Holocene massive ground ice near the Sabettayakha River mouth, on the coast of the Gulf of Ob, Yamal Peninsula, northwest Siberia is studied. Three boreholes (Nr 12, 17 and 42) were drilled within the Holocene lagoon-marine floodplain of the Ob Bay and the first lagoon-marine terrace near the Sabettayakha River mouth in winter 2014 using a light portable drill. The drilling retrieved a 12 cm diameter core in an almost undisturbed condition. Massive ice was sampled from these boreholes for isotope, chemical and palynologic analyses. 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. 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 vertically layered brown ice formed during freezing of water-saturated sands of the Ob Gulf; brown non-laminated ice formed as a result of freezing of sublake talik water; and white ultra-fresh ice also formed from lake and river water.

Fragments about 30 cm long of three ice cores were taken from each borehole, transported in frozen state to Moscow, and kept in a freezer.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) and the Russian Foundation for Basic Research (Award nr. 18-05-60272, isotope analysis).