Oligocene bivalve faunas from the Silesian Nappe, Polish Outer Carpathians: Evidence for the early history of the Paratethys

Abstract

The study is focused on the taxonomic inventory of an intriguing bivalve fauna from the Lower Oligocene Menilite Beds (Dynów Marls) within the Silesian Nappe, Polish Outer Carpathians. Sixteen bivalve species have been identified within the material collected in two small quarries in Jabłonica Polska near Krosno. Stratigraphic and geographic distributions of all recognized species are considered. This assemblage, the first of this kind in Poland and one of three recognized in the Outer Carpathians, shows clear affinities to coeval typical Solenovian faunas from Ukraine to Kazakhstan, with particular comparison made to bivalve faunas from the Menilite Formation (Subchert Member) within the Boryslav-Pokuttya Nappe, Ukrainian Outer Carpathians. Moreover, this study presents an overview of the main aspects and definitions of the date of the Paratethys origin. The main criterion used to define the time of the Paratethys birth is the distinct faunal turnover from the moderately diverse boreal or Tethyan bivalve faunas populating particular basins of the Northern Peri-Tethys in the earliest Oligocene to the uniform, highly endemic fauna inhabiting the newly formed semi-closed basin. This vast inland sea, named Paratethys, was populated by representatives of eight euryhaline bivalve families. They are characterized by extinct Paratethyan genera, such as Bessia Kojumdgieva et Sapungieva, Merklinicardium Popov, Korobkoviella Merklin, Urbnisia Goncharova, Ergenica G. Popov and Janschinella Merklin