干旱区生态环境知识资源中心

Compared with the sand grain size of the other sand seas, central Taklimakan Sand Sea has some of the finest sands seen globally. The dunes are composed of fine and very fine sands with a diameter between 2.00 and 4.00 phi (0.25-0.063 mm). There are differences in the grain size distributions for different dune types. Mean grain size of the compound/complex crescent dune sands is 3.08 phi; the compound dome dunes 3.21 phi; the compound/complex linear dune sands between 2.63 and 3.41 phi; and the star dunes 2.81 phi. From the northern edge of the sand sea towards southern edge, the components of fine and very fine sands increase, closely related to the wind regimes, time scale for dune development, and underlying sediments. Compared with the foregoing, there are some differences for the compound/complex linear dunes in the centre of Taklimakan. Though the pattern of coarser crests does exist, the sorting parameters indicate that the sands on the west flank of compound/complex linear dunes are better sorted than that on the east flank and crest. Sampling on the superimposed dunes developed on the surface of the complex linear dunes suggests that the patterns of finer crest, coarser crest all existed in central Taklimakan. Under the conditions of low energy wind regime when fine sand is available, the frequency of the pattern for finer crest and better sorting will increase. Sampling on the simple crescent dunes developed on the interdunes suggests that the simple duties are developed originally with nearly the same grain size distributions and parameters. With the development of the dunes and evolution of the dune morphology, the grain size distributions of the dune sands varied under the actions of the wind regimes, time scale and underlying sediments. (C) 2002 Elsevier Science B.V. All rights reserved.