Cenomanian-Turonian dinocysts of North Hemisphere: some aspects of biogeography and paleogeography

Abstract

Taxonomic typization of dinocyst assemblages was carried out on the basis of a qualitative and quantitative assessment of their generic composition for the Northern Hemisphere in the Cenomanian-Turonian time in order to identify correlation taxa. Typization was carried out by the method of cluster analysis according to the Jacquard calculation model (BioDiversity Professional program, 1997). To combine clusters into a hierarchical structure, the method of group average connection was used. Three types of dinocyst assemblages have been identified in the Cenomanian. Cenomanian dinocyst assemblages are poorly differentiated; a number of cosmopolitan genera have been identified, which is in good agreement with paleobotanical data on a very warm, humid climate. Three types of dinocyst assemblages have been established for the Turonian time. The number of cosmopolitan genera of dinocysts decreases, and species endemism sharply increases in some Turonian basins. The differentiation of assemblages increases and the correlation potential decreases. However, the identified common genera and species of dinocysts in various types of assemblages provide the possibility of interregional correlation of Upper Cretaceous deposits at the stage, substage, and, at some sections, at a more detailed level in different climatic zones.