The Formation of the Tarbagataika River Terraces (Western Transbaikalia) in the Late Glacial and the Holocene

2021 
The sequence of sediment accumulation of the first and second terraces of the Tarbagataika River and changes in the stages of incision and filling, as well as sedimentation and soil formation over the last 14 kyr in the river valley were revealed. The dynamics of the sedimentation stages and of the phases of their stabilization and pedogenesis was determined by landscape-climatic changes in the study area. The period of geomorphologic formation of above-floodplain terraces was determined. The floodplain sedimentation regime was changed by the subaerial regime on the second terrace of the Tarbagataika River approximately 8 kyr BP. The accumulation of cover deposits on the first terrace began approximately 3.4 kyr BP. Deposits of the second terrace of the Tarbagataika River were formed during the Late Glacial and the Holocene during the last 14 kyr. They are composed of alluvial sediments that accumulated 14.0–8.0 kyr BP and of cover deposits, which accumulated 8.0–0 kyr BP. The first terrace of the Tarbagataika River of the Holocene age is composed of alluvial deposits, which were accumulated 7.0–3.4 kyr BP, and of deposits of the covering complex, which were formed over the last 3.4 kyr. The phases of intensification of erosion-accumulative processes related to increased water discharge were identified. The main stages of soil formation in the study area were determined. The data we obtained are in good agreement with the previously identified stages of pedogenesis in the Selenga middle mountains and adjacent regions of South-Eastern Siberia and Mongolia.
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