不同发育阶段新月形沙丘表面粒度特征

The Surface Grain-size Characteristics of Transverse Crescent Dune at Different Development Stages

以塔克拉玛干沙漠腹地垄间平地新月形沙丘的4个发育阶段(饼状沙丘(PD)、盾状沙丘(SD)、雏形新月形沙丘(PCD)、新月形沙丘(TCD))为研究对象,对沙丘表面不同地貌部位的沙物质取样并进行粒度分析,以期发现新月形沙丘不同发育阶段表面粒度的变化规律,结果表明:4种沙丘丘顶或临近丘顶处细砂及极细砂含量最小、粒径最粗、分选性最差,向两侧细砂及极细砂含量逐渐增大、粒径逐渐变细、分选逐渐变好。各发育阶段之间沙粒级配、平均粒径、分选系数的变化规律则需区分不同地貌部位。在迎风坡这3者没有较大差异;在背风坡,细砂及极细砂含量、平均粒径、分选系数均随着沙丘的发育而增大。另外,峰度和偏度并不随着新月形沙丘的发育有明显的变化,均属于近对称中等峰态且为单峰。

Taking the four development stages of crescent dunes,pie sand dunes(PD),shield dunes(SD),prototype crescent dunes(PCD)and transverse crescent dune(TCD),in the interdune corridors of Taklimakan Desert central as the research object,this paper analyzed grain-size characteristics of samples from the surface of sand dunes in different topographies,to find the change law of surface grain-size characteristics of crescent dune on different development stages.The result showed that the least content of fine sand and very find sand,the coarsest grain-size and the worst sorted sands are found at the crests or near the crests of four stages dunes.The content of fine sand and very find sand gradually increases,the grains become finer and the sorting becomes well.The change law of grainsize distribution,mean grain size and sorting coefficient between each development stages depends on different geomorphological positions.There are no big differences at the windward slope,but at slip faces the three parameters increase with the development of dunes.In addition,kurtosis and skewness have not obvious change with the development of crescent dunes,and all belong to nearly symmetric skewness and mesokurtic and unimodal.