Peculiarities of Paleogeography of the Ubsunur Basin in 2022

Abstract

Studies of the paleogeographical properties of the Ubsunur Basin located on the territory of northwestern Mongolia and southern Tuva are based on the discovery of buried ice veins under Aeolian sediments in the region of Lake Khar-Nur in the eastern mountainous frame of the Great Lakes Basin of Western Mongolia. Satellite images have shown outlines of fields along the periphery of the sand deposits, the natural irrigation of which, in our opinion, was due to the melting of the abovementioned ice. Deposits similar to glacial ones have been found in the river valleys of the northern mountainous framing of the Ubsunur Basin, in its foothill part, suggesting the presence of Pleistocene glaciers extending into its flat plains. It is also assumed on this basis that, similarly to Lake Khar-Nur, the peculiar sandy massifs located in the basin could preserve relic zones of permafrost, the thawing of which contributed to the moistening of local landscapes. Such humidification zones have been seen on satellite images. There are no glacial deposits in this territory in geological legends. At this stage of research, we confirm the presence in the past of thin glaciers in the study site, caused by mountain-forming processes, and the eruption of Quaternary volcanoes on the territory of Tuva and Mongolia. Tectonic processes contributed to the damming of the Tes Khem River, the main waterway flowing along the northern mountain rim of the basin, the formation of dammed lakes, and their subsequent descent. Extended original sandy massifs located in the basin within the Agardag mountain range, previously considered fluvioglacial deposits, are a result of the descent of dammed lakes.