库姆塔格沙漠沙丘的粒度特征

Analysis of Grain Size of Different Sand Dunes Types in Kumtag Desert

通过两次野外实地调查取样和室内分析,结果表明：库姆塔格沙漠中沙丘形态丰富多样,金字塔（星形）沙丘、线形沙垄、格状沙丘、羽毛状沙丘在这里都有分布。组成金字塔沙丘、线形沙垄、格状沙丘、羽毛状沙丘羽轴的沙粒中0.25～0.063 mm颗粒占绝大多数,其次是0.5～0.25 mm和1～0.5 mm的颗粒,形成羽毛状沙丘羽枝的颗粒在暗带以2～0.5 mm的颗粒为主,在明带以0.5～0.063 mm的颗粒为主,各沙丘沙粒的分选性较好。由于各自形成地形、气候等条件的差异,各沙丘类型沙粒粒径在沙丘不同部位都有各自的特点。金字塔沙丘东北坡沙粒粒径从顶部到基部保持一致,南坡和西北坡从顶部到基部沙粒逐渐变粗;线形沙垄除西南坡基部较粗外,其它部位沙粒粒径分布一致;格状沙丘格子外部坡面沙粒相对格子内部坡面的同一部位沙粒要粗;新月形沙丘基部和顶部沙粒较粗,而中部颗粒较细;羽毛状沙丘“羽轴”沙粒分布与新月形沙丘相似,“羽枝”由较粗和较细沙粒含量高低间隔分布形成。

The geomorphologic characteristics of different type of sand dunes in Kumtag desert were investigated. On-the-spot sand samples were eolleeted and the eharaeteristies of grain size were analyzed in laboratory. The result shows： there are various types of sand dunes in Kumtag desert, sueh as： pyramid dunes （stare dunes）, sim- ple linear dunes, network dunes, ereseent dunes and featherlike dunes. The majority grain size of sand dunes is 0.25～0. 063 ram, and the minority is 0.5～0.25 mm andl～0. 5 ram. The grain of eaeh dune is good in sandsorting, whieh had been seleeted by wind. The grain size of pyramid dunes in topside of NE slope is the same as that in downside, and beeome thieker and thieker from top to bottom in South and WS slope; the grain size of two sides of simple linear dunes are the same, while the downside of south slope is thieker. The grain size of outside network dunes slope is thieker than that inside. The grain size of middle part of ereseent dunes is thinner than that on topside and downside; the grain size of featherlike dunes ＂quill＂ is same as that in ereseent dunes, and grain size of ＂plume＂ is alternately ehanged between thiek and thin grains.