Pacific inflow into South China Sea related to post-rift opening of Luzon gateway: consequences for the East Asian monsoon

The South China Sea (SCS) is the most important source of water vapor for the East Asian monsoon (EAM). Late Cenozoic (~34–30 Ma) opening of the SCS likely contributed significantly to the establishment of a strong, modern-like EAM at ~25 Ma per climate sensitivity studies. However, the importance of SCS tectonics in contributing to the evolution of the EAM has been neglected due to the temporal mismatch between both events (5–9 million years). Here, we investigate the bathymetric, sedimentary and oceanographic evolution of the SCS basin by combining Sr-Nd isotopic analyses of rift- to drift sediments from recent ocean drilling expeditions, high-resolution paleobathymetry reconstructions and ocean circulation simulations of this crucial time period. We show that the transition from fluvial, to shallow- and deep-marine environment in the SCS and its opening to the Pacific Ocean occurred well after the onset of seafloor spreading. We highlight a rapid (