The Scythicus Zone (Middle Volgian) in Poland: its ammonites and biostratigraphic subdivision

Abstract

New paleontological material comprising Middle Volgian ammonites from the classical region of Tomaszów Mazowiecki in Central Poland, chiefly from the section at Brzostówka, is presented. A new species, Zaraiskites regularis sp.n., is established. Four new horizons are established in the Scythicus Zone of Poland: the Quenstedti and Scythicus Horizons in the Scythicus Subzone, followed by the Regularis and Zarajskensis Horizones in the Zarajskensis Subzone. These horizones are based on four successive assemblages of Zaraiskites, interpreted as biospecies. The new horizons allow to establish some more precise interregional stratigraphic correlations; e.g., the Regularis Horizon has its age equivalent at some level in the Calpionellid Zone A in the Upper Tithonian Substage.