基于GPR图像的福建长乐海岸沙丘沉积构造与海岸环境演变

Sedimentary structure of coastal dunes and evolution of coastal environment in Changle, Fujian, China, by groundpenetrating radar

为了探讨福建长乐东部海岸环境演变,运用探地雷达(GPR)探测了研究区海岸沙丘的沉积构造,初步得出以下结论:(1)研究区海岸沙丘沉积构造主要由海滩沉积和海岸沙丘沉积构成,其中下伏沉积为海滩波浪作用形成的波状交错层理,上覆沉积为风成大角度倾斜的交错层理以及局部的水平层理;(2)上部发育的倾向向背的大角度风成交错层理,反映了研究区丰富的沙源、宽阔的海滩、植被扩张的进积海岸特点;(3)从沉积序列分析,研究区海岸地貌环境演变经历了早期的滨岸浅海到晚期的海岸沙丘带两个阶段,反映了海岸向东的进积过程中,外力作用由波浪作用为主演变为风沙沉积作用为主。

The east coast of Changle City, Fujian Province, China, is famous for its marvelous coastal dunes. Located to the south of the Min River Estuary, it receives large volumes of sediment from the northeast wind waves and Zhemin coastal currents. Using two parallel lines perpendicular to the shoreline, we applied ground-penetrating radar as a non-invasive technology to determine the sedimentary structure of the coastal dunes. Some preliminary conclusions are as follows： （1） The coastal dunes mainly comprise two parts—wave-deposited beach sands at the bottom capped by aeolian sands, which present hummocky cross stratification and high-angle cross bedding mingled with horizontal bedding, respectively. （2） High-angle cross bedding dipped inversely corresponds to abundant sand sources, a wide beach, and vegetation expansion, which are the characteristics of a progradational coast. （3） On the basis of our sedimentary structure sequence analysis, we infer that two stages occurred in the coastal environment evolution： a shallow sea in the early times and the occurrence and development of coastal dunes.