新疆喀拉库姆沙漠新月形沙丘不同部位粒度特征

Grain Size Characteristics of Different Parts of the Crescent Dunes in Karakum Desert,Xinjiang,China

对新疆叶尔羌河流域绿洲边缘喀拉库姆沙漠高度在3～12m的新月形沙丘进行了粒度分析。结果表明：表层和下层沉积物均以细砂和极细砂为主，二者含量达82％以上。表层沉积物较下层稍粗，平均粒径分别为2．09中和2．16φ 。下层沉积物较表层分选性好，一均值分别为0．48和0．62。表层和下层沉积物偏度均为正偏，SK均值分别为O．21和O．24。峰态均为尖窄，K。均值分别为1．18和1．11。表层和下层沉积物平均粒径均表现为丘顶最粗，背风坡坡脚最细，由两侧坡脚至丘顶平均粒径变粗，平均粒径与其他粒度特征参数之间均存在良好的相关性。分析表明，喀拉库姆沙漠沙丘沉积物粒度特征除受物源这一背景制约外，还与区域构造、沙漠地貌、植被、气候和较为复杂的风沙动力学过程等众多因素有关。

The analysis on the sand particle grain size from different parts of selected crescent dunes in Kara kum Desert of Xinjiang, China shows that the surface layer and the underlying sediments layer are both mainly the fine sand and extreme fine sand with content more than 82 %. The average grain size of the un derlying layer sediments is 2.16φ and the surface sediments is 2.09φ. The underlying layer sediments has a better sorting characteristics than the surface layer sediments, the standard variation values of those two layers are 0.48 and 0.62 respectively. Both the surface layer and the underlying layer sediments skewness are positive, SK values are 0.21 and 0.24 respectively. Kurtosis are both narrow and pointed, Kg values are 1.18 and 1.11 respectively. The average sand particle grain size of the dune crest is the coarsest, and sand from the dunes root of leeward slope is the finest. The sand particle grain size of crescent dunes gradu ally become coarser from dune root to dune crest. And the average sand particle grain size is also well relat ed to other particle size parameters. The sand particle grain size characteristics of crescent dunes in Kara kum Desert is not only restricted by provenance background, but also constrained by regional tectonic, des ert landforms, vegetation, climate, comnlex aeolian sand dynamic orocess and many other factors.