3.2. DESCRIPTIONS
3.2.1. Nismes Formation - NIS
Authors: Bultynck, Casier, Coen, Coen-Aubert, Godefroid, Jacobs, Loboziak, Sartenaer & Streel, 1988; Bultynck & Coen, 1999.
Description:The Nismes Fm is an essentially greenish shaly unit with subordinate nodules, subnodular or nodular limestone beds and some limestone lenses mainly developed in the lower and middle members (Pont d'Avignon and Sourd d'Ave). The top of the shaly upper member (La Prée) is either below a marked bedded limestone bar or a sequence with interbedded shales and limestones. The two lower members contain rich atrypid and spiriferid brachiopod faunas.
Stratotype: Nismes, outcrops on the northern border of the Bois du Mousti.
Area: Southern, central and eastern part of the Dinant Synclinorium; some parts of the northern flank of the Dinant Synclinorium and the Vesdre Nappe.
Thickness: between 39 and 20 m in the three former areas, between 10 and 5 m in the two latter areas.
Age: Apart the Pont d'Avignon Mbr in the central part of the southern flank of the Dinant Synclinorium, the Nismes Fm is of early frasnian age (Lower falsiovalis to lower part of transitans conodont Zones) based on the first occurrence of the conodont Ancyrodella rotundiloba (see Bultynck et al., 1988). The formation corresponds to a major Devonian transgressive phase and its base becomes younger from the south to the north-east and the north.
3.3.2. Moulin Liènaux Formation – MLX (revised December 2009, F. Boulvain and M. Coen-Aubert)
Authors: Tsien, 1974: Chalon, Arche and Ermitage Members; Bultynck & Mouravieff, 1999. Boulvain & Coen-Aubert, 2006: La Boverie Member; Coen-Aubert, 2009.
Description: In its type locality the Moulin Liènaux Fm is divided in ascending stratigraphic order into the Chalon, Arche and Ermitage Members. The lower part of the Chalon Mbr consists of interbedded grey-brownish shales and thin argillaceous nodular limestone beds, in the upper part thickness and frequence of limestone beds increase; the macrofauna consists of corals and brachiopods. The Arche Mbr is represented by large bioherms (up to 120 m thick) with stromatactis, corals and stromatoporoids. In the lower part the limestone is pinkish-reddish, in the upper part light-grey. Development of the bioherms starts in the upper part of the Chalon Mbr and continues in the major part of the Ermitage Mbr. The latter consists essentially of greenish shales with at some levels argillaceous nodular limestone beds. In the reefal areas of Couvin and Rochefort, the La Boverie Member corresponds to the carbonate deposits lying between the Arche Member and the Bieumont Member of the Grands Breux Formation, laterally to the upper part of the Ermitage Member. It starts with bedded limestones which are often argillaceous or bioclastic and it ends with light grey massive limestone which is more or less biohermal. The La Boverie Member is 31 m to 34 m thick in the type locality.
Stratotype: Abandoned Arche Quarry immediately south of Frasnes; the boundary with the overlaying Grands Breux Fm is exposed in the nearby railway cut Couvin-Charleroi. Active quarries La Boverie at Rochefort.
Area: Southern part of the Dinant Synclinorium and south-eastern border of this synclinorium up to Durbuy (Chalon Mbr) and Aywaille (Ermitage Mbr). The bioherms of the Arche and La Boverie Members are known in the reefal areas of Couvin and Rochefort, on the south side of the Dinant Synclinorium and in the southeastern part of the Philippeville Anticlinorium.
Thickness: About 150 m in the type area. The formation is thinning out and away on the south-eastern border of the Dinant Synclinorium.
Age:Early and middle Frasnian, upper part of transitans conodont Zone, punctata Zone and lower part of hassi sl Zone (Vandelaer et al., 1989).
3.3.3. Grands Breux Formation - GBR
Authors: Tsien, 1974: Bieumont, Lion and Boussu-en-Fagne Members; Coen-Aubert & Boulvain, 1999.
Description: In its type locality the Grands Breux FM is divided in ascending stratigraphic order into the Bieumont Mbr and the Boussu-en-Fagne Mbr. Large bioherms are developed in the uppermost part of the former member and the main part of the latter member. The Bieumont Mbr consists of greyish micritic, sometimes bioclastic, well bedded to nodular limestones with shaly intercalation in its upper part. The Boussu-en-Fagne Mbr essentially consists of greenish shales with calcareous nodules, alternating at some levels with nodular or bedded limestones. The Lion Mbr bioherms are made up mainly of greyish massif, micritic limestones with local development of stromatactis, stromatoporoids and tabulate corals. Talus-like structures of bedded argillaceous and bioclastic limestones indent the flanks of the bioherm in its upper part.
