Grain-size Characteristics of Typical Linear Dunes in the Kumtagh Desert
The sediment samples from different geomorphological positions of typical linear dunes were collected in the northeastern,eastern,central,southern and western parts of the Kumtagh Desert which is located in the west of China,and analyzed by means of sieving.The results show that the main grain composition of linear dunes is medium sand,fine sand and very fine sand,their proportions being 28.85 ％,30.92 ％ and 25.98 ％ respectively,and the cumulative content of these three size fractions accounts for different percentages in the surface sediments of the foot and middle of windward slope,the top of the dune,the middle and foot of leeward slope,being 69.45％,90.62％,91.72％,96.22％ and 80.72％ respectively.The linear dunes in the Kumtagh Desert are divided into two categories according to the profile shape and the characteristics of grain size parameters of the dunes.The profile shape of the first type is not symmetrical,their sediments gradually tend to become finer,better sorted from the foot to the top on both slopes,and the dunes of the first type are distributed in the northeast,central,southern and western desert.The profile shape of the second type is more symmetrical than that of the first type,the sediments on two middle slopes are the finest,those on the top are the coarsest and those at the foot take second place,and the sorting characteristics show no obvious regularity.The dunes of the second type are located in the east of desert.This paper discussed the causation of grain size characteristics of two types of linear dunes,and drew a preliminary conclusion that the formation of the first type of linear dunes is mainly caused by wind sorting,while the second type of linear dunes are the results of wind sorting and the source of sediments,and may be caused by underlying physiognomy,weathering and wind sorting as well.
linear dunesgrain sizecause of formationKumtagh Deser
NETL
NSTL
万方数据
维普
