Recent Data of Multidisciplinary Studies of the Major Pleistocene Climatic Events: Glaciations, Formation of Ice-Dammed Lakes, and Their Catastrophic Drainage in Altai (Mountains of Southern Siberia)
The use of geologicalgeomorphological and geochronological (14C, OSL) methods allowed establishing that the bordering mountains of the Chuya basin (Russian Altai) were affected by glaciation as early as the Middle Pleistocene, about 160180 ka (MIS 6). However, the ice-dammed lake with the highest (up to 2100 m a.s.l.) strandlines in the Chuya and Kurai basins existed later than 9080 ka, i.e., in the Late Pleistocene. This chronological benchmark limits the influence of the catastrophic outburst floods of the largest lakes on the accumulation of the Inya formation in the Chuya and Katun river valleys. It is confirmed that a large ice-dammed lake existed and had a water level of at least 1730 m a.s.l. in MIS 2 in the Kurai basin. The lake drained no later than 16 ka. Synchronously (about 1716 ka) the accumulation of diluviallacustrine cyclites began in the Inya mouth. It was found that the accumulation of the Saldzhar formation in the Katun River valley between the mouths of the Chuya and Sema rivers was long-lasting during the entire MIS 2 not only as a result of flood events, but also due to gradual hydrological processes. It is necessary to revise the concept adopted by SibRISC in 2018. This concept assumes (i) the absence of ice-dammed lakes in intermont basins of Russian Altai in MIS 2 and (ii) the accumulation of the Inya and Saldzhar catafluvial formations, as well as the high and medium terraces they deposited in the valleys of the Chuya and Katun rivers before 90 ka.
