SEDIMENT FAILURES IN THE SHENHU AREA, NORTHERN CONTINENTAL SLOPE OF THE SOUTH CHINA SEA
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摘要:
利用广州海洋地质调查局采集的2D和准3D地震资料，从整体形态、期次性和内部结构等方面对南海北部陆坡神狐海域内广泛发育的沉积物失稳进行了类型划分和特征描述，并将沉积物失稳的分布特征和陆坡限制型海底峡谷群的分段性进行耦合关联，进而分析沉积物失稳的空间变化规律。研究结果显示，沉积物失稳可以划分为两种类型：第一种类型位于峡谷群的下游段，几乎不受峡谷群地貌的影响，表现为多期次、内部连续和自北向南的块体运动方式，主要以“残留”的形式位于峡谷群脊部；另一种类型主要表现为沿峡谷群脊部向谷底的块体运动方式，受到峡谷群地形起伏的影响，在峡谷群头部，主要为多期次滑移体，中游段变形强度最大，滑塌体是主要的类型，而在下游段-嘴部，表现为滑移块体。第四纪以来，源自北部珠江水系充足的沉积物供给和自北向南较陡的海底地形，是沉积物失稳发育的关键控制因素；陆坡限制型海底峡谷群可能造成了沉积物的再次变形作用，使得沉积物失稳的空间变化规律与峡谷群分段性具有对应关系。此外，神狐海域含气流体的垂向运移以及水合物矿体的存在，也是研究区内沉积物失稳的重要控制因素。
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关键词:
- 沉积物失稳 /
- 滑移 /
- 滑塌 /
- 陆坡限制型海底峡谷群 /
- 神狐海域
Abstract:With the seismic data acquired by the Guangzhou Marine Geological Survey, we studied the types and characteristics of the frequently developed sediments failures in the Shenhu area of the northern South China Sea. The distribution pattern of sediment failures is adopted to reveal the relationship between slope-confined submarine canyons and sediment failures. The sediments failures in the study area can be grouped to two types. The first type, which is mainly located at the ridges in the lower reach of a canyon and hardly affected by seafloor geomorphology, is characterized by multiple continuous wavy reflectors in a pattern of southwards mass movement. The second type is mainly the products of the mass movement from the ridge to the bottom of a canyon, and is obviously affected by the topography of the canyons. At the head of a canyon, sediment failures always occur as slides with continuous reflectors. And in the middle reach there is intensive deformation and dominated by slumps. From the lower reach to the canyon mouth, however sliding/slumping blocks dominate. Since Quaternary, Great amount of sediment charges come from the Pearl River system towards the north. With the help of steep seafloor topography, the activity of sediment failures is accelerated. Sediment re-deformation may widely occur in submarine canyons. In addition, the vertical migration of gas-bearing fluids coming from gas hydrate is also an important factor for sediment instabilities in the study area.
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Key words:
- sediment instability /
- slide /
- slump /
- slope-confined submarine canyons /
- Shenhu Area
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