Depositional environments of the Pleistocene loess-soil series inferred from sand grain morphoscopy—A case study of the East European Plain

摘要

Morphoscopy of sand grains from the Late Pleistocene loess-paleosol series exposed on the East European Plain along a longitudinal profile, from the southern limit of the Late Pleistocene ice sheet to the Azov Sea coasts is examined. The data presented refer to three main zones of the loess accumulation different in characteristics of the processes: the northern zone, including the vicinity of the Valdai ice sheet; the middle zone with the maximum sedimentation rate; and the southern zone adjoining seacoasts. The earlier part of the Valdai glacial epoch (before the Bryansk interstadial) was distinct for a rather moderate rate of subaerial processes without any noticeable spatial differentiation with respect to the latitudinal zones. In post-Bryansk time (after ～24 ka BP) the most active dust accumulation is recorded in the middle zone. The maximum thickness of the Late Pleistocene loess has been recorded there, in the middle reaches of the Dnieper River. In the northern zone the rate of dust settling was not so high, presumably due to high speed of descending winds from the ice sheet. In the southern periglacial zone aeolian abrasion of sand grains was less pronounced as compared with areas farther to the north.