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5.41.2. Anhée Formation – ANH

 

Authors: de Dorlodot, 1909; Pirlet, 1968a; Paproth et al., 1983; Poty et al., 1988.

Description: The Anhée Fm, as defined here, does not correspond to the definition of Paproth et al. (1983) in that: (1) it excludes parasequences with dominant lime mudstones and stromatolitic boundstones which are now attributed to the underlying Poilvache Mbr of the Bonne River Fm, and (2) it includes the overlying Warnant Fm of Paproth et al. (1983).

The formation therefore includes two members:

- The Lower Member – AMI Mbr nov. (Poty) comprises parasequences of dark limestones dominated by wackestones and packstones, with gigantoproductids and some corals. Locally (Hoyoux valley, Chabôfosse Facies - CHB, Poty), the parasequences include very fossiliferous, coarse-grained packstones and grainstones with coral biostromes (Pirlet, 1964; Poty et al., 1988). This unit includes limestones previously attributed to the lower part (Lower Mbr, “lower V3c”) of the Warnant Fm of Paproth et al. (1983).

- The Upper Member – AMS Mbr nov. (Poty) comprises argillaceous limestones, shales and siliceous shales, with phosphatic nodules, previously attributed to the upper part (Upper Mbr, “upper V3c”) of the Warnant Fm of Paproth et al. (1983).

The formation is locally brecciated (“Grande Brèche Viséenne”).

Stratotype: Old underground quarry Watrisse at Anhée, on the western bank of the Meuse valley, about 6 km north of Dinant (DSA). Chabôfosse Facies: road and hill sections at Chabôfosse (Royseux) in the Hoyoux valley, 2 km north of Pont-de-Bonne.

Thickness: Lower Mbr, 25 m; Upper Mbr, from zero to 8 m.

Area: DSA, CSA, western part of the NSA. The Upper Mbr is locally absent (i.e. Hoyoux valley)

Age: Mid and late Warnantian. Upper part of the Cf6gand Cf6dForaminifer Subzones (Conil et al., 1991); RC7bCoral Subzone and base of the RC8 Zone (appearance of Lonsdaleia) (Poty et al., 1988). The Lower Mbr of the Anhée Fm corresponds to the HST of third-order sequence 9 (Hance et al., 2001), whereas the Upper Mbr (previously the upper member of the Warnant Fm) possibly corresponds to the TST of a following third-order sequence.