Late quaternary evolution and paleoclimates, western Alashan Plateau, Inner Mongolia, China

The western Alashan Plateau of Inner Mongolia, China, is a potentially impo rtant region for understanding late Quaternary atmospheric circulation chan ges associated with shifts in the westerlies and the Asian monsoon climate systems. As a result of past and present geomorphic processes, the present- day topography is dominated by megadunes, desert plains, lake beds, pedimen ts and desert gorges. The megadunes consist of active and relict formations . The consolidated surfaces of dunes, ancient lake sediments and terraces o f the dune fields and their margins show a roughly 10 ka-scale periodic app earance of a more humid climate. The chronology was provided by comparison of radiocarbon dates obtained from different landforms. Sedimentological an alysis of sand samples confirms the diversity of dune sand sources and the long existence of lakes among the dunes. The alluvial fans and desert gorge s are evidences of past fluviatile processes. The increased precipitation a t ca. 30 ka BP and 19 ka BP is ascribed to the influences of westerly air m asses. The Holocene periods of more humid conditions were caused by fluctua tions of the Asian summer monsoon.