CHRONOLOGY OF CORAL REEFS AT THE XISHA ISLANDS AND ITS INTERPRETATION

The chronological data measured with the methods of ¹⁴C, ²³⁰Th/²³⁴U and ESR dating is compared in this paper for the coral reef samples collected from the Xisha Islands. The ages are found different with the methods used. Based upon the principles of the dating methods and the mineral composition of the coral reefs, we analyzed and discussed the reasons of the difference as such in connection of the ages of the geological events in the region, and the ages of the coral reefs are recalculated. It is assumed that the original corals were formed about 30000 years ago, the mineral composition of corals were changed in 6000-7000 years ago as the sea level rising to the peak. Coral reefs with high density were formed about 5000 years ago by enhanced carbonate cementation. The results of this work provided a reasonable interpretation to the difference in ages gained by various techniques, and the conclusion is certainly helpful to the selection of a reasonable method for coral reefs dating in the future.