毛乌素沙地现代沙丘沙的粒度特征及其意义

Grain Size Characteristics of Modern Dune Sand and Its Significance in the Mu Us Sandy Land,China

对毛乌素沙地不同类型41个现代沙丘的沙粒度分析结果表明,流动沙丘沙主要由细沙和中沙组成,平均粒径为2.17Φ;固定-半固定沙丘沙的主要粒级是细沙和极细沙,平均粒径为3.09Φ。流动沙丘沙平均粒径整体自西北到东南减小,而分选性总体表现为中等-较好,无明显空间变化规律。概率累计曲线和粒度特征参数散点图表明,毛乌素沙地沙丘沙以跃移搬运方式为主,存在着就地起沙和就地堆积的可能。平均粒径和分选性空间变化规律的差异,是在频繁强烈的风沙活动环境下物源和大气环流共同作用的结果。

In the Mu Us Sandy Land,41 modern dune sand samples were collected and analyzed by laser particle analyzer.The results show that modern mobile dune sand is mainly composed of fine sand and medium sand with mean grain size of 2.17Φ,While the main grain size fraction of modern fixed/semi-fixed dune sand is fine sand and very fine sandwith the mean grain size of 3.09Φ.On the whole,the mean grain size of modern mobile dune sand becomes gradually shorter from the northwest to the southeast in the Mu Us Sandy Land,but the sorting don＇t see the similarity space change rule.The log-probability cumulative curves and grain size parameters scatter diagram show the Mu Us Sandy Land is in a frequent and strong wind activity environment,and the most important aeolian transports style is saltation,which implys a possibility of the local sand source and local accumulation.However,different space change rules of the mean grain size and sorting is the result of the interaction of the frequent strong wind environment,sand source and the atmospheric circulation.