河西走廊不同类型地表沉积物粒度研究

Particle Size Analysis of Surface Sediments and Its Significance in Hexi Corridor of China

对河西走廊地区的戈壁滩、沙漠沙、河流和祁连山表层沉积物样品进行了系统的粒度分析,获得以下认识:1细粒沉积物粒度一般由多个组分叠加构成,表现为多组分粒度分布特征,表明其受控于搬运介质的性质、动力强度和搬运方式等因素;2沙漠沙、戈壁滩、河漫滩表层沉积物样品以及祁连山表土样品在中值粒径、偏度、分选性等粒度参数上差异明显,可明显区分,沿祁连山—河流(石羊河、黑河)—稳定戈壁滩—沙漠化戈壁滩—沙漠方向,中值粒径和分选系数逐步增大,偏度逐渐向负偏发展;3石羊河和黑河将物质从祁连山搬运至河漫滩,在洪水条件下形成广袤的洪积平原,这些平原在干旱化的条件下形成了戈壁滩和腾格里沙漠与巴丹吉林沙漠,河漫滩、洪积平原、沙漠的带状分布是近地面风对山前冲、洪积物质的风力分异的结果;在搬运过程中,河漫滩、洪积平原、沙漠虽然都可以作为粉尘源区,但这些亚区之间在空间上是有联系的,且在物质上具有继承性;在祁连山—河漫滩—戈壁滩沙漠搬运途径方向上,细粒物质逐渐被搬运迁移至黄土高原等地区,从而中值粒径和平均粒径逐渐增大;4西北地区包括巴丹吉林、腾格里等沙漠在内的戈壁、沙漠地区是重要的粉尘源区,包括冰川研磨作用、山体剥蚀作用、山前冲洪积作用等在内的"高山过程",是产生大量粉土级物质的原因。

This paper systematically collected surface sediment samples,including Gobi,desert sand and river sediments in Hexi Corridor and Qilian Mountains. Based on the researches on the grain size parameters,it obtains the following results：a）the grain size of fine grained sediment generally superimposed by multiple component composition,expressed as multi component particle size distribution characteristics,indicating the nature of the transportation,power intensity,handling methods and so on are controlling factors;b）the grain size parameters characteristics of desert sand,the Gobi surface sediment samples,the river floodplain surface sediment samples and surface sediment samples of Qilian Mountains are clearly different. Along the Qilian Mountains to the river（Shiyang River and Heihe River）to stable Gobi desert to the Gobi desert to the stabilized desert,the median particle size increases,sorting coefficient also increases and the skewness becomes to be negative gradually;c）Shiyang River and Heihe River would carry materials from Qilian Mountains to the washland,then the washland turns to be flood plain under the conditions of floods,these plain will form gobi desert and Tengger Desert and Badain Jaran Desert eventually with the aridification. Zonal distribution of washland,flood plain and desert are the results of wind differentiation on the piedmont alluvial materi als. All these can be used as the dust source areas during the transmission,and these sub regions are connected and inherited in the materi al. Due to prevailing northwest wind or north wind in Hexi Corridor and the frequent dust storms,caused from the Qilian Mountains to wash land to gobi desert to desert,the fine grained material is transported gradually to the Chinese Loess Plateau and other areas,and thus the me dian particle diameter and the average particle size gradually increase. d）Gobi,washland and deserts,including Tengger Desert and Badain Jaran Desert,in Northwestern China are the source areas of dust,mountain processes（including glacial grinding,frost weathering,foreland fluvial and so on）in northwestern China have played an important role in producing the vast amounts of dust.