The oxygen isotope composition of Late Pleistocene syngenetic ice wedges of the Seyakha yedoma is studied, based on detailed sampling of the Seyakha yedoma section in the sequence of the Late Pleistocene third lagoonal-marine terrace near the mouth of the Seyakha (Zelenaya) River, on the shore of the Gulf of Ob. According to the obtained new radiocarbon data, the approximate age of the ice wedge ranges from 23 to 15-18 ka. The mean January temperature in the period 23-15 (18) ka BP ranged from -35 to -39°C.

¹⁴C ages of bulk samples were obtained at the Institute for the History of Material Culture, St. Petersburg by conventional radiocarbon dating.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.The research was financially supported by the Russian Scientific Foundation (grant Nr 19-17-00126, field studies and isotope analysis) and Russian Foundation for Basic Research (grant Nr 18-05-60272, radiocarbon dating and calculations).