Record of Holocene Changes in High-Mountain Landscapes of Southeastern Altai in the Soil-Sedimentary Sequence of the Boguty River Valley

摘要

The results of morphosubstantive genetic study of a soil-sedimentary sequence with four buried soils in the Boguty River basin (southeastern Altai) are discussed. A comparative analysis of the surface and buried soils in the valley of a tributary of the Boguty River allows us to distinguish between the following stages of the development of valley landscapes: (1) 11-8 ka BP, humid to semihumid stage with the warmest climate and widespread development of forest vegetation with the formation of texture-differentiated soils with a dark humus horizon; (2) 8-7 ka BP, the stage of relative cooling and humidization of the climate; disturbance of the valley landscapes by a mudflow; the formation of thin short-living dark-humus gleyic soils with cryogenic features under the meadow-steppe vegetation; (3) about 7 ka BP, the stage of transformation of the earlier formed profiles by solifluction processes; (4) 7-&2.7 ka BP, the stage of stabilization of the slopes and the development of cold meadow-steppe/steppe pedogenesis under conditions of a small deficit of moisture; (5)about 2.7 ka BP, a short stage of aridization and activation of eolian followed by stage (6) Al-Fe-humus pedogenesis under the tundra/meadow-steppe phytocenoses with a shift from humid to arid climatic conditions of the next (7) stage of the cryoaridic steppe pedogenesis. Modern pedogenesis proceeds under the cold and dry conditions that are most severe since the beginning of the Holocene. The obtained data are in agreement with the existing notions about the evolution of geosystems in the southeastern Altai in the Holocene and make them more detailed.