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1.2.16. Bois d'Ausse Formation - BAU

Authors: d'Omalius d'Halloy, 1868; Asselberghs, 1946; Dejonghe, Hance & Steemans, 1994c.
Description:  The lower limit is placed at the first grey, blue grey or light-coloured quartzite bank overlying the green siltstones and sandstones of the Fooz Fm.  The upper limit is situated below the red rocks of the overlying Acoz Fm.  In the Treko valley, three members are distinguished, respectively from bottom to top:
·       The Bôlia Member (50 m) : grey or beige quartzites with cross-stratification;
·       The Tréko Member (20 m) : alternating siltstones and green argillaceous sandstones;
·       The Masuis Member (30 m): lenticular beige grey quartzite banks with rust-coloured spots and thin grey shale intercalations.  In some levels, occurrence of shale pebbles and plants remains.
Stratotypes: Bois d'Ausse,Sart-Bernard, Namur-Arlon railway; Vitrival, Treko valley; Dave, Ruisseau des Chevreuils.
Area: N and E sides of the Dinant Synclinorium and in the Vesdre Nappe.
Thickness: 100 m in the Treko valley, 135 m in the Vesdre Nappe, 180 m at Acoz, 360 m in the Meuse valley.
Age: Lochkovian (SibSubzone of the MN Oppel Miospore Biozonation) to Upper Pragian (SuSubzone of the PoW Oppel Miospore Biozonation).