The facies architecture, sedimentary dynamics and palaeogeographic evolution were reconstructed for a number of middle–late Frasnian carbonate mounds from the south side of the Dinant Synclinorium (Belgium). Nine facies were recognized in the buildups, each characterized by a specific range of textures and assemblage of organisms: spiculitic wackestone with stromatactis (facies Pm1), which becomes progressively enriched in crinoids and corals (Pm2); grey or pinkish limestone with stromatactis, corals and stromatoporoids (A3–L3, Pm3); grey limestone with corals, peloids and dasycladales (A4–L4, Pm4); grey, microbial limestone (A5–L5, Pm5); grey limestone with dendroid stromatoporoids (A6–L6); grey, laminar fenestral limestone, (A7–L7); and grey, bioturbated limestone (A8–L8). Sedimentological evidence suggests that facies Pm1 and Pm2 correspond to iron bacteria– sponge-dominated communities, developing in a quiet aphotic and hypoxic environment. A3–L3 developed between storm and fair-weather wave base, in an oligophotic environment. Facies A5–L5 developed close to fair-weather wave base. Facies A6–L6 and the fenestral limestone A7–L7 correspond to an environment with slightly restricted water circulation. Facies A8–L8 developed at subtidal depths in a quiet, lagoonal environment. The main differences between the middle and late Frasnian mounds concern facies architecture, and are a consequence of different palaeoceanographic settings. The large flattened middle Frasnian Arche and Lion buildups show limited vertical differentiation, large-scale progradation features, extensive exportation of material towards off-reef environment and development of inner lagoonal facies. They grew offshore from a well-developed carbonate platform with a healthy carbonate factory. Middle Frasnian sea-level fluctuations were relatively mild, and sedimentation was able to keep up with sea-level rise. At the opposite extreme, during the late Frasnian, severe eustatic rises, together with rising oceanic hypoxic conditions, were ...