Dinoflagellates and calpionellids of the Jurassic-Cretaceous boundary, Outer Western Carpathians (Czech Republic)

Abstract

A palynological analysis and study of calpionellids and calcareous dinoflagellate cysts across the Jurassic-Cretaceous (J/K) boundary succession in the Outer Western Carpathians, Bruzovice section is presented. It is a one of few sections of the Tethyan Realm suitable for the palynological study. The lower part of the section is formed by anoxic deposits consisting of dark grey calcareous claystones. The upper part of the profile is represented by flysch-like alternation of grey limestones, spotted claystones and marlstones. The section spans the stratigraphic range from the upper Tithonian, Cadosina semiradiata calcareous dinoflagellate Zone to the lower Berriasian, calpionellid Calpionella elliptica Subzone. The J/K boundary is marked by a high abundance of small forms of Calpionella alpina. The Tithonian-Berriasian succession of non-calcareous dinoflagellates is as follows: the base of the section is correlated with the dinocyst Semiradiata Zone along with the presence of Glossodinium dimorphum. The first occurrence (FO) of Amphorula metaelliptica and the last occurrence (LO) of Prolixosphaeridium anasillum are recorded in the Cadosina semiradiata Zone followed by the Cadosina tenuis-Colomisphaera fortis Zone. An aboudance of the spherical C. alpina indicates the onset of the Calpionella Zone and the Calpionella alpina Subzone at the base of the Berriasian Stage. The FO of Diacanthum hollisteri is situated in the lower part of the Calpionella alpina Subzone. The FO of Dichadogonyaulax bensonii coincides approximately with the base of the calpionellid Remaniella ferasini Subzone, and the FO's of Muderongia longicorna, M. tabulata and Spirnferites cf. ramosus were found in the upper part of the calpionellid Remaniella ferasini Subzone. The FO of Achomosphaera neptunii was found in the lower part of the Calpionella elliptica Subzone. The work is a contribution to the ICS Berriasian Working Group.