3.11 Grandcourt Formation - GRT

Author : Dumont, 1842.

Description: Generally bituminous grey clay and marl with a thin silty-calcareous lamination, and laminar limestone nodules ("Schistes Cartons" Member), passing toward the top to sandier laminated marl, rich in septaria. Occurrences of centimetric to decimetric limestone beds.

Stratotype: Latour borehole.

Area and thickness: The formation outcrops in the south of Belgian Lorraine, with a thickness of approximately 40 m in the western area. It thickens towards the east to reach about 60 m near the Luxemburg border.

Age: The Grandcourt Formation is dated from Toarcian, from Harpoceras falciferum Zone to Grammoceras thouarcense Zone (Delsate, 1990; Laenen, 1991).