In the major part of the Dinant Synclinorium, the Couvinian is characterized by a mixed siliciclasticcarbonate sequence, about 750 m thick in the Couvin area. S e stage is part of a major transgressive cycle that starts in the underlying upper Emsian Hierges Formation. In the southern part of the Namur Synclinorium, its base rests with an angular unconformity on Silurian rocks. In the past, it was internationally used as the lower stage of the Middle Devonian. However, the Eifelian which base is slightly younger was also internationally used in the same sense. In 1980, by a majority vote of the international Subcommission on Devonian Stratigraphy, the base of the Eifelian was chosen as the base of the Middle Devonian Series.