STRUCTURE AND DEVELOPMENT STAGES OF THE NORTHEAST PART OF THE EAST EUROPEAN PLATFORM SEDIMENTARY BASIN IN THE PROTEROZOIC AND PALEOZOIC BASED ON LONG-TERM GEOLOGICAL SECTIONS OUTCROPS OBSERVATIONS AND STUDIES OF DEEP WELLS

Abstract

The relevance of the study is caused by the need to rethink the structure of the sedimentary cover in the northeast part of the East European Platform from the standpoint of sequence-stratigraphic analysis, which will make it possible to construct the eustatic curve and to become the basis for a more detailed study. Purpose: dividing sediments into first and second order sequences and plotting a sea level fluctuation curve. Objects: outcrops of the western slope of the Urals, and the northeast part of the East European and deep platform, deep wells of Nirimskaya, Kuliginskaya, Sokolovskaya, Sivinskaya, Severokamskaya, Sukhobizyarskaya, Yumyshskaya, Veslyanskaya and Osintsevskaya areas. Methods: field work, cross-well correlation, lithological-facies, eustatic and basin analysis. Results. The comprehensive generalization of deep drilling data and field observations of outcrops made it possible, from the standpoint of sequence-stratigraphic analysis, to identify and describe five first-order sequences (megasequences) following from bottom to top: Riphean; Vendian; Lower Devonian – Tournaisian; Visean – Lower Permian; Lower Permian – Upper Permian. Mega-sequences, in their turn, were divided into second-order sequences (super-sequences): Lower Devonian; Lower Devonian – Lower Frasnian; Middle Frasnian – Tournaisian; Visean – Bashkirian; Moscowian – Asselian; Sakmarian – Kungurian; Ufaimian – Upper Permian. Stratigraphic breaks of different duration are confined to the boundaries of the sequences. The longest ones are the intervals between the Lower Riphean and the Upper Vendian, as well as the Upper Vendian and the Lower Devonian. Sequential stratigraphic analysis allowed constructing a eustatic curve for a given area. The maximum regressions occurred in the Emskian, Visean, and Moscowian ages and in the Middle-Late Permian epoch. They are associated with a tract of low sea level (lowstand system tract) and the main terrigenous reservoirs. The maximum transgressions were noted in the Famennian, Tournaisian, Bashkirian Asselianian centuries. They are associated with organogenic structures, which were formed on the high sea level highstand system tract. Thus, the geological history of sedimentation in the northeast of the East European Platform is traced.

Keywords

• sequence stratigraphy
• upper paleozoic
• east european platform
• volga-ural oil and gas province
• perm region
• borehole correlation
• lithological-facies analysis
• eustatic analysi
• basin analysis