The Sand Seas of northern China: Important sinks and sources of global sediment fluxes and their changing roles during different climate conditions of Late Quaternary

Abstract:

Although the occurrence of aeolian sands in sedimentary sequences has been widely used as indicators of desert formation or proxies of desert climate, one should be aware that accumulation of aeolian sands does occur along river channels, in lake shores not necessarily associated with arid environment. Our ongoing geomorphological and paleoenvironmental studies in the deserts of northern China reconfirm that formation of sand seas is dependent on not only erodibility (arising from bare surface due to aridity) and wind power but more importantly sand availability related to sediment cycles under interactions between fluvial, lacustrine and aeolian processes. Here we present our ongoing geomorphological and paleoclimatic research on the Late Quaternary landscape and climatic changes in the Taklamkan Desert of northwestern China, the largest sand sea of China in arid zone, and in the Hunshandake Sandy Land at the east part of the Asian mid-latitude desert belt under semiarid climate. We find out that the occurrence of tall sand dunes in the over 300,000 km² large Taklamakan Sand Sea is closely related to the sites of intensive fluvial sedimentation and convergence zone of surface winds. In the case of Hunshandake, the dunes (although much smaller) mainly occur along the shorelines of the former lake basins, and sediment sources are generally limited because of open hydrological systems in the south and east portions of this desert. The sedimentological and geomorphological records suggest that the climate has changed between arid and less-arid conditions in both of these deserts during Late Quaternary. Under wetter conditions the Taklamakan acts as an important sink of sediments brought by rivers with headwaters in the Tibetan Plateau and Tianshan, while under more arid conditions it acts as an important global sediment source whose dust is transported not only to East Asia and Pacific but also to Greenland ice via westerlies. The Hunshandake has the same pattern of function in global sedimentary cycles but with a much smaller role because of smaller extension and weaker relief energy. The Taklamkan and Hunshandake are potentially ideal laboratories for understanding interactions between global sediments fluxes, climate change, hydrological systems and tectonics.