New type of Cambrian section in eastern part of West Siberian Plate (based on Vostok-1 stratigraphic well data)

A new type of Cambrian section penetrated by the Vostok-1 stratigraphic test well in the east of the West Siberian Plate, Tomsk Region, is described in terms of paleontology. It can be considered a key section for this region. According to a complex of geological and geophysical characteristics, the section in the depth range of 2766–5010 m was divided into the Churbiga, Paidugina, Pudzhelga, Podelga, Kondes, Shedelga, and Pyzhina Formations, and their first description was made. The Cambrian section in Vostok-1 well is most similar to those of the Kotui-Igarka area of the northwestern Siberian Platform, where Cambrian deposits formed in the pre-reef zone of an open sea basin. In the lower section of the borehole the highly carbonaceous siliceous-argillaceous-carbonate Paidugina Formation was stripped, which is an analog of the Lower-Middle Cambrian Shumnaya and Kuonamka Formations of the Siberian Platform. The Paidugina Formation, which accumulated on the shelf and slope of the open sea facing the Paleo-Asian ocean, is considered oil-producing and suggests the high petroleum potential of the cis-Yenisei basin. Also, a highly promising generation-accumulation petroleum system has been revealed.