【摘要】 一系列的钻探和拖网取样都表明南沙群岛海区东、南部存在中生代海相沉积。新的国家重点基础研究发展计划地震测线经过南沙群岛海区北部,调查采用了长排列、高分辩率技术。所获地震剖面显示在披覆沉积和裂谷式充填沉积之下,还存在大套具有密集反射、倾斜形变和高角度断裂的下构造层。结合南海的构造演化过程以及钻探和拖网取样结果对比,将上覆构造层划为裂谷期及裂谷后期沉积,下构造层划为中生代沉积。残留的厚层海相中生界呈北东―西南向条带状相间分布,反映新生代拉张具有明显的块断特点。根据中生界的地层和变形特点,进一步推断南沙群岛海区北部位于中生代东亚陆缘弧前盆地的近弧一侧。更多还原

【Abstract】 It was inferred that there were Mesozoic marine deposits in the Nansha Islands waters through extensive seismic reflection profiles,drilling and dredge sample.A new high resolution 2D seismic survey with long cable was carried out along a NNW-SSE line from the southwestern sub-basins of the South China Sea into the northern part of the Nansha Islands waters area in the South China Sea in 2009.It was shown that there is a great set of infrastructure with dipping and closely spaced reflection with high angle fault below rift and drape sedimentation.Through analysis of the drilling and dredge sample of Mesozoic samples in the Nansha Islands waters area,the sedimentary strata are divided into three structure layers by an angular disconformity,which are post-rift,syn-rift and Mesozoic marine sediments,respectively.The NE to WS trending thick Mesozoic was remained in banding distribution,which indicates that the Cenozoic rift structure is primarily characterized by the occurrence of tectonic block.It is inferred that the northern margin of the Nansha Islands waters is located in the fore-arc basin of the East Asian continental margin,close to the magmatic arc,in the Mesozoic.更多还原