Foraminifera and Biostratigraphy of the Pokurskian Overhorizon in Western Siberia

Factual data on the foraminifera and litology of containing rocks have been obtained from the newly drilled boreholes in the northern district of Western Siberia. Similarity in the systematic composition of foraminifera of the four Horizons - those of the Vikulovskian (the Aptian), Chanty-Mansiskian (the Albian), Uvatskian (the Cenomanian) and the Kuznetsovskian (the Turonian) allowed us to unite them in one association of these organisms. Containing rocks consisting of interbedding of analogous in lithology sandstones, aleurolites and argillites make up a unified series of deposits of the Pokurskian Overhorizon of Western Siberia. Distinctive foraminifera and containing rocks have been isolates in the section for the first time as a Middle epoch of the Cretaceous System.