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2.3.2. Folx-les-Caves Member - FOX

Authors: Rutot & Van den Broeck (1888).

Description: From bottom to top, the Cretaceous strata at Folx-les-Caves comprise:

-        arenaceous facies of the white chalk (“craie arénacée”);

-        conglomerate, with pebble bed; pebbles consist of petrified calcarenites but also of older strata;

-        calcarenites with Thecidea papillata and Bourgueticrinus ellipticus (“tufeau jaune” of Rutot & Van den Broeck, 1888)   

-     unconformably overlain by  “Tuffeau de Lincent” of  Palaeocene age.

The “Folx-les-Caves Formation” is restricted to the “craie arénacée” in the section above.

Stratotype: Entrance to the underground quarry “ Folx-les-Caves”at Jauche (Orp-Jauche, eastern Brabant)  (not in the territory of Folx-les-Caves as shown by Groessens, 1998).    

Area: Valley of the Petite Gette, eastern Brabant

Thickness: 3 to 6 m fide Bless et al., 1991

Age: The belemniteGonioteuthis quadrata indicates an Early Campanian age for the “craie arénacée” (= Tuffeau de Folx-les-Caves).

The coccolith assemblage CC 22  (Lithastrinus grilli, Aspidolithus parcus, Rheinhardtites anthophorus, Eiffelithus eximius, Uniplanarius sissinghii) mentioned by Mulder & Mai (1999) from one sample of the “Tuffeau jaune” (not “jaunâtre” as stated by these authors) is probably based on reworked material.

Fossils (such as very numerous specimens of the brachiopod Thecidea papillata) in the collections of the IRSNB/KBIN, confirmed by the publications of Rutot & Van den Broeck (1888), from the same “tuffeau jaune”, indicate an undoubted Late Maastrichtian age for this younger tuffeau, thus confirming the existence of a a hiatus between the Early Campanian “Tuffeau de Folx-les-Caves” and the overlying “Tuffeau de Jauche” (see below).

Remarks: Previously also known as ”Tuffeau de Folx-les-Caves” Rutot & Van den Broeck (1888); historical review by Groessens (1998). Recently studied by Bless et al. (1991), Kennedy (1987), Mulder & Mai  (1999).