2.1. The Dinantian – Silesian transition
2.1.1. Gottignies Formation - GOT
Authors: Conil (1959); Paproth, Conil et al. (1983).
Description: Finely bedded silicites (completely silicified limestone beds or ‘phtanites’ and siliceous ‘radiolarian’ shales), transitional between Dinantian limestones and Namurian siliciclastics (‘Phtanites tachetés de Gottignies’). The contact with underlying massive limestones is conspicious and marked by an angular unconformity.
Boundaries: lower boundary coinciding with top of Dinantian carbonate units; upper boundary to the Belgian Coal Measures Group seems more transitional and traced below first shale bed with goniatite horizon, assigned to the Chokier Formation.
Stratotype: Northeast of Gottignies (Conil, 1959); parastratotype: Mont des Groseillers section, canal Blaton-Basècles (Bouckaert et al., 1961).
Area: Western part of the Namur Synclinorium (‘Auge hennuyère’, Blaton - Saint Ghislain area); corresponding beds in the northern (Turnhout well) and eastern Campine basin, including the Visé-Puth High are incorporated in the Souvré Formation.
Thickness: Up to 75 m in the Blaton area.
Age: Viséan – Serpukhovian transition. Unspecified, between Warnantian (Brigantian) and Arnsbergian-dated beds. The association of marker fossils such as Caneyella membranacea - Eumorphoceras sp. in Blaton points to a Pendleian (E1) age (earliest Serpukhovian).
Remark: The Gottignies and Souvré Formations are generally included in the Dinantian lithostratigraphic sequence, in accordance with Paproth, Conil et al. (1983). However, lithological change and hiatus tend to be greater at the base of this unit, which may favour its inclusion in the Belgian Coal Measures Group.
2.1.2. Souvré Formation – SOU
Authors: Charles, 1924; Calembert, 1945; Pirlet, 1967; Barchy & Marion, 2000.
Description: Thinly bedded laminated dark grey to black silicites (“phtanites”), or silicified shales and limestones, strongly weathered and porous at outcrop. The contact with underlying massive limestones of the Visé Formation is marked by an angular unconformity. Upper boundary locally transformed as a paleosol of Cretaceous age; otherwise covered by Chokier Formation (Charles, 1924; Calembert, 1945).
Stratotype: Top beds of Richelle quarries F, L and M, south of Visé (Pirlet, 1967).
Area: Visé-Puth High, probably extending in the northern (Turnhout well) and eastern Campine basin; corresponding beds in the western part of the Namur Synclinorium (‘Auge hennuyère’, Blaton - Saint Ghislain area) are assigned to the Gottignies Formation.
Thickness: About 15 m in Visé – Campine basin.
Age: Viséan – Serpukhovian transition. Unspecified, between Warnantian (Brigantian) and Arnsbergian-dated beds.
Remark: Lateral equivalent to the Gottignies Formation. Defined as a mappable unit on the mapsheet Dalhem-Herve (Barchy & Marion, 2000).