南黄海西南部海域表层沉积物粒度特征及其对沉积动力环境的指示意义

对南黄海南部海域414个站位表层沉积物进行了粒度分析,获取了粒级分布和粒度参数。采用Shepard分类方法,将沉积物划分为5种主要类型,以砂和砂质粉砂为主。应用端元分析模型对表层沉积物粒度数据进行了反演,分离出2个端元,根据各端元频率分布曲线和空间分布特征,结合南黄海西南部沉积动力格局,分析了各端元与研究区沉积物物源和水动力环境的对应关系。结果显示:2个端元所指示的物源主要为具有长江和黄河混合物源的沉积物,且反映了海洋动力过程对现代陆源沉积物的改造、输运和分选。较细的端元1和较粗的端元2分布特征分别与现代潮流通道和潮流沙脊在空间上有很好的对应关系。沉积物粒径趋势分析表明,研究区西北部沙脊和南部潮流通道口门延伸至外海的深槽尾部是沉积物集中输运区域,与EMMA分析结果基本一致。粒径趋势分析结果所揭示的沉积物输运格局与研究区水动力条件和物源吻合较好,可为研究区港口航道建设和管理提供科学依据。

MODERN SEDIMENTATION AND GRAIN SIZE DISTRIBUTION IN THE SOUTHWEST OF THE SOUTH YELLOW SEA: DYNAMIC ENVIRONMENTAL CONSTRAINT

Grain size distribution of 414 surface sediment samples collected from the southern South Yellow Sea was studied. Five types of sediment were recognized, of which sand and sandy silt were most common. The grain-size fractions sensitive to the source area were determined using end-member-modeling algorithm (EMMA), and the content and distribution were attained. We find that the data could be reproduced by two end-members (EMs), reflecting greatly the sedimentary dynamics. Meanwhile, relationship between provenance and hydrodynamic environment was revealed from the frequency distribution, the spatial distribution, and the sedimentary dynamic pattern. The grain sizes showed two EMs indicative of the Changjiang (Yangtze) and the Huanghe (Yellow) River sources, and reflected the reworking, transport, and separation of these terrigenous sediments by regional marine dynamic processes. The distribution patterns of the finer EM1 and the coarser EM2 were in good agreement with those of modern tidal channels and tidal ridges. In addition, trend analysis revealed two zones of convergence in grain size located in sand ridges northwest of the study area and in the tide channel tail situated from the tidal entrance to open waters, which is largely consistent with the result of EMMA. Meanwhile, the transport trend of the surface sediments uncovered by the Gao-Collins grain size trend analysis model (GSTA model) was highly consistent with the provenance of sediments and the local hydrodynamics. Therefore, this study could offer knowledge to the decision-makers in port construction and waterway engineering.