the impact of the Middle Miocene Climate Transition, the Langhian-Serravallian glacial Mi-3b event, the syn-rift climax of the Pannonian Basin and the Badenian Salinity Crisis. Moreover, we present the first high resolution age model for the regional Badenian stage based on integrated biomagnetostratigraphy. According to our age model, the marine flooding reached the area at ~14.15 Ma, during the regional Badenian stage. Open marine conditions persisted until ~12.6 Ma when the extinction of the fully marine fauna marks the beginning of the regional Sarmatian stage. Sea-level fluctuations are reflected in the section by four transgressive regressive cycles coinciding roughly with 400-kyr-eccentricity periods. The largest sea-level fall occurred after the first cycle and corresponds to the end of the Middle Miocene Climate Transition marked by glacial event Mi-3b. Elsewhere in the Pannonian Basin, this marked drop in base-level triggered deposition of evaporites during the Badenian Salinity Crisis. At Ugljevik however, there are no evaporites and the short-term Mi-3b regression was followed by a transgression and re-establishment of deeper marine conditions at 13.76 Ma, i.e. during the earliest Serravallian. Diversified planktonic and benthic assemblages suggest fully marine conditions with a persistent connection to the Mediterranean at this time. Such conditions prevailed until the mid Serravallian (latest Badenian) when sediment input increased and coastal environments prograded seawards. The Badenian/Sarmatian boundary roughly coincided with a 400-kyr-eccentricity as well as with a 1.2-Myr obliquity minimum.