Tectonic and climatic control on the evolution of the southern Pannonian Basin System during the Badenian (Middle Miocene)
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Due to a complex interplay of tectonics and climate the Paratethys Sea became separated from the former Tethys Ocean during the Oligocene. Its stepwise isolation resulted in the development of endemic faunal assemblages that are difficult to correlate to the standard global time scale. Therefore regional Paratethys time scales were constructed. The Badenian stage (early Middle Miocene) marks a widespread marine transgression during the opening of the Pannonian back-arc basin. Recent structural, sedimentological and chronostratigraphic studies in the Carpathian Foredeep and southern Pannonian Basin System (PBS) have improved understanding of the geodynamic and climatic evolution of the basin. Nevertheless, more age constraints are needed to better understand the processes that contro¬l events like the Early Badenian transgression, the mid-Badenian salinity crisis and the paleoenvironmental changes at the Badenian/Sarmatian (B/S) boundary. In this report I present magnetostratigraphic results of the continuous Badenian succession of Ugljevik (NE Bosnia and Herzegovina) located at the southernmost edge of the PBS. I conclude that the marine flooding invaded the marginal Ugljevik Basin around 14.2 Ma (base of chron C5ACr). This occurred later than in PBS sub-basins to the north confirming that the Early Badenian marine flooding is controlled by tectonic subsidence with a north-south younging trend. A rapid decrease in depositional depth in Ugljevik is coeval with the Mi3b global cooling event at ~13.9 Ma. The event is not associated with evaporite deposits such as in the Carpathian Foredeep. The middle and upper Badenian deposits in Ugljevik form one transgressive/regressive cycle up to the B/S boundary, which is characterized by weak erosion. Overall, strong erosion has been reported in the central and northwestern part of the PBS in this period. The paleomagnetic directions throughout the Ugljevik section are very similar. This suggests that the tectonic activity at least from ~14.2 Ma onwards did not involve rotations, but only vertical motions. The observation also supports the hypothesis that the southern PBS and Dinarides were already decoupled from the Adria and Tisza-Dacia Units during the Miocene.