The highest Kimmeridgian and Lower Volgian in Central Poland; their ammonites and biostratigraphy

Abstract

The Upper Kimmeridgian Eudoxus and Autissiodorensis Zones, with the Fallax Subzone at the top of the latter zone, as well as the Lower Volgian Klimovi, Sokolovi, Pseudoscythica, and Tenuicostata Zones, can be recognized in several expanded and continuous sections of the Paluki Formation in Central Poland. There can be reconstructed a Subboreal lineage of the Perisphinctaceae, leading from Discosphinctoides subborealis sp.n. and Sarmatisphinctes gen.n. in the Autissiodorensis Zone, through Ilowaiskya and Pseudovirgatites in the Lower Volgian, to Zaraiskites in the Middle Volgian. The ammonite assemblages of the Paluki Formation, which also include Aulacostephanus and Amoeboceras in the Upper Kimmeridgian, are predominantly of Subboreal type, but Mediterranean/Submediterranean ammonites, chiefly the Haplocerataceae, are also represented at some stratigraphic levels. Interregional stratigraphic correlations are discussed in the paper, especially those between the Tithonian and Volgian Stages. The new biostratigraphic material permits e.g. to correlate the top of the Klimovi Zone with the top of the Tithonian Hybonotum Zone, and the top of the Sokolovi Zone with a level situated slightly beneath the base of the Middle Tithonian in Franconia.