Abstract:

On the basis of investigation of modern coral reefs of Hainan and Xisha Islands of China,fundamental sedimentary facies of these regions have been identified,and the diagnostic criteria for the discrimination of various reef facies are proposed.From the fore- to the back-reefs,the sedimentary facies zones can be sbdivided as follows:the epeiric sea sand-mud facies,the fore-reef colluvial facies,the protogenous reef facies,the marginal reef conglomeratic facies,the reef flat sandy-conglomeratic facies,the sand cay(barrier)conglomerate-sandy facies and the lagoonal sand-mud facies.The differences between various types of coral reefs are in relation with the associations and the distribution of these sedimentary facies.It has been realized that submarine relief is the main factor in determining the patterns and sizes of the sedimentary facies zones.The sediments of coral reefs in the area of the Pacific-Indian Oceans are predominatly composed of the algal debris,and yet sediments of coral reefs in the South China Sea are predominatly composed of Petraiidae.