Darhad megaflood (southern Siberia): cause, age and consequence

A combined geomorphological and geochronological investigation was carried out aiming at determining the cause of the Darhad paleolake formation and dating the Darhad megaflood. Based on the analysis of satellite image mapping, new data were obtained revealing conditions of glacial dams along the Shishkhid Gol valley. We hypothesize that large glaciers in Khara-Baryangiin Gol and Ikh-James Gol downstream of the Tengis Gol mouth were the main causes of the highest Shishkhid Gol backwater. The estimated height of this glacial dam there was about 300 m. The presence of paleolake shorelines at an altitude of 1713 m in the immediate vicinity of this glacial dam confirms its dominant role for the formation of the Darhad paleolake. Based on cosmogenic 10Be exposure ages obtained on boulders from four fields of gravel dunes and of an erratic boulder exposed within a bar along the Yenisei River valley in the Tuva Basin, we infer that two among the three age peaks observed may correspond to megafloods at 36–38 ka and 18–23 ka. © 2022