Loess Accumulation in the Southern Part of European Russia at the End of the Quaternary Period

The origin of the loess deposits of the Cis-Caucasus Region, which form an almost continuous cover on the plains from the Sea of Azov to the Peri-Caspian Depression, is one of the controversial issues of paleogeography of the southern part of European Russia. The remarkably high thickness (up to 140 m) and extended coastal outcrops in the west and in the east of the region studied is of special interest to geologists and geographers who consider the loess strata as a unique record of climate conditions of the Quaternary period. The data on the structure, texture, and geochronology of the Upper Pleistocene and Holocene loess deposits, obtained from the study of 25 borehole logs and outcrop sections, distributed through the territory of the Cis-Caucasus region were received. The average sedimentation rates and the average sand fraction content were estimated for the stratigraphic units correlated with the global climatostratigraphic units (marine isotope stages (MIS)). It has been established that the source of the loess (wind erosion areas), are the valleys and estuary alluvial plains of large rivers: the Terek, Kuma, Volga, Kuban, and Don. The Peri-Caspian Depression was the dominant source of mineral dust throughout Late Pleistocene and Holocene. Large massifs of weakly fixed sands and sandy loams of the western Caspian region in combination with a high level of climate aridity and strong east winds created the prerequisites for the transport of huge volumes of mineral dust westward as far as the Sea of Azov.