雅鲁藏布江米林宽谷段新月形沙丘粒度分异研究

雅鲁藏布江中游米林宽谷段阶地面上广泛发育带状延伸,由上段风蚀槽、中段过渡区和下段堆积区组成的风沙活动带。风沙活动带各段新月形沙丘表面沉积物粒度分析表明,沙丘表面沉积物总体为细沙、中等分选、极细偏、多峰,表面粒度分布模式多属丘顶最粗型。受沙源和分选距离的影响,沙丘沙粒度特征在风沙活动带内表现出一定的空间差异性,上段风蚀槽内发育的沙丘规模小,粒径细,分选差,极细偏,多峰;中段和下段沙丘表面沉积物粒径变粗,分选变好,正偏转向近对称,多峰转为单峰。

Variation of Grain Size on Surface of Barchans in Mainling Great Valley,Yarlung Zangbo River

The aeolian sand belts are distributed extensively in Mainling great valley section of the Yarlung Zangbo River. Each belt can be divided into eroded area, erosion and deposition transition area, and deposition area by distinct aeolian sand activities. The two belts with aeolian sand activity were studied. The results show that sediments of the dune are mainly composed of fine sands with moderate sorting, fine skewness, and muti-modal grain size distribution. Grain size distribution on the surface of barchans can be attributed to the 'dune crest coarser’pattern as a whole with limited exception where grain size distribution shows a "finer crest" pattern. Spatial variations of grain size distribution among the barchans within the same aeolian sand belt were shown. Small barchans developed in the eroded area exhibit finer grain size, poor sorting, very fine skewness and multi-mode. In the erosion and deposition transition area and downwind deposition area, dune grain size becomes coarser with sorting better, fine skewness converting to nearly symmetry, and muti-mode grain size distribution pattern turning to be uni-mode.