FORAMINIFERAL BIOSTRATIGRAPHY OF THE CALLOVIAN–VOLGIAN SEDIMENTS AND BIOFACIES OF THE SOUTHWESTERN WEST SIBERIAN LOWLAND
E.V. Zaichikova, L.K. Levchuk
Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
Keywords: Foraminifera, biostratigraphy, Jurassic, Callovian, Kimmeridgian, Volgian, biofacies, West Siberia
Abstract
The study explored the taxonomic composition of foraminiferal assemblages from cores sampled in the Sil’ga and Yamal-Tyumen’ facies regions-the southern and southwestern West Siberian sedimentary basin. A complete sequence of biostratons was established for the Callovian-Kimmeridgian sediments of the southwestern West Siberian Lowland and was correlated with the units of the General Stratigraphic Scale. A number of biostratons have been revealed for the south of West Siberia. The biofacies analysis of the foraminiferal assemblages revealed that the Yamal-Tyumen’ facies region belonged to a relatively deep marine environment, far away from the Jurassic Sea littoral zone, in the Callovian through the Kimmeridgian and that the Sil’ga facies region was a relatively shallow marine environment in the Oxfordian through the Middle Volgian.
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