Distribution Characteristics, Sources, And Sedimentary Environmental Indications Of The Sediment In Xiamen Bay

The present study investigated spatial and temporal distribution characteristics of sediment in Xiamen bay, and the interaction with depositional environment through analyzing grain size, mineral, the parameter of chronology. We also discuss the source and transport characteristics of the grain in the target area according to the sediment dynamics technique.We analyzed the types, mineral component, transport trend and sediment source through grain size, mineralogy, chronology and sediment dynamics . Sediment cores were analyzed comprehensively in combination with the data of 210Pb, mineralogy and chronology,. Source of sediment and it interaction with the depositional environment of sea was discussed on the basis of these data.We obtained the following results on the horizontal distribution of sediment: 1)There are eight types of surface sediment. Their granularity revealed the thickness, hydrodynamic and environment of sediment.2)Fifty kinds of minerals were found in surface sediment, including 38 kinds of heavy minerals and 12 kinds of light minerals. The dominant are magnetite, ilmenite, hornblende, epidote, limonite, hematite, isinglass, zircon et al. Seven mineral assemblage zones and eightee sub-zones were classified according to the distribution characteristics of heavy minerals.3) The analysis of the trend of surface sediment transport by GSTA model revealed that the substance from Jiulong river was mostly transited to the sea through Xiamen outer harbor, some went into LiaoLuo Bay, and a few went into Xiamen west harbor during high tide. The substance in the north of Xiamen west harbor transited to the south and the mouth of culvert of Gaoqi-Jimei Gauseway; They transited from the top to the interior in the TongAn Bay, with a general trend toward Gaoqi-Jimei Gauseway and the mouth of the TongAn Bay. The substance in the east of Xiamen island moved to the north, those in the south of XiangAn transited to the mouth of TongAn bay and Aotou, or to the DaDeng and XiaoDeng island. The sediment substance in WeiTou Bay tended to move from the outside to the inside, and diffused along the coast. The substance in Liaoluo bay transported from southeast to northwest in the anticlockwise direction.We acquired the result of vertical (temporal) distribution characteristics of sediments:1)The result of grain size analysis of core sediment indicated the difference and transformation, reappearanced the effects by nature and human activity in every sea area.2)The dominant mineral assemblage zones are metal minerals in core sediment. The metal minerals mostly consisted of magnetite and ilmenite which have good weatherproof ability.3) Sedimentary rate in Xiamen sea area has increased in past years. We acquired the result about the source, substance transport and depositional environment on the basis of horizontal and vertical distribution characteristics of sediment.1)The depositional substance in Xiamen bay was mostly from Jiulong River and efflorescent rock nearby Xiamen Bay. Some of them come from Fujian and Zhejiang longshore currents.2)Sand from land and the lithology nearby Xiamen Bay control the mineral assemblage zones. The factors that affect heavy mineral distribution are the weatherproof ability of mineral, water power, source, depositional environment and so on. Deposit velocity increased due to human activity.3)The factor that effect depositional environment are mostly water power and topographty, and physiognomy.