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2.2.15. Bois de Bordeaux Formation - BOR

Authors: Légende carte géologique 1/40.000, 1929; Lacroix, 1991b.
Description: Lacroix (1991) sudivided the Bois de Bordeaux Fm into three members, in ascending order Mautiennes, Alvaux and Mazy Members.
The contact between the conglomeratic base of the Mautiennes Mbr and the underlaying Silurian rockx represents an angular unconformity. The member is composed essentially of red, greenish or variegated sandy-argillaceous rocks. The main part of the Alvaux Mbr consists of organoclastic limestones with thin interbedded shale layers and intercalations of oolithic limestones. The macrofauna includes colonial rugose corals, brachiopods and a biostromal level with stromatoporoids near the top. The Mazy Member essentially consists of red sandy-silty shales with a few intercalations of reddish and greyish limestone beds.
Stratotype: Gembloux, between Mazy and Les Mautiennes on the east banks of the Orneau river.
Area: Northern flank of the Namur Syncline between Soignies and Lavoir.
Thickness: About 120m in the Orneau Valley in the central part of the northern flank of the Namur Syncline, only 10m at Soignies in the western part and about 20m at Lavoir in the eastern part.
Age: Givetian; conodont data from the Mautiennnes and Alvaux Members support correlation with the upper part of the Terres d'Haurs Fm, the Mont d'Haurs Fm and the lower part of the Fromelennes Fm on the southern flank of the Dinant Synclinorium. The base of the overlaying Bovesse Fm belongs to the Lower falsiovalis Zone (Lacroix, 1999).