2.2. DESCRIPTIONS
2.2.1. St-Joseph Formation - STJ
Authors: Bultynck & Godefroid, 1974; Bultynck, 1991a.
Description: The most striking characteristics are the light-greyish shelly and crinoidal limestones, occasionally silty, intercalated in a chiefly grey-greenish silty shaly succession. The macrofauna is essentially composed of brachiopods.
Stratotype: Nismes, hamlet St-Joseph, local road to Regniésart.
Hypostratotype: Olloy-sur-Viroin, cut along path 200m south-west of the village church.
Area: Southern and south-eastern flank of the Dinant-Synclinorium up to Hotton-Hampteau; from Villers-Ste-Gertrude on the St-Joseph Fm and the overlaying Eau noire Fm cannot be clearly separated.
Thickness: About 40m between Couvin and Olloy-sur-Viroin, 160m in the Wellin-Halma area, about 50m at Grupont and 30m near Marche.
Age: Latest Emsian; conodonts from the St-Joseph Fm belong to the patulus Zone (Bultynck & Godefroid, 1974).
Remarks: The St-Joseph Fm corresponds to Formation 2 described by Bultynck & Godefroid (1974). The St-Joseph Fm constitutes the lowest part of the Couvinian, formerly used as lower stage of the Middle Devonian in the Ardenne.
2.2.2. Eau Noire Formation – ENR
Authors: Bultynck & Godefroid, 1974; Bultynck, 1991b.
Description: The lower part consists essentially of greyish calcareous shales with bioclasts and a few nodules and argillaceous mostly nodular limestone beds. The upper part alternates between calcareous shales with bioclasts and crinoidal limestone beds. The macrofauna consists mainly of solitary rugose and tabulate corals.
Stratotype: Couvin (La Foulerie), section along the west banks of the Eau Noire river, about 100m north of the foot-bridge.
Area: Southern and south-eastern flank of the Dinant Synclinorium up to Hotton-Hampteau; from Villers-Ste-Gertrude on it becomes difficult to separate the Eau Noire Fm from the underlaying St-Joseph Formation.
Thickness: About 60m between Couvin and Olloy-sur-Viroin, farther to the east the thickness increases to a maximum of 160m in the Wellin-Halma area; east of this area the thickness decreases, 55m at Grupont, 45 at Jemelle and about 15m at Hampteau.
Age: Latest Emsian-earliest Eifelian. The base of the Eifelian, recognized by conodonts belonging to the partitus Zone, is 50m above the base of the formation in the Eau Noire section at Couvin (BULTYNCK et al., 2000).
2.2.3. Couvin Formation – CVN (revised April 2012, V. Dumoulin and S. Blockmans)
Authors: Gosselet, 1860; Bultynck & Godefroid, 1974; Bultynck, 1991c.
Description; In the type area the formation consists chiefly of biostromal beds and it is subdivided into two members, the Foulerie Member and the overlaying Abîme Member.
The lower part of the Foulerie Mbr is made up of bedded dark bluish crinoidal limestones with laminar and domical stromatoporoids and rugose corals; thin calcareous shale intercalations occur near the base. The middle part consists of dark bluish argillaceous limestone beds with occasionally thin calcareous nodular shales; the macrofauna consists of solitary rugose and tabulate corals, brachiopods gastropods and trilobites. Crinoidal limestone beds, frequently dolomitised, with domical stromatoporoids and branched tabulate corals make up the upper part. In the Abîme Member biostromal beds with globular stromatoporoids, branched tabulate corals and phaceloid colonial rugose corals alternate with micritic limestones mostly barren of megafauna.
Stratotype: The Foulerie Mbr and the lower part of the Abîme Mbr are exposed along the west banks of the Eau Noire river at Couvin (La Foulerie); the upper part of the Abîme Mbr is exposed in the cliff above the "Trou de l'Abîme" cavern downtown on the east side of the Eau Noire river.
Area: Southern flank of the Dinant Synclinorium between Macon to the west and Dion east of the Meuse river.
