Characteristics of blown sand deposits in the Sanjiangyuan region

The source area of the Yangtze, Yellow and Lancang (Mekong) Rivers is named Sanjiangyuan in China and is situated in the northeastern Tibetan Plateau. Blown sand deposits are widely distributed in Sanjiangyuan. Field investigations and laboratory analyses were used to determine the size distributions and mineral compositions of 20 samples of blown sand deposits and 15 samples of water erosion deposits from this region. The size distributions of 21 samples of moving sand dunes and 63 samples of water erosion and gravity erosion deposits were also obtained from the literature. The research shows that blown sand deposits in different regions have well-sorted size distributions that are totally different from water erosion and gravity erosion deposits. Moving sand dunes were fixed by vegetation and experience long-term weathering so the clay minerals and humus are increased. The fraction of clay mineral in fixed sand deposits is twice that of moving sand dunes. The humus content in fixed sand deposits is three times that in moving sand dunes. As a result, fixed sand deposits contain twice as many fine particles than moving sand dunes. Thus, sorting coefficient of fixed sand deposits is then twice than that of moving sand dunes.