福建近海河口潮流沉积沙体特征

发布时间：2018-11-23 18:34

【摘要】：福建近海岸线蜿蜒曲折，沿岸发育众多河口，海洋环境受台湾海峡影响较大。河口是连接陆域和海域水体的媒介，与人类活动息息相关。福建近海闽江口和九龙江口等河口均属于中小型强潮河口,河口沙体分布特征和演化趋势直接影响人类活动和经济发展。基于较新数据资料，对河口外沙体的研究有助于加强对我国近海半封闭中小型河口湾海底潮流地貌的认识。本文通过多波束调查采集数据和浅剖、沉积物等资料的分析和研究，结合前人海平面变化的研究资料，对河口外沉积沙体的成因进行了探讨和论述，初步认为其为潮流沙脊。研究结论如下：（1）在平面分布上，闽江口外潮流沙脊走向近SW-NE向，沙脊局部连片；九龙江口外沙脊走向近ENE-WSW向，沙脊末端有分叉现象。（2）研究区沙脊主体生长受现代水动力影响较小，从沙脊相对于现代河口的距离和沉积物粒度特征来看，沙脊主体发育时的物源并非现代河口沉积物，沙脊表层覆盖有较薄的现代近海陆架沉积物层,下部地层为保留古河道相沉积的残留沉积。（3）通过沙脊间距推算出的古水深与前人研究全新世古海平面位置及当时南黄海和东海大量潮流沙脊形成水深是一致的，其中,闽江口外的潮流沙脊主体发育时期约为11-11.5ka B.P.处于中国近海沙脊演化早期,九龙江口外的潮流沙脊主体发育时期约为7-8ka B.P.处于演化中期。（4）研究区沙脊为古水下三角洲砂质浅滩遭受潮流等水动力侵蚀而成，形成的潮流水动力环境强于现代的浅水陆架平原环境；在随后的海平面变化过程中，沙脊上覆水深逐渐大于沙脊发育的最佳深度，在现代水动力改造作用下，，沙脊顶端圆滑，两侧坡度较缓，沙脊间沟槽较为平缓，表面发育沙波，基本处于动力平衡的状态。
[Abstract]:Fujian has a winding coastline with many estuaries along the coast, and the marine environment is greatly affected by the Taiwan Strait. Estuaries are the medium that connects land and sea waters and is closely related to human activities. The estuaries such as Minjiang Estuary and Jiulong Estuary in the coastal waters of Fujian Province belong to the middle and small strong tidal estuaries. The distribution characteristics and evolution trend of sediment body in estuaries directly affect human activities and economic development. Based on the new data, the study of the sediment body outside the estuary is helpful to strengthen the understanding of the tidal current landform in the middle and small sized estuarine gulf in the coastal waters of China. Based on the analysis and study of the data collected by multi-beam survey, shallow profile and sediment, combined with the previous research data of sea level change, the origin of sediment body outside the estuary is discussed and discussed, which is considered as tidal current ridge. The results are as follows: (1) in plane distribution, the trend of tidal current sand ridge outside Minjiang Estuary is close to SW-NE direction, and that of sand ridge is locally connected, and the direction of sand ridge outside Jiulong River Estuary is near ENE-WSW direction, with bifurcation at the end of sand ridge. (2) the main body growth of sand ridges in the study area is less affected by modern hydrodynamics. According to the distance between sand ridges and modern estuaries and the grain size characteristics of sediments, the material source of the main body of sand ridges is not modern estuary sediments. The surface layer of sand ridge is covered with a thin layer of modern offshore shelf sediments, and the lower layer is a remnant deposit of paleochannel facies. (3) the paleo-water depth calculated from the distance between sand ridges is consistent with the paleo-sea level position of Holocene and the formation of tidal current ridges in the South Huang Hai and the East China Sea at that time, among which, The main development period of tidal current ridge outside Minjiang Estuary is about 11-11.5ka B.P. The main body of tidal current ridge outside Jiulong River Estuary is about 7-8ka B.P. In the middle of evolution. (4) the sand ridge in the study area is formed by the erosion of sandy shoals in the paleo-underwater deltas by tidal current isohydrodynamic erosion, which is stronger than that of the modern shallow shelf plain environment. During the subsequent sea level change, the water depth on the sand ridge is gradually greater than the optimum depth of the sand ridge development. Under the action of modern hydrodynamic transformation, the top of the sand ridge is smooth, the slope on both sides is relatively slow, the channel between the sand ridges is relatively gentle, and the sand waves are developed on the surface. Basically in a state of dynamic balance.
【学位授予单位】：国家海洋局第三海洋研究所
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P736.21

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