AEOLIAN-DUST DEPOSIT TO THE SOUTHWEST OF THE POYANG LAKE DURING THE LAST GLACIAL AGE

The sandy hills (namely Shashan) on the shore of Poyang Lake were aeolian-dunes formed by winter-monsoon in the last glacial age. In the course of investigating the environment of the sandy hills, the authors found that deposit strata situated to the leeward of the Shashan, were very similar to the northern aeolian-dust loess and the Xiashu loess near the Yangtze River. According to typical study on Daguling section in Xinyu City, they were the aeolian-dust deposit developed in the last glacial age. On the basis of analyses on the features of distribution, material component, sedimentary structure,and spatial change of grain-size and formation age of the Quaternary deposit from Poyang lakeside to Xinyu City, the authors suggested that they should have been the aeolian-dunes and their derivative aeolian-dust system formed by paleo-monsoon in the special climatic condition since the last glacial stage. During the last glacial stage, the continental climate in the south Yangtze River area greatly strengthened and the strong winter-paleo monsoon deflated the Poyang Lake area. It revealed the abundant sands of the lakes and rivers and developed "desertification environment". The coarse sand on the beaches of the lakes and rivers was eroded and gathered near the Poyang lakeside, and formed aeolian-dunes (namely Shashan). While the fine sand and dust material were carried and transported to leeward, and deposited around the Xinyu as the derivative aeolian-dust of the Shashan. The aeolian-dunes near the Poyang lakeside and their derivative aeolian-dust near the Xinyu constitute a special geographic environment system formed by the interaction of atmosphere, hydrosphere and geosphere since last glacial stage in the Poyang Lake area. Their development provided evidence for environment degeneration of Boyang Lake area since late Pleistocene, and is also regional response to the desert-loess deposition in northwest China.