福建安海湾表层沉积物粒度特征及其现代沉积过程分析

Analysis of Surface Sediment Grain Size Characteristics and Modern Sedimentary Process in Fujian Anhai Gulf

通过对福建安海湾表层沉积物的粒度分析和对比,应用系统聚类分析、粒径趋势模型和切应力计算公式,探讨了研究区粒度的分布特征、沉积环境分区、表层沉积物输运趋势及其影响因素。研究结果表明,研究区包括6种表层沉积物类型,以黏土质粉砂和粉砂为主,沉积物大体呈现自海湾两侧潮滩向潮汐通道变粗的分布趋势。表层沉积物粒度的分布特征与水动力条件和物质来源密切相关,湾口附近及湾内深槽内,细颗粒的沉积物被再悬浮带走,粗颗粒的含量增大;在湾内潮滩上,悬浮物质因水动力作用逐渐减弱发生分选沉降,形成向岸变细的横向分异。海湾外泥沙随潮流不断地向海湾东侧岸滩运移,海湾周边陆源来沙由湾顶部往湾口方向下泄,两者是导致表层沉积物出现明显的顺时针方向汇聚趋势的原因之一;表层沉积物的输运趋势、悬浮泥沙的输运、潮滩植被与湾口沙嘴的遮蔽效应共同影响了研究区内浅滩地形的形成和变化。研究区可分为四类沉积环境区,以潮滩和潮汐通道环境为主,不同沉积区内的粒度参数、粒级频率和敏感粒级均有差异,动力条件差异和不同物源的影响程度是现代沉积环境格局的主要影响因素。

Surface sediments in Fujian Anhai gulf were collected and analyzed by grain size laser particle sizer. The grain size distribution characteristics, sedimentary environment partition, trend of surface sediment transport and its influencing factors were discussed by application system clustering analysis, grain size trend model and the formula of shear stress. The results shows that surface sediment include six types of sediment, give priority to the two main types which are clayey silt and silty sand. The grain size trends to coarse form tidal fiat in both sides of the bay to the tidal channel. The grain size distribution characteristics are closely related to the hydrodynamic and material source. The fine particles material were removed by resuspension near the bay mouth and in tidal channel, lead to the content of coarse particles increased. On the tidal fiat in the bay, the selective deposition of suspended material happen due to the hydrodynamic effect weakened, formed the horizontal differentiation which particles material become more finer to- ward the shore. The transportation to the east side tidal flats of the suspended sediment carried by the tide current form the outside bay, and the discharge of terrigenous sediment derived from surrounding the gulf towards the top of the bay to the bay mouth, can influence the migration trend of sediment shows obviously clockwise convergence. The formation and change of the shoals are affected by the migration trend of sediment and transport of suspended sediment together with vegetation and the shading effect of the sand spit in bay mouth. The study area can be divided into four types of sedimentary environment, give priority to tidal fiat and tidal charmel environment. The grain size parameters, frequen- cy and sensitive fraction have difference in different sedimentary environment. The modern pattern sediment environ- ment is mainly impacted by hydrodynamic difference and the influence of different material source.