Abstract:

The early carboniferous coral reef of the Cat Ba Island, Vietnam is mainly developed in the interior of the carbonate platform. In this article, we present our new study results on microfacies characteristics and the sedimentary environment of the rocks in the coral reef profiles based on the analysis of the carbonate microfacies as the major means. Three types of microfacies have been identified: Bioclastic packstone, coral framestone, bioclastic grainstone. The facies model is composed of the open platform facies, coral reef facies and the shoal facies. According to this microfacies analysis, the sedimentary environment during the coral reef evolution was reconstructed. It is indicated by the assemblage of microfacies and its longitudinal regularities along the profiles; Generally, the coral reef has developed in the shallow water environment while the open platform has formed in the subtidal zon.