A 3D Snapshot of Crustal Breakup Deduced From Seismic Analysis of the Tip of the NW South China Sea

Based on a high-resolution seismic reflection data set, we describe and map rift domains at the tip of the V-shaped NW-South China Sea (NW-SCS) Basin. We compare our rift domain map with seismic refraction, magnetic and gravity field data, and previously mapped Continent-Ocean Boundaries (COB). We also define and map syn-breakup sedimentary and magmatic sequences across the sediment-rich NW-SCS, which enables us to reconstruct the tectono-stratigraphic evolution of the area. This work enables us to describe and discuss the 3D architecture and nature of the crust at the tip of the NW-SCS, investigate how extensional and magmatic processes interacted during the breakup, and propose a kinematic model for late rifting, breakup, and finally stalling of the seafloor spreading system. This study provides exceptionally well-documented insights into the spatial and temporal evolution at the tip of a so-called "rift propagator," and enables us to show that breakup in the NW-SCS may rather correspond to a "retrogrador," in which the extension zone retreats due to the reorganization of a failing rift system.