Uppermost Jurassic and lowermost Cretaceous dinocyst successions of Siberia, the Subarctic Urals and Russian Platform and their interregional correlation

Abstract

Uppermost Jurassic and lowermost Cretaceous dinocyst successions of Siberia, the Subarctic Urals and Russian Platform and their interregional correlationUppermost Jurassic and lowermost Cretaceous dinocyst successions calibrated against ammonite and foraminiferal zones were studied in five sections from North Siberia, the Subarctic Urals and the Russian Platform. Together with analysis of published palynological material on additional contemporaneous sections from the Russian Platform, our research provides a reliable regional correlation. The obtained biostratigraphic results are compared to palynological data from different regions of Europe, America, Australia and Antarctica using the method of first/last appearances of selected key species and evolutionary trends of dinocyst floras. Four correlative levels are defined in the middle parts of the Volgian and Berriasian and near their tops providing interregional correlation of dinocyst successions. These levels range within 1-1.5 ammonite zones as the first/last appearances of some key species have minor stratigraphic shifts in different sections that may be related to migration processes or to a different understanding of the stratigraphic position of ammonite zones.