关键词: 格状沙丘, 粒径与分选, 表面过程, 成因, 腾格里沙漠

Abstract: Two transect of samples were obtained from the ridges of the network dune in the southeastern fringe of Tengger Desert. The result shows that the grain size and sorting parameters vary with position on the both ridges of the dune due to the interaction between forms and flows. On the main ridge, mean grain size decreases and sorting improves from the bottom to the top, which can be explained in terms of that avalanching sands down slipsurface give rise to accumalation of coarser grains on the base of slipsurface and this grading mechanism reappears on windward slope where deflation takes place. On the secondary ridge, mean grain size becomes coarser from the mid slop to both the base and the crest while sorting becomes better from the base to the crest. The reason is that, two directional winds operating alternatively on this rigde result in erosion to take place on both windward slope and the lower part of leeward slope and deposition on the upper part of leeward slope near crest. According to the analysis of dune morphology and wind regime and supplemental observation of surface processes, the network dune in Tengger Desert is a complex form of longitudinal element (seconday ridge) and transverse dune (main ridge), in which the main ridge was formed in the dominent northwest wind while the secondary ridge was developed and maintained in an alternative bi directional wind regime.

Key words: network dune, grain size and sorting, surface processe, mechanism, Tengger desert