Paleoecology and paragenesis of lower Silurian micrite-supported bioherms: East Point Member, Jupiter Formation, Anticosti Island, Quebec, Canada

Early Silurian, micrite-supported carbonate bioherms, containing an inexplicable abundance of spar-filled shelter and stromatactoid cavities, are exposed at the south-eastern end of Anticosti Island, Quebec, Canada. Based on the controversial postulate that these structures are related to the evolution of gas clathrate hydrate, this study attempts to refine this theory with respect to another set of well-preserved carbonate bioherms from the geological record. Detailed field, petrographic, and geochemical analysis suggest that deposition occurred in a middle- to outer-ramp setting, in water depths on the order of 15 to 200 m. This study also reveals a complicated early diagenetic history in which hypogenic processes, specifically H 2S migration, may have been an important contributing factor towards cavity creation, enlargement, shape, and infilling characteristics. These observations contradict previous interpretations of the bioherms which (1) suggest deposition occurred in very shallow water conditions (< 15-30 m) (2) that the internal cavities resulted from erosion and winnowing by seafloor currents.