5.17 Ecaussine Formation - ECA

Authors: Bouckaert et al., 1971; Paproth et al., 1983; Hibo, 1994; Doremus & Hennebert, 1995a, 1995b.

Description: The formation includes 2 members: the Perlonjour Mbr overlain by the Soignies Mbr.

- Perlonjour Member – PLJ (Hibo, 1994): Argillaceous and siliceous, cherty limestones, in metre-thick beds with some thin shaly intercalations.

- Soignies Member – SOI (Groessens, 1978): This member corresponds to the well-known “Petit Granit”. It comprises thick-bedded to massive, dark blue-grey limestones which are very crinoidal (encrinite). The rich and varied fauna is mainly of brachiopods and corals. An argillaceous marker bed, the "Délit à la terre bleue", occurs 3 to 5 metres below the top of the member.

Stratotype: Perlonjour Mbr: Perlonjour quarry, east of Soignies. Soignies Mbr: Hainaut quarry at Soignies.

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

Thickness: 52 – 54 m. Perlonjour Mbr, 22 m in the type area; Soignies Mbr, 30-32 m in the type area.

Age: Ivorian (Cc2aConodont Zone, Conil et al., 1991).