Abstract

—A member and bed-by-bed division of the Upper Vendian formations in the boreholes drilled in the Baikit anteclise and the Angara fold zone in the west of the Siberian Platform has revealed sedimentation gaps above the Danilovka Horizon and above and within the Tira Horizon as well as amplitude erosion of the sediments. Lower beds appear in the above-gap Il’bokich basal argillaceous-dolomite-marl member of the Katanga Formation of the Danilovka Horizon. The thicknesses of all beds gradually increase from north (Baikit anteclise) to south in the Angara fold zone. The upper members of the Tira Horizon did not accumulate below the gap in the north. The Yurubchen Plateau (uplift) was in this area. South of it, the formation thicknesses increase; there are apparently no gaps in the Beryambinskaya area of the Angara fold zone. The Il’bokich member makes up the top of the Moshakovka Formation but is part of the Danilovka Horizon. The Moshakovka Formation spans the top of the Tira Horizon and the bottom of the Danilovka Horizon. In general, stratigraphic bodies in areas with a rapid increase in the tectonic-downwarping amplitudes have a typical geologic structure.

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