【摘要】 南流江河口有四个水动力区,各动力区的沉积物类型、平均粒径、标准偏差、碎屑重矿物含量、有机碳含量等沉积特征,均受水动力强弱控制而有明显差异.沉积物的变化可从沉积物类型分布图分别得到反映.并划分三角洲平原相、三角洲前缘相、三角洲相.更多还原

【Abstract】 The Nanliujiang Delta is a small tide-dominated delta, in the south of Hepu county, Guangxi province, with an area of 450 square kilometers. Based on the information from grain size analysis, the mouth area is divided into four provinces hydrodynamically, which are in accordance with the hydrodynamic conditions of the area. Sediment types, mean grain size, standard deviation terrigenous heavy mineral content and organic carbon percentage etc. of these provinces differ distinctively from each other and vary in a regular way. From province A to D, sediments become coarser and better sorted, their contentof mud (>4φ) and organic carbon is decreased, while that of terrigenous heavyminerals is increased, reflecting an increase in hydrodynamic energy.All the changes mentioned are shown in diagram of distribution of sediments, isogram of mean grain size, isogram of standard deviation, isogram of terrigenous heavy mineral content and isogram of organic carbon percentage. With the information from sedimentary structure and mineralogy, the sedimentary characteristics are dosely related to the hydrodynamic division of the area, indicating that hydrodynamic condition dominates in the deltaic deposition.According, to the hydrodynamic condition, sedimentary characteristics and floral assemblages, Nanliujiang delta is essentially divided into three parts: delta plain, delta front and prodelta, which are subdivided into several subfacies. Delta plain includes tidal plain, flood plain, distributary channel, strand sand bar and strand swamp. Delta front is composed of distributary mouth bar, inte-rtidal shoal and delta front slope.It is revealed through analysing the information from more than 20 drillings that since 7000 B. P., the delta has prograded 10-12 kilometers seaward and formed a vertical sequence of 9 meters thick, the facies sequence of which is basically consistent with the facies change from land to sea. In about two thirds of the delta area this vertical sequence is well preserved, but in the rest the sequence is found to have undergone strong reworking of the river.The following questions are also discussed in the paper: the developement stages of the delta, sediment variation in the delta, characteristics and distribution of plant remains in the delta plain, characteristics and distribution of tidal sand bodies and the authigenic iron-saponite in the delta.更多还原