Aeolian Processes in Forest-Steppe Landscapes in the Upper Angara Region in the Holocene

Abstract

Presented are the results from investigating the aeolian sand massifs in the Belaya river valley. The Belaya, Kholmushino and Usolye massifs with the area of 2, 1.4 and 269 km, respectively, are singled out. They are differentiated by the degree and magnitude of manifestation of aeolian processes, and by the morphology of landforms. The Belaya massif is characterized by narrow gully‒low ridge topography. The initial fluvial relief is moderately modified because of the isolated location of the area in the spur of the incised meander and its boundedness by the slope of the narrow segment of the valley. In the Kholmushino massif located in the zone of contact of the segment of the incised channel and the broadening of the valley, aeolian forms were able to evolve fully but they occur only along narrow terraced surfaces of the rectilinear segment of the valley. The more favorable conditions emerged for the evolution of the Usolye massif. The broad-floodplain type of Belaya channel promoted accumulation of significant volumes of sandy material and its free transport in the process of aeolian morphogenesis. The most intense aeolian accumulation was observed in the lower reaches of the Belaya at the interface of the Late Glacial and Holocene (from 13.1 kyr BP) and was proceeding throughout the Early Holocene until 8.9 kyr BP when there occurred a decrease in activity of the aeolian processes and an intense soil formation began. The landscape-climatic conditions of the Atlantic period were favorable for the attenuation of aeolian activity and for a gradual fixation of sands by vegetation. The intensification phases of the aeolian processes were replaced by stages of a decrease in activity of the aeolian morphogenesis and soil formation in the intervals 9.3‒8.6; 6.7‒6; 3.5‒2.6 and 1.2‒0.9 kyr BP. The pedogenesis stages coincided with an increase in heat and moisture availability. Analysis of the findings suggests the rhythmic behavior in the evolution of the region’s natural environment in the Late Glacial with the manifestation of aeolian phases every 4‒5 ka and phases of intense soil formation every 1.9‒2.5 ka.