塔克拉玛干沙漠新月形沙丘不同部位的粒度特征

GRAIN SIZE FEATURES OF SANDS IN DIFFERENT LOCALITIES OF BARCHAN DUNES,TAKLAMAKAN DESERT

通过对塔克拉玛干沙漠东经84°沿线,北纬38°50′～40°50′之间复合型沙垄垄间平地新月形沙丘的粒度筛析资料分析表明:沙丘沙以极细沙和细沙为主,二者含量达80～90%以上。平均粒径3.34φ。落沙坡脚最细,往迎风坡脚越来越粗。分选程度以沙丘脊部最好,向两坡逐渐较差。沙丘上沙子搬运以跃移为主,该组分含量占90%左右。粗截点2～3φ、细截点4φ左右。地面滚动组分平均含量<6%,悬移组分平均含量<3%。丘间地平均粒径2.94φ,分选也较沙丘差。作为对照,文中还论述了纵向沙垄的粒度特征。

Sand samples were collected from Taklamakan Desert, individually by the positions of a barchan dune, e. g. plinth, mid slip face, crest, mid & plinth of stoss slope. The 68 samples were sieved at 1 phi. interval. Grain size distribution were calculated in weight percentage. The results show that the fine and very fine sands are dominated,accounting for about 80-90%. The mean grain diameter is 3.34 phi., at the plinthes of slip face it is the finest, and at the plinth of stoss side it is the coarsest. The sorting of sands is the best on the crest of a dune, and getting to worse and worse increasingly from crest to plinth. Saltation is the main transporting process that transports about 90% of sands. The coarse trunca- tion point is from 2 to 3 phi., and the fine is 2-3 phi. The tract- ion population is less than 6%, and the suspension one, less than 3%.