Factors controlling the development of Fomichevella coral bioconstructions in the Gzhelian-Asselian (Late Pennsylvanian-early Permian) of Houchang, southern Guizhou, South China

Bioconstructions (five biostromes, one patch reef, and one large reef) of the colonial coral Fomichevella are well exposed, if infrequent, in the Upper Pennsylvanian-lower Permian of the Houchang area (southern Guizhou, China). Though they are primarily built by the same species, different growth morphologies and internal constructions are evident, which indicate different factors controlling their formation and development. The coral biostromes alternate with shoal deposits, being attributed to level-bottom communities that were closest to the reef ecosystem. The patch reef consists of a simple coral framework and a low biodiversity community. In contrast, rigid skeletal frameworks of Fomichevella are common and the biodiversity of the community is relatively higher in the large coral reef. Comparing these coral biostromes, the patch reef, and the large coral reef, several factors controlling their formation and development are suggested: stable substrate, water turbulence, sea-level fluctuation, and community structure. Hard substrates can provide stable habitats for the coral larvae during the initial colonisation stage, while the frequently changing sedimentary conditions were not conducive to the healthy development of Fomichevella . The simple community (e.g. the biostromes, patch reef) lacking encrusters and binders was too fragile to tolerate a turbulent environment. In Houchang, though intrinsic and extrinsic factors influenced the development of the Fomichevella bioconstructions, the extrinsic factors seem more important, which may be the key aspects controlling the Carboniferous coral bioconstructions.