The first section of vendian deposits in the basement complex of the West Siberian petroleum megabasin (resulting from the drilling of the Vostok-3 parametric borehole in the Eastern Tomsk region)

Until recently, information about pre-Mesozoic deposits in the eastern part of the West Siberian megabasin, the largest petroleum basin in the world, was scanty. In the 1980s-1990s, as a result of regional geophysical works and the drilling of the Tyya-1, Vezdekhodnaya-4, Lemok-1, and Averinskaya-150 bore-holes, a great scope of new information was acquired, the analysis of which made it possible not only to create a stratigraphic outline and to reconstruct geo-dynamic and paleogeographic depositional environments for pre-Mesozoic deposits in the West Siberian megabasin, but to substantiate the distinguishing of a new late Proterozoic-Cambrian sedimentary basin on the left bank of the Yenisei River as well. Parametric borehole (BH) Vostok-3, which was drilled in 2006 down to the depth of 5002 m with detailed coring, penetrated the section of carbonate-type deposits within the interval of 50023870 m. The late Vendian CloudinaNamacalathusPlatysolenites fossil assemblage previously unknown on the territory of Siberia has been established in these deposits.