南海琼东陆架海洋沉积物粒度分形特征及其影响因素

通过对2013年南海西部综合航次于南海琼东陆架海域采集的3根沉积柱(C1、C2、C4)样品进行粒度分析，对粒度的分形特征及其影响因素进行探讨。使用矩法计算出沿离岸方向3根沉积柱样的平均粒径分别为5.33 Φ、6.14 Φ、6.26 Φ，粒度总体上较细；标准偏差平均值分别为2.59 Φ、2.19 Φ、1.82 Φ，表示分选性逐渐变好；偏度平均值分别为0.40、-0.02、0.48，其变化规律不明显；峰度平均值分别为1.75、2.27、2.70，其值逐渐增大。利用幂指数法，在累积体积百分比5%~95%范围的无标度区间内计算得到沉积物样品的粒度分维值，总体范围为2.24~2.54，平均值分别为2.52、2.45和2.30，处于较高水平；随着离岸距离的增加，样品粒度分维值逐渐降低，但分选性变好；粒度分维值与标准偏差存在显著正相关关系，说明分选性对粒度的分形特征产生影响。根据C-M图，沉积柱样的流体为牵引流，颗粒的主体搬运方式由沉积柱C1的滚动逐渐转变为沉积柱C4的悬移；对比发现，以滚动组分为主的颗粒粒度分维值较大，以悬移组分为主的颗粒粒度分维值较小，说明分形程度受搬运方式和水动力条件的影响。

Fractal Characteristics of Marine Sediments from the East Continental Shelf of Hainan Island,South China Sea and Their Influence Factors

Grain size compositions of samples from three sediment cores (namely C1, C2, C4) collected from the east continental shelf of Hainan Island, South China Sea during an integrated investigation to western South China Sea in 2013 were analyzed, and the fractal characteristics and influence factors were discussed. Based on moment method, it is obtained that the mean grain sizes of samples from three sediment cores along the offshore direction are 5.33 Φ, 6.14 Φ and 6.26 Φ, respectively, and the grain sizes of samples are generally fine; the mean standard deviations are 2.59 Φ, 2.19 Φ and 1.82 Φ, respectively, showing that the sorting gets better along the offshore direction; the mean skewness values are 0.40, -0.02 and 0.48, showing unobvious changes; the mean kurtosis values are 1.75, 2.27 and 2.70, and increase gradually. The fractal dimensions of samples range from 2.24 to 2.54 by the power index method in a scale-free interval with the cumulative volume percent of 5%-95%, and their mean values are 2.52, 2.45 and 2.30, respectively, indicating a higher level; with the increase of offshore distance, the fractal dimensions of samples decrease gradually, but the sorting becomes better; the fractal dimension is positively and significantly correlated with standard deviation, showing the sorting impacts on the fractal characteristics of grain size. Based on C-M plot, it is found that the fluid at the samples from sediment cores is traction flow, and the main transportation form of particles changes gradually from the rolling at sediment core C1 to suspension at sediment core C4; the comparison results show that the fractal dimension of rolling component is greater than that of suspension component, implying that the fractal is both affected by the transportation form of grains and hydrodynamic conditions.