汉江蔡甸段沉积物粒度特征及其地质意义

Sedimentary Particle Size Characteristics and Geological Significance of Caidian Segment of Hanjiang

摘要: 汉江作为长江最大的支流，其曲流发育，沉积环境多变，与人类生产生活息息相关，在沉积研究的相关课题中对于长江与黄河的研究很充分，但是对于汉江的相关研究明显是不足的，因此深入解剖汉江不仅仅具有地质意义，还对于人类社会生产生活具有一定的指导意义。粒度特征是河流以及湖泊沉积物最基本的物理特征，通过粒度特征得到的粒度曲线是沉积环境分析的重要参考标志。本次研究利用汉江蔡甸段34个沉积物粒度资料，采用图解法对沉积物展开粒度参数分析，并综合粒度概率累积曲线分析以及C-M图对汉江蔡甸段进行分析得出：汉江蔡甸段具有典型的曲流河特征，其上游沉积物分选性较好，沉积期环境较稳定；下游沉积物分选性中等，沉积期环境不稳定，这可能是一定的流水作用导致了分选变差。粒度主要集中在粗粒部分，粒度分布曲线中粒度相对集中。其概率累积曲线都呈现“两段式”的特征，跳跃总体只发育一段，缺少牵引总体，表明研究区总体上的沉积物以跳跃总体为主；从上至下细截点向右移动，体现出上游研究区的沉积物整体粒度要大于下游研究区的沉积物，在汉江蔡甸段的曲流部分与顺直部分采集的沉积物其粒度数据受到环境控制明显，但是粒度数据受到了下游沉积物中的云母等沉积物的影响，因此分析河流沉积物粒度特征时需要从多个方法，多个方面，多个角度去解释。

Abstract: As the largest tributary of the Yangtze River, Hanjiang is a typical meander. The sedimentary en-vironment of Hanjiang is highly varied, and plays an important role to human life. The researches on the Yangtze River and the Yellow River are very adequate, but the relevant research on Hanjiang is obviously inadequate. Therefore, in-depth dissection of Hanjiang does not only have geological significance, but also has certain guiding significance for human social production activities. The particle size is the most basic physical characteristics of rivers and lake deposits. The particle size curve obtained by granularity characteristics is an important reference sign of deposition environmental analysis. This study uses 34 deposit particle size data of Caidian segment of Hanjiang. Graphical method is used to obtain particle size parameters of sediments. Integrating the analyzation of probability cumulative curve and the analyzation of C-M diagram, the result of the study on Caidian segment of Hanjiang is as following: Caidian segment of Hanjiang has typical meander characteristics, the upstream sediment sorting is good, the deposition period is relatively stable; the downstream sediment sorting is medium, the deposition period is unstable, which may be a certain amount of flow of water results in the deterioration. The particle size is mainly concentrated in the coarse portion, and the particle size in the particle size distribution curve is relatively concentrated. Its probability accumulation curve shows a two-stage characteristic. The jumping portion is only developed one, and no pulling portion is developed, indicating that deposits in the research area are mainly based on the jumping portion. Cut point T moves to the right from the top, indicating that the overall particle size of the upstream research area is coarser than the sediments of the downstream research area. The particle size data of the sediments collected in Caidian segment of Hanjiang is remarkably controlled by sediment environment. However, the particle size data is affected by particular sediments such as mica in downstream sediments. Thus to analyze and to explain particle characteristics of fluvial sediment need to integrate multiple methods and aspects.