EVOLUTION OF THE WEST SIBERIAN BASIN

Abstract

The West Siberian Basin is one of the largest intra-cratonic basins of the world and an important hydrocarbon province of Russia. Perhaps the most important geologic event in Siberia was the emplacement of basalts around ~250 Ma (i.e. Permo-Triassic boundary) covering an area of about 5×106 km2. This volcanism may be responsible for a mass extinction that occurred around Permian-Triassic time. The pre-basaltic rifting event was limited to the north-northeastern sector of the basin. Initial basin wide subsidence took place in the Jurassic as a result of which the western part of Siberia became the West Siberian Basin bounded by uplifts to the east and to the west. One of the surprising aspects of the West Siberian Basin is the abundance of sub-vertical faults believed to be result of strike-slip movement. While intra-plate inversions and fault reactivation structures have been observed in many cratons, sub-vertical faults observed in the West Siberian Basin are unique because of their geometries and abundance. The differentiation between the effects of tectonics and eustasy in cratonic basins is simple - the global eustatic signal is basin-wide with regional and local tectonics playing an overprinting role. Thus, the Middle Jurassic-Turonian 1st, 2nd, and 3rd order cycles in the West Siberian Basin were primarily driven by eustasy. The Middle Jurassic-Turonian series can be subdivided into two second-order and 16 third-order transgressive-regressive cycles (within dataset extent). Fourth-order cycles appear to be controlled by delta shifting. Although extensively studied, a number of fundamental questions regarding the origin and evolution of the West Siberian Basin remain unresolved or poorly documented in the literature. © 2005 Elsevier Ltd. All rights reserved.