Sartanian (MIS 2) ice wedge pseudomorphs with hydromorphic pedosediments in the north of West Siberia as an indicator for paleoenvironmental reconstruction and stratigraphic correlation

Abstract

Within the glacier-free scenario of the MIS 2 (Sartanian cryochron) environment in the north of West Siberia, it is important to search for the new regional paleoecological records and stratigraphic markers for this period. We studied large ice-wedge pseudomorphs filled with gleyic pedosediments developed on the high river terraces in the Nadym and Taz rivers basins as a tracer of the surface cryogenic and pedogenic processes during MIS 2. Field morphological observations and measurements, palynological analysis and radiocarbon dating of organic matter from soils and pedosediments were performed. Two sets of paleoecological indicators were discriminated: pseudomorph geometry evidence of the processes and conditions of ice wedge formation during the Last Glacial Maximum whereas the paleopedological and paleobotanic results from the fills recorded the environments of ice wedge melting at the end of MIS 2. Paleotemperatures 7–10 °C lower than at present are inferred during the major part of Sartanian, even at its end continuous permafrost persisted providing development of swampy tundra vegetation and cryohydromorphic palaeosols. We propose to define Taz-Nadym cryopedogenic horizon as a representative regional unit for MIS 2 and to correlate it with synchronous cryogenic and palaeosol units in Central and Eastern Europe.