Reconstruction of the Cretaceous Palaeogeographic Position of Hainan Island and Its Tectonic Significance

Reconstruction of the palaeogeographical location of Hainan Island is important for understanding the interaction between Indochina and South China. In this study, we integrate topographic relief, gravity anomalies, and magnetic anomalies, along with geological constraints, to determine the Cretaceous location of Hainan Island. The results show that Hainan Island was connected with South China in the Cretaceous and located in the Beibu Gulf Basin, and then rifted from South China with about 230 km displacement along the southeast direction during the Cenozoic. Further geological evidence suggests that Hainan Island and South China have co-evolved since at least the Permian. Hainan Island was rifted from South China from the Palaeocene to the Oligocene due to escape tectonics caused by the India–Asia collision. These new findings provide important clues for investigating the impact of the India–Asia collision and the continental margin evolution of South China.