A review on research of loess and environmental change in west Sichuan Plateau of the eastern Qinghai-Tibetan Plateau

Loess widely distributes in river valleys and fault basins of west Sichuan Province in the eastern Tibetan Plateau.It is mainly aeolian deposit carried by Westerlies,Plateau Winter Monsoon or near surface wind.The dust came from kinds of sediments from local or the interior of the Qinghai-Tibetan Plateau,such as glacial deposits,congelifraction materials,fluvial,lacustrine,aeolian and slope deposits,etc.Secondary loess caused by overland flow could be seen in parts of this area.The earliest loess,which is now mainly preserved in the older physiographical positions,started to deposit at Early Pleistocene(1150 ka).However,the most widely distributed loess,which is now preserved in the younger physiographical positions,deposited since early Late Pleistocene.The Qinghai-Tibetan Plateau might be elevated into cryosphere in Early Pleistocene as influenced by Kunlun-Yellow River Movement.After that,the atmospheric circulation changed,accompanied by strengthening plateau winter monsoon and sustained aridity.Thus initial loess accumulated in west Sichuan.Gonghe Movement caused rapid uplift of Qinghai-Tibetan Plateau since early Late Pleistocene.This resulted in acceleration of deposition rate and expansion of loess in west Sichuan.The climatic fluctuation of cold-dry and warm-humid since Early Pleistocene had been recorded by the loess-paleosol sequences in this area.And it has experienced multiple strong/weak alternation of winter and summer monsoon since Late Pleistocene.Issues like origin,provenance,ages and deposition rate of loess,high resolution climatic change and the driving force of climate recorded by loess strata in this area,are still needed to deeply investigate.