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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.