Thickness: Estimated at about 380m between Couvin and Nismes (Foulerie Mbr 220m thick and Abîme Mbr about 160m thick). More eastward the thickness gradually decreases, the lower part being replaced by the Jemelle Formation. The Couvin Formation disappears to the west of Wellin at the locality Les Maurlières.
Age: Lower to middle Eifelian, partitus and costatus conodont Zones (Bultynck & Godefroid, 1974; Bultynck et al., 2000).
2.2.4. Jemelle Formation – JEM (revised June 2009, V. Dumoulin and M. Coen-Aubert)
Authors: Bultynck & Godefroid, 1974; Godefroid, 1991a.
Description: The Jemelle Fm is a chiefly shaly unit, in the type area it is subdivided into three members, from base to top the Station, "Cimetière" and Chavées Members. The Station Mbr consists of sandy shales with a few thin sandstone beds and rare calcareous nodules. Sandy shales occasionally with nodules and intercallation of dark, micritic thin limestone beds or lenses make up the "Cimetière" Mbr. In the Chavées Mbr thicker shale beds with nodules and limestone lenses alternate with thinner bedded or nodular argillaceous or crinoidal limestones; this member contains a rich macrofauna with rugose and tabulate corals, brachiopods, bivalves and trilobites. Small biohermal lenses occur in the Chavées Mbr at Wellin, Nismes, Couvin and Macon.
In the area between Couvin and Wellin (Les Maurlières), the Chavées Mbr overlies the upper part of the Couvin Limestone with a thickness of 230 m to 250 m. Between Nismes and Wellin, the lower and middle parts of the Couvin Limestone pass laterally into the lower part of the Jemelle Formation represented there by the Vieux Moulin Member. This member has been introduced between the Eau Noire Formation and the Abîme Member of the Couvin Limestone by Dumoulin & Coen (2008) and Dumoulin & Blockmans (2008); it was already mentioned by Dumoulin et al. (2006). At Olloy-sur-Viroin (near Nismes), it starts with 130 m of black shales containing the trilobite-rich locality of the “Mur des Douaniers” at Vireux and it ends with 130 m of siltstones or even locally sandstones at its top. Between Wellin and Pondrôme, the Vieux Moulin Member attains 300 m of thickness, in a parallel direction to the decrease of the Couvin Formation (Abîme Member).
Stratotype: Jemelle, section along the N849 road to Forrières, about 300m south of the railway station (Station Mbr overlaying the Eau Noire Fm and "Cimetière" Mbr) and section along the disused railway Jemelle-Rochefort, immediately west of the bridge over the Lomme river (Station, "Cimetière" and Chavées Members). Hamlet of Najauge to the east of Treignes, under the railway bridge and at the “Vieux Moulin” crossroads, along the road to Treignes (Vieux Moulin Member).
Area: Southern and south-eastern flank of the Dinant Synclinorium up to the Xhoris Fault.
Thickness: 345m at Jemelle; north-eastwards the thickness increases up to Hotton (550m) and then gradually decreases. Westwards from Jemelle the thickness also increases, about 600m in the Wellin-Resteigne area.
Age: Early to late Eifelian, partitus into ensensis conodont Zones (Bultynck & Godefroid, 1974; Bultynck et al., 2000).
Remark:For the Pondrôme area, Godefroid (1995b) defined the Pondrôme Member overlying the Chavées Mbr, at the top of the Jemelle Fm. According to the correlations made by Coen-Aubert (1997 and 1998) and Blockmans & Dumoulin (submitted) between the sections of Pondrôme, Wellin and Resteigne, the facies of the Pondrôme Mbr pass gradually and laterally into the lower part of the Hanonet Fm. In the area of Nismes-Olloy, close to the type area of Hanonet at Couvin, Dumoulin & Coen (2008, p. 39) observed also more or less important argillaceous and shaly intercalations in the Hanonet Fm, above a level of limestone characteristic of its base. In conclusion, the Pondrôme Mbr does not belong to the Jemelle Fm and there is no utility to retain it in the succeeding Hanonet Fm.
2.2.5. Lomme Formation – LOM
Authors: Godefroid, 1991b.
