Résumé : A global view of the geology of "F2j' mud mounds from the upper part of the Belgian Frasnian is briefly presented. The paper deals successively with the stratigraphy and the sedimentology of the mounds and the paleogeographic evolution of the Frasnian ramp in relation with eustatism. Diagenetic evolution of buildups and enclosing rocks is also considered. A selection of sections from mound, peri-mound and off-mound environments is described in detail. -English summary