Grain Size Characteristics and Origin of the "Wushan Loess" at Wushan Area

Based on the grain size analyses of "Wushan Loess" at Wushan area, the causes of "Wushan Loess" are discussed in this paper. The results show as follows. The component particles of the "Wushan Loess" are predominantly less than 50 μm with the average content of > 50 μm about 16.9%; the average content of coarse silt (10-50 μm) is 43.1% as the "dominant group" of the "Wushan Loess"; the average content of 5-10 μm group is 14.5% and < 5 μm group makes up 25.5%. The characteristics of grain size parameters and frequency and probability cumulative distribution curves are the same as those of typical atmospheric dust sediment, which shows that the "Wushan Loess" is of aeolian origin. C-M, L-M, A-M chart and statistical indices of grain size distribution are obviously different from those of fluvial sediment and are the same as those of Xiashu Loess distributed in the middle and lower reaches of the Yangtze River. The most discriminant analysis result is of negative value, which displays that the aeolian origin is prevailing and individual layer is affected by water flow action.