Development of Exogenous Processes and Soil Formation in Steppe Landscapes of the Selenga Middle Mountains (Western Transbaikalia) in the Late Glacial and Holocene

Abstract

Based on the study of sections of unconsolidated sediments and soils formed on area between Selenga and Chikoy rivers, the dynamics of sedimentation and pedogenesis during last 15000 years have been reconstructed. It is shown that the formation of sediments and soils during the Late Glacial took place in conditions of taiga and/or forest-steppe landscapes, which changed into steppe landscapes in Holocene due to climate aridization. Permafrost had a great influence on the formation of soils and the development of exogenous processes in the Late Glacial (15.0–11.7 kyr BP). The warming that occurred in the early Holocene (11.7–8.8 kyr BP), has led to the permafrost degradation, an increase of the active layer and the activation of erosionaccumulative processes. The most intensive sedimentation associated with an aridisation was ~10.5–9.4 kyr BP. In the time span 9.4–8.6 kyr BP, corresponds with an increase in moisture, there was an active development of pedogenic processes. In the Middle Holocene (8.6–3.4 kyr BP) due to the aridity denudation-accumulative processes proceeded fairly rapidly, fading in periods of pedogenesis, the most prominent of which appeared 6.9–5.9 and 4.9–3.6 kyr BP. High dynamics of exogenous processes, which served as the main limiting factor for the pedogenesis were typical for the Late Holocene (3.4–0 kyr BP). This time is characterized by the formation of stratozems and immature organic-accumulative soils. The reconstructed dynamics of sedimentation and pedogenesis correlates with the landscape-climatic changes in the north of Mongolia and the Baikal region. There is a large convergence of climatic variations in the studied area with changes in the climate and vegetation of the North of Mongolia.