2.1.7. Bernissart Calcirudites Formation- BRN

Authors: Marlière (1936b), Robaszynski (1975).

Description:Granular to gravelly, organo-detritic, grey to yellow at outcrop, only slightly glauconitic limestones, with flints and a chalcedony cement, with sandy and glauconitic marl beds. Towards the base the limestones are coarse, conglomeratic, glauconitic and ferruginous: this is the Hautrage Conglomerate Bed (Robaszynski, 1975c) or "Tourtia", as seen in local names such as "Tourtia de Tournai", "Tourtia de Montignies-sur-Roc"; "Tourtia du Pas-de-Calais" in northern France, "Tourtia" or "Sarrazin de Bellignies".

Stratotype: Pit n°1 at Harchies, between 53.50 m and 82 m.

Area: From the western part of the Mons Basin to the north of France.

Thickness:2 to 30 m and sometimes more in the most subsided parts of the basin.

Age:  Early and Middle Cenomanian age on the basis of the ammonites Mantelliceras mantelli (Early Cenomanian), Acanthoceras rhotomagense (Middle Cenomanian) and Schloenbachia varians and the oyster Amphidonte obliquatum.   

Remarks:- This is the "Assise de Bernissart" or "meule cénomanienne" of  Marlière(1936a, b, 1939, 1957), raised to rank of formation by Robaszynski  (1975).

- The term "Formation du Cornet" used by Doremus (1997) is a junior synonym of the Hautrage Conglomeratic Bed, which indicates the "Tourtia de Tournai" (Robaszynski, 1975).