PALEOZOIC STRATIGRAPHY OF THE SOUTHEASTERN PERIPHERY OF THE WEST-SIBERIAN PLATE: NEW DATA FROM DEEP DRILLING (VEZDEKHODNAYA OIL FIELD, TOMSK REGION)

Abstract

The pre-Mesozoic section exposed by reference Vezdekhodnaya BH-4 to a depth of 5005 m is made up of Cambrian (?) granodiorites at its base followed upward by the volcanoterrigeous sequence of the Lisitsa measures and a rather dolomitic section at the top. The absolute age of the top of the Lisitsa measures is 520 Ma. The dolomites are correlated to those of the section exposed in a neighboring borehole (Vezdekhodnaya BH-3) which are assigned to the Vezdekhodnaya measures. The dolomites contain algae and foraminifers that indicate their Late Devonian (Late Frasnian) age. Correlations of the Paleozoic sections of three boreholes drilled on the Vladimirovka Dome (Vezdekhodnaya BH-3, Vezdekhodnaya BH-4, Nyarginskaya BH-1) on the basis of their lithology and seismic data as well as a distinguished biochronological marker permitted us to refine the stratigraphic position of the Vezdekhodnaya (Frasnian) and Dunaev (tentatively Famennian) measures and to exclude the Zhigalovo measures from the regional stratigraphic scale. It is noted that, according to obtained data, two independent facies districts could be distinguished with the Chulym-Yenisei structure-facies zone: the Vezdekhodnaya district in the west and the Tyya one in the east.