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

Key words: 
• grain size /
• sedimentary environment /
• sediment dynamics /
• grain size trends analysis

Abstract: 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 flat 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 flat 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 toward 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 flat and tidal channel environment. The grain size parameters, frequency and sensitive fraction have difference in different sedimentary environment. The modern pattern sediment environment is mainly impacted by hydrodynamic difference and the influence of different material source.