Timing and mode of initial marine flooding in the southern Pannonian Basin: new U-Pb age constraints from the Prnjavor and Tuzla basin

The Pannonian Basin in Central and Southeastern Europe is a huge landlocked basin delineated by Alpine-Carpathian-Dinarides chain. This extensional backarc basin originating by tectonic rifting in the Early Miocene, was successively flooded by the Central Paratethys Sea. Slovenian Corridor along the Alpine-Dinarides junction enabled its communication with the Mediterranean Sea.  Marine flooding of the southern part of the Pannonian Basin - between the Styrian Basin in Austria and Velika Morava Basin in Serbia - is still poorly understood. While the conflicting biostratigraphic interpretations contribute to ongoing discussion on timing and mode of this major environmental turnover, independent radiometric data are still rare.  The present study contributes three new U-Pb zircon ages which are the very first such data on the Miocene marine transgression in northern Bosnia and Herzegovina. Dating from autochthonous tephra airfalls prove uniformly the middle Badenian age for marine transgression, with a 0.5 Ma eastwards-younging trend of its onset. This trend stays in line with the literature data suggesting a steady eastwards propagation of extension along the Pannonian Basin southern margin. Towards a better understanding of interplay between tectonic and glacioeustatic forcing of the regional marine progression, a review of published stratigraphic data has been conducted, depicted correspondingly in four paleogeographic maps of one-million-year resolution. Building on these data, we bracket the initial gradual flooding interval to the late Burdigalian–early Serravallian time interval, respectively, attaining up to 3.5 Myr overall duration in a step-wise manner.  Although the tectonic phases were main drivers in the creation of accommodation space, along the NE Dinarides, glacioeustasy driven by the global climate suspended landward propagation of the coastline during sea-level low-stands at long obliquity nodes. This result enables a more precise reconstruction of the interplay between landward sea ingression, regional climate change and effects to endemic evolution of biota inhabiting long-lived paleolakes in adjoining intramountainous basins.

This research was funded by the Austrian Science Fund (FWF) grant DOI 10.55776/I6504 and by the Deutsche Forschungsgemeinschaft (DFG) grant no. TO 1364/3-1.