Coral- and oyster-microbialite patch reefs in the aftermath of the Triassic–Jurassic biotic crisis (Sinemurian, Southeast France)

International audienceThe end of the Triassic and the Early Jurassic are intervals characterised by profound biotic and environmental changes,accompanied by dramatic decreases in marine fauna diversity. Corals were strongly affected and assemblages underwent asevere reduction; compared with those of the Upper Triassic, the Early Jurassic is traditionally defined as holding a ‘‘reefgap’’. A Sinemurian coral-microbialites patch reef, located in southern France in the He´rault department (Le Perthuslocality), is here described. This bioconstruction developed in a shallow mixed siliciclastic-carbonate inner ramp setting.The reef volume is composed of up to 70% of an intercoral facies mostly microbialites, with subordinated sediments(approximately 20–30% of the intercoral facies). Therefore, the patch reef can be defined as a coral-microbialite bioconstruction,in which microbialites were the main framebuilders. The coral assemblage has low diversity and is dominatedby massive to branching colonies of Chondrocoenia clavellata. This highlights the reef diversity after the T/J boundarycrisis. The Le Perthus patch reef could have acted as an edge for the dominant currents and probably induced reductions inhydrodynamic energy and sedimentation on one of its sides. Consequently, it could have triggered the growth of smalllateral bioconstructions, composed of oysters and microbialites, uniquely on one of its sides. The evolution of the faciesshows that the Le Perthus patch reef grew in a shallowing-upward setting accompanied by an increase in siliciclastic inputs.The rate of bioerosion and the faunal assemblage suggest that the bioconstructions could have been developed in amesotrophic environment