About the deep structure of the Omsk syneclise of the West Siberian lowland

Abstract

The Omsk syneclise is composed of Jurassic, Cretaceous and Tertiary sandy-clayey sediments. These are almost undislocated and non-metamorphosed sedimentary rocks with no effusive or intrusive formations. The thickness of sedimentary rocks lies on the eroded surface of the folded basement, which has a two-tiered structure in most of the territory of the syneclise. The upper tier is represented by effusive-sedimentary rocks, weakly dislocated and weakly metamorphosed, within which there are strata with different degrees of dislocation and separated by erosion surfaces. The rocks appear to be of Lower Jurassic to Devonian age. For example, in Barabinsk the structure of the upper tier of the basement is as follows. In the interval of 2215-2234 m lie tuffites, sandstones and mudstones of Lower Jurassic - Upper Triassic age with dip angles of 5-8°. Below, from the depth of 2234 m to the bottom of the well stopped at the depth of 2470 m, the rocks are argillites with thin interbeds of tuffogenic sandstones and tuffs. These layers are inclined at an angle of 45°. Initially, the age of the rocks, determined by spore analysis, was considered to be Upper Devonian, later it was considered to be simply Paleozoic.