MAGNETOSTRATIGRAPHY AND PALEOCLIMATIC SIGNIFICANCE OF AN EOLLIAN SEQUENCE FROM THE XUANCHENG AREA,ANHUI PROVINCE

A loess-soil sequence near Xuancheng from the Yangtze valley is investigated using magnetostratigraphy and luminescence dating to determine the location of B/M boundary.This boundary is found to be located within the middle-lower part of the so-called plinthitic laterite.,a widely distributed mid-Pleistocene tropical soils in southern China.The magnetostratigraphy data,combining with the OSL age suggests a basal age of the typical eolian depositional loess-soil sequence is about 0 85Ma.This age boundary corresponds to a significant global climate change,also is recorded in the marine sediments and in the loess-paleosol sequence in northern China.It also coincides with two geological events,intensive uplift of the Tibetan Plateau and the extension of the global ice volume.We interpret the onset of eolian loess deposition in the middle-lower reaches of Yangtze River as a result of hydrological and circulation changes associated with above two events occurring at the mid-Pleistocene.