Geographic Differentiation of the Last Interglacial Paleosol Layer in the Chinese Loess Plateau: Its Climatic and Chronological Implications

The Loess Plateau of China has the most complete and extensive terrestrial records of Quaternary sedimentation on Earth, and analysis of the soil formation and its geographic differentiation should provide useful information on climate history and global circulation modeling. This project will study the last interglacial paleosol (called 'S1' and dates from 128,000 to 73,000 years ago) with soil samples selected along a SE-NW transect in the Chinese Loess Plateau. The goal of the research is to reconstruct the detailed history of the last interglacial Asian monsoons. To achieve the goal, four sets of analyses will be conducted. First, the paleosol S1 pedostratigraphy and chronology will be established through sample dating and other laboratory analyses. Second, the soil characteristics will be examined, including the meso-scale and mirco-scale morphology. Third, the summer monsoon proxy will be calibrated through analyses of the histories of leaching and general weathering of the soil profiles. Fourth, the winter monsoon proxy will be calibrated through analyses of the bulk size distribution and larger quartz size to determine the degree of post-depositional weathering.

To comprehend the scope of future climate changes with considerations of severe human impacts, the last interglacial period deserves special attentions because it serves us best in understanding the natural processes of interglacial times. However, the global records of climate change for this period are inconsistent, and more data are needed from different regions to validate the spatial scale of various abrupt climatic events. A number of basic questions require an improved knowledge of climate histories of continental interiors. For instance, what are the relative roles played by atmospheric and oceanic circulation in transporting heat and water vapor from low to high latitudes and from oceans to interiors. Only by defining and quantifying the specific responses of regional environmental systems to global changes will major uncertainties about the mechanisms of global changes be understood. The Chinese Loess Plateau, a product of interactions between a high-latitude continental winter monsoon and a low-latitude oceanic summer monsoon, is perfectly located to validate the various hypotheses of the mechanisms of global changes. This study of monsoon history will be useful to future more accurate global change modeling.