Grainsize Characteristics of the Surface Sediments and Their Seasonal Variability in the Mud Depocenter off the Southern ZhejiangFujian Coast

Key words: 
• the mud depocenter off the southern ZhejiangFujian coast

Abstract: 
Samples of surface sediments at 15 stations in the mud depocenter off the southern ZhejiangFujian coast were collected in both summer and winter seasons. The distribution pattern, seasonal variability of grainsize of the surface sediments in this area and their influential factors were discussed based on the grainsize measurements. The results indicate that surface sediments were mainly clayey silts with slight variations in the grain size parameters such as median grain size (Mz), standard deviation (SD), skewness (Sk) and kurtosis (Kg). There exists an evidently negative correlation between Mz and SD, while a weakly negative correlation is found between Sk and Kg. Two peak values around 4.92～6.46 and 25.32～33.27 μm, and a low value around 11.16～13.39 μm are identified from the SD of grainsize curves. Meanwhile, significant seasonal variability is found as indicated by the large differences between the parameters of surface sediments collected in summer and winter season. The ranges of all the four parameters in the winter samples are higher than those in the summer samples, while the  values of Mz in winter samples are generally smaller than those in the summer samples. And the gradients of Sk and Kg are larger than those in the summer samples at the same station. The variability in SD of grain size in the winter samples was evidently higher than that in the summer samples. The variations of the parameters of surface sediments in this area are mostly attributed to sediment sources and the seasonal difference in marine dynamic environment.