["Shchetnikov, A. A","Bezrukova, E. V"]2025-06-01期刊论文
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This article presents the results of a comprehensive geomorphological and paleogeographic study of the central part of the Oka Plateau (Eastern Sayan). The relief structure of the region is characterized in detail. A special place in it is occupied by elements of the paleohydronetwork: basins of drained moraine-dammed water bodies and abandoned fragments of valleys, including marginal channel. A comprehensive record has been obtained from the bottom sediments of Lake Sagan-Nur, which makes it possible to reconstruct a consistent picture of changes in the natural environment in the lake basin in the Holocene. It is shown that, about 8600-7100 BP, the lake was fed by glaciers, large flood events occurred in its basin, the water level in the lake was higher than today, and it was probably connected to a moraine-dammed paleowater body (traces of which are recorded in the estuary part of the Aynak River valley). Later, about 7100-5500 BP, a sharp drop in the rate of lacustrine sedimentation and a gradual attenuation of the relative amplitude of flood events occurred. After 5500 BP, the warming of the regional climate, especially in winter, and the disappearance of the remnants of the late Pleistocene glaciers caused a gradual expansion of dry areas at lower hypsometric levels favorable for the regional development of pine forests and the rise of the upper boundary of pine on the slopes. At the end of this time interval, the last restructuring of the local hydrographic network occurred and the modern river system was finally formed. Reconstructions for the last 5500 years show a much calmer hydrological regime and sedimentation pattern. Palynological indices also suggest a warming of the regional climate and a decrease in soil moisture, which took place following a change in the influx of solar radiation in the temperate latitudes of the Northern Hemisphere.
