Stromatolites in the Paratethys Sea during the Middle Miocene climate transition as witness of the Badenian salinity crisis

Abstract

This is the first documentation of Middle Miocene (late Langhian) stromatolites from the Central Paratethys Sea. These microbialites formed in a lagoonal setting in the Austrian Oberpullendorf Basin, which is part of the Pannonian Basin Complex. Sedimentological and paleontological data indicate that an initial marine transgression led to the establishment of a gravelly and sandy shore. Subsequently, an agitated lagoon with shallow-marine sublittoral conditions and a diverse mollusc fauna developed. Diminishing accommodation space forced the development of a restricted, muddy lagoon. A rather hostile environment and probably hypersaline conditions led to the disappearance of metazoans and triggered the formation of a short succession of microbialites. Minor oscillations of the relative sea-level are reflected by alternations of undulate/planar stromatolites to domal stromatolites and distorted stromatolites with frequent emersion surfaces. The microbialites can be traced across a large area of the basin. They are coeval with the thick evaporites of the Carpathian Foredeep and the Transylvanian Basin, which formed during the Badenian salinity crisis. This coincidence suggests that the mid-Badenian Paratethyan stromatolites are ecological analogs of Mediterranean stromatolites that formed during the Messinian salinity crisis.