Biostratigraphy of Slavgorodskian Horizon (Santonian, Lower Campanian) of Western Siberia (based on Foraminifera)

The Slavgorodskian Horizon, except of the upper layers consist of two zones of the early and late Santonian age: Ammobaculites dignus, Pseudoclavulina admota (the lower one) and Cribrostomoides exploratus, Ammomarginulina crispa (the upper one). Of interest are the data on the Tym River (Paydugina basin) where the layers with the calcareous Cibicidoides eriksdalensis assemblages have been revealed. They are characteristic for the littoral-marine facies of the Santonian basin, and these layers containing the calcareous foramin-ifers correlating with the above mentioned, widespread through the Slavgorodskian Horizon - Santonian zones with agglutinated quartz-siliceous foraminifers. The Campanian deposits (the upper layers of the Slavgorodskian Horizon) and the lower layers of the Gankinskian one) exist in the short bulk. In the upper layers of the Slavgorodskian Horizon is the upper zone - the third one with Bathysiphon vitta, Recurvoides magnificus - presumably of the earlier Campanian. All zones of Slavgorodskian Horizon have been correlated with the established foraminiferal (local biostratigraphical) zones in the European part of Russia as well as in Northen Alaska and Canada of the Canadian province. Of special interest are the new data on the foraminiferal assemblages of the Santonian age, receiving in the analogs rocks on the South-East of West Siberian province, accompanied by the specific foraminiferal finds. The assemblages have been assigned the Slavgorodskian Horizon being, by the author's data, an upper part of the Berezovskian Superhorizon.

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