ИСТИНА

The team of Earth Cryosphere Institute together with Moscow State University (faculty of Geography) and VNIIOkeangelogii (St. Petersburg) investigated the geological and cryogenic structure of coastal exposures of the Kara Sea region. This work focused on the key sites on the Western Yamal (Cape Marre-Sale), Western Taymyr (near Dixon village, estuary of Krestyanka river, Sopochnaya Karga cape and etc.), and Gydan peninsula (near the mouth of the river Ery-Maretayaha and Paha-Sale cape). An integrated study was carried out in each of the key sites. It includes detailed description of geological and cryogenic structure, sampling of frozen Quaternary sediments and ground ice for the grain size, chemical and isotope analysis of sediments and ice. The gas composition of frozen sediments and ground ice of various geneses has been analyzed and quantitatively described. New data of geological and cryogenic structure, geological age has been obtained that expand the existing knowledge of conditions for formation and freezing of quaternary deposits and underground ice. Based on the findings, the scheme of Late Pleistocene - Holocene History for Kara Sea region has been developed. Marine sediments of Sanchugovskaya suite (MIS 8-6) and Kazantsevo horizon (MIS 5) take up the alluvial-marine plains. Really dated deposits of Zyrjankaya time (MIS 4) have not been identified. Karginsky time (MIS 3) is represented by continental deposits. The syngenetic ice wedges are formed mainly into two stages - at the Sartan cryochron (MIS 2) about 20-11 kBP and at the Holocene (MIS 1). The climatic conditions of that time were reflected in the stable isotopes composition. It allowed to reconstruct paleoclimatic conditions and ice wedges age on the base of isotopic analysis. Paleotemperature reconstruction based on stable isotope content showed that average winter temperature of the Holocene was 3-6⁰C below the present and at the end of the Late Pleistocene was 8-10⁰C colder than present. Spatial and temporal distribution of paleotemperature is discussed in this report.