New Cambrian volcanoterrigenous section and position of the western boundary of the Siberian Platform (by data of parametric drilling in the Vezdekhodnaya area, Tomsk Region)

Parametric Vezdekhodnaya BH-4 more than 5 km deep, drilled in the southeast of the Tomsk Region, has penetrated a previously unknown complex of Cambri an deposits composed of effusive-sedimentary rocks and overlain by a Paleoz oic predominantly dolomitic series. This paper considers the petrochemical characteristics of rocks composing t he, section and the petrologosedimentary and general geological prerequisit es of their formation. The determined rock ages and results of paleomagneti c studies are presented. It is suggested that these deposits might have formed under the deep-water conditions of back-are basin, east of which Lower Cambrian shallow-sea carb onate-evaporitic platform facies dominated. Variants of the tectonic histor y of the region are proposed.