Brackish-Water Solenovian Mollusks from the Lower Oligocene of the Polish Carpathians

摘要

Upper part of the Lower Oligocene deposits of the Paratethys contain peculiar endemic bivalves and ostracodes which mark an important stratigraphic level established as the Solenovian Regional Stage. Solenovian-type bivalves are also known from three localities of the Flysch Carpathians: Krepice in Moravia, Czech Republic (Ctyroky, 1991), Piatra Neam in Romania (Rusu, 1999), and Jablonica Polska in Poland (Studencka et al., 2009). The Oligocene bivalve-bearing sequence at Jab onica Polska (Silesian Nappe) is established as the Dynow Marls Member of the Menilite Formation, which directly overlies the Kotow Chert Member (Kotlarczyk et al., 2006). Based on the nannoplankton flora, the Dynow Marls Member is referred to the NP23 Zone (mid-Rupelian). The bivalve fauna from the Jab onica Polska locality includes 16 species of the genera Loripes, Cerastoderma, Korobkoviella, Lentidium, Lenticorbula, Janschinella, and Congeria. Six species are Paratethyan endemics, which are only known from the Solenovian Sea, with pliohaline (salinity less than 13-15%) water oxygenated at the surface and euxinic environmental conditions at the bottom.