HIGH-RESOLUTION STRATIGRAPHY OF THE LOWER AND MIDDLE JURASSIC PETROLIFEROUS DEPOSITS OF NORTHERN WEST SIBERIA
G. G. Shemin, A. Yu. Nekhaev, L. V. Ryabkova, B. N. Shurygin, A. L. Beizel, M. A. Levchuk, A. M. Brekhuntsov, V. S. Bochkarev, and N. P. Deshchenya
Keywords: Lower Jurassic and Middle Jurassic deposits, horizon, formation, subformation, zonal cyclite, bed, correlation, facies zonation
Pages: 749-765
Abstract
The Lower-Middle Jurassic petroleum-promising deposits of northern West Siberia have a complicated structure and are poorly investigated by drilling. Correlation of these deposits, in particular, petroleum-producing and promising sand beds, is often disputable. We present results of a detailed correlation of the deposits by bio- and lithostrigraphy at the level of zonal cyclites (ZC). Twenty-two ZC have been recognized and traced in various structure-facies areas. The stratigraphic positions and volumes of sand beds and their notation have been refined. Nineteen regional beds at the bottom of ZC and thirty local beds occurring at various stratigraphic levels of the middle and upper predominantly clayey part of ZC have been recognized. A version of sand bed notation is proposed in which numerals are assigned only to beds of regional occurrence. Local beds are marked with the number of the main bed and a letter. In this case, the indices of beds more precisely reflect their stratigraphic position. A regional gap has been found at the bottom of the Dzhangodskoe Horizon. The facies zonation of the Lower Jurassic deposits is refined.
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