ИСТИНА

Unique Holocene massive ground ice drilled in detail for the first time on the coast of the Gulf of Ob (also known as Ob Bay) near the Sabettayaha mouth. This area presents syngenetic permafrost for lagoonmarine deposits located in the zone of high tides and surges of water of the Gulf of Ob. Massive ground ice is so commonly distributed in the Holocene strata of this area - unusual and extremely rare in permafrost in general. Massive ice bodies that have capacity up to 5.7 m occur in the Holocene sediments of modern lagoon-sea floodplain and the first terrace and they undoubtedly also have the Holocene age. Due to the stable isotope and pollen spectra analysis it is shown that massive ground ice is mostly autochthonous type and segregated origin. Massive ice bodies were syngenetically formed in Late Holocene during freezing of water-saturated grounds, intensive cryogenic fractionation lead to significant stable isotope variation in the ice. Very low values of deltaD and delta18O of the massive ice are unique not only for Holocene ground ice of Yamal Peninsula, but even for significantly isotopically light Late Pleistocene ice wedges and for massive ice of the northwest of Siberia. This work was financially supported by Russian Scientific Foundation (grant RSF № 14-27-00083)