High-Resolution Oxygen Isotope Diagram of Late Pleistocene Ice Wedges of Seyakha Yedoma, Eastern Yamal Peninsula

Аннотация

The main aim of this work is to study the oxygen isotope composition of Late Pleistocene syngenetic repeated ice wedges and to obtain a high-resolution isotope diagram 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 three new radiocarbon ages (25.2 to 23.3 ka BP) from absolute heights of +2 to +5 m and also ages obtained earlier (17.3 ka BP from +18.8 m; 11.6 ka BP from +21.2 m), the approximate age of this ice wedge ranges from 23 to 15–18 ka. The values of δ¹⁸О in the upper fragment of the ice wedge vary from –25.75 to –23.15‰. The amplitude of horizontal variations in δ¹⁸О at +15.2 m height is 1.49‰ (–23.41 to –24.9‰). The lower fragment of the ice wedge at +6 m height is characterized by a broader variation range of δ¹⁸О compared to the upper one: δ¹⁸О varies in the horizontal direction from –23.41 to –26.63‰. The detalization step of the oxygen isotope diagram obtained is 80–100 years. The mean January temperature in the period 23–15 (18) ka BP ranged from –35 to –39°C.