Description: The formation is subdivided into two members. The Fond des Valennes Member, corresponding to the lower part of the formation, chiefly consists of sandy, occasionally micaceous or feldspathic, shales with intercalations of massif or micaceous sandstones. The overlaying Wamme Member consists of massif, micaceous sandstones in the lower part and alternating calcareous sandstones and shales in the upper part.
Statotype: Jemelle, section along the disused railway Jemelle-Rochefort, near km 2 and section in the Lhoist quarry, about 500m north-east of the village church.
Area: South-eastern flank of the Dinant Synclinorium between Tellin and the Xhoris Fault;? Couvin area.
Thickness: About 110m in the Jemelle area, thickness increasing eastward up to the Hotton area and then gradually decreasing up to the Xhoris area.
Age: Late Eifelian, kockelianus and ensensis conodont Zones (Godefroid, 1968; Bultynck, 1999; Bultynck et al. 2000).
Remarks: At Couvin a thin unit at the top of the Jemmelle Fm and about 15m thick, consisting of silty shales alternating with argillaceous, calcareous, micaceous siltstones may represent the Lomme Fm.
2.2.6. X Formation – WEL
Authors: Coen-Aubert, 1991a.
Description: Lenticular limestone bodies consisting of bedded or massif crinoidal limestones, occasionally argillaceous or dolomitic and including parts with abundant corals and stromatoporoids.
Reference section: Wellin, Fond des Vaux about 1 km north of the village church.
Area: Locally on the southern flank of the Dinant Synclinorium at Wellin and? Nismes.
Thickness: About 120m at Wellin and 115m at Nismes.
Age: Late Eifelian-? early Givetian; ensensis-? hemiansatus condodont Zones (Bultynck et al., 2000).
2.2.7. Hanonet Formation - HNT
Authors: Tsien, 1976; Preat & Tourneur, 1991a.
Description: The lower, most typical part of the Hanonet Fm consists of blackish, argillaceous, pyritic nodulalar thin limestone beds alternating with thin calcareous shale beds; in the lowest part the limestones are slightly silty and micaceous; the megafauna contains chiefly brachiopods and rugose corals. The middle part is composed of dark thin bluish limestone beds with thin laminar anastomosed and globular tabulates. The upper part is made up of two biostromal units with stromatoporoids, rugose and tabultate corals and separated by an interval with argillaceous limestones and shales.
Stratotype; Couvin, La Couvinoise Quarry about 400m north-east of the railway-station.
Area: Southern and south-eastern flank of the Dinant Synclinorium up to the Xhoris Fault.
Thickness: 50 to 70m between Couvin and Givet; about 30m at Pondrôme, 70m at Resteigne and 30 to 70m in the Wellin area where the formation passes laterally into the Formation X.
Age: Latest Eifelian-Early Givetian; in the stratotype section the hemiansatus conodont Zone defining the base of the Givetian has been recognized near the top of the lower part of the Hanonet Fm.
2.2.8. Trois Fontaines Formation - TRF
Authors: Gosselet, 1876; Bonte & Ricour, 1949; Errera, Mamet & Sartenaer, 1972; Preat & Tourneur, 1991b.
Description: The lowest part, only a few meters thick consists of bedded argillaceous crinoidal limestones. The overlaying part consists of thick biostromal beds with locally coquinoid beds with stringocephalids. The major, upper part of the formation, consists of micritic, occasionally laminated limestones.
Stratotype: Quarry at Les Trois Fontaines on the north-west bank of the Meuse, about 1.5 km south-west of Givet.
Area: Southern and south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault.
Thickness: In the Couvin-Givet area the thickness is about 80m and about 100m between Wellin and Resteigne. From Hotton on the thickness decreases in north-eastern direction.
Age: Early Givetian. Based on conodont data, the base of the Trois Fontaines Fm is a few dozens of meters above te Eifelian-Givetian boundary and belongs entirely to the hemiansatus Zone (Bultynck, 1987).
Remarks: On the south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault, there is an increasing influx, of terrigeneous material.
2.2.9. Terres d'Haurs Formation - THR
Authors: Pel, 1975; Preat & Tourneur, 1991c.
