Holocene massive ground ice near the Sabettayakha River mouth, on the coast of the Gulf of Ob, Yamal Peninsula, northwest Siberia is studied. The multistage massive-ice bodies have thickness up to 5.7 m and occur in Holocene sediments of modern floodplain and the first terrace of the coastal lagoon. Stable isotope analyses revealed that the multistage massive ice bodies formed syngenetically during the freezing of water- saturated sediment, under intensive cryogenic fractionation.

Isotopic analyses were performed in the Stable Isotope Laboratory of the Geographical Department of Lomonosov Moscow State University using a mass spectrometer Finnigan Delta-V with the standard gas -bench option. International standards V-SMOW (Vienna Standard Mean Ocean Water), GISP (Greenland Ice Sheet Precipitation) and SLAP (Standard Light Antarctic Precipitation), as well as the laboratory's own standard -fresh snow of the Cauca- sus glacier Garabashi ( δ¹⁸О= -15.60 ‰ , δ²H = -110.0 ‰ ) were used for the measurements. The precision of the δ¹⁸О and δ²H measurements is 0.1 and 0.6 ‰, respectively.Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University.Funding was received from the Russian Science Foundation (Award nr. 19-17-00126, field research), the Russian Foundation for Basic Research (Award nr. 18-05-60272, isotope analysis).