GRAIN SIZE OF SURFACE SEDIMENTS IN THE EASTERN MIN-ZHE COAST: AN INDICATOR OF SEDIMENTARY ENVIRONMENTS

The grain size of the 83 surface sediment samples taken from the eastern Min-Zhe coast are studied for sediment types and the distribution pattern of grain size parameters. The effect of sediment source and hydrodynamic conditions on the sediment distribution pattern is discussed. The following results have been achieved based on the detailed study of these samples:(1)There are six types of sediment in the study area and they are sand, silty sand, muddy sand, sandy silt, silt and mud. (2)The mean grain size is in a range of 2.01~7.58 φ, and the grains are coarsening seaward with the increase in sand and decrease in silt and mud. (3)The standard deviation varies between 0.48~2.86 φ. It shows a poor sorting in the whole study area and the lowest is in the middle of the study area, and from there the sorting is improved eastward and westward. (4)The inshore fine sediments are from the Yangtze River and other coastal rivers, and the offshore coarse sediments are the reworked relict deposits on shelf. Both the coastal current along the Min-Zhe coast and the Kuroshio current contribute to the distribution of sediments. Based on the data, the Min-Zhe coast is divided into three depositional zones, i.e. the inshore muddy zone, multi-sediments zone in the middle and eastern Min-Zhe coast and offshore reworked sand zone on the outer shelf.