GRAIN SIZE INFORMATION IN DIFFERENT EVOLUTION PERIODS OF XINYANGGANG TIDAL FLAT IN JIANGSU PROVINCE

Six sediment cores were collected in Xinyanggang, Jiangsu Province, in August 2007. Sediment spatial distribution characteristics were studied by analyzing grain size. Grain size parameters and typical frequency distribution curves combining with the changes in color of different core sediments were analyzed for extraction of grain size information in different evolution periods. Standard deviation of grain size components was used for environmental sensitivity analysis to understand the impact of dynamic characteristics on distribution of tidal flat sediments. Deposition rates were estimated in accordance with the evolution periods of tidal flat. The results showed that, core sediment of silt Flat gave grain size evolution information from silt flat to Spartina angilica flat, and then to silt flat again. However, core sediments of Spartina alterniflora flat,Suaeda salsa flat and transitional Spartina alterniflora and Suaeda salsa flats recorded grain size evolution information of Spartina angilica flat-Spartina alterniflora flat, Suaeda salsa flat-Spartina angilica flat-Suaeda salsa flat, Suaeda salsa flat-Spartina angilica flat-transitional Suaeda salsa and Spartina alterniflora flats, respectively. The difference and variation of hydrodynamics in different positions of tidal flat led to the coarse-fine variety of sediments horizontally from silt flat-Spartina alterni-flora flat-Suaeda salsa flat gradually, and resulted in the fact that reed flat became an independent environmental system which was very stable. And vegetation covers impelled this process, which was evidently reflected in grain size variation of surface sediments. Deposition rates of silt flat, Spartina alterniflora flat, transitional Spartina alterniflora and Suaeda salsa flats and Suaeda salsa flat were 2.34 cm/a, 3.09 cm/a, 2.45 cm/a and 2.09 cm/a respectively.