南海南沙海槽大型海底滑坡的发育特征及成因机制  

A Giant Submarine Landslide and Its Triggering Mechanisms on the Nansha Trough Margin, South China Sea

作　　者：任金锋 孙鸣[3] 韩冰[3] Ren Jinfeng;Sun Ming;Han Bing(Gas Hydrate Engineering Technology Center,China Geological Survey,Guangzhou 510075,China;Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China;Guangzhou Marine Geological Survey,Guangzhou 510075,China)

机构地区：[1]中国地质调查局天然气水合物工程技术中心,广东广州510075 [2]南方海洋科学与工程广东省实验室(广州),广东广州511458 [3]广州海洋地质调查局,广东广州510075

出　　处：《地球科学》2021年第3期1058-1071,共14页Earth Science

基　　金：南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(No.GML2019AD0102);中国地质调查局地质调查项目(No.DD20190230);国土资源部海底矿产资源重点实验室开放基金(No.KLMMR-2017-A-05);广州市科技计划项目(No.201909010002)。

摘　　要：大型海底滑坡的研究对认识海底斜坡的稳定性具有重要意义.利用最新的高精度多波束数据和重处理的二维地震资料,识别了南海南沙海槽一处大型海底滑坡,描述了其发育特征,探讨了其可能的形成原因.该滑坡体覆盖面积达6 300 km2,横向最宽50 km,延伸最远140 km.上部源头区外形呈半环形,滑坡后壁的高度落差200~350 m,平均坡度0.7°,发育基底剪切面和掀斜断块.中部滑移区呈拱形,分布于1 600~2 400 m水深段,平均坡度1°~3°,发育基底侵蚀面和大量残余块体.下部堆积区呈扇形,分布于2 400~2 800 m水深段,平均坡度0.1°~1.0°,发育大型碎屑流朵体和逃逸块体.研究表明不断隆升的背斜脊对高供给率沉积物的阻挡是海底斜坡失稳的内在条件,而高通量流体的聚集以及天然气水合物的分解使其变得更加不稳定.The research on large-scale submarine landslides is of great significance to understanding the stability of submarine slopes. In this paper, a giant submarine landslide on the Nansha trough margin, South China Sea was identified by using the latest high-precision multibeam bathymetry and reprocessed two-dimensional seismic data, and its development characteristics were described. The possible triggering mechanism was discussed. The landslide covers an area of 6 300 km2, spanning 50 km and extending 140 km at most. The upper semicircular headwall domain has developed a basal shear surface and tilted fault blocks. The headwall scarp is 200-350 m high with an average slope of 0.7°. The middle arch-shaped translational domain has a erosional unconformity and voluminous remnant blocks. It is distributed in the depth section of 1 600-2 400 m with an average slope of 1°-3°. The lower fan-shaped toe domain has a detrital lobe deposit and some out-runner blocks. It is distributed in the water depth section of 2 400-2 800 m with an average slope of 0.1°-1.0°. The study indicates that the barrier of the rising anticline ridge to the sediment with high supply rate is an internal condition, but high flux upward fluids and gas hydrates dissociation may be two key preconditioning factors bringing anticlines closer to failure.

关 键 词：海底滑坡 背斜脊 天然气水合物分解 南沙海槽 海洋地质 

分 类 号：P737[天文地球—海洋地质]