Contribution of Loose Sediments in Local Areas to Loess Deposits in the Mu Us Desert

The extensive loess deposits in northern China provide important terrestrial archives of Quaternary climate and environmental changes. Loess records have been studied extensively in the Chinese Loess Plateau, but loess records in the Mu Us Desert are often underrepresented. The material sources and sedimentary characteristics of loess in the Mu Us Desert are poorly understood. To address this, 10 loess sections and a set of surface samples with different sedimentation types in the Mu Us Desert are analyzed for their grain size distribution. The grain size dataset of 10 loess sections is subdivided in four end members (EMs) by means of the end member modeling, and the EMs are compared with the grain size of surface samples. Through the above work, we obtain the following information. (1) The modes of EM1 4 are 14μm, 44μm, 76μm and 177μm, respectively, representing the different transport and deposition processes from different sources. Among them, EM1 is identified in long-term suspension from distant sources, EM2 and EM4 are identified in short-term suspension and saltation driven by dust storms from local sources, EM3 is somewhere in between EM2 and EM4. (2) The proportional contribution of EM2 4 is gradually increasing or changing irregularly in the northwest-southeast direction, which is inconsistent with the East Asian winter monsoon. It indicates that the loess in the Mu Us Desert has been supplied from a proximal dust source, which is because the richness and grain size of loose sediments such as alluvial sediments, alluvial-lacustrine sediments and dune sands in the vicinity of loess sections are in coincidence with the grain size of loess. (3) The dense vegetation in the southeast of Mu Us Desert is more likely to capture the dust transported by low level, which may promote the spatial difference of the proportional distribution of the EMs.