Tianheban epoch
33% archaeocyaths but only one genus
Abstract of ref. 2127:
The limestone of the Tianheban Formation on the Yangtze Gorges belongs to open shelf marine deposit in middle Early Cambrian age. Two distinct types of archaeocyath reefs are preserved - an isolated archaeocyath mud mound, and a patch reef. The reefs are composed of irregular archaeocyathids and calcified microbial microfossils such as Epiphyton, Renalcis, Givanella, etc., belonging to baffling reef mounds. The patch reef succession shows the hydrodynamic changing from low energy to moderately high energy, and then to a low energy environment. 