The isolation of the Pannonian basin (Central Paratethys): New constraints from magnetostratigraphy and biostratigraphy

In this paper we establish when and how the Pannonian basin and associated Central Paratethys basins were isolated from the remainder of the Paratethys, a system of back-arc basins and inland seas that once extended over a large part of Europe. The isolation, which occurred at the beginning of the Late Miocene, is marked by a paleoenvironmental change from marine to fresh water conditions that caused the regional Sarmatian–Pannonian Extinction Event. It also had significant paleogeographical implications for the basin fill and for sedimentary transport across the Carpathian Mountains. The exact age of and cause for the isolation are still subject to debate. Here, we use magnetostratigraphic dating coupled to ostracod and mollusc biostratigraphy to establish the isolation age of the Pannonian basin. We dated the isolation of the Pannonian basin at 11.63 ± 0.04 Ma in a section on the northern flank of the Fruška Gora inselberg (northern Serbia). This age is in line with recent results from the Vienna basin but predates the isolation of the Transylvanian by 0.33 Myr, suggesting that isolation took place in two steps. We conclude that the uplift of the Carpathian Mountains caused the isolation but that eustatic sea level fluctuations may have had a minor influence as well.