MULTIPROXY EVIDENCE FOR LONG-TERM AND MID-PLEISTOCENE CHANGES IN MONSOON DYNAMICS ON THE CHINESE LOESS PLATEAU

We have assembled a multiproxy database for the Chinese loess section at Jiaodao, Shaanxi Province, China (50 km N of Luochuan), that provides new insight into the dynamics of the summer and winter monsoons over the past 2.6 Ma. The database includes information about environmental magnetic properties, pedogenic and total iron concentrations, color indices (rubification and melanization), particle size distribution, and carbonate content. Several paleoclimate proxies, especially soil color index rubification, show a gradual long-term decrease in temperature accompanied with a gradual increase in winter monsoon strength from 2.6 Ma to present, similar to the long-term increase in oxygen isotope values seen in the marine record. In addition, following the mid-Pleistocene climate rearrangement (in loess/paleosol layers younger than 0.65 Ma), some proxies, such as magnetic properties and depth of decalcification, indicate a significant increase in summer monsoon precipitation during soil-forming (interglacial) periods while other proxies, such as particle size, show an increase in winter monsoon strength during depositional (glacial) episodes. This evidence from our continuous multiproxy database from the 170-m thick loess/paleosol section near Jiadoao contributes significantly to the understanding of long term changes in Asian monsoon dynamics of the past 2.6 Ma.