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

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 FeO(Fed) and total FeO(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 δO record. The firstsuggests a rather stable summer monsoon pattern during the Last Interglacial period (marine δOstage 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.