Key section of Karginsk deposits in the middle reach of the Chulym River (Tomsk Region)

The outcrop of the Upper Pleistocene sediments in Sergeyevo is described (57°15'15” N, 86°05' E), in the middle reach of the Chulym river (Tomsk region; West Siberian plain). It includes two bone-beds. The richest remains of large mammals are the deposits of layer 4. The layer is represented by an alternation of brown loams and bluish-gray clays (the thickness of loam layers is 0.3-1.0 cm, clay layers - 1-3 cm) with ochreous spots and spots of carbon-bearing detritus. Loams are sanded and replaced with red sand in the lower part of the layer. The thickness of clay layers is increased down the section up to 20 cm. Loams become darker (change their color from gray-brown to black) and include numerous fragments of fossil tree trunks and branches in the middle part of the outcrop. Remains of large mammals from mammoth complex (from 13 species) are confined to the upper border of these loams. Various malacofauna and palynological data were obtained from the deposits in addition to theriofauna. Radiocarbon dates obtained from the skull fragment of Coelodonta antiquitatis - 32100 ± 390 years (COAH-5552) and the metacarpal bone of Panthera spelaea Goldf - 34280 ± 737 (UBA-38455) indicate the Karginsk period (MIS 3) of layer 4 deposit accumulation. The outcrop (layer 4) is proposed as a basis for Karginsk horizon deposits. It has the following important characteristics: 1) constant upgrading and good exposure of the section; 2) good attachment to the layers (only insite material was found) of paleontological remains; 3) high richness (with annual finds) of mammal remains, their good preservation and reliable taxonomic definition; 4) significant taxonomic diversity of mammal remains, malacofauna and spore-pollen spectra; 5) good combination of results of radiocarbon dating, biostratigraphic, paleogeographic and paleoecologic data.

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