Upper Devonian lithostratigraphy of Belgium

The lithostratigraphic scale of Belgium, which is the cradle of several global Devonian stages, has been revised after completion of the update of the Geological Map of Wallonia (Carte géologique de Wallonie) at a scale of 1/25,000 and recent stratigraphic and sedimentological research. As a result, 100 lithostratigraphic units (groups, formations, members, facies, horizons) for the Upper Devonian Series have been re-defined. Whereas most of the units discussed in this overview are traditional divisions of the Belgian lithostratigraphic scale, this update includes revisions to their definitions, boundaries, and ages. New terms have been introduced essentially for notable horizons and facies. Additionally, some previously described formations have been reclassified as members as they are difficult to distinguish and separate on geological maps. The Frasnian lithostratigraphic units reflect the development of mixed argillaceous-carbonate deposits during the major transgressions that culminated at the end of the stage. This was followed by the gradual emergence of littoral siliciclastic facies that took place during the Famennian regression. Re-installation of carbonate deposits was recorded during the latest Famennian (Strunian transgression), heralding the lower Carboniferous carbonate succession to come. Reefs occur in the Frasnian (buildups, mud mounds, biostromes) and their presence in the middle Famennian is remarkable.