Depositional architecture and structural evolution of a region immediately inboard of the locus of continental breakup (Liwan Sub-basin, South China Sea)
Depositional architecture and structural evolution of a region immediately inboard of the locus of continental breakup (Liwan Sub-basin, South China Sea)
复制标题
大陆裂解地点近海区域（南海荔湾次盆地）沉积构型与构造演化
DOI：
10.1130/b35001.1
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发表时间：
2019-07-01
影响因子：
4.9
通讯作者：
Liu, Jun
中科院分区：
文献类型：
--
作者：
Lei, Chao;Alves, Tiago M.;Liu, Jun
新的三维地震数据和区域二维地震剖面从南海北方，最广泛的数据集成像远裂边缘在世界上，被用来描述一个地区位于内侧的新生代大陆分裂的轨迹。经解释的数据集描绘了一个1.66公里厚的大陆地壳，其中莫霍面和同裂谷沉积物的底部被观察到清晰、分辨率良好的地震反射。这个极薄的大陆地壳在其底部被一个复杂的拆离断层系统所抵消，从这个系统中，向海洋倾斜的铲式断层垂直传播，以类似于构造筏的方式将六个独立的倾斜块体结合在一起。地震反射数据使我们能够调查倾斜块体上方的同裂谷和后裂谷地层的厚度，揭示了早-中始新世同裂谷地形在始新世晚期（约100年）逐渐被覆盖。38 Ma）。33 Ma（渐新世早期）以后，边缘主要沉积中心迁移到荔湾凹陷南部，向海洋的方向，如断裂序列中地层增厚所记录的。这项工作是重要的，因为它展示了如何密切的结构和沉积荔湾次盆地内的基础，裂谷相关的拆离系统，这是详细的三维地震数据首次在裂谷大陆边缘成像控制。大陆解体的标志是沉降（和地壳拉伸）的轨迹向洋壳的转移，时间跨度为1.16亿年。我们将我们的发现从南中国海推断到世界各地不对称被动边缘的发展。
New 3-D seismic data and regional 2-D seismic profiles from the northern South China Sea, the most extensive data set imaging a distal rifted margin in the world, are used to characterize a region located immediately inboard of the locus of Cenozoic continental breakup. The interpreted data set images a ∼6-km-thick continental crust in which the Moho and the base of syn-rift sediment are observed as clear, well-resolved seismic reflections. This extremely thinned continental crust was offset at its base by a complex detachment fault system from which oceanward-dipping listric faults propagated vertically to bound six separate tilted blocks, in a style akin to tectonic rafts. The seismic reflection data allowed us to investigate the thickness of syn- and post-rift strata above tilt blocks, revealing that the early-middle Eocene syn-rift topography was gradually blanketed in the late Eocene (ca. 38 Ma). After 33 Ma (earliest Oligocene), the main depocenter on the margin migrated to the south of the Liwan Sub-basin, i.e., oceanwards, as recorded by the thickening of strata within a breakup sequence. This work is important as it demonstrates how closely structures and sedimentation within the Liwan Sub-basin were controlled by a basal, rift-related detachment system, which is imaged in detail by 3-D seismic data for the first time on a rifted continental margin. Continental breakup was marked by a shift in the locus of subsidence (and crustal stretching) toward ocean crust, within a time period spanning ∼16 m.y. We extrapolate our findings from the South China Sea to the development of asymmetric passive margins across the world.