摘要
腾格里沙漠东南缘的横向沙丘因断面形态不同可分为凸形和凹形两种类型。横向沙丘丘顶至落沙坡为风沙堆积区，沙粒沿滑落面作重力下滑时，较粗颗粒先到坡脚，背风坡的沉积物下粗上细。沙丘迎风坡则因断面形态不同而影响沙丘表面过程。其中，凸形沙丘迎风坡为高饱和风沙流环境，下部有大量蚀余粗颗粒，上部发生加积，故下粗上细；而凹形沙丘的迎风坡则为低饱和风沙流环境，表面普遍风蚀，前积纹层出露表面，沉积物下粗上细，实际上是背风坡沉积物重力分异结果的重现。沙丘高度与平均粒径和分选参数之间具有良好的一致性。风成床面作为一种地形，对风沙地貌表面过程产生了重要影响，这是风沙地貌尚须努力开拓的领域之一。
ranseverse dunes in the southeastern fringe of Tengger Desert can be divided intotwo 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 slopeof 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 bedforms,as one kind of landforms,play san important role in aeolian surface processes,it is also a field for further study.
出处
《中国沙漠》
CSCD
北大核心
1996年第3期215-220,共6页
Journal of Desert Research
基金
国家自然科学基金
中科院兰州沙漠所所长基金
关键词
腾格里沙漠
沙丘
粒度特征
坡面形态
侵蚀
堆积
Transeverse dune Grain size characteristics Slope morphology Deflation and depostition Tengger Desert
