Evolution of West Siberian Petroliferous in the Phanerozoic
NESTEROV, I. I., V. S. BOCHKAREV, and F. K. SALMANOV, Ministry of Geology, Moscow, USSR
Evolution of a basin implies interaction of two general processes: the process of crust collapse with regeneration of geosyncline belts, and the process of cratonization of the crust.
The process of geosyncline belt regeneration with partial displacement across the area occurred three times in western Siberia. The first displacement is dated as long ago as 1.6 Ga, the second one took place at 650 Ma, and the third one at 500 Ma. In intensity, cratonization of the crust was multirank (gradational), and had been complicated by collapsing of the second and the third order. There were three cratonizations of the first rank: 680 Ma, 520 Ma, and 250 Ma.
The last, Hercynian, cratonization has been more intensive in the southern part of the region and has resulted in Triassic-Middle Jurassic taphrogenesis on the background of arched uplifts. Regional basement downwarping began in the north of the region, and was centrifugal in character. By the end of Permian, the Yamal-Tax megasyneclise had appeared in the north of the region; it increased in the Triassic, and in the Jurassic it underwent a five-fold extension. During the Early Cretaceous, the extension of the depression continued. In the Late Jurassic and the Early Cretaceous, marine sedimentation dominated and was accompanied by undercompensated argillaceous and bituminous facies. Sharp uplifting of eastern and southeastern remote areas adjacent to the basin caused a partial recompe sation of the eastern and southern areas of the depression. In these areas, shallow terrestrial facies dominated during the Valanginian, Hauterivian, and Barremian. In the Aptian-Albian-Senomanian and the Oligocene, terrestrial facies prevailed.
Organic-matter transformation and formation of oil and gas pools repeated in the Paleozoic and Mesozoic. In the Cenozoic, the formation of oil and gas pools took place only locally. The process intensity varied depending on the basin geodynamics and geothermal regime. This caused a considerable range of oil and gas interval and resources in different regions.
The distribution of hydrocarbon pools is of regular character only in separate oil- and gas-bearing complexes, except the secondary pools which are confined to Paleozoic basement weathered rocks occurring in all areas of the petroliferous basin. The largest hydrocarbon pools of Lower Jurassic deposits are more common in the western regions, and pools of Upper Jurassic deposits occur in the eastern ones.
AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)