腾格里沙漠南缘风积物粒度空间分布及物源指示

为探讨腾格里沙漠南缘风积物物源,基于粒度参数分析其空间分布,采用粒度端元分析并与潜在源区对比,结合常量元素法进行了多角度探究。结果表明:黄河北岸沉积物粒度较南岸粗,两岸沉积物粒度存在较明显的空间差异性。粒度空间分布差异结合风沙活动、地形特征,可表明腾格里沙漠南缘的黄河北岸为南岸沉积物的上风向源区之一; 就地球化学元素分析表明,沙漠南缘与祁连山区常量元素特征具有一定相似性,与沙漠腹地差异较大。提取4个端元,多角度分析表明端元1(峰值粒径范围是30～50 μm)为全由祁连山北麓风成沙所组成的沉积体,端元2(100～120 μm)主要由沿黄北岸风成沙和黄河二次搬运所组成。端元3(170～250 μm和15～25 μm)为沿黄以北就地起沙,端元4(300～600 μm和10～20 μm)由黄河搬运沉积物所组成。综上,可认为腾格里沙漠南部边缘区沙物质主要是由黄河、沿黄以北和祁连山北麓所提供。

Spatial Bistribution of Granularity Parameter and Provenance Indication of Aeolian Deposits on the Southern Margin of the Tengger Desert

In order to explore the aeolian material source in the southern margin of the Tengger Desert, the spatial distribution of aeolian material was analysed based on the particle size parameters. The particle size and element analysis was used and compared with the potential source area, the constant element method was used to explore from multiple angles. The results show that: The grain size of sediment on the North of the Yellow River is coarser than that of the South, and there are obvious spatial differences between the two banks. The spatial distribution difference of grain size, combined with sandstorm activities and topographic characteristics indicates that the North of the Yellow River in the southern edge of Tengger desert is one of the upwind source areas of the sediment on the South of the Tengger Desert. The geochemical element analysis shows that the characteristics of major elements in the south of the Yellow River are similar to those in the Qilian mountainous area, and are quite different from those in the desert hinterland. Therefore, it can be considered that the Qilian mountainous area may be one of the provenances south of the Yellow River; four end-members are extracted, and the multi angle analysis shows that end-member 1 is composed of Aeolian sand at the northern foot of the Qilian Mountain, and end-member 2 is mainly composed of Aeolian sand along the North Bank of the Yellow River and the secondary transport of the Yellow River. End-element 3 is composed of sediments transported by the Yellow River. It can be considered that the Yellow River, its banks and the Qilian mountains provide provenance for the southern edge of Tengger Desert. It is of great significance to extract the provenance information of desert sediment from grain size data. However, in order to accurately determine the source of desert sediment, it is still necessary to make comprehensive analysis from other means such as geochemical elements.