The Study On Characteristics Of Surficial Sediments And Their Source Indication In Xiamen Harbor

The analysis of marine sediments is a fundamental content of marine geology, and also one of the core problems in deposition researches nowadays. As the foundation of deposit classification, it not only embodies sediment' s essence of the physical and chemical characteristics, but also dominates the historical evolution. The research of marine sediments is almost involving analysises of the particle size and mineral. Among these, the character of particle size in surface is the basis of trace sediment provenance and sedimentary environment analysis. Each deposition system can be regarded as a complicated function of some factors: the sediment environment (including hydrodynamic conditions, sediment supply, biological activity, etc.) and the sediment composition (physics and chemistry), and so on. At the same time, the study of fragmentary mineral can resolve some problems about marine sediments such as the composition of fragmentary mineral,distribution characteristic,sediment source and so on, so as to expound the component about parent rock and the difference of the mineral when they dissolve into the sea further. It has importantly scientific meanings in the study of the marine environment changes, oceanic mineral resources exploitation,marine environment protection,port construction and renovation,adjacent coastal continental shelves and the sea sedimentology theory development , and it is a important content of marine sedimentology.This article relies on the Fujian Province fund project and transverse direction problem cooperating with Taiwan, choosing Xiamen harbor where has the complex hydrodynamic force as the study area. To explain two above-mentioned aspects, use the laser grain size analyzer, light and heavy mineral analysis and cluster analysis to study, and discuss sediment' s distribution, source and the relationship whit sedimentary environment. Provide the basis for the reasonable exploitation and to utilize bay resource, and to protect channel stability,to develop Xiamen' s marine transportation enterprise, and to promote periphery area economic development.1. Grain size analysis of the 36 suficial samples from the study area was carried out by using the laser grain size analyzer. Isoline distributing chart is protracted according to percents of each level and parameters of granularity .Combination the chart and hydrodynamic conditions analysizes granularity distributing trends of Xiamen port . The result is following: Sediments in the area could be divided into 4 types: clayer silt,sand-silt-clay,silty sand and sandy silt, and clayer silt take the majority. Distribution of sediment is mainly affected by hydrodynamic conditions and sediment sources. The area where runoff and tidal current interact strongly and the hydrodynamic force becomes weak in favor of sediment subsidence, is enriched area of sand and heavy mineral.2. Clusters of 36 samples are identified by using microscopes, and heavy minerals are analyzed according to R and Q types clustering. The results show that there are 9 kinds of light minerals, 49 kinds of heavy minerals. Light minerals take the majority. The dominant and characteristic minerals are magnetite,limonite,epidote,mica and amphibole. Four mineral assemblage zones can be divided based on the result of clustering analysis and heavy mineral contents and the distribution characteristics.3. According to Computing and analyzing characteristic index of heavy mineral, combining dynamic conditions and granularity distributing characters , deem that the source of sediment is nearby harbor and the source regions include Jiulong River watershed and peripheral land, where distribute acidic intrusive rocks,neutral intrusive rocks,volcanic and dynamo-metamorphic rock in Yanshanian.4. From the size composition in study area, the content of silt is dominate. Relatively, the content of sandy is lower. The result shows that the hydrodynamic force is weak. In the result of heavy mineral identification shows that the chance of occurrence of autogenic pyrite which indicates reducing environment is higher, and proves the study area is a weak reducing and low-energy environment.