Stratotype:Railway cut Couvin-Charleroi south of Frasnes (Bieumont and Boussu-en-Fagne Mbrs); the Lion Mbr is exposed in the nearby Lion Quarry.
Area: The Bieumont and Boussu-en-Fagne Mbrs occur along the southern and south-eastern borders of the Dinant Synclinorium up to Barvaux. Bioherms representing the Lion Mbr are well developed in the western part of southern border of the Dinant Synclinorium, between Dourbes and Trélon (NE France).
Isolated occurrences are known from Rochefort and the south-western part of the Philippeville Anticlinorium.
Thickness: About 120 m for the Bieumont and Boussu-en-Fagne Mbrs together in the type area; thickness of the Lion Mbr bioherms is estimated at 120 m - 250 m. The formation is gradually thinning to the east and farther to the north-east.
Age: Middle Frasnian, containing conodonts of the hassi sl, jamieae and lower part of the Lower rhenana Zones (Mouravieff, 1982; Coen-Aubert & Boulvain, 1999).
3.3.4. Neuville Formation - NEU
Authors: Tsien, 1974: lower part; Boulvain, Coen & Coen-Aubert, 1993, 1999a.
Description: Typically dense nodular shales, with only few inferior nodular and argillaceous limestone beds. The macrofauna mainly consists of colonial corals. Reddish-pinkish, massive limestone mounds with typical stromatactis, colonial corals and brachiopods (Petit-Mont Member) occur in the Neuville Fm and the overlaying Valisettes Fm.
Stratotype: Southern Neuvillerailway cut and abandoned Petit-Mont Quarry at Vodelée, type locality of the Petit-Mont Mbr.
Area: Southern and South-eastern border of the Dinant Synclinorium up to Sy and in the Philippeville Anticlinorium.
Thickness: On the southern and south-eastern border of the Dinant Synclinorium the thickness varies between about 25 m in the Frasnes-Nismes area, 40 m at Givet, 110 m at Han-sur-Lesse and 50 m at Sy. In the Philippeville Anticlinorium thickness is about 15 m tot 25 m. The thickness of the Petit-Mont mounds is from about 20 m tot 80 m.
Age:Late Frasnian, Lower rhenanaconodont Zone (Coen & Coen-Aubert, 1976; Bultynck et al., 1998).
3.3.5. Valisettes Formation - VAL
Authors: Mourlon & Bayet, 1902: Fr2; Boulvain, Coen & Coen-Aubert, 1993, 1999b.
Description: Fine dark-grey, greenish and violet shales with a few thin limestone beds at the base. The shales become nodular in the vicinity of locally developing reddish-pinkish limestone mounds belonging to the Petit-Mont Mbr (see Neuville Fm).
Stratotype: Southern Neuvillerailway cut.
Area:Typically developed in the Philippeville Massif; it also occurs locally, with reduced thickness, on the southern border (Nismes) and the south-eastern border (Barvaux area) of the Dinant Synclinorium.
Thickness: At least 90 m in the type area.
Age:Late Frasnian, the Upper rhenana conodont Zone starts close
to the base of the formation (Coen & Coen-Aubert, 1976; Bultynck et al., 1998).
3.3.6. Matagne Formation - MAT
Authors: Gosselet, 1871; Coen, Casier, Helsen & Mouravieff, 1999.
Description:Fine dark greenish-brown to black shales with generally a few dark limestone beds in the lowermost part. The macrofauna consists of the small bivalve Buchiola, brachiopods and goniatites.
Stratotype: Railway section Mariembourg-Nismes, immediately south-west of the "Tienne aux Pauquet".
Area: Southern border of the Dinant Synclinorium and Philippeville Anticlinorium.
Thickness: At least 50 m on the southern border of the Dinant Synclinorium and about 10 m in the Philippeville Anticlinorium.
Age: Late Frasnian; on the southern border of the Dinant Synclinorium the lower part of the Matagne Fm belongs to the Upper rhenana conodont Zone; in the Philippeville Anticlinorium the formation is within the linguiformis Zone (Bultynck et al., 1998).
3.3.7. Barvaux Formation - BAR
Authors: Gosselet, 1880b; Coen, 1999.
