Cambrian section in the east of the West Siberian geosyneclise (based on data from Vostok 4 well)

The study presents a description of a new type of Cambrian section penetrated in Vostok 4 well in the southeastern part of the West Siberian geosyneclise (Krasnoyarsk Territory). The drilled succession is well characterized by the fossil evidence and can be considered a key section for the east of the WSG. The section comprises all three divisions of the Cambrian and is subdivided into the Oksym, Tyya, Averin, Kolchum, and Evenki Formations, based on the composite log data for an interval of 2262–5105 m. The Oksym Formation (the age equivalent of the Usol’e Formation) and Kolchum Formation are first identified and described in this study. The section is mostly carbonate, argillaceous–carbonate, sulfate–carbonate, and terrigenous sediments deposited in a back-reef setting of the Yenisei salt-bearing basin.