Weathering Signals of Millennial-Scale Oscillations of the East-Asian Summer Monsoon over the Last 220 ka  

作　　者：GU0 Zhengtang PENG Shuzhen WEI Lanying LIU Tungsheng Institute of Geology, Chinese Academy of Sciences. P. O. Box 9825, Beijing 100029, China 

出　　处：《Chinese Science Bulletin》1999年第S1期20-25,共6页

摘　　要：This study generated a high-resolution paleoweathering record of the loess-soilsequence from the central Loess Plateau covering the last 220 ka using the ratio between the CBD（citrate-bicarbonate-dithionite） extractable free Fe₂O₃ （Fed） and total Fe₂O₃ （Fet）. The new proxyshows a series of millennial oscillations, which are not necessarily documented by magneticsusceptibility from the same site. Because chemical weathering in the region depends mainly uponsummer precipitation and temperature, we interpret these changes to be a result of millennial-scalevariations in the strength of the East-Asian summer monsoon. Over the last glacial period, there isgeneral agreement between the loess weathering record and the GRIP ice δ¹⁸O record. The firstsuggests a rather stable summer monsoon pattern during the Last Interglacial period (marine δ¹⁸Ostage 5e). Large amplitude millennial oscillations of the summer monsoon seem to be particularlycharacteristic of the last glacial period whereas the fluctuations for the older periods are smoother.This study generated a high-resolution paleoweathering record of the loess-soil sequence from the central Loess Plateau covering the last 220 ka using the ratio between the CBD (citrate-bicarbonate-dithionite) extractable free Fe_2O_3 (Fed) and total Fe_2O_3 (Fet). The new proxy shows a series of millennial oscillations, which are not necessarily documented by magnetic susceptibility from the same site. Because chemical weathering in the region depends mainly upon summer precipitation and temperature, we interpret these changes to be a result of millennial-scale variations in the strength of the East-Asian summer monsoon. Over the last glacial period, there is general agreement between the loess weathering record and the GRIP ice δ^(18)O record. The first suggests a rather stable summer monsoon pattern during the Last Interglacial period (marine δ^(18)O stage 5e). Large amplitude millennial oscillations of the summer monsoon seem to be particularly characteristic of the last glacial period whereas the fluctuations for the older periods are smoother.

关 键 词：MILLENNIAL-SCALE changes loess-soil sequence MONSOON 

分 类 号：P532[天文地球—古生物学与地层学]