Description: Violet shales, slightly nodular in the lower and upper part; some levels are characterized by large cyrtospiriferids and coquinoid and sandy layers. Reddish mudmounds occur locally in the lower part.
Stratotype:Railway section south of Barvaux, west of Biron.
Area: Mainly south-eastern border of the Dinant Synclinorium up to the Sy-Hamoir area and also in the most eastern part of the southern border of the Dinant Synclinorium (Houyet).
Thickness: About 90 m in the type area.
Age: Late Frasnian to early Famennian; Upper rhenana to Lower triangularis conodont Zones (Coen, 1999).
3.3.8. Pont de la Folle Formation – FOL (revised December 2009, V. Dumoulin and M. Coen-Aubert)
Authors: Boulvain, Coen & Coen-Aubert, 1993, 1999c.
Description: The lower part corresponding to the La Fontaine Samart Mbr, consists of a biostromal unit with stromatactis, stromatoporoids and tabulate corals overlain by dark bedded limestones. The overlying Machenées Mbr consists of nodular shales and nodular limestones in the lower and middle parts and of shale in the upper part. In some areas from the western part of the Entre-Sambre-et-Meuse, the Pont de la Folle Formation starts with a thick level of dolomites which corresponds to the Brayelles Mbr capped by bedded and often reefal limestones belonging to the top of the Fontaine Samart Mbr. The Brayelles Mbr has been defined by Dumoulin & Marion (1997, p. 11) and Dumoulin (2001, pp. 16-20); it was already mentioned by Boulvain et al. (1999, p. 67).
Stratotype:Road section Charleroi-Couvin, immediately south of Philippeville.
Area: Northwestern part of the Dinant Synclinorium.
Thickness: 90 m in the type area.
Age: Early to middle Frasnian; from upper part of transitans into lower par of hassi sl conodont Zones (Coen, 1977).
3.3.9. Philippeville Formation - PHV
Authors: Boulvain, Coen & Coen-Aubert, 1993, 1999d.
Description: The lower part comprises dark thin-bedded limestones with some reef lentils; the upper part consists of a thick-bedded biostromal unit with stromatoporoids and massif colonial rugose corals near the top. In some localities the limestones are affected by dolomitisation.
Stratotypes: Road section Charleroi-Couvin, immediately south of Philippeville, north of Km-stone 79; the biostromal unit is better exposed in the northern Neuville railway section, south-west of Neuville.
Area: Philippeville Anticlinorium, Avesnois area (north-eastern France), and south-eastern border of the Dinant Synclinorium between Nettinne and Sy.
Age:Middle Frasnian; probably from the lower part of the hassi sl conodont Zone into the lower part of the Lower rhenana Zone (Coen, 1977; Gouwy & Bultynck, 2000).
3.3.10. Presles Formation - PRE
Authors: Coen-Aubert, Dejonghe, Cnudde & Tourneur, 1985; Coen-Aubert, 1999a.
Description: In the lower part argillaceous and bioclastic limestones containing a few horizons with haematitic ooliths, overlaid by fine greenish shales. In some areas the limestones are dolomitic.
Stratotype:Section along the Namur-Charleroi road, immediately south of Presles.
Area: Northern border of the Dinant Synclinorium from Lustin to Tilff, southern border of the Namur Synclinorium and the Vesdre Nappe.
Thickness: About 10 m in the type area, in other areas between 1 and 16 m.
Age:Lower Frasnian; from the top of Upper falsiovalis to the lower part of the transitans conodont Zones (Coen-Aubert, 1999).
3.3.11. Lustin Formation - LUS
Authors: Coen-Aubert & Coen, 1975; Coen-Aubert, 1999b.
Description: The lower part consists chiefly of a massif biostrome with branched stromatoporoids and corals with a few beds of crinoidal and dolomitic limestone below its base and overlaid by argillaceous limestone with branched colonial corals; the middle part consists of biostromal limestone mainly with tabular stromatoporoids; the upper part consists of well bedded micritic limestone with massif stromatoporoids in the uppermost part.
Stratotype: Frênes Cliffs at Lustin; the formation is also well exposed in the nearby Tailfer Quarry.
Area: northern part of the Dinant Synclinorium, southern part of the Namur Synclinorium, south-eastern border of the Dinant Synclinorium between Remouchamps and Aywaille and Vesdre Nappe.
Thickness:a little more than 100 m in the type area.
