关键词: 腾格里沙漠, 横向沙丘, 粒度特征, 坡面形成, 侵蚀与堆积

Abstract: Transeverse dunes in the southeastern fringe of Tengger Desert can be divided into two morphological types: convex and concave, according to the relative position of dune crest and brink. Systematical sampling of surface sediments on these dunes shows thatgrain size and sorting vary with position of the dunes. On the slipface of both dunes, mean grain size decreases and sorting improves from base to brink or crest as the largergrains will take precedence to avalanche down the slipface than smaller ones. Slope morphology showed significant influences on surface sorting processes of the stoss slope of the dunes. On the convex dune, formed in highly saturated sand airflow environment, coarser grains as a lag on lower and steeper slope and finer grains deposited on the upper and gentle slope. So the mean grain size becomes better toward the crest. On the concave dune, formed in low saturated sand airflow environment, mean grain size decreases and sorting improves toward the crestdue to the emergence of the leeside cross strta caused by deflation of stoss slope and duneadvance, which resulted from, in fact, the reappearance of avalanching grading mechanism of slipface. In addition, there is good agreement among the mean grain size, sorting parameter and the dune height. Therefore, aeolian bed forms, as one kind of landforms, play san important role in aeolian surface processes, it is also a field for further study.

Key words: Transeverse dune, Grain size characteristics, Slope morphology, Deflation and depostition, Tengger Desert