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3.1.4. Vitrival-Bruyère Formation - VTB

Authors: Maillieux, 1926a; emend. Michot, 1954.

Description: Blackish, silky and fine micaceous shale with quartzite intercalations and graptolites (Maillieux, 1926a); micaceous pelitic unit (Michot, 1928); the higher part contains clayey quartzitic sandstone in thick beds, covering black or blue shale with intercalations of black or dark coloured mudstone, siltstone and fine sandstone.

Stratotype: outcrops in the river bed of the Ruisseau Le Treko, west of the hamlet La Bruyère, 500 to 1050 m east of the church of the village Vitrival.

Area: Condroz inlier; possibly the Oxhe Fm is a lateral equivalent or synonym for the unit in the Oxhe inlier.

Thickness: Not estimated yet, except for the upper part with quartzite beds: 20-30 m.

Age: Graptolites in a locality at Vitrival-Bruyère in the upper part of the unit indicate the Climacograptus peltifer biozone (Maillieux, 1933). A restudy of the fauna by Bulman (1950) confirmed the presence of the Climacograptus peltifer biozone (now equivalent to the foliaceus biozone), which is situated in the uppermost Costonian to lower Longvillian substages, uppermost Aurelucian and most of the Burrellian stages, Caradoc (Fortey et al., 1995).

(J. VERNIERS)