GEOLOGICAL RECORD OF THE VICISSITUDES OF THE PALAEO-MONSOON IN NORTH PART OF THE EAST CHINA SEA DURING THE LAST STAGE OF LATE PLEISTOCENE

The paleao-monsoon activities in East Asia experienced a change of vicissitudes since 18 kaBP. In the maximum phase of last glacial age,dry and cold climate prevailed,resulting in the desertization in most part of the Bohai Sea,the Yellow Sea and the East China Sea. Then,with the withering of dry and cold climate,there appeared stiff clay sediment in the delta of the Changjiang River. Because the further declining of paleao-monsoon and the gradual rising of sea level after 15ka approached,the northeast wind from shelf area was not the dry and cold air-current any more,but the cold and damp one with higher humidity,which produce an advantageous environment for the development of the swamp. As a result,a thin-layered turf was formed before the seawater transgression in Holocene. The developing process of the paleao-monsoon since the last stage of late Pleistocene is well correspondent to the formation of shelf desert, stiff clay and turf layer respectively. It is suggested that the such sequences in the delta region of the Changjiang River may be the best record of the vicissitudes of the palaeo-monsoon.