Description:The formation mainly consists of alternating argillaceous, crinoidal bedded or nodular limestones and mostly calcareous shales with corals, brachiopods and trilobites. Locally the base of the formation is characterized by the development of patch-reefs with stromatoporoids and rugose and tabulate corals.
Stratotype: South-eastern walls of Mont d'Haurs fortress, 1km south-east of Givet.
Area: Southern and south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault.
Thickness:Between 65 and 70m in the stratotype. Due to the more argillaceous-shaly character than the underlying Trois Fontaines Fm and the overlaying Mont d'Haurs Fm, the formation is generally not well exposed and lateral thickness changes cannot be accurately established.
Age: Early Givetian. Conodonts from the stratotype section are assigned to the timorensis Zone (= lower part of Lower varcus Zone; Bultynck, 1987).
Remarks:As for the Trois Fontaines Fm an increasing influx of terrigenous material is noticed on the south-eastern flank of the Dinant Synclinorium. In former literature the Terres d'Haurs Fm was designed as a transitional zone between the Trois Fontaines and the Mont d'Haurs Formations (Bonte & Ricour, 1949) or partially included respectively in the upper part and lower part of the two latter formations (Errera et al., 1972).
2.2.10. Mont d'Haurs Formation - MHR
Authors: Bonte & Ricour, 1949; Errera, Mamet & Sartenaer, 1972; Preat & Tourneur, 1991d.
Description: The formation chiefly consists of alternating thick bedded biostromal limestones with stromatoporoids, rugose and tabulate corals and occasionally stringocephalids and mostly thinner bedded micritic limestones. Dolomitic shales and limestones occasionally occur near the top of the lower part and in the middle part of the formation.
Stratotype: South-eastern walls of the Mont d'Haurs fortress, 1km south-east of Givet.
Area: Southern and south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault and Philippeville Massif.
Thickness: About 160m in the stratotype and along the southern flank of the Dinant Synclinorium; from Hotton on the thickness decreases in north-eastern direction. In the Philippeville Massif only the upper part of the formation is exposed and about 100m thick.
Age: Early Givetian. According to the conodont data from the stratotype section the Mont d'Haurs Fm belongs to the timorensis Zone (= lower part of Lower varcus Zone; Bultynck, 1987).
2.2.11. Fromelennes Formation - FRO
Authors: Maillieux, 1922; Errera, Mamet & Sartenaer, 1972; Coen-Aubert, 1991b.
Description: In an unpublished Ph. D. dissertation ERRERA (1976) subdivided the Fromelennes Fm into three members, in ascending order the Flohimont, Moulin Boreux and Fort Hulobiet Members. These subdivisions were subsequently adopted in several publications. The lowest part of the Flohimont Mbr consists of thin bedded argillaceous limestones with brachiopods. The major part of the member consists of alternating nodular shales and argillaceous limestones with a rich brachiopod fauna. The Moulin Boreux Mbr consists of alternating biostromal beds with domical and branched stromatoporoids and micritic, occasionally dolomitic limestones, sometimes finely laminated. The Fort Hulobiet Member is made up of platy limestones typically with bivalves and phaceloid colonial rugose corals in the upper part. In some sections the platy limestones are less developped and biostromal beds with globular and branched stromatoporoids occur.
Stratotype: Section along the local road D46 between Fromelennes and Flohimont (France), about 3km south-east of Givet completed by the nearby Cul de Houille quarry.
Area: Southern and south-eastern flank of the Dinant Synclinorium and Philippeville Massif. To the north the Fromelennes Fm passes into the Le Roux Fm.
Thickness:About 135m in the stratotype. The formation is 10 to 15m thicker to the east between Dion and Hotton. More to the north-east the thickness decreases. In the Philippeville Massif the thickness is about 80m.
Age: Middle to late Givetian. In the stratotype section the lowest part of the Flohimont Mbr is assigned to the rhenanus/varcus conodont Zone (= upper part of Lower varcus Zone) and the overlaying part to the ansatus Zone (= Middle varcus Zone). Not any conodont fauna was obtained from the Moulin Boreux Member. In Nismes and Wellin the Fort Hulobiet Mbr can be assigned to the Lower falsiovalis Zone (Bultynck, 1987; Bultynck et al., 2000).
