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Liu Tungsheng; Ding Zhongli(Institute of Geology, Chinese Academy of Sciences, Beijing 100029)  
The summer monsoonal winds over the Asia-African continents consist of three branches: the East-Asia southeast monsoon, the Indian southwest monsoon and the west African monsoon. As these monsoons are forced by different factors,it would be expected that they may have been established in different ages and undergone adifferent evolution history. To date,the bine when the three monsoon circulations wereinitiated in geologic past is still open to debate,but their evolution in the Plio-Pleistocene period has been relatively completely documented by sediments such ascontinental loess and marine eolian deposits. In this study,we conducted a comparisonof the Plio-Pleistocene climatic records derived from the Chinese Loess Plateau,Arabian Sea and low-latitude Atlantic Ocean. The marine climatic records weregenerated from eolian sediments,thus indicative of changes in intensity of monsoonalwinds or the climate in the source regions. Results show that the eolian sequenceshave recorded three climatic shifts of the Pli0-Pleistocene period.They occurred near 2.8~2.5MaB. P., 1.8~ 1.6Ma B. P. and 1.2~ 0.6 MaB. P., respectively. The 2.8~2.5MaB. P. shift is characterized by the increase in amplitude of climatic oscillationsand the occurrence of the 41 000a tilt periodicity. The 41 000a Period becomepredominant near 1.8~1.6MaB. P. At about 1.0 Ma, the 100 000a climatic Periodappeared and become dominant near 0.6MaB. P. Although the details of climaticchanges in the three regions are not necessarily the same, the similarity of the climatic shifts still suggests a common trends of monsoonal evolution over the Asia-African continents. It is indicated that the similar evolution of the monsoonalcirculations may have important implications for human evolution in the late Cenozoic.
【Fund】: 国家自然科学基金!49894170
【CateGory Index】: P531
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