Formation and development of coral reefs in the South China Sea

Coral reefs are unique geologic bodies that are formed by biological activity in tropical and subtropical oceans and coastal areas. When and how these reefs came into being and reached their present scales in the ocean remain controversial. Based on strontium, carbon and oxygen isotopes and mineralogical, micropaleontological and elemental analyses of the coral Meiji Reef in the Nansha Islands, South China Sea, we reconstructed the formation and evolutionary history of the island. The results show that the coral reef developed on top of a volcanic basement under the combined influence of diverse factors, especially regional tectonic movement and long-term climatic change. The evolution of the reef was divided into eight stages based on these factors. Extensive exposure was frequently found on the island, and an almost 1000-m thick coral reef eroded simultaneously. The entire development process of coral reefs on the island may be explained by a phased erosion deposition model, which was also found to be suitable for studying the development of coral reefs in the Xisha Islands. We suggest that many coral reefs in the tropics may not flourish continuously over long periods of time, and sedimentary hiatuses normally occur in the layers of coral reefs.