2.2.12. Rivière Formation - RIV
Authors: de Dorlodot, 1895; Bultynck, 1991d.
Description: The Rivière Fm is subdivided into two members, in ascending order the Rouillon and Claminforge Members. The Rouillon Mbr chiefly consists of sandy red and greenish shales and some sandstone beds. Bioclastic limestone lenses and coquinoid brachiopod layers occur in the lower part, overlaying in the stratotype section a conglomeratic bed (= Tailfer Conglomerate of Stainier, 1891). The Rouillon Mbr succeeds the last thick conglomerate bed of the Burnot Fm.
The Claminforge Mbr is composed essentially of light-greyish calcareous very fine sandstones and calcareous shales with intercalations of reddish and greenish shales and occasionally calcareous nodular and rare limestone beds. Some of the calcareous sandstones are laminated.
Composite stratotype: The stratotype for the lower boundary is exposed along the west side of the N96 Namur-Dinant between km14 and km15 at Rivière. The boundary between the Rivière Fm and the overlying Névremont Fm is exposed at Godinne (Tantachau) along the south side of the road Rivière-Mont, about 600m east of the bridge over the railway Namur-Dinant.
Area: Northern flank of the Dinant Synclinorium and southern flank of the Namur Syncline.
Thickness: In the central part of the northern flank of the Dinant Synclinorium the thickness of the Rivière Fm varies between 50 and about 80m, in the western part it is about 50m thick. In the Aisemont section situated in the central part of the southern flank of the Namur Syncline the formation is about 75m thick.
Age: Eifelian-? early Givetian. In the type area of the formation the lower part of the Rouillon Mbr belongs to the boundary interval between the partitus and costatus conodont Zones and the top of the Claminforge Mbr probably belongs to boundary interval between the ensensis and thetimorensis (= lower part of Lower varcus Zone) Zones. There may be a stratigraphic gap between the Rivière and Névremont Formations (Bultynck & Boonen, 1976; Bultynck et al., 2000).
Remarks: The Rouillon Mbr approximately corresponds to the "Grauwacke rouge de Rouillon" of Gosselet (1873) and the Claminforge Mbr to the "Macigno de Claminforge" of de Dorlodot (1895).
In the stratotype section of the Névremont Fm at Aisemont the base of this formation is lowered herein in comparison to its position indicated in Bultynck et al. (1991, p.71). The boundary between the Rivière and the Névremont Formations should be at the top of the argillaceous limestone bed 11.30m above the base of the column. The arguments for this change are expressed in Coen-Aubert (2000, pp.10-11).
2.2.13. Névremont Formation - NEV
Authors: Lacroix, 1974, 1991a; Coen-Aubert, 2000.
Description:The lower part consists of alternating shales and micritic or fine bioclastic limestones with solitary and colonial rugose corals and more rare tabulates and brachiopods. The upper part is composed essentially of dolomitic limestones with stromatoporoids and rugose corals. The uppermost part consists of nodular limestones.
Stratotype: Fosses-la-Ville (Aisemont), section along the disused railway, 200m east of the former railway station of Aisemont between km 6.1 and 6.2.
Area: Northern flank of the Dinant Synclinorium, southern flank of the Namur Syncline, south-eastern flank of the Dinant Synclinorium north of the Xhoris Fault and in some parts of the Vesdre Nappe.
Thickness: About 70m in the stratotype section in the central part of the southern flank of the Namur Syncline, the thickness decreases to the east.
Age: Early Givetian, conodont data are scarce and the formation most likely belongs to the timorensis and rhenanus/varcus Zones (= Lower varcus Zone) (Bultynck et al., 2000).
Remarks: See Rivière Formation.
2.2.14. Le Roux Formation - ROU
Authors: de Dorlodot, 1893; Lacroix, 1974; Coen-Aubert, 1991c.
