Geological structure and correlation of upper devonian and lower carboniferous deposits of the Kurgan region (southwest of Western Siberia, Russia)

The relevance of the work is due to the need to study the geological setting and the stratigraphy of the Pre-Jurassic basement of the Kurgan region, located at the junction of the Western Siberian Plate, the Ural fold belt and folded- block structures of Central Kazakhstan, making possible to discover new hydrocarbon deposits, confidently solve theoretical issues of the given territory geology. The purpose of the study is stratigraphically subdivision and characterization of the Paleozoic section based on fossils: foraminifers, brachiopods and bryozoans, and data on algal and palynomorph assemblages. The study is based on cores from Kurgan-Uspenskaya-1 (KU-1) key borehole and from some other stratigraphic test boreholes. Results and conclusions. The deposits are represented by marine shelf, lagoon and continental facies. The succession penetrated by the KU-1 borehole is divided by overlap faults into six uneven-aged blocks. For the first time in this region, the Paleozoic section has been stratigraphically subdivided based on fossils, with the Upper Devonian Famennian Stage, the lower Carboniferous (Mississippian) Tournaisian Stage and the lower substage of the Visean Stage characterized. The succession of foraminiferal assemblages is consistent with the zonal scheme of the General Stratigraphic Scale (GSS) of Russia. Several reference levels have been recognized based on bryozoans and brachiopods; those have been correlated with the foraminiferal zonation. The faunal assemblages are dominated by taxa characteristic of the coeval deposits from Central Kazakhstan and the Kuznetsk Basin in the Altai-Sayan folded area, and to a lesser degree, from the eastern slope of the Middle Urals. The formations in question were correlated with the sections from the adjacent and remote regions.