关键词: 粒度, 植被, 沉积环境, 高大沙山, 巴丹吉林沙漠

Abstract: The formation and evolution of dune is a dynamic systematic process with the interaction of wind, sediments, and other geographical factors, through grain size analysis we could know part of the environmental information contained in this process, so it is widely used in aeolian research. This article analyzed the grain size characteristic of mega-dunes in the Badain Jaran Sand Sea and its correlation with vegetation and landform, the results showed that the main gain size of sediments had homogeneity in different layer of the upper-middle and middle sections of windward slope and were respectively composed of middle sand and fine sand; But in the lower-middle and bottom sections, the grain size distribution had complexity, different layer alternated with different main grain size including fine sand and middle sand and coarse sand, the reasons for that may include the protective action of coarse sand and the seasonal change of wind direction and the climate change in geological periods; The surface sediments were mainly composed of fine sand in the leeward slope, but toward bottom the content of coarse sand and middle sand and very fine sand increased, this indicated the discrepancy of different particle size on the response of the wind and gravity; The scatter diagram of grain size parameters could distinguish the samples very well in different parts of mega-dunes, toward the bottom sections of windward slope, the sorting of sand particles became worse, and the sand layer alternated with positive or negative or near symmetrical skewness, these demonstrated that there existed discrepancy of wind action in different parts and some other exogene processes. The grain size distribution had an impact on vegetation diversity, and vegetation aslo affected it, for example, the high content of middle sand in the upper-middle section of windward slope and the sudden increase content of very fine sand and fine sand greater than 2.65 Φ in the middle part with a little higher of leeward slope; The different depositional environment in the windward slope indicated that with the climate change in geological periods the mega-dunes may undergo at least two important formation stages, the first period was the basement formation with the alternate layer of aeolian or nor-aeoline depositional environment under the influence of wind and hydraulic action, the second period was the formation of modern mega-dunes mainly based on the wind action.

Key words: grain size, vegetation, depositional environment, mega-dune, Badain Jaran Sand Sea