Paleocryogenic Structures of the Late Pleistocene in the Severnaya Dvina River Valley

The first results of a detailed paleocryolithological study (Permogorie section case study) in the upper reaches of the Severnaya Dvina River show that existing paleoenvironment enabled the development of thermal contraction cracking in Northeastern Europe at the end of the Bølling-Allerød interstadial (ca. 13.3–12.7 cal. kyr BP). Freezing occurred in two stages—syncryogenic with the formation of ice-wedges and epicryogenic with the formation of composite ice-wedges. The relic layer of seasonal thawing could reach a thickness of 1.0–1.5 m. The data obtained confirm the formation of permafrost in the Late Glacial period, but do not yet allow us to judge the continuous or discontinuous permafrost in the northeast of the East European Plain at the Pleistocene-Holocene boundary.