Description: The lower part consists of alternating shales and argillaceous sandstones; the middle part is composed of sandy limestone overlaid by micritic dolomites; the upper part consists of dark micritic limestones with a few intercalations of shales and micritic dolomites.
Stratotype: Fosses-la-Ville (Aisemont), road cut at the southern corner of the Moreau quarry.
Area: Northern flank of the Dinant Synclinorium; southern flank of the Namur Syncline between Presles and the Meuse and Vesdre Nappe.
Thickness: About 30m in the stratotype section on the southern flank of the Namur Syncline, where the thickness decreases to the east and the formation disappears east of the Meuse. On the northern flank of the Dinant Synclinorium the thickness varies between 22 and about 40m, in the Vesdre Nappe between 16 and 85m.
Age: Middle to late Givetian; the Roux Fm is a northern lateral equivalent of the Fromelennes Formation (Coen-Aubert, 1991).
2.2.15. Bois de Bordeaux Formation - BOR
Authors: Légende carte géologique 1/40.000, 1929; Lacroix, 1991b.
Description: Lacroix (1991) sudivided the Bois de Bordeaux Fm into three members, in ascending order Mautiennes, Alvaux and Mazy Members.
The contact between the conglomeratic base of the Mautiennes Mbr and the underlaying Silurian rockx represents an angular unconformity. The member is composed essentially of red, greenish or variegated sandy-argillaceous rocks. The main part of the Alvaux Mbr consists of organoclastic limestones with thin interbedded shale layers and intercalations of oolithic limestones. The macrofauna includes colonial rugose corals, brachiopods and a biostromal level with stromatoporoids near the top. The Mazy Member essentially consists of red sandy-silty shales with a few intercalations of reddish and greyish limestone beds.
Stratotype: Gembloux, between Mazy and Les Mautiennes on the east banks of the Orneau river.
Area: Northern flank of the Namur Syncline between Soignies and Lavoir.
Thickness: About 120m in the Orneau Valley in the central part of the northern flank of the Namur Syncline, only 10m at Soignies in the western part and about 20m at Lavoir in the eastern part.
Age: Givetian; conodont data from the Mautiennnes and Alvaux Members support correlation with the upper part of the Terres d'Haurs Fm, the Mont d'Haurs Fm and the lower part of the Fromelennes Fm on the southern flank of the Dinant Synclinorium. The base of the overlaying Bovesse Fm belongs to the Lower falsiovalis Zone (Lacroix, 1999).
2.2.16. Vicht Formation - VIC
Authors: Holzapfel, 1910; Dejonghe, Hance & Steemans, 1991a.
Descriptions: Alternating thick bedded reddish conglomerates, sandstones and siltstones with rare shaly intercalations.
Stratotype: VichtValleyat Vicht near Stolberg (Germany).
Hypostratotype: Eupen, bottom of the Helle river.
Area: Vesdre Nappe.
Thickness: about 80m at Vicht, about 20m at Eupen and 6m at Fraipont.
Age: Eifelian; spores from a level near the middle part of the formation in Eupen are assigned to the AD assemblage Zone (Hance et al., 1992).
2.2.17. Pépinster Formation - PER
Authors: Dejonghe, Hance & Steemans, 1991b.
Description: The formation essentially consists of greenish, reddish and variegated shales, siltstones and sandstones. The rocks become calcareous in the upper part. A characteristic unit with greenish sandstones and two conglomerate beds and containing plant fragments, brachiopods and tentaculites occurs about 10m above the base of the formation; it coresponds to the Heusy Member of Hance et al., 1989.
Stratotype: composite stratotype based on three sections at Pépinster: west banks of the Hogne, railway section Pépinster Spa and railway section Liège-Eupen, km 121.
Area: South-eastern flank of the Dinant Synclinorium, north of the Xhoris Fault and Vesdre Nappe.
Thickness: 213m at Remouchamps (south-eastern flank of the Dinant Synclinorium); in the Vesdre Nappe the thickness of the formation increases from west to east, 53m at Prayon and 95m at Pépinster.
Age: Late Eifelian-early Givetian based on spores (Steemans, 1991).