3.3.2. Moulin Liènaux Formation - MLX
Version: revised December 2009, F. Boulvain and M. Coen-Aubert
Authors: Tsien, 1974: Chalon, Arche and Ermitage Members; Bultynck & Mouravieff, 1999. Boulvain & Coen-Aubert, 2006: La Boverie Member; Coen-Aubert, 2009.
Description: In its type locality the Moulin Liènaux Fm is divided in ascending stratigraphic order into the Chalon, Arche and Ermitage Members. The lower part of the Chalon Mbr consists of interbedded grey-brownish shales and thin argillaceous nodular limestone beds, in the upper part thickness and frequence of limestone beds increase; the macrofauna consists of corals and brachiopods. The Arche Mbr is represented by large bioherms (up to 120 m thick) with stromatactis, corals and stromatoporoids. In the lower part the limestone is pinkish-reddish, in the upper part light-grey. Development of the bioherms starts in the upper part of the Chalon Mbr and continues in the major part of the Ermitage Mbr. The latter consists essentially of greenish shales with at some levels argillaceous nodular limestone beds. In the reefal areas of Couvin and Rochefort, the La Boverie Member corresponds to the carbonate deposits lying between the Arche Member and the Bieumont Member of the Grands Breux Formation, laterally to the upper part of the Ermitage Member. It starts with bedded limestones which are often argillaceous or bioclastic and it ends with light grey massive limestone which is more or less biohermal. The La Boverie Member is 31 m to 34 m thick in the type locality.
Stratotype: Abandoned Arche Quarry immediately south of Frasnes; the boundary with the overlaying Grands Breux Fm is exposed in the nearby railway cut Couvin-Charleroi. Active quarries La Boverie at Rochefort.
Area: Southern part of the Dinant Synclinorium and south-eastern border of this synclinorium up to Durbuy (Chalon Mbr) and Aywaille (Ermitage Mbr). The bioherms of the Arche and La Boverie Members are known in the reefal areas of Couvin and Rochefort, on the south side of the Dinant Synclinorium and in the southeastern part of the Philippeville Anticlinorium.
Thickness: About 150 m in the type area. The formation is thinning out and away on the south-eastern border of the Dinant Synclinorium.
Age:Early and middle Frasnian, upper part of transitans conodont Zone, punctata Zone and lower part of hassi sl Zone (Vandelaer et al., 1989).