内蒙古额济纳盆地沉积物粒度特征及沉积环境

The characteristic of grain-size in Ejina Basin and associated sedimentary dynamic environmental analysis

沉积物的粒度特征对于分析区域沉积动力环境有着重要意义。本文以额济纳盆地为研究区,以戈壁、河床和沙丘3个主要地貌单元采集的表层沉积物样本的粒度测量结果为数据源,基于粒度参数分析和端元建模分析,研究了沉积物的粒度特征、端元构成和反映的沉积动力环境。结果表明:(1)额济纳盆地表层沉积物粒度曲线具有单峰和多峰分布,其中戈壁和沙丘沉积物组成上以砂质为主,河床沉积物组成上以砂质和粉砂质为主。(2)表层沉积物可分解出4个主要端元,端元1到端元4的主要物质依次为粗粉砂、细砂、中砂和细砂混合物以及粗砂和中砂混合物。(3)区域环境特点分析表明,表层沉积物端元1主要代表了以流水为主的动力过程,端元2主要代表了风力作用和局部地形环境复合的过程,端元3和端元4主要是风力主导下的多外营力复合以及局部环境共同作用的结果。

The grain-size characteristics of sediments are of great significance for the analysis of regional sedimentary dynamic environment.In this study,we take the Ejina Basin as the research area,and uses the grainsize measurement results of the surface sediment samples collected from three main geomorphological units of the Gobi,riverbed and sand dunes as data source.Based on the analysis of grain-size parameters and end-member modeling analysis,the grain size characteristics,end-member composition and reflected sedimentary dynamic environment of sediments were analyzed.The results show that:(1)The grain size curve of the surface sediments in the Ejina Basin has a single-peak and multi-peak distribution.The Gobi and sand dune samples mainly include sandy sediment,and the riverbed samples mainly include sand and silty.(2)Surface sediments is decomposed into four main end-members.The main sediment of end-member 1 to end-member 4 are coarse silt,fine sand,medium-fine sand mixture and coarse-medium sand mixture in order.(3)End-member 1 of the surface sediments mainly represent a dynamic process dominated by flowing water;end-member 2 mainly represent the process of wind action and local topographic environment compounding;end-member 3 and end-member 4 are result of multiple external forces dominated by wind and local environment compounding.