Holocene multistage massive ice, Sabettayakha river mouth, Yamal Peninsula, northwest Siberia

Massive ground ice of Holocene age occurs in multiple boreholes near the Sabettayakha River mouth, on the coast of the Gulf of Ob (Ob Bay), Yamal Peninsula, northwest Siberia. The multistage massive-ice bodies are up to 5.7 m thick and occur in Holocene sediments of modern floodplain and the first terrace of the coastal lagoon. Massive-ice bodies and cryopegs occur at three to four depths. According to stable isotope analyses, the multistage massive ice bodies formed syngenetically during the freezing of water-saturated sediment, under intensive cryogenic fractionation. Very negative values of δ²H (up to –199.7 ‰) and δ¹⁸O (up to –26.48 ‰) for the massive ice are unique not only for Holocene ground ice of Yamal Peninsula, but also for Late Pleistocene ice of northwest Siberia. The ratio of the chloride and sulfate anions, pollen spectra and presence of algae in three different types of massive ice near the Sabettayakha River mouth suggest that (1) vertically layered brown ice formed during freezing of water-saturated sands of the Ob Gulf; (2) brown non-laminated ice formed as a result of freezing of sublake talik water; and (3) white ultra-fresh ice also formed from lake and river water.