Osl Dating Of Holocene Sequence And Palaeoclimate Change Records In Southern Margin Of Mu Us Desert, North China

One of the characteristics of Quaternary climate is frequent changes. Especially like ecological fragile environment area in the desert-loess edge is sensitive to climate changes. Dune fields with several palaeosoil layers are common in marginal desert in Northern China and potentially reflect drought-moist variability in Holocene, which archive millennial-scale patterns of palaeoenvironmental variability. Combining Holocene high-resolute regional climate records with the evolution of East Asian monsoon, the relationship between regional climate changes and global climate changes would be discussed.Three Holocene profiles of aeolian deposits with alternating units of dune sands and sandy palaeosoils record dune building and stabilization at least eight times. In order to establish reliable timing of dune development, this study applied quartz optically stimulated luminescence (OSL) dating techniques to the aeolian sediments features.15 luminescence samples obtained from the three profiles were dated using the single aliquot regeneration (SAR) protocol. Combining with palaeoclimate proxies(e. g., grain sizes, magnetic susceptibilities, element oxide ratio and Rb/Sr ratio, etc), the records revealed as many as eight periods of significant rapid climate changes during Holocene in the region of southern Mu Us desert. The spatial and temporal extent of the data have allowed for correlations to be made with evidence from global climate changes.The first arid episode occurred before 8.5 ka in the early Holocene, with widespread aeolian sand mobilization and sparse vegetation. During 8.5-4.0 ka, climate turned to be warmer and more humid with the occurrence of thick palaeosoil layer, at the same period with Holocene Optimum. When it comes to 4.0～3.0 ka, the dunes rebounded to reactive with strong winter monsoon, and the climate became arid again. Up to late Holocene (since 3 ka), climate fluctuated more frequently, and both of two kinds of monsoon just occupied short time. This period was divided to five stages:3.0～1.7 ka, there is a brief warm episode; an arid stage controlled by winter monsoon in 1.7～1.0 ka; 1.0～0.5 ka, the climate improved and was at the same time with European Medieval Warm Period; then a Little Ice Age during 480～340 a; around 2,300 a experienced a warmer climate with lakes in the desert. It revealed that the human significance of Holocene climate variability since 2 ka, little impact at the beginning. However, after establishment of ancient Tongwan City (1.55 ka), people activity interfered to climate changes. At last, industrial development (500 year ago) played an important role at this region in controlling and rebuilding environment.To sum up, the Holocene climate changes and evolution records from the three sections could be correlated with the worldwide millennial-scale climate shifts, suggesting that the activities of East Asia monsoon in the Holocene may have directly been controlled or affected by global climate system. Since 1500 a, the impact of human being is more and more significant.