Visean

The quality exposure of Viséan rocks in southern Belgium, the diversity of facies, the pioneer palaeontological works that started in the mid 19th century and the development of the foraminifer, conodont and rugose corals zonations in the last decades were the main elements for the promotion of the international use of the Viséan Stage. Southern Belgium is probably the best-documented area for the Viséan Stage in the world. In the Namur-Dinant Basin the submarine topographic irregularities inherited from the late Tournaisian and due to different sedimentation rates on the platform, in the basin and on the Waulsortian buildups were progressively smoothed out by the Viséan sedimentation. During the Tournaisian/Viséan transition, the central Dinant type area was in a peculiar, restricted environment and poorly fossiliferous, peri-Waulsortian facies developed. A new criterion for a better definition of the base of the stage was needed and has now been adopted. It is based on the evolutionary lineage of the foraminifer Eoparastaffella. A proposed new GSSP (Global Stratotype Section and Point) in Southern China (the Pengchong section) is still under discussion, but the term Viséan will remain as a stage corresponding to the Middle Series of the Mississippian Subsystem. Service de Paléontologie animale, Université de Liège, Bâtiment B18, Allée du 6 août, Sart Tilman, B-4000 Liège; E-mail: [email protected]