The middle-late Cambrian reef transition and related geological events: A review and new view

Several geological events occurred across the boundary between the Cambrian Epoch 3 and the Furongian, including positive carbon and sulfur isotope excursions, a eustatic sea-level drop, major faunal turnover of trilobites, and diversification of new organisms. The coincidence of these events and the transition in reefal fabrics suggest that reef ecosystems were significantly influenced by at least some of these events. Among the events, it is likely that sea-level change would have affected reefs, although further studies are required in order to test whether and how the other events influenced the reef transition. Epiphyton and Renalcis (and thrombolites and dendrolites formed by them) declined greatly most likely due to sea-level fall and thus decreased in shallow marine habitat at the end of Cambrian Epoch 3. The Cambrian Epoch 3 thrombolites and dendrolites were gradually replaced by a sponge-microbial association of the maze-like, maceriate reefs and the columnar stromatolites in the Furongian, coincident with a sea-level rise.