Main periods of soil formation and sedimentation in forest-steppe landscapes of the Selenga midland during the Late Glacial and Holocene

Abstract

On the basis of a comprehensive study of soil-sedimentary sequences, we reconstructed the history of soils and landscapes development in the central part of the Selenga midland (Kuitunka river basin). For the Late Glacial and Holocene four stages of deposition and soil formation have been identified: Late Glacial (15.0-11.7 kyr BP), Early- (11.7-8.8 kyr BP), Mid- (8.8-4.7 kyr BP), and Mid-Late Holocene (4.7-0 kyr BP). The Late Glacial period is characterized by short-lasting and contrasting climatic changes, leading to frequent successions of the phases of activation of erosion-accumulation processes and soil formation. We identified three phases of pedogenesis and the corresponding stages of climate warming and humidification (14.5-14.1; 14.0-13.3, and 13.0-12.6 kyr BP). Intensification of exogenous processes occurred in the time intervals 15.0-14.5; 14.1-14.0; 13.3-13.0, and 12.6-11.7 kyr BP. During the Early Holocene period the most optimal conditions for soil formation take place in the first half of the Preboreal (11.7-11.0 kyr BP). Later, there occurred an enhancement in climate aridization whose evidence manifests itself as high-carbonate aeolian-colluvial deposits. Pedogenesis in the second half of the Preboreal (11.0-10.5 kyr BP) and during the Boreal period (10.5-8.8 kyr BP) was proceeding in steppe/forest-steppe conditions under warmer and less humid climate in comparison with soils formed in the Late Glacial and first half of Preboreal. The Mid-Holocene and the Mid-Late Holocene periods were distinguished by relatively stable landscape-climatic conditions, implying formation of well-developed soils and stabilization of erosion-accumulation landforms. Two long-lasting intervals of intense pedogenesis (8.8-6.9, and 4.7-0 kyr BP) can be identified. Soil formation was proceeding under steppe vegetation in rather warm and slight moistening climatic conditions. From the Atlantic to the Subatlantic climate became more arid. Activisation of exogenous processes occurred in interval 6.9-4.7 kyr BP.