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通过对黄河晋陕峡谷的深入调查研究,在延长永和县河段发现了典型的全新世晚期洪水滞流沉积剖面。在野外考察中,对沉积物的宏观特征和沉积环境及其分布特征进行观察,并进行了系统采样。在实验室对沉积物样品进行了粒度成分、磁化率、烧失量、CaCO3含量等测定。通过综合分析论证,表明黄河中游晋陕峡谷全新世晚期洪水滞流沉积物以粉砂为主,细砂含量次之,粘粒含量很少,分选性好,磁化率很低。其沉积学分类为细砂质粉砂,是黄河洪水悬移质泥沙在高水位滞流环境下的沉积物。将其与典型的全新世风成黄土和古土壤进行对比,可知其粒度成分比黄土和古土壤更粗,粒级分布更为集中。此外,将其与延河郭家川全新世洪水滞流沉积物对比,发现其粒度频率分布基本相似。该研究结果对于揭示黄河中游洪水水文泥沙特性及其历史演变具有重要意义。
Through in-depth investigation of the Yellow River Jin-Shan Canyon, a typical late Holocene flood stagnant sedimentary section was found in Yanhe County. In field investigation, the macroscopic characteristics of sediments and sedimentary environment and their distribution characteristics were observed and systematically sampled. Sediment samples in the laboratory were measured particle size composition, magnetic susceptibility, loss on ignition, CaCO3 content. Through the comprehensive analysis and demonstration, it shows that the late Holocene flood stagnant sediments in the middle Yellow River valley are mainly silt, the fine sand content is the second, the clay content is small, the sorting is good, and the magnetic susceptibility is very low. Its sedimentology is classified as fine sandy silt, which is a sediment of the suspended sediment of the Yellow River flood suspended under high water level and stagnant conditions. Compared with typical Holocene aeolian loess and paleosol, it can be seen that the grain size is thicker than that of loess and paleosol, and the grain size distribution is more concentrated. In addition, comparing with the Holocene flood stagnant sediments in the Guohe River in the Yanhe River, it is found that the frequency distribution of the grain size is similar. The results of this study are of great significance for revealing the characteristics of flood hydrology and sediment in the middle reaches of the Yellow River and its historical evolution.