海南岛崖州湾表层沉积物空间分布特征及其受控机制

Spatial distribution and its controlling mechanism of surface sediments in the Yazhou Bay,Hainan Island

基于崖州湾海域141个表层沉积物粒度分析数据,研究表层沉积物的粒级组分、粒度参数及其沉积动力环境特征。结果表明,研究区底质类型主要有泥质砂质砾、砾质泥质砂、砂、粉砂质砂、砂质粉砂和粉砂6种,砂质粉砂分布最为广泛;粒径总体趋势表现为自北向南由细变粗再变细的NEE条带状分布特征,分选系数总体偏高,反映了该区复杂的物源和水动力条件。运用Flemming三角图式,结合粒度象、研究区物源、水动力条件及地形特征,将研究区划分为3个沉积环境:近岸主要受控于波浪掀沙和搬运作用,粒径较细,表现为波控沉积特征;中部主要受控于径流、波浪和潮流共同作用,粒径粗,分选差,表现为河口沉积特征;南部主要受控于潮流输沙作用,波浪作用减弱,粒径细,分选相对较好,表现为相对低能的沉积环境。沉积物输移趋势分析显示研究区中西部为一沉积物汇聚中心,近岸侵蚀物质、宁远河输运物质以及外海潮流输运物质均向该处运移。

Based on the 141 surface sediments collected from the Yazhou Bay,Hainan Island,the distribution characteristics of grain size components,grain size parameters and sediment types were analyzed.The results indicate that the samples can be classified into 6 types as argillaceous arenaceous gravel,gravelly argillaceous sand,sand,silty sand,arenaceous silt and silt in the study area.In particular,the arenaceous silt is most widely distributed.The grain size diameters increase and then decrease,showing a banding distribution from north to south.The separation coefficient is generally high,which indicates the complex sediment sources and hydrodynamic conditions in this area.Base on Flemming ternary diagram,combined with sediment sources,hydrodynamic conditions and topographic features,the study area is divided into three sedimentary districts from north to south:the nearshore zone which showing the characteristics of wave-controlled deposition is mostly impacted by wave winnowing and transport,and the grain size is relatively small;the central Yazhou Bay zone is a high-energy coarse grained sand area,mainly controlled by the combined action of runoff,wave and tidal current;relatively,the southern zone is mainly affected by tidal current load,where the wave action is weakened,the sediment is the finest and deposited in a lower energy environment.In addition,the analysis of sediment transport trend shows that the midwest part of the study area is a depositional center,the silt of coastal erosion,Ningyuan River and offshore tidal current transport are carried to this area.