Palaezoogeography and Late Cenomanian foraminifera of Western Siberia

The research done on the biostratigraphy and palaezoogeography of the Late Cenomanian of the West-Siberian Province is based on the most abundant foraminiferal assemblages. In contrast to the other centuries (Turonian, Santonian, Maastrichtian), the Late Cenomanian boreal transgression was not widely distributed in the province. Previously, the Cenomanian sea facies (the Uvatskian Horizon) had been established only in Transuralia, while continental facies were known in the other territories. The author of the paper, however, has discovered agglutinated foraminifera in a number of sections in the boreholes located in the Purpeyskaya and Tazovskaya areas (the interfluve of the Pur and Taz rivers) which gave rise to the estab-lising of the Cenomanian sea facies in the north of the West-Siberian Province. Previously, V.M. Podobina had done the palaezoogeographical division of this province into the specific centuries of the Late Cretaceous which determined the location of Transuralia as a western region. Late Cenomanian foraminifera finds somewhat northwards of the latitudinal stream of the Ob' river (the Van-Eganskaya area) defined the southern border of distribution of the northern area. Within the past few years the south-eastern area of the province has been discovered on the basis of the finds of the agglutinated quartz-siliceous foraminifera assemblage with Tro-chammina wetteri tumida, Verneuilinoides kansasensis, earlier identified by the author in the northern area of the province (the Van-Eganskaya area). This assemblage was discovered by V.M. Podobina in the section of E-150 borehole (the Uvatskian Horizon) in the south-east (the suburbs of Tomsk and Seversk). The zonal kinds of the assemblage were previously known at the same stratigraphic level in the Canadian Province (Western Canada, Northern Alaska) which give grounds to think that sea faunas (including the foraminifera) of both the Provinces (West-Siberian and Canadian) were connected with each other through the Arctic Region, and the boreal transgression expanded within these provinces during the specific Cretaceous centuries. In the Late Cenomanian, the distribution of this transgression was limited, therefore its sea facies are known in the western, northern and south-eastern areas. The detection of agglutinated foraminifera in the south-east of the Province suggests the existence of the over-Yenisei Bay, which was widely introduced due to the point in time of expanding and deepening the Late Cenomanian boreal transgression. The foraminiferal similarity of West-Siberian and Canadian Provinces offers an opportunity to relate them to the Arctic palaezoogeographical realm of just the same circumpolar belt.

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