新疆策勒戈壁沉积物粒度特征及其沉积环境分析

Grain size characteristics and sedimentary environment of Cele Gobi sediments in Xinjiang

【目的】揭示新疆策勒戈壁沉积物粒度特征及沉积环境,为戈壁沉积物沙尘释放、沉积环境演变及合理利用土地资源、减少沙尘灾害提供理论依据和科学支撑。【方法】以新疆策勒戈壁为研究区,通过野外实地调查与沉积物粒度以及磁化率的研究,对新疆策勒戈壁沉积物的粒度分布特征及其沉积环境进行分析。【结果】戈壁表层0~2 cm沉积物受到风蚀与降尘的影响较大,表层沉积物较粗粒级含量随着海拔降低呈现出逐渐增大的趋势,2~40、40~80 cm深度沉积物总体上受洪水的作用较大,沉积物较粗粒级含量随着海拔降低呈现出先减少后增大的趋势;在戈壁各剖面各深度中,沉积物粒度分布频率曲线大部分为双峰曲线,说明沉积物来源是多源的,粒径组成中跃移组分占绝对优势,跃移的平均含量为49.43%;戈壁各剖面沉积物的平均粒径随海拔降低呈现出先变细后变粗的趋势,平均粒径介于56.08~139.71μm;除剖面2外,其余各剖面均属于差分选性,偏度为负偏与极负偏,峰态均为窄或极窄峰态;0~2 cm深度沉积物磁化率值受到风蚀与降尘的影响较大,明显大于下层沉积物磁化率值,2~40、40~80 cm深度的沉积物可能为同一时期沉积,且沉积环境与沉积动力相同;沉积物的沉积环境主要以水成沉积环境为主。【结论】新疆策勒戈壁表层0~2 cm沉积物以风蚀与降尘为主,沉积环境主要是以水成沉积环境为主。

【Objective】To reveal the grain size characteristics and sedimentary environment of sediments in Cele Gobi in Xinjiang,and to provide theoretical basis and scientific support for the release of sedimentary dust,the evolution of sedimentary environment,the rational use of land resources and the reduction of dust disasters.【Method】Taking Cele Gobi in Xinjiang as the research area,the grain size distribution characteristics and sedimentary environment of sediments were analyzed by field investigation,particle size and magnetic susceptibility study.【Result】The gobi surface of 0~2 cm sediment under the influence of wind erosion and dust is larger,surface sediment content of coarser grained as lower altitudes shows a gradually increasing trend,2~40,40~80 cm depth sediment by flood is larger,the effect of the total sediment is relatively coarse grained content as the tendency of increase with the lower altitudes showed reduced after.The frequency curves of sediment particle size distribution in each gobi section and each depth are mostly bimodal curves,indicating that the sediment source is multi-source,and the saltation component is the absolutely dominant particle size composition,the average content of saltation is 49.43%.With the decrease in altitude,the average particle size of sediments in the gobi sections first became fine and then coarse,with the average particle size ranging from 56.08μm to 139.71μm.Except for section 2,all other sections belong to differential sorting,with negative skewness and very negative skewness,and narrow or very narrow peak state.The magnetic susceptibility of the sediments at 0~2 cm depth was strongly affected by wind erosion and dust fall,which was significantly higher than that of the underlying sediments.The sediments at 2~40 cm depth and 40~80 cm depth may have been deposited at the same time,and the sedimentary environment and sedimentary dynamics were the same.【Conclusion】Wind erosion and dust fall are the main causes of the 0~2 cm sediments in the surface layer of the Cele Gobi in Xinjiang,and the sedimentary environment is mainly hydrogenic sedimentary environment.