Kinematic models for the opening of the South China Sea: An upwelling divergent flow origin

We investigate the kinematics of continent breakup and seafloor spreading in response to the upwelling divergent mantle flow using the optimal nearly-analytical discrete method, Modeling results show that a larger upwelling rate (V-z) in the upwelling divergent flow system favors the earlier development of continent breakup and seafloor spreading and the formation of narrow continental rifted margins and mantle exhumation; while a larger half divergent rate (V-z) favors the diffusive lithospheric thinning and the formation of wide continental rifted margins and mantle exhumation. The upwelling divergent flow-driven continent extension is strongly depth-dependent at the proximal margins, but it behaves approximately in a depth-uniform manner at the distal margins. Application of this model to the South China Sea (SCS) demonstrates that: (1) an upwelling flow operation with V-z = 0.3 cm/yr can explain the pre-spreading continent extension of the SCS between ca. 65 Ma and ca. 33 Ma; (2) the followed upwelling divergent flow with V-z = 2.5 cm/yr and V-z =0.3 cm/yr can reproduce the seafloor spreading history at ca. 33-16 Ma in the SCS central oceanic basin; and (3) the post-16 Ma thermal cooling since the cessation of the SCS seafloor spreading contributed similar to 1.2 km to the present-day bathymetry at the relict spreading ridge. The upwelling divergent flow with a high ratio of V-x/V-z was also likely responsible for the occurrence of the very wide rifted continental margins bounded the SCS. We suggest that an upwelling divergent mantle flow played a leading role in the opening of the SCS. (C) 2017 Elsevier Ltd. All rights reserved.