Extension of drylands in northern China around 250 kaBP linked with the uplift of the southeast margin of Tibetan Plateau  

作　　者：WU Haibin GUO Zhengtang FANG Xiaomin ZHANG Jiawu CHEN Fahu 

机构地区：[1]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China [2]Department of Geography,Lanzhou University,Lanzhou 730000,China [3]Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710075,China

出　　处：《Chinese Science Bulletin》2002年第20期1739-1745,共7页

基　　金：This work was supportedby the National Natural Science Foundation of China (Grant Nos. 49894176, 40125001 and 49928101);the National Project for the Basic Research on Tibetan Plateau (Grant No. G1998040809).

摘　　要：Study on two loess sections, one located at Wu-wei near the Tengger Desert in northwestern China, another located near Ganzi at the southeast margin of the Tibetan Plateau in southwest China, reveals a coeval drying step occurred at -250 kaBP. It is expressed by the increase in eolian grain-size at Wuwei, and by a drastic extension of C4 plants and a decrease of loess chemical weathering intensity at Ganzi. Examination of the available eolian data indicates that the event has also been clearly documented in the loess sections near the deserts in northern China, and in the eolian records from the North Pacific. On the contrary, the signal is rather weak for the central and southern Loess Plateau regions as well as for Central Asia, where the climates are influenced by the southeast Asian monsoon and the westerlies, respectively. Since the climate at Ganzi is under strong control of the southwest Asian monsoon, we interpret this drying step as a result of decreased influence of the southwest summerStudy on two loess sections, one located at Wuwei near the Tengger Desert in northwestern China, another located near Ganzi at the southeast margin of the Tibetan Plateau in southwest China, reveals a coeval drying step occurred at ～250 kaBP. It is expressed by the increase in eolian grain-size at Wuwei, and by a drastic extension of C4 plants and a decrease of loess chemical weathering intensity at Ganzi. Examination of the available eolian data indicates that the event has also been clearly documented in the loess sections near the deserts in northern China, and in the eolian records from the North Pacific. On the contrary, the signal is rather weak for the central and southern Loess Plateau regions as well as for Central Asia, where the climates are influenced by the southeast Asian monsoon and the westerlies, respectively. Since the climate at Ganzi is under strong control of the southwest Asian monsoon, we interpret this drying step as a result of decreased influence of the southwest summer monsoon. This decrease in monsoon moisture is attributable to the uplift of the Hengduan Mountains, the southeast margin of the Tibetan Plateau at ～ 250 ka ago.

关 键 词：ARIDIFICATION LOESS-PALEOSOL sequences organic carbon isotope chemical weathering intensity Tibetan Plateau. 

分 类 号：P532[天文地球—古生物学与地层学] P59[天文地球—地质学]