PLEISTOCENE ICE-DAMMED LAKES AND MODERN RESERVOIRS: SIMILARITY AND DIFFERENCE IN GEODYNAMICS AND SEDIMENTATION
The paper provides a comparative analysis of the lithological composition and structure of lake sediments occurring in the Vychegda valley with sediments present in the bed of large flat reservoirs. Studies have shown their close similarity in many characteristics. Sediment transport and storm sedimentation in the coastal zone of ice-dammed lakes, like in modern reservoirs, were the leading processes of morpholithogenesis. A feature of the lithological structure of lake sediments is intercalation of sand and loam. Sands, in this case, are most often of small- and fine-grained polymictic type, containing pebbles and gravel. The deposits are characterized by thin horizontal (usually rhythmic) layering. Morphological signs complicating the identification of the Late Valdai lake are its spatial coincidence with the location of the Middle Pleistocene and Early Valdai lakes, as well as the active modeling of the bed by channel processes at the end of the LGM and swamp formation in the Holocene. The solution to the problem of the existence of a ‘polar’ lake with a level exceeding the Keltma runoff threshold is possible by studying the southern part of the Keltminskaya Hollow (from the village of Kanava to the Kama valley), where it is possible to record the manifestation of lake waters overflow.