Early Middle Ordovician biostromes, bioherms and bioherm complexes (up to 6 m thick).
Lithistid sponges (10-30 % of reef volume), seven genera
Bryozoans relatively diverse (encrusting and branching), ten genera
Tabulate corals up to 20 % of reef volume (Billingsaria and Eofletcheria).
Solenoporaceans rare.
Micritic crusts (microbes).
Very rare stromatoporoids.
Includes Petite Ile au Marteau locality