| 摘要: |
| 高分辨率地震资料显示, 南海北部西沙海域碳酸盐台地周缘广泛发育水道沉积体系。礁缘水道底界面表现出强反射特征, 内部充填弱-强、连续性好的地震相, 可见底部杂乱反射特征; 斜坡水道在地震剖面上表现为横向上连续发育的“V”型特征, 且下切深度较浅。西沙隆起与广乐隆起之间的南北向低洼地带发育大型深水水道, 并且受古地貌高点影响, 水道分为南北两个分支。北分支水道可分为5 期, 且水道迁移现象明显; 南分支水道可分为4 期, 水道以充填强振幅、连续性好的浊流沉积体和弱振幅、杂乱的块体搬运体系(Mass Transport Deposits, MTDs)为特征, 每期水道均表现出侵蚀-充填-废弃的旋回性。分析认为西沙碳酸盐台地周缘水道沉积物源来自西沙隆起和广乐隆起的碳酸盐台地和生物礁碎屑及由火成作用产生的火成岩碎屑。西沙-广乐碳酸盐台地水道相互贯通, 构成台地-斜坡-深水的水道沉积体系, 为碳酸盐岩、生物礁及火山碎屑向台地周缘输送提供了良好的通道。 |
| 关键词: 水道沉积体系 碳酸盐台地 西沙海域 南海北部 |
| DOI：10.11759/hykx20150323001 |
| 分类号: |
| 基金项目:基金南海重大计划重点项目(91228208); 三亚所知识创新工程领域前沿项目(SIDSSE-201403) |
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| Characteristics of periplatform channels of the Xisha area, northern South China Sea |
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TIAN Jie,WU Shi-guo,WAND Da-wei,LÜ Fu-liang,WANG Bin,ZHANG Xin-yuan
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| Abstract: |
| High-resolution seismic data reveal the wide existence of periplatform channel systems in the Xisha area, northern South China sea. Channels around reefs display strong amplitude reflections and are filled with weak–strong and continuous reflections; furthermore, chaotic seismic reflections can be dectected at the bottom of the channels. Small-scale channels on the slope show a series of V-shaped reflections with incised shallows on the underlying strata. The Zhongjian deep-water channel developed in the graben lying between the Xisha uplift and Guangle uplift and is separated into two branches because of the paleo-highland. The north branch can be divided into five stages with significant migration. The south branch can be divided into four stages with inner high amplitude and continuous reflections. Each stage of it shows an erosion-infill-abandon sedimentary cycle. Paleogeographic analysis reveals the channel-filled deposits to be composed of carbonate and reef debris and volcaniclastic rocks. Channels in the Xisha area constitute a platform-ramp-deep water channel sedimentary system and provide good conditions for the transport of carbonate and reef debris and volcaniclastic rocks into deep-water areas. Thus, the carbonate platforms can provide carbonate clastic sediments to the adjacent environment. |
| Key words: periplatform channels seismic characteristics Xisha carbonate platforms northern South China Sea |
