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

Abstract

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).