FORMATION OF THE TARBAGATAIKA RIVER TERRACES (WESTERN TRANSBAIKALIA) IN THE LATE GLACIAL AND HOLOCENE
Yu.V. RYZHOV1,2,3, V.A. GOLUBTSOV1, M.Yu. OPEKUNOVA1
1V.B. Sochava Institute of Geography, Siberian Branch, Russian Academy of Sciences, 664033, Irkutsk, ul. Ulan-Batorskaya, 1, Russia
2Irkutsk State University, Pedagogical Institute, 664003, Irkutsk, ul. Lenina, 1, Russia
3Institute of the Earth’s Crust, Siberian Branch, Russian Academy of Sciences, 664033, Irkutsk, ul. Lermontova, 128, Russia
Keywords: river terraces, exogenous processes, sedimentation, soil formation, Western Transbaikalia
Abstract
The sequence of sediment accumulation of the first and second terraces above floodplain of the Tarbagataika river and changes in the stages of incision and filling, sedimentation and soil formation over the last 14 kyr BP in the river valley were revealed. The dynamics of the stages of sedimentation and of the phases of their stabilization and pedogenesis was subordinated to landscape-climatic changes in the study area. The time of geomorphological forming of terraces above floodplain is determined. For the second terrace of the Tarbagataika river, a change of the floodplain sedimentation regime for the subaerial regime occurred about 8 kyr BP. The accumulation of sediments of the cover genetic complex on the first terrace began about 3,4 kyr BP. Deposits of the second terrace above floodplain of the Tarbagataika river formed during the Late Glacial and Holocene, over the last 14 kyr BP. They are composed of alluvial sediments, accumulating 14.0-8.0 kyr BP and deposits of the cover genetic complex, the accumulation of which has continued since 8,0-0 kyr BP till the present. The first terrace of the Tarbagataika river has the Holocene age and is composed of alluvial deposits, accumulating 7.0-3.4 kyr BP and deposits of the cover complex which formed over the last 3.4 kyr BP. The phases of intensification of erosion-accumulative processes associated with the stages of increased water discharge were identified. The main stages of soil formation in the study area were determined. The data obtained are in good agreement with the previously identified stages of pedogenesis in the Selenga highlands and adjacent regions of Siberia and Mongolia.
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