关键词: 粒度, 石英砂, 显微特征, 沉积分异

Abstract: To study the transportation, deposition and differentiation of till and outwash in Allah valley area of Tianshan and dune sand in Tazhong area, the characteristics of particles in the two areas were comparatively analyzed. Results show that in the glacial sediments, the content of the silt grain was the largest, followed by sand grain, and clay grain was the least, besides there were lots of more-angulars, worn ridges, large conchoidal fractures, impact pits on the surface of quartz sands, which indicated the strong crushing and grinding force at the bottom of the glacier. The particle characteristics of outwash sediments were similar to that of glacial sediments’, and silt grain was still the dominant component, but the features of quartz sand surface showed that it was slightly reformed by water. In the eolian sediments, sand grain was the main component, and the surface of those grains had lots of subround-round edges, dished pits and irregular small pockmarked pits which were caused by wind action. In addition, there were some large conchoidal fractures, cracks and worn ridges that reflected glaciation and a few V-shaped pits that indicated fluviation. It could be concluded that till is the dominant source of the sand in the Taklimakan Desert, and the silt of till is the main supply for the loess in the edge of Tarim Basin.

Key words: grain size, quartz grain, microtexture, sedimentary differentiation