Contrast Between Modern Reefs And Carboniferous Reefs In Guizhou Province

Large-scale reefs were developed in the Late-Carboniferous in south Guizhou, and the size of the reefs were rare in metazoa frame-building reef. Modern reefs are well developed in tropic sea and most of them are coral reefs.In this paper, the Late-Carboniferous coral reef in south Guizhou and modern reefs in' South Sea of China and along Continental Coast of South China are taken for examples to show the contrast between two kinds coral reef in terms of the characteristics and evolusion.The reef structure is, from the bottom to top, composed of four subunits:bioclastic shore, patchy reefs and mud mound, bioclastic limestone and Fomitchevella framestone. Five sedimentary facies belts are marked off according to the characteristics of the sediment in the reef rock.Some biological groups of different trophic levels are marked off according to biotic life and predation habits, and the trophic structure and trophic mechanism of the reef community are analyzed. The community evolved all through the process of reef development. From the aspect of cycle features of the reef rock, the reef community can be divided into four subcommunities:Phylloid algae, Ivanovia cf. manchurica, Ivanovia cf. manchurica-Antheria and Fomitchevella community. Based on analysis of contribution to reef development, different functional groups are marked off, and they build the reef together.Reef community's evolution determined reef's growth and development. The process of reef-building was:firstly the bioclastic shore was formed, then cyanobacteria, Phylloid algae and Ivanovia cf. manchurica acted respectively and built the patch-reef subunit together, and then another sediment was received due to the environmental changes and new bioclastic shore was formed, and afterwards Fomitchevella colonized and grew dispersedly and no reef-building community was formed, and at last Fomitchevella community developed rapidly and dominated the ocean floor, another environmental change resulted in Fomitchevella's death, and reef-building was over then.The formation of modern coral reef experienced several stages:coral colonizing, community bloom, arrest of development and reef development. After some grow-detention cycles, large-scale reef was formed and kept growing.Based on the research on these two kinds of reef, similarities and differences on morphological characteristics, internal structure, biological characteristics, reef-building mechanism, community evolution and reef development are obtained. Modern reefs and the late-Carboniferous reefs in southern Guizhou have the similar basic characteristics, and sediment features, reef-building mechanisms and reef-building processes are also alike. The only difference lies in biological features. The biologic species in modern coral reef community are more advanced and biomass and diversity are also higher. The several growth retardations of the late-Carboniferous coral reefs in southern Guizhou explain that this region went through massive environmental changes, and the degree of transgression, regression and climate changes are much higher than modern period.