AMS radiocarbon dating (22-27 cal Ka BP) of massive ice on the coast of Mechigmen and Lavrentia Bays, Eastern Chukotka, and stable isotope (δ18O, δ2H) composition of dated ice

Field studies of the Eastern Chukotka's massive ice carried out in 2016, 2017, and 2020. The three key sites of the studied massive ice bodies are located on the coast of Mechigmen Bay: a) 2 km southeast from the Chulkheveem (Akkani) River; b) 2 km south of the Lavrentiya settlement; and c) 7 km south of the Lavrentiya settlement. Direct AMS radiocarbon dating of organic micro-inclusions extracted from the ice determined the radiocarbon age of three massive ice bodies with a high degree of accuracy. The study revealed the intrasedimental origin of the studied massive ice bodies, which formed epigenetically at the end of the Late Pleistocene (22–27 cal ka BP) during the final stage of MIS2. Variations of δ18O and δ2H values in ice samples are insignificant: by about 10‰ for δ18O values (from –14.8‰ to –24.5‰) and about 75‰ for the δ2H values (from -116‰ to -191‰). Slopes of the δ2H-δ18O lines lower than 8 indicate the evaporation of initial water or 18O isotope fractionation during freezing.