5.13 Pont-à-Nôle Formation - PNL
Authors: Delcambre & Pingot, 2000.
Description: Well-bedded, dark grey dolomitic limestones, with calcite nodules. The formation comprises three units:
- A lower unit composed of some beds of crinoidal limestone.
- A middle unit of crinoidal limestone with dark chert.
- An upper unit of limestone including beds of decayed, brown dolomite, rich in corals and brachiopods.
The formation overlies the Maurenne Fm and is overlain by the Mont-sur-Marchienne Fm.
Stratotype: Gralex quarry at Mont-sur-Marchienne, in the Eau d’Heure valley.
Area: Mont-sur-Marchienne area (NSA). The formation, when dolomitized, passes laterally to the lower part of the Namur Group.
Thickness: About 100 m.
Age: Ivorian and Early Moliniacian (Late Tournaisian). Cf3 and Cf4a1 Foraminifer Zones.