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4.2.1. Famenne Group - FAM
Authors: d’Omalius d’Halloy, 1839; Thorez & Dreesen, 1986.
Description: The Famenne Grp  is essentially made up of green (sometimes violet) shales or pelites alternating with more silty beds.  Siltstone beds are increasing towards the top.  Locally, the group is rich in carbonate nodules (of some cm long) and in lenticular sandy or calcareous-sandy beds (of some cm thick) containing crinoids and brachiopods accumulations (among which, rhynchonellids).  Fossils are often decalcified.  The Famenne Grp contains one or several oolitic hematite beds hypothetically attributed to debris-flows and characterizing a fluxo-turbiditic mechanism.
Former name : Famenne shales or schists, subdivided into Senzeille “assise” in the lower part and Mariembourg “assise” in the upper part; also named Famenne Fm in many recent works.
Stratotype: see Senzeille and Mariembourg Formations.
Area: Namur and Dinant Synclinoria.  The Famenne Grp pass laterally to the Hodimont Fm in the Vesdre Nappe.
Thickness: 0 to < 50 m at the northern side of the Namur Synclinorium; 50 to 60 m at the southern side of the de Namur Synclinorium and at the northern side of the Dinant Synclinorium; 260 m in the Silenrieux-Walcourt area; 400 m in the Achêne-Leignon area (central part of the Dinant Synclinorium); maximum development on the southern side of the Dinant Synclinorium.
Age: Lower Famennian (Fa1a and Fa1b-c units, corresponding respectively to the old Senzeille and Mariembourg “assises”); Palmatolepis triangularis and Palmatolepis crepida crepida conodont biozones.
Remark: To consider Mariembourg and Senzeille as lithological units is questionable as for the limit between them is essentially based on paleontological markers or on a discrete (condensed) oolitic ironstone bed.  Indeed, up to now (in 2001), in the various sheets of the new geological map of Wallonia, the distinction between them has not been made.  The authors refer to the Famenne Fm, but the terminology of  Famenne Grp, used by Thorez & Dreesen (1986), is preferred.
4.2.2. Senzeille Formation - SEN
Authors: Gosselet, 1877, 1880b; Sartenaer, 1960.
Description: Greenish, argillaceous shales, with thin interbedded sandstone or limestone layers.
Stratotype:  Senzeille, former railway trench, south of the former railway station.
Area:  Namur and Dinant Synclinoria.
Thickness: ±40 m in the Namur Synclinorium; 150 m at the southern margin of the Dinant Synclinorium.
Age: Lower Famennian (Fa1a).  Palmatolepis triangularis conodont zones.  Brachiopod succession: Pampoecilorhynchus lecomptei, Eoparaphorhynchus triaequalis praetriaequalis, E. triaequalis triaequalis, Tenuisinurostrum crenulatum, Evanescirostrum. lentiformis, Ptychomaletaechia omaliusi.
Remarks:  See comment in the Famenne Grp section concerning the validity of the concept of Senzeille Fm.
Senzeille is sometimes written in the literature with a s, sometimes without s.  After the Royal Decree of the 23th of December 1963, the word must be written without s.
4.2.3. Mariembourg Formation - MAB
Author: Gosselet, 1879b.
Description:  Greenish, purplish-blue or reddish argillaceous shales, with nodules or thin interbedded arenaceous rocks or limestone layers.
Stratotype:  North of Mariembourg, slopes of the Roly road.
Area:  Namur and Dinant Synclinoria.
Thickness: very variable.
Age: Lower Famennian (Fa1b-c).  P. crepida conodont zone.  The base of the Mariembourg Fm corresponds at Silenrieux to the base of the P. dumonti zone.
Remark: See comment in the Famenne Grp section concerning the validity of the concept of Mariembourg Fm.
4.2.4. Hodimont Formation - HOD
Authors:Laloux et al., 1996.
Description:  In the type locality, the Hodimont Fm is made up of grey greenish micaceous shales (silstones) occurring in decimetric to metric thick beds, with locally, numerous decimetric limestone nodules containing brachiopods and goniatites.  The Hodimont Fm also contain several (locally, at least 4) levels of oolitic hematite lenticular beds, up to ± 1 m thick, made up of mottled sandy limestones with crinoids, brachiopods and cephalopods.  The lowermost oolitic hematite bed is considered as the base of the formation; the uppermost, as the top.
Stratotype: Hodimont, near Verviers.  Reference section : La Grappe street, Dison.
Area: Vesdre Nappe, Theux Window.
Thickness: 50 to 110 m.
Age: Lower Famennian (Fa1a) and base of the Middle Famennian (Fa2a).  The lowermost hematite bed corresponds to a condensation of the 2 Lower Famennian conodont zones (P. triangularis and P. crepida); the uppermost hematite bed, to a condensation of parts of the 2 first conodont biozones of the lowermost Middle Famennian (Palmatolepis rhomboidea and Palmatolepis marginifera marginifera).  The presence of goniatite Cheiloceras in the two upper hematite levels is an important marker for international correlations.
4.2.5. Condroz Group - CON
Authors:d’Omalius d’Halloy, 1839; Thorez et al., 1977, 1988; Thorez & Dreesen, 1986.
Description: In the Dinant Synclinorium, the Vesdre Nappe and the Theux Window, the Condroz Grp is made up of interfingering siliciclastic formations which are coarser-grained than those of the Famenne Grp and contain subordinate carbonate.  In the lower part, shales (Aye Fm), pass laterally to siltstones and sandstones (Esneux Fm).  They are overlaid by nodular limestones (Souverain-Pré Fm) or by both carbonate and siliciclastic rocks (Ciney Fm).  The Monfort Fm (and the time-equivalent Comblain-la-Tour Fm), situated in the middle of the Condroz Grp, is essentially made up of sandstones.  It is surmounted by the Evieux Fm (and the time-equivalent Beverire Fm), a complex of shale and argillaceous micaceous sandstones.
Stratotypes: Ourthe valley, between Esneux and Comblain-Fairon.
Area: Namur and Dinant Synclinoria; Vesdre Nappe, Theux Window.
Thickness: 290 to 350 m in the Dinant Synclinorium (350 m in the Ourthe valley)
Age: Middle and Upper Famennian (Fa2a, b and c). Palmatolepis rhomboidea to Bispathodus costatus or toPalmatolepis gracilis expansa conodont biozones.
Remarks: The former name of the Condroz Grp is "Condroz psammites”.  Originally, the name corresponded to a wide stratigraphic range, from part of the Middle Frasnian to the Strunian.  Later on, it was restricted to gather the Evieux and Monfort Fms.  Thorez et al. (1977), Thorez & Dreesen (1986) and others in more recent papers consider all the formations ranging from the Esneux/Aye Fms (in the lower part) up to the Evieux Fm (in the upper part) as belonging to the Condroz Grp.
4.2.6. Esneux Formation – ESN (revised June 2009, V. Dumoulin and M. Coen-Aubert)
Author: Mourlon, 1886.
Description: The Esneux Fm (former name: stratoid “psammite” of Esneux or Esneux “assise”) consists of cm to dm- , sometimes up to m-, and even several m-thick green