Convergent mantle flow and plate kinematics contribute to South China Sea rifting

Continental rifting in marginal seas remains debated, particularly regarding the role of mantle dynamics in lithospheric extension. The South China Sea, the largest marginal sea in the western Pacific, provides a well-constrained case for exploring this issue. Seismic observations reveal a major transition from early Paleogene distributed extension to late Paleogene hyper-extension along its northern margin, with systematic westward rift propagation. Numerical mantle flow models predict upper-mantle flows beneath Southeast Asia, comprising southwestward Pacific flow in the east and converging Pacific and Tethyan/Eurasian flows in the west, which are dynamically consistent with the westward migration of rifting. Subduction of the fossil Wharton Ridge to the southwest may have enhanced mantle-pressure gradients and influenced the transition from distributed extension to hyper-extension. Here, we show that mantle flow, together with plate kinematics, contributes to the regional stress framework of rifting, helping to explain the spatiotemporal organization of extension in marginal sea systems.