THE AZAS ICE SHEET AND ITS ROLE IN THE FORMATION OF LATE PLEISTOCENE ICE-DAMMED LAKES IN SOUTHERN SIBERIA: CASE STUDY OF UPPER KHARAL PALEOLAKE
I.S. Novikov1, D.V. Nazarov2,3, M.V. Mikharevich4,5, A.S. Gladysheva2, M.V. Ruchkin2,3, S.G. Prudnikov6
1V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Russian Geological Research Institute, Federal Agency of Mineral Resources, St. Petersburg, Russia
3St. Petersburg University, St. Petersburg, Russia
4Siberian Research Institute of Geology, Geophysics, and Mineral Resources, Novosibirsk, Russia
5Melnikov Institute of Permafrost, Siberian Branch of the Russian Academy of Sciences, Yakutsk, Russia
6Tuva Institute of Integrated Subsoil Use, Siberian Branch of the Russian Academy of Sciences, Kyzyl, Russia
Keywords: Paleogeography, facies analysis, spore-pollen analysis, paleocarpological analysis, ice-dammed lake, varved clay, Ar/Ar and OSL dating, Tyva
Abstract
The paper focuses on the surface topography and deposits associated with the Late Pleistocene ice-dammed lake in the valley of the Kharal River dammed by the Azas ice sheet in a depression between the East Sayan and Akademik Obruchev Range. The study includes paleogeographic reconstructions for the time spans before the lake formation and drainage; reconstruction of vegetation in the lake area based on pollen and paleocarpological data; and dating by optically stimulated luminescence (OSL) and 40Ar/39Ar methods. The OSL and Ar-Ar dates provide more rigorous constraints on the history of deposition and topography in the western Serligkhem Basin. The territory was affected by erosion and subsequent basaltic volcanism at 6.9 ± 0.7 and 2.2 ± 0.7 Ma. The erosion valleys were dammed by the edge of an ice sheet and then by its moraine, which produced large Upper Kharal damlake. According to OSL data, the lake existed between 36 ± 4 and 14 ± 3 ka BP. The related glacial, glaciolimnic, and glaciofluvial facies in the area were deposited at the end of the Late Pleistocene (stages III and IV of regional stratigraphy).
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