【摘要】 河床沙波向风成沙丘演变的过程具有特殊的沉积动力机制。笔者等以68份长江武汉段天兴洲洲头低滩沉积物的粒度分布数据为例，利用端元分析方法从每个粒度分布中分离提取4个粒度端元组分(EM1、EM2、EM3和EM4),探讨了河流—风成沙丘不同沉积环境中粒度端元的异同。研究结果表明：EM1和EM3组分在粒度分布中占比与沉积物粒度中值分别呈较好的线性正相关和负相关；河流沉积物主要由EM1、EM2和EM3组成的跳跃方式搬运，对应滚动次总体的EM4组分占比5%～10%,少悬浮搬运；风成沙纹沉积物主要包括两段跳跃次总体，以EM2组分为主、EM1和EM3组分为辅，少EM4组分；沙丘背风面沉积物主要靠颗粒流顺坡滑塌，以EM2组分为主、EM1和EM3组分为辅，含占比约为5%的EM4组分；未被风成沙纹覆盖的沙丘波谷沉积物记录了河流和小型滞水洼地的沉积特征，代表滚动次总体的EM4组分占比7%～15%,悬浮次总体占比可达20%。本文提取的沉积物粒度端元为弱风环境中河道内局部小型河流—风成沙丘的沉积环境和演化过程研究提供了参考。更多还原

【Abstract】 Objectives: Grain-size distribution is the information carrier of depositional environment for sediments. The evolution processes from river-bed sand-wave to aeolian dune is in complicated and special sedimentary dynamic mechanism. In order to discuss fluvial——aeolian dune depositional environment features,modern sedimentary of low-beach at the head of Tianxing Central-bar in Wuhan section of Yangtze River was investigated in this paper.Methods: 68 sediment samples were taken in different depositional environment,and grain-size distributions are acquired by corresponding experiment. Based on this data set,4 grain-size end-members,EM1,EM2,EM3 and EM4,are optimized and extracted from each grain-size distribution using end-member analysis. Similarities and differences of grain-size end-members in different depositional environments are discussed further.Results: The results show that percentage of EM1 and EM3 components in grain-size distribution are well linear positive and negative correlation with grain-size median respectively. Fluvial sediments are mainly transported by jumping subpopulation which is composed of EM1,EM2 and EM3 components; EM4 component suggests the rolling subpopulation and its percentage is about 5% ～ 10%; suspending subpopulation is few. Aeolian sand-ripple sediments include 2 jumping subpopulations; EM2 is dominant end-member,EM1 and EM3 are secondary components,few EM4 components. In the leeward slope of the dune,sediments slump by grain-flow downslope; EM2 is primary,and EM1 and EM3 is secondary components; percentage of EM4 components is about 5%. Some dune wave-troughs are not been transformed by wind,and not covered by aeolian sand-ripples. These sediments recorded the depositional environment characteristics of fluvial and small stagnant water simultaneously; corresponding fluvial rolling subpopulation,percentage of EM4 components is about 7% ～ 15%; percentage of suspending subpopulations may be up to 20%.Conclusions: Grain-size end-member extracted in this paper offers reference information for researching sedimentary environments and evolutionary processes of small-scale fluvial—aeolian dune in river channel with weak wind.更多还原