Full-fit reconstruction of the South China Sea conjugate margins

• Conjugate margins of the South China Sea were restored.
• The first full-fit reconstruction including uncertainties was modeled.
• Formation of NW Sub-basin and ridge jump were affected by the Xisha Trough.

Although the South China Sea margins have been well-studied, there are no full-fit reconstructions that document the complex rifting history in a regional geodynamic context. We restored conjugate margins to their original Late Cretaceous unstretched geometries, and generated the first full-fit reconstructions of the South China Sea conjugate margins. The impact of magmatic underplating on restoration and full-fit reconstruction was estimated quantitatively. The full-fit reconstruction model includes restoration uncertainties and results in minimum gaps and overlaps between the restored conjugate margin geometries. Based on our restoration, the full-fit reconstruction and the continental basement thickness distribution, we estimate that there was more extension of continental basement on the western part of the conjugate margins compared with the eastern margin prior to the initiation of seafloor spreading. Therefore, the mid ocean ridge initially formed in the east and propagated westward to open the South China Sea. Seafloor spreading propagated along the Xisha Trough during NW Sub-basin formation, but continental breakup occurred along the southern side of the Zhongsha–Xisha Islands where the lithosphere was probably weaker than along the Xisha Trough, consistent with the geometry and evolution of the NW Sub-basin and the southward jump of the mid oceanic ridge.