EXOGENETIC PROCESSES AND PEDOGENESIS EVOLUTION IN THE TUGNUI DEPRESSION DURING LATE GLACIAL AND HOLOCENE
YU. V. RYZHOV1, V. A. GOLUBTSOV2
1Irkutsk Scientific Center SB RAS, 664033, Irkutsk, Lermontova str., 134, Russia
ryv@irigs.irk.ru
2V. B. Sochava Institute of Geography SB RAS, 664033, Irkutsk, Ulan-Batorskaya str., 1, Russia
tea_88@inbox.ru
Keywords: экзогенные процессы рельефообразования, осадконакопление, почвообразование, ландшафтно климатические изменения, голоцен, позднеледниковье, Селенгинское среднегорье, Западное Забайкалье, relief-forming exogenetic processes, sedimentation, pedogenesis, landscape-climate changes, Holocene, Late Glacial, Selenga Middle Mountains, Western Transbaikalia
Abstract
A comprehensive study of unconsolidated deposits in the Nikolsk section allowed to reconstruct exogenetic and pedogenesis processes developing within the Tugnui Depression (the Selenga Middle Mountains), with the sedimentary strata accumulation dynamics restored at different time intervals. The phases of erosion-accumulative and eolian processes activation have been established (12,9-11,7; 10,2-8,6; 2,1-1,8 cal ka BP), which permitted reconstructing chronology and specific features of the pedogenic stages. Soils indicating stabilization stages of the relief-forming processes are represented by chernozems. Concurrent stages of pedogenesis and sedimentation processes benefited the formation of light- and dark-humus stratozems due to gradual washout and inwash of material in the uppermost soil horizons persistently affected by pedogenesis. Chronologically, the most pronounced phases of pedogenesis are associated with the time intervals of 11,7-10,2; 8,6-2,1 and 1,8-0,6 cal ka BP. The dynamics of sedimentation stages, phases of their stabilization and intensive pedogenesis have been determined primarily by climatic and environmental changes over the past fifteen thousand years in the study area. The obtained results are in good agreement with the stages of pedogenesis and manifestations of exogenetic processes in the adjacent territories of Russia and Mongolia. A polychronous development of exogenetic and soil-forming processes controlled by the landscape-climatic heterogeneity of the study area has been revealed, which makes itself evident in better pronounced stages of enhanced sedimentation in more arid southern areas of the Selenga Middle Mountains, while in more humid environments of their central part the periods of pedo genesis tend to be more extended. The structure of the pedo-sedimentary series of Nikolsk section thus demonstrates the alternating periods of pedogenesis and more intense exogenetic processes and represents changes of regional landscape and climate occurred over the last fifteen thousand years.
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