Miocene connectivity between the Central and Eastern Paratethys: Constraints from the western Dacian Basin

The Dacian Basin formed an important link between the central and eastern parts of the Paratethys, a chain of late Tertiary inland seas and lakes. This study presents constraints on Miocene sea and lake level fluctuations in the Dacian Basin and on the connectivity between it and other Paratethys basins, based on the interpretation of seismic lines, a micropalaeontological study and lithofacies analysis of a large number of outcrops. It is shown that relative sea level fluctuations in the western part of the Dacian Basin during the Middle Miocene were primarily driven by tectonic activity in the nearby Carpathian Mountains. From the Maeotian (Late Miocene) onwards, however, tectonic activity was minor and relative sea level fluctuations were primarily driven by changes in basin connectivity and climate. The connection between the Central and Eastern Paratethys was broken at the end of the Middle Miocene, leading to the development of an endemic fauna in the former, but new data presented here suggest that isolation was not sustained completely as Central Paratethys species appeared in the Dacian Basin during the Maeotian (Late Miocene). Besides the isolation two falls in water level occurred in the basin during the latest Miocene: Of these, the intra-Pontian sea-level drop is the best known. We show, however, that this drop was preceded by a larger sea or lake-level drop in the late Sarmatian/Maeotian. This latter event may have affected much larger parts of the Paratethys, and we recommend more study of the bordering basins. The hypothesis that the connection between the Dacian and Central Paratethys basins was located in the region where the Danube River presently crosses the Carpathians was tested, but no supporting evidence was found.