Distribution and Compositions of Loess Sediments in Yili Basin,Central Asia

The loess record of Central Asia provides an important archive of regional climate and environmental change. However, in contrast to the intensively investigated loess deposits in the Chinese Loess Plateau, Central Asian loess sediments are still insufficiently known and poorly understood. Based on satellite and topography, coupling with previous literature and field investigation, the authors investigate the distribution of loess sediments in the Yili Basin, central Asia. In order to identify the physical, chemical and mineral compositions, the authors carried out grain-size, geochemical and mineralogical analyses on collected surface soil and loess samples. Grain size measurements reveal that the loess in Yili Basin is dominated by silt and have minor sand, which is coarser than that of the Chinese Loess Plateau, indicating a close source. The mineral components of loess in this region are dominated by quartz, feldspar and carbonate with minor chlorite and muscovite. Geochemistry of loess in the Yili Basin are characterized by high contents of SiO2, Al2O3 and CaO, and by minor Fe2O3, MgO,K2O and Na2O. In contrast to the Chinese Loess Plateau, the loess in Yili Basin is rich Na2O and CaO, which indicates that loess in Yili Basin originated from a relative dry-clod and weak chemical weathering environment.