peer reviewed ; The facies architecture, sedimentary dynamics and paleogeographic evolution were reconstructed for a number of Frasnian buildups developed on a carbonate platform on the south side of the Dinant Synclinorium (Belgium). Bed-by-bed sampling and detailed petrography were complemented by magnetic susceptibility analysis, allowing for high-precision lateral correlation. Six facies were recognised in the buildups, each characterized by a specific range of textures and assemblage of organisms: grey, pinkish or greenish limestone, with stromatactis, corals and stromatoporoids (facies A3-L3); grey limestone with corals, peloids and dasycladales (facies A4-L4); grey, microbial limestone (facies A5-L5); grey limestone with dendroid stromatoporoids (facies A6-L6); grey, laminar fenestral limestone, (facies A7-L7); grey, bioturbated limestone (facies A8-L8). The time-equivalent off -buildup sediments include a large amount of transported material that originally came from the buildups. Sedimentological evidence suggests that facies A3-L3 developed between the storm wavebase and the fairweather wavebase, in a oligophotic environment. This facies contains lenses of facies A5-L5, with stromatolitic coatings and Renalcis-rich thrombolitic bushes. These lenses were developed in greatest abundance closest to the fairweather wavebase, and they became anastomosing. Facies A6-L6 was developed in an environment with slightly restricted water circulation; there is a steady transition between this facies and the fenestral limestone A7-L7, which were deposited in a moderately protected subtidal to intertidal area. Facies A8-L8 developed at subtidal depths in a quiet, lagoonal environment. The buildups started with the development of facies A3-L3, with microbial lenses and algal facies becoming progressively more abundant upwards. Above about 20m in each buildup, more protected facies are found in the buildup’s central part. This atoll-like geometry suggests the development of restricted sedimentation in this central area, ...