【摘要】 通过对中国干旱区8种不同成因沉积物吹蚀速率的风洞实验,从风蚀动力机制上讨论沙漠的物质来源及其与沙丘发育和沙漠形成的关系。对比风洞实验测定结果发现,在我国西北干旱区及其周围分布最广的8种沉积物中,吹蚀速率从大到小依次是:湖相沙>河流沙>砂页岩风化物>洪积物>冰水沙>花岗岩风化物>坡积物>冰碛物。吹蚀速率与沉积物组成中0.063￣2 mm的易蚀性颗粒含量和分选性成显著线性正相关,与<0.063 mm的粉粘粒和>2 mm的砾石含量成显著线性负相关。根据不同沉积物吹蚀速率的差异性,可以将这8种沉积物划分为4类:(1)湖相沙和河流沙在干燥条件下极易遭受风蚀,是最主要的沙源物质;(2)砂页岩风化物、洪积物和冰水沙吹蚀速率较强,为次要的沙源物质;(3)花岗岩风化物和坡积物吹蚀速率较差,仅能提供少量沙物质;(4)冰碛物对风力有较强的抗蚀性,所能提供的沙物质数量甚微。我国沙漠的形成除了强盛的风力条件以外,内陆湖盆的干涸导致大范围湖相沙层的暴露以及流水对碎屑物质的前期分选起到了关键作用,这可能是我国沙漠一般分布在内陆湖盆周围或河流沿岸的主要物质原因。更多还原

【Abstract】 By the wind tunnel experiment,we studied the deflation rates of 8 different sediments in arid regions of China,discussed the sources of aeolian sand and its influence on the development of sand dunes and formation of desert from the view of dynamics of wind erosion.Results of the study indicated that the average deflation rates of 8 typical sediments in arid regions of China can be arranged down: lacustrine sand > alluvial sand > weathered particles developed from sandshale > pluvial sediments > fluvioglacial sand > weathered particles developed from granite > slope deposit > glacial sediments.The deflation rates exhibited strong positive correlations with the erodible fraction-sand(0.063-2mm) content and sorting features.In contrast,the deflation rates have obvious negative correlations with the silt clay(< 0.063 mm) and gravel(> 2 mm) content.According to the deflation rates,the 8 typical sediments can be divided into four categories:(1) lacustrine sand and alluvial sand,which are prone to wind erosion,and are the main sources of aeolian sand;(2) weathered particles developed from sandshale,pluvial sediments and fluvioglacial sand,with the larger deflation rates,being the minor source of aeolian sand;(3) weathered particles developed from granite and slope deposit having the smaller deflation rates,only providing a small amount of aeolian sand;and(4) glacial sediments with a strong anti-erodibility,hardly offering any aeolian sand.Other than the strong wind conditions,the exposure of extensive lacustrine sand induced by the desiccation of inland lake basin,as well as the pre-sorting of sediments by flowing water are key factors in the development of deserts in China.It is the possible reason that deserts in China are mostly distributed along the inland lake basin and riverbank in a material light.更多还原