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5.14. Bayard Formation – BAY

 

Authors: Conil, 1968; Groessens & Noël, 1975; Paproth et al., 1983; Delcambre & Pingot, 1993.

Description: Well-bedded (although some is solution-seam pseudo-bedding), dark grey or brownish-grey, crinoidal limestones, locally cherty. The formation forms the proximal lateral equivalent of the lower part of the Waulsortian buildups, and locally occurs immediately below and as intercalations in the buildups. It overlies the Maurenne Fm and grades up into the Leffe Fm.

Stratotype: Dinant, immediately south of the Roche à Bayard (DSA).

Area: The formation is restricted to the peri-Waulsortian areas of the DSA and passes laterally into the lower part of the Yvoir Fm when traced away from the buildups.

Thickness: 5 to 30 m. 11.6 m in the stratotype.

Age: Early Ivorian based on the entry of the conodont Polygnathus communis carina near the base of the formation. Spatognathodus bultyncki enters near the top of the formation in the type section. Corals are uncommon and poorly known. Plurilocular foraminifera are absent. The Bayard Fm corresponds to the third-order sequence 3 and to the TST of the sequence 4 of Hance et al. (2001).