Multiproxy Evidence for Long-term Changes in Summer and Winter Monsoon Dynamics on the Chinese Loess Plateau

We have assembled a multiproxy database from a 170-m thick loess/paleosol section near Jiadoao, Shaanxi Province, China. The database includes information about environmental magnetic properties, pedogenic and total iron concentrations, color indices, particle size distribution, carbonate content, and stable isotope ratios. These data from Jiaodao section, which is only 50 km north of the classic Luochuan section, provide excellent insight into the dynamics of the summer and winter monsoons over the past 2.6 Ma. Several paleoclimate proxies imply a long-term decrease in temperature accompanied with a gradual increase in winter monsoon strength from 2.6 Ma to present. These trends are similar to the long-term increase in oxygen isotope values seen in the marine record. In addition, for the interval after 0.65 ka, 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. Our multiproxy approach contributes significantly to the understanding of long-term changes in Asian monsoon dynamics and provides a terrestrial insight into the nature of a mid-Pleistocene climate shift.