腾格里沙漠东南缘不同发育阶段横向沙丘粒度特征

选取了腾格里沙漠东南缘风沙观测场内经人工平整后流动沙地上出现的新生横向沙丘和观测场外围未经人工干预的原始横向沙丘,采集了其表层的沉积物进行试验分析,探讨了不同发育阶段沙丘之间和沙丘表层不同部位之间沉积物粒度组成的空间差异及其所反映的近地层风沙运动过程.结果表明:腾格里沙漠东南缘横向沙丘以细沙为主(53.87%),其次为中沙(42.57%),粗沙和极细沙含量很少;新生沙丘表层沙粒的平均粒径(1.98 Φ)略大于原始沙丘(2.16 Φ),而分选性都很好.两类沙丘的偏度都表现为近对称,峰度都表现为中等类型;由于沙丘所处发育阶段和尺度不同,即使在同一种风能环境下,两类沙丘及其表层不同部位沙粒的粒径分布也存在明显差异.

Grain-Size Characteristics of Transverse Dune during Different Developmental Stages in the Southeastern Edge of the Tengger Desert

Sand samples are selected from two different kinds of sand dunes, the transverse neonatal sand dune and the transverse untouched sand dune, in southeast margin of the Tengger Desert. The transverse neonatal sand dunes were newly formed on the flat floating sand where sand dunes are bulldozed in a sandstorm observation field. The transverse untouched sand dune is out of the sand storm observation field and never be affected by human. Samples are taken from the near-surface to analyze grain size distribution. The goal of our work is to explore the spatial differences of the composition of particle size on the sediment surface between the two kinds of sand dunes, and between the different parts of the same kind of sand dunes, which reflect the process of the sand movement around the surface. The results have shown that the main sand of the transverse dunes in the southeast edge of the Tengger Desert was thin sand (53.87%),the subsequent part is medium sand (42.57%), but the coarse sand and the more subtle sand are all scarce. The average diameter of the neonatal sand dune was bigger than the untouched sand dune, and both of the two types of sand dunes have good separation characteristic. The gradient of them is characterized by symmetrical type, and the kurtosis of them is belong to medium type; Because of the difference of two types of sand dunes in developmental stages and scales, even in the same wind conditions, there are obvious difference about the particle size distribution on the surface and these two kinds of sand dunes at different position.