Slab Pull Driven South China Sea Opening Implies a Mesozoic Proto South China Sea

Most paleo-reconstruction models agree that the South China Sea (SCS) opens within a continental domain located at the trailing edge of the subducting plate of a vanished ocean named Proto South China Sea (PSCS). Existing models do not agree on the age, size, and location of the putative oceanic domain, thus hindering the reconstruction of the plate circuit in the distant past. In this study, we test the relevance and implication of the opening of the SCS in the downgoing plate with a series of thermomechanical simulations which appear to impact the possible age of the PSCS. Our findings suggest that the oceanic domain must be stronger than the continental margin for the slab pull force to be transmitted to the continental margin, resulting in continental breakup. Our simulations support a Cretaceous age, rather than an Eocene, for at least part of the PSCS sea-floor spreading. Most scientists agree that the South China Sea formed within the China margin through the subduction of an ancient oceanic plate, known as the Proto South China Sea (PSCS), beneath Borneo. Today, this oceanic plate has nearly vanished from the Earth's surface. Only a few scattered fragments found on the islands of Borneo and Palawan confirm its existence. The history of an ocean that no longer exist can be approach by physically driven models. In this study, we use numerical simulations of subduction zones to evaluate the mechanical conditions required for the PSCS subduction to be responsible of the South China Sea formation. We find that the subduction of old oceanic plate are more likely to generate new basin opening within continental margin. Combining our results with the limited age derived from the remaining fragments of the PSCS seafloor, we propose that this oceanic plate formed at least 65 million years ago, probably around 100 million years. The slab pull such as the one of the Proto South China Sea (PSCS) may drive spreading within the continental margin of the lower plateSimulations show that the PSCS domain must be stronger than the China continental margin in order to localize the breakup on the continentA minimum Cretaceous age is required for at least part of the PSCS oceanic lithosphere