Paleocene Foraminifera and Biostratigraphy of Western Siberia

The Paleocene deposits of Western Siberia are principally represented by the Talitskaya Suite (a local stratum) in which two foraminiferal zones were established: the lower - Ammoscalaria friabilis assigned to the Selandian Stage and the upper - Glomospira gordialiformis - Cibicidoides favorabilis of the Thanetian Stage. These assemblages are composed predominantly by agglutinated quartz-siliceous forms. In the coastal facies framing the deep-water part of the West-Siberian Selandian basin, calcareous benthic foraminifera of the Cibicidoides proprius Assemblage are identified including species characteristic for the Selandian stratotype Assemblage (Zealand, Denmark). The superjacent Thanetian assemblage is dominated everywhere by agglutinated sugary-white foraminifera represented by Glomospira, Asanospira and others similar in aspect with the subjacent Selandian Cyclammina coksuvorovae Assemblage distributed in the eastern district. Danian deposits of reduced thickness occur through the depressional areas of Transuralia and some localities of the central district. They are distinguished as the Brotzenella praeacuta Zone in the top part of the Gankinskaya Suite (Maastrichtian) or in the transitional beds to the Talitskaya Suite (Selandian). In the east (Ust-Tym depression and Tym basin) the continuous sections of the Cretaceous-Paleogene contain the Danian Bathysiphon nodosarieformis - Glomospira gordialiformis Assemblage composed by foraminifera characteristic of the Lower Paleocene.