Quantitative measurements on the paleo-weathering intensity of the loess-soil sequences and implication on paleomonsoon

The loess-soil sequences in northern China provide a near continuous record of Quaternary paleoclimate. The pedogenetic intensity of the sequences is closely linked with the variations of the East Asian summer monsoon. In thi s study, 2181 samples from the Changwu and Xifeng loess sections are analyz ed and two high-resolution paleo-weathering timeseries of the last 1.2 Ma a re generated, using the ratio of CBD extractable free Fe2O3(FeD) versus the total iron (FeT), This new index is compared with micromorphological featu res, low-frequency magnetic susceptibility, frequency-dependent magnetic su sceptibility, and the Rb/Sr ratio([5,6]). The results suggest that the FeD/ FeT ratio is able to better reflect the degree of soil development. Since t he chemical weathering of loess in the Loess Plateau region mainly depends upon the summer precipitation and temperature under modern climate conditio n, which are closely associated with strength of summer monsoon, and the ch emical weathering intensity of loess primarily reflects the variations of t he summer monsoon circulation.