作　　者： ; ; ;

机构地区： 中国科学院南海海洋研究所

出　　处： 《海洋科学》 2019年第6期48-59,共12页

摘　　要： 通过对南沙群岛永暑礁、西门礁和安达礁 3 个砾洲的现场调查,基于理论最低潮面和平均海面分别计算了砾洲的可能分布范围和平均出露范围,获得了砾洲的地形地貌特征。 3 个砾洲均为向西北凸出的弧形,呈北东-南西向展布。永暑礁和西门礁砾洲周边地势较高,中部相对低洼,分布有多条砾脊,边缘向海侧主砾脊高度最大,内部多条较低的次砾脊相交于主砾脊并汇聚于砾洲东部;安达礁砾洲则中部凸起地势较高,周边较低,无多重砾脊分布。推断砾洲的发育由最初珊瑚枝块堆积于中部形成凸起,逐渐向北东和南西两侧以砾脊形式扩展,最终形成砾洲由内向外的洼地-砾脊-砾滩的地貌分带模式。砾洲的地形地貌特征表明,南沙群岛砾洲的发育主要受北东-南西向水动力条件季节性交替的控制,反映了南海海区盛行季风的影响。南沙群岛珊瑚礁砾洲的地貌特征为深入研究南海珊瑚礁灰沙岛地貌发育演化及动力机制提供了基础数据。 In this study, three coral shingle cays each located on the Yongshu Reef, the Ximen Reef, and the Anda Reef in the Nansha Islands were investigated. Based on the theoretical lowest tide (TLT) and mean sea level (MSL), we calculated the areas of possible distribution and the average outcrop of the cays and obtained the topographic and geomorphic features of the cays. The three cays are northwest-facing and arc-shaped and spread within the northeastern southwestern direction. In the cays on the Yongshu Reef and the Ximen Reef, the surrounding areas are relatively high and the central parts are relatively low. Shingle ridges are present in the two cays, whereby a high main ridge is located at the seaward edge, and multiple low sub-ridges are distributed in the interior intersect- ing the main ridge and gather in the eastern part. Different from the other two cays, the cay on the Anda Reef is bulging on the central part and is low-lying on the edge area and is without shingle ridge. It is speculated that coral branches and gravels accumulated and bulged initially at the central part and extended toward northeast and south- west, respectively, as shingle ridges, and finally formed a shingle cay with geomorphic zones of depression-shingle ridge-shingle beach from its inner to outer regions. The topography and geomorphology of these cays indicate that the seasonal northeastern southwestern hydrodynamic condition controlled the development of shingle cays in the Nansha Islands, reflecting the influence of the prevailing monsoon in the South China Sea. The geomorphic features of coral shingle cays in the Nansha Islands provide basic data for in-depth research on the geomorphic development and dynamic mechanism of the coral islands in the South China Sea.

关 键 词： 南沙群岛 灰沙岛 砾洲 地貌特征 水动力环境

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