安达曼海东南部海域表层沉积物粒度特征及净输运趋势

海底沉积物粒度是反映水动力格局最直接的指标，可以有效指示不同时间尺度陆源碎屑物质输运过程。利用激光粒度仪对取自安达曼海东南部海域的98个表层沉积物样品进行粒度分析，结果表明，研究区表层沉积物以粉砂、砂质粉砂及粉砂质砂为主，且粒度组成空间分区明显：北部陆架为粗粒级且分选差的残留砂质沉积区；南部内陆架为混合沉积区，以砂质粉砂、粉砂质砂和粉砂沉积为主；丹老阶地和陆坡为细粒级且分选较好的粉砂和泥质沉积区。在此基础上选用Gao-Collins“粒径趋势”方法分析了该区域表层沉积物的净输运趋势，结果显示，当特征距离<0.8°时，普吉岛东南部海域存在沉积中心，研究区沉积物有向该区域汇聚的明显趋势，沉积物分布特征和输运趋势主要受陆源物质供给、季节性变化的西南季风流以及潮流的综合影响。

Grain size characteristics of surface sediments and net transport patterns in the southeastern Andaman Sea

The grain size of seafloor sediments is the most direct indicator of hydrodynamic pattern, which could effectively indicate the transport process of terrestrial detritus material at different time scales. Grain size was analyzed with the Malvern Mastersize 2000 particle size analyzer for 98 surface sediment samples collected from the southeast continental shelf, Andaman Sea. Results show that sediments on the southeast continental shelf could be divided into four categories: silty sand, sandy silt, silt, and mud. The grain size distribution of the study area revealed four distinct zones in terms of sediment texture: the northern shelf zone with relict sands; the southern inner shelf zone of mixed sediments with silty sand, sandy silt and silt; the Mergui Terrace zone with silt; and the continental slope zone with fine-grained and well-sorted mud. Based on the grain size analysis and Gao-Collins grain size trend analysis, the net transport patterns in the study area were discussed. The characteristic distance was defined less than 0.8° by geostatistical analysis and the results indicate that southwest area near Phuket was the depositional center of the southeastern Andaman Sea and the sediments displayed a net transport trend toward it. It was believed that the distribution and transport pattern of sediments in the study area were controlled by source supply, southwest monsoon currents, and tidal movement.