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Abstract The surface and sublayer gobi sediment grain size composition, average grain size, sorting coefficient, skewness and kurtosis were analyzed by collecting sediment samples in field and testing grain size characteristics in laboratory. The results show that except for the top of alluvial-proluvial fan, the majority grain size of surface sediment was occupied by stone, but that of sublayer sediment was sand. In surface sediment, the mean grain diameter was relatively large composed by stone and gravel, but in the sublayer, the mean grain size had significantly thinner trend. Therefore, the average grain size changed smaller from low residual mountain to alluvial-proluvial fan edge. The grain sorting in different sediment layers was poor or poorer, but only was medium on low residual mountain and nearshore lake shallow. The grain skewness of surface sediment was positive or very positive, accounting for 76.93% of the total sampling，while the skewness of sublayer sediment was negative or very negative，accounted for 84.62% of the overall sampling. Kurtosis frequency curve of grain size in surface sediment was sharp or very sharp，accounting for 69.23%，followed by medium, accounting for 15.38%，while in sublayer sediment was flat, very flat or medium, accounting for 76.93%. In general, gobi sediments appeared the characteristics of coarse grain size, bad sorting, positive skewness and sharp curve features, which reflected the sedimentary environment, morphological characteristics, erosion and deposition pattern. The results could provide the reference for the gobi classification.
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Received: 04 July 2012
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