Late Pleistocene Paleosols in the North of Western Siberia: Paleorecords of Natural Environment and the Component of the Modern Soil Cover

The article presents the results of the search and study of the Late Pleistocene soils in the north of Western Siberia. The theoretical basis was an ice-free model of the evolution of the Pleistocene landscapes in the region, since the alternative model with its glacial cover excluded pedogenesis under them. In sections of high river terraces, disclosing the Late and Middle Pleistocene sediments were revealed, in the absence of glacial deposits, and paleosurface levels were corresponding to chronointervals with landscapes favorable for the development of pedogenesis. These are the soils of the Kazantsev thermochron – the marine isotope-oxygen stage (MIS) 5, lying on the Middle Pleistocene alluvium, and of the Karginsky interstadial – MIS-3, and of the end of the Sartan cryochron – MIS-2. Based on morphogenetic analysis, including micromorphological observations, a pedogenetic interpretation of paleosols was carried out. It was revealed that in the polygenetic profile of the MIS-5 paleosol, the stage of taiga soil formation with clay illuviation was replaced by a colder tundra phase with over-permafrost gleization, and the MIS-3 paleosols are characterized by tundra-steppe features, in which gleization and cryogenic processes are combined with the formation of carbonates, whereas the paleosol level of the end of MIS-2 is a product of tundra-swamp pedogenesis and includes gleiing pedosediments that fill pseudomorphs along ice wedges. The latter allowed us to identify the Late Sartan Tazovo-Nadym soil-cryogenic horizon. As a result, the correlation of the obtained results with synchronous stratigraphic schemes for adjacent regions was carried out and the question of creating a soil-permafrost paleorecord of the north of Western Siberia was raised. This is important because the interpretation of modern surface soils requires special approaches in order to take into account that in their profiles relict pedogenic horizons are often found.