5.16 Lalaing Formation - LAL

Authors: Conil & Delcourt, 1989; Doremus & Hennebert, 1995a, 1995b.

Description: In the west (Mévergnies), the formation comprises grey to brown, crinoidal dolomite, locally calcareous, with silicified fossils. Black and grey chert occurs in the lower part.In the east, the formation becomes mainly limestone with dolomitic and cherty levels ("Cliquantes" partim). In the stratotype, grey to blue-grey argillaceous limestones form the dominant lithology. Crinoidal and shelly layers are interbedded with thin marlstone layers. Chert nodules occur locally.

Stratotype: Section at Lalaing castle, at Ecaussinnes-Lalaing.

Area: Western HSA, at least from Ath to Seneffe.

Thickness: 19 to 21 m.

Age: Early Ivorian (Polygnathus communis carina Conodont Zone, Conil et al., 1991).