The Environmental Changes In The Upper Reaches Of Wei River Of The Last Interglacial

The upper reaches of Wei River is located at the southwest part of Loess Plateau. Since the Quaternary there has been quite thick sedimentary loess, which mainly is affected by the East Asian monsoon, therefore it can exhibit the evolvement of the East Asian monsoon perfectly.With the analysis on the high resolution climate proxies, we rebuild the gyration climate change sequence in the upper reaches of Wei River from the last interglacial to present, study the response to the signal of global climate changes and regional characters of the climate evolvement, discuss the driving force and interaction mechanism of the climate evolvement.Because of the effects of global climate change, Fanjiatai section records some special global climate events and represents the global characters. In the last interglacial, the upper reaches of Wei River were mainly controlled by the summer monsoon, so it presented much wetter as compared with the northwest of the loess plateau. Because the summer monsoon was stronger and the deposition of dust were little during the early of the last interglacial (the Stage 5e of the marine oxygen isotope records) ,the paleosol developed downwards, and its grain size was bigger.In the whole Last glacial,the winter monsoon was much powerful,even in MIS3 stage, the climate was still dry and cold. The lakes in the dust source had more water,and it induced that the grain size was little during the early of the stage MIS2 than the late,all that showed the regional climatic character, we got more sections from the former,and divided them into districts,we found that those secthons mainly distributed in the middle and southern of the Loess Plateau.However,those sections that near the margin of the desert could not record more information because the material of vicinity interfered in.Heinrich events and Dansgaar-oeschger cycles were well presented in coarse fraction (>63μm) ,and corresponding to ¹⁸O in GISP2,it indicated that the coarse fraction (>63μm) well represented stronger winter monsoon of dust events in the south of Loess Plateau.The driving force of the winter monsoon and the summer monsoon was different.The winter monsoon was driven by the global ice volume,and it was wellcompared with the SPECMAP.The summer monsoon was driven by global ice volume in the glacial-interglacial scale,and also driven by other factors in more little scale.