5.2.5 Vieux-Moulins de Thilay Formation - VMT

Description: Dark and light grey laminated siltstone and slate, “quartzophyllades zonaires” from the literature, with black slate levels.

Stratotype: not yet defined; type area in the outcrops north of the hamlet of Vieux-Moulins de Thilay, close to Croix Scaille.

Area: In the core of a fold in the eastern part of the massif at Vieux-Moulins de Thilay, Franc-Bois de Willerzie, les Hubiets (Geukens, 1981; Roche et al., 1986).

Thickness: unknown.

Age: Outcrops west of Vieux-Moulins de Thilay are dated with acritarchs as Arenig to Llanvirn (Early to Middle Ordovician) by Roche et al. (1986). New evidence on the range of the genus Frankea and the species F. sartbernardensis (Servais, 1993; Brocke et al., 1995) allow to restrict the age of the unit from late Arenig to Llanvirn (Mid Ordovician).

Remarks: here defined after Beugnies, 1960.

(M. VANGUESTAINE, I. BELANGER)