福建长乐海岸沙丘沉积序列记录的海岸环境演变

The Evolution of Coastal Environment Recorded by Sedimentary Sequences of Coastal Dune in Changle City,Fujian Province

福建长乐海岸是中国东部海岸沙丘分布最典型的区域之一.选取长乐东部的海岸沙丘分布区,在研究区平行布设2条垂直海岸带的探测剖面,运用探地雷达技术探测以获取海岸带沉积构造信息,并结合海岸沙丘探坑剖面和海岸演变历史地图的对比分析,对探测获得的海岸沙丘沉积构造和沉积序列进行综合分析.结果表明:1)研究区海岸沙丘沉积主要由海滩沉积和海岸风沙沉积构成,其中下伏沉积为海洋波浪作用形成的波状层理,上覆沉积为风力作用为主形成的交错层理,这些沉积构造特征在探测线附近的探坑剖面上有清晰的反映;2)在沉积序列的组合特征上,研究区海岸环境存在早期的滨岸浅滩和晚期的海岸沙丘带两个演变阶段,记录了长乐海岸向东的进积演变历史.结合研究区历史时期海岸演变地图分析,所探测海岸沙丘的沉积序列,长乐海岸沙丘记录了由汉代至唐宋时期以波浪作用为主,逐渐演变为清代以来以风沙沉积作用为主的外力作用变化过程.

The coast in Changle city of Fujian province is one of the most typical distribution areas of eastern coastal dunes in China. The coastal dune in eastern Changle city is selected as the study area. Two profiles which are perpendicular to the coastal zone are set parallelly,the sedimentary structure and sedimentary sequences of the coastal dune are detected and analyzed using ground penetrating radar （GPR） technology and comparison with profile of coastal dunes and coastal evolution history maps. Results show that coastal dunes in the study area are mainly composed of beach sediments and coastal dunes. The under lying sediments are wavy bedding formed by ocean waves. The overlying sediments are cross bedding formed mainly by aeolian action. These sedimentary structure features are reflected clearly in the profiles near detecting-line. By analyzing the combination feature of sedimentary sequences,the evolution of coastal environment in the study area includes early shallow shore shoal stage and the late coastal dune stage, and the process of the coastal dunes expanding eastward is recorded. By analyzing the sedimentary sequences with coastal evolution history maps in the study area,Changle coastal dunes records the process of dominant exogenic action changing from wave action （from Han Dynasty to Tang and Song Dynasties） to aeolian sedimentation（since Qing Dynasty）.