Rifted margins result from continental lithosphere extension, breakup, and transition to seafloor spreading by modes typically described by end‐member conceptual models. However, current geophysical data challenge these archetypes showing a more complex spectrum of rifting styles. Here, we integrate geophysical and geological observations to constrain the time and space evolution of the central South China Sea (SCS) rift system. We provide new insights into the continental extension mechanisms and continent‐ocean transition (COT) formation from a seismic transect parallel to the extensional direction of the central SCS rift system. We present 850‐km‐wide region of continental crust where distributed extensional deformation formed a pattern of lithospheric boudinage defined by seven 100‐ to 200‐km‐long structural segments. Each segment is formed by an 18‐ to 24‐km‐thick crust sector laterally thinning into an interboudin neck with ≤10‐km ultrathin crust (ß factors ~3.3–6.5). Drill and stratigraphic information support that extension continued at all six interboudin necks in the central SCS until ~23 Ma, when breakup by seafloor spreading propagation reached one of them. We propose that the seven segments evolved as discrete subsystems from early rifting to breakup. Structurally equivalent ultrathin crust grabens occur NE and SW of both SCS conjugate margins, supporting a 3D wide rift mode of deformation across the SCS rift system. The six ultrathin crust contemporaneous necks and the abrupt nature and location of the COT support that the breakup was not controlled by further continental lithospheric thinning but rather was determined by the seafloor spreading propagation toward the SW.

中文翻译：

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了解大裂谷的3D形成：南海中部裂谷系统

大陆边缘岩石圈的扩展，破裂和过渡到海底扩展，这是由最终成员概念模型通常描述的模式造成的。但是，当前的地球物理数据对这些原型提出了挑战，这些原型显示出更复杂的裂谷样式。在这里，我们整合了地球物理和地质观测资料，以约束南海中部裂谷系统的时空演化。我们从平行于中央SCS裂谷系统伸展方向的地震剖面上提供了有关大陆伸展机制和大陆-海洋过渡（COT）形成的新见解。我们提出了约850 km宽的大陆壳区域，其中分布的伸展形变形成了由七个100 km至200 km长的结构段定义的岩石圈联结模式。ß因子〜3.3–6.5）。钻探和地层信息表明，延伸一直持续到南海中部的全部六个交汇处，直到〜23 Ma，海底扩展传播造成的破裂达到其中之一。我们建议从早期裂谷到破裂，这七个部分演变成离散的子系统。结构上等效的超薄结c发生在两个SCS共轭边缘的NE和SW处，支持整个SCS裂谷系统的3D宽裂谷变形模式。六个同时期的超薄地壳颈和COT的突然性质和位置支持该破裂不受进一步的大陆岩石圈变薄控制，而取决于海床向西南方向的扩展传播。