Age: Middle Frasnian; the lower part of the Lustin Formation most likely belongs to the punctata conodont Zone and the upper part to the Lower rhenana Zone (Coen- Aubert & Coen, 1975; Gouwy & Bultynck, 2000).
3.3.12. Aisemont Formation - AIS
Authors: Graulich, 1961; Lacroix, 1974, 1999a.
Description: The lower part consists of bedded argillaceous limestones with massif colonial rugose corals; the middle part is made up by nodular shales and shales; the upper part consists of dolostones or locally of limestones with algae, massif colonial rugose corals, stromatoporoids, tabulate corals and bryozoans.
Area: Southern border of the Namur Synclinorium, eastern part of the northern border of the same synclinorium, northern border of the Dinant Synclinorium, Remouchamps area and in the Vesdre Nappe.
Thickness: about 22 m in the type area.
Age: Late Frasnian, within the Lower and lowest part of the Upper rhenana conodont Zones (Coen-Aubert & Lacroix, 1979 and 1985).
3.3.13. Lambermont Formation - LAM
Authors: Laloux & Ghysel, 1999.
Description: Chiefly a shaly unit with a few nodules and rare thin limestone and silty beds. Most of the middle part is characterized by nodular shales with a biostromal bed with massif colonial rugose corals at its base. Brachiopod coquinas occur in the uppermost part. The shales are mostly greenish, greyish or violet at some levels. The upper boundary corresponds to the oolithic haematite bed at the base of the overlaying Hodimont Formation.
Stratotype: Western access road to the highway Verviers-Prüm at Lambermont.
Area: Northern border of the Dinant Synclinorium, Remouchamps area, Vesdre Nappe and southern border of the Namur Synclinorium.
Thickness: 50 m to 100 m in the Vesdre Nappe.
Age:Upper Frasnian-lower Famennian, from the Upper rhenana into the triangularis conodont Zones (Coen-Aubert, 1974; Dreesen, 1982).
3.3.14. Bovesse Formation - BOV
Authors: Stainier, 1903; Lacroix, 1999b.
Description: thin conglomeratic and sandy-silty unit at the base; the middle part consists of micritic limestones alternating with dolostones; the upper part is shaly with a few argillaceous limestone beds.
Stratotype: Mehaigne Valley east of Huccorgne.
Area: Northern border of the Namur Synclinorium.
Thickness: about 80 m in the type area.
Age: Lower Frasnian, from falsiovalis into punctata conodont Zones (Coen-Aubert et al., 1981; Gouwy & Bultynck, 2000).
3.3.15. Rhisnes Formation - RHI
Authors: Malaise, 1902; Lacroix, 1999c.
Description:Consists mainly of a nodular brachiopod limestone, dolomitized at some levels. In some localities the middle part either consists of bedded bioclastic limestones overlaid by coral and stromatoporoid beds or of black micritic limestones.
Type areas:Sennette Valley north of Ecaussinnes and Samme Valley north-east of Feluy. Because of the discontinuous nature of the exposures a formal stratotype cannot be designated.
Area: Central and western part of the northern border of the Namur Synclinorium.
Thickness: About 60 to 90 m.
Age: Middle Frasnian, laterally equivalent to the Huccorngne Fm (Lacroix, 1999).
3.3.16. Huccorgne Formation - HUC
Authors: Coen-Aubert & Lacroix, 1985, 1999d.
Description:The lower part, Biénonsart Member, consists of dark bioclastic bedded coral limestones; the overlaying Robiewez Mbr is a thin bedded light-grey micritic limestone, often dolomitic; the Mehaigne Mbr consists chiefly of dark bedded limestones with stromatoporoid and colonial rugose corals.
Stratotypes: different outcrops east of Huccorgne.
Area: Eastern part of the northern border of the Namur Synclinorium.
Thickness: about 75 m in the type area.
Age: Middle Frasnian, probably lower part of hassi sl conodont Zone to early rhenana Zone (Coen-Aubert & Lacroix, 1999).
3.3.17. Franc-Waret Formation - FRW
Authors: Stainier, 1892; Lacroix, 1999e.
Description: Greenish-greyish shales with a few calcareous-dolomitic beds overlaying either the Rhisnes Fm or Aisemont Fm and overlaid either by sandy beds or by an oolithic hematite.
Type area: Franc-Waret, about 10 km north-east of Namur. Because of the poor nature of the exposures a formal stratotype cannot be designated.
Area: northern border of the Namur Synclinorium.
Thickness: about 10 m.
Age: Latest Frasnian - ? Early Famennian.