Different expressions of rifting on the South China Sea margins
Different expressions of rifting on the South China Sea margins
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DOI：
10.1016/j.marpetgeo.2014.05.023
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发表时间：
2014-12
影响因子：
4.2
通讯作者：
D. Savva;M. Pubellier;D. Franke;N. Chamot‐Rooke;F. Meresse;S. Steuer;J. Auxietre
中科院分区：
文献类型：
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作者：
D. Savva;M. Pubellier;D. Franke;N. Chamot‐Rooke;F. Meresse;S. Steuer;J. Auxietre
大陆边的裂断一般是沿大陆断裂的地带沿着发生的，断裂的原因有多种，包括引发伸展力的边界条件，以及大陆边的组成和地质历史所固有的内部物理边界。中国南海（SCS）在第三纪以剪刀状的方式打开，提供了一幅裂谷构造的图像，它沿着走向盆地边缘变化。南海有着悠久的伸展历史，可以追溯到晚白垩世，并使我们能够观察到北方大陆边缘和华南近海的早期伸展，大型低角度断层将三叠纪至早白垩世花岗岩上的中生代沉积物分离，或沿着影响古生代至早白垩世系列的宽褶皱的短肢分离。这些早期断层形成狭窄的槽，槽中充满粗的多源砾岩，向上逐渐变粗为粗砂岩。由于这些低角度断层重新激活了旧的趋势，它们的几何形状根据褶皱或花岗岩边界的方向而变化。在始新世期间，一组较晚的断层占主导地位，其特征是一般的东西向低角度和高角度正断层。随着盆地填充大陆或非常浅的海洋沉积物，相关的半地堑基底加深。这一后续方向在南海北部和西南部都有很好的表现，并经常重新激活早期的determination。在某些地方，这两个断层集的交叉导致极端拉伸与地壳石香肠和地幔折返，如在越南断层东部的富庆盆地。第三个方向的断层，很少重新激活的detentries是NE-SW和良好的发展附近的洋壳在南部和西南部的盆地。尽管海底扩张主要在北方发展，但与之前的方向相交的这个方向是活跃的，并在中新世晚期结束，在区域性中新世中期不整合面（称为MMU）开始之后，该方向约为15.5 Ma。晚中新世的标志是区域基底下降和靠近海岸的陆架上的局部正断层。南海东南边缘不像北方边缘那样具有伸展特征。滑脱现象在危险地带和里德浅滩地区很常见，偶尔可能导致地幔折返。伸展地壳上的沉积环境在整个沿着裂谷和大部分伸展过程中一直保持较浅，直到晚中新世突然加深。这一时期也对应于巴拉望、沙巴和沙捞越的西北婆罗洲楔缩短的停止。我们相关的变化的边缘结构和组成的边缘，主要是花岗岩基和中生代广泛的褶皱的发生，与位置的determination和主要的正断层的条件下的风格裂谷，地壳boudinage，因此地壳厚度。
Rifting of continental margins is generally diachronous along the zones where continents break due to various factors including the boundary conditions which trigger the extensional forces, but also the internal physical boundaries which are inherent to the composition and thus the geological history of the continental margin. Being opened quite recently in the Tertiary in a scissor-shape manner, the South China Sea (SCS) offers an image of the rifting structures which varies along strike the basin margins. The SCS has a long history of extension, which dates back from the Late Cretaceous, and allows us to observe an early stretching on the northern margin onshore and offshore South China, with large low angle faults which detach the Mesozoic sediments either over Triassic to Early Cretaceous granites, or along the short limbs of broad folds affecting Palaeozoic to Early Cretaceous series. These early faults create narrow troughs filled with coarse polygenic conglomerate grading upward to coarse sandstone. Because these low-angle faults reactivate older trends, they vary in geometry according to the direction of the folds or the granite boundaries. A later set of faults, characterized by generally E–W low and high angle normal faults was dominant during the Eocene. Associated half-graben basement deepened as the basins were filling with continental or very shallow marine sediments. This subsequent direction is well expressed both in the north and the SW of the South China Sea and often reactivated earlier detachments. At places, the intersection of these two fault sets resulting in extreme stretching with crustal boudinage and mantle exhumation such as in the Phu Khanh Basin East of the Vietnam fault. A third direction of faults, which rarely reactivates the detachments is NE–SW and well developed near the oceanic crust in the southern and southwestern part of the basin. This direction which intersects the previous ones was active although sea floor spreading was largely developed in the northern part, and ended by the Late Miocene after the onset of the regional Mid Miocene unconformity known as MMU and dated around 15.5 Ma. Latest Miocene is marked by a regional basement drop and localized normal faults on the shelf closer to the coast. The SE margin of the South China Sea does not show the extensional features as well as the Northern margin. Detachments are common in the Dangerous Grounds and Reed Bank area and may occasionally lead to mantle exhumation. The sedimentary environment on the extended crust remained shallow all along the rifting and a large part of the spreading until the Late Miocene, when it suddenly deepened. This period also corresponds to the cessation of the shortening of the NW Borneo wedge in Palawan, Sabah, and Sarawak. We correlate the variation of margin structure and composition of the margin; mainly the occurrence of granitic batholiths and Mesozoic broad folds, with the location of the detachments and major normal faults which condition the style of rifting, the crustal boudinage and therefore the crustal thickness.