ESTABLISHMENT (RE-ESTABLISHMENT) OF THE DUNE SYSTEMS AND PROVENANCE OF THE AEOLIAN SANDS IN THE HUNSHANDAKE SANDY LAND, EASTERN INNER MONGOLIA, CHINA

Sedimentary sequences occurring in desert dunes reflect changes in desert systems, and as such may contain signals useful for recognizing spatial and temporal changes of deserts and their response to regional and global climate fluctuations. Recognizing provenance of aeolian sediments is helpful for understanding the dynamics of the dune formation, the role of various surface processes and their interactions. Geomorphological, geochemical and palaeoenvironmental studies within the dune fields of the Asian middle-latitudes have provided some solid evidence for interpreting the history of these sand seas and their sediment sources. Using the Hunshandake (Otindag) Sandy Land, a 24,000 square kilometer-large area currently covered primarily by stabilized dunes and located in the semi-arid zone of eastern Inner Mongolia, China, as an example, we studied the initiation and variation in the dune landscape and the sediment sources in the eastern portion of the desert belt in northern China. On the basis of physical, biochemical and geochemical indicators in the sediments and OSL chronology, we herein argue that current dune system in the middle latitudes of eastern Asia is established (re-established) in the late Holocene, much younger than previously assumed and that the region has responded sensitively to climate change during the late Quaternary. Our major and trace elements data show that the sources of the coarse and medium fractions of the dune sands change distinctly within the Hunshandake, suggesting diverse sources constrained by local geology and geomorphology. In the other hand, the fine fractions in the entire sandy lands are quite geochemically homogeneous, indicating intensive mixture by aeolian processes. Immobile element features suggest that the sands of the Hunshadake should be transported mainly from the surrounding mountains by fluvial processes rather than from any remote regions via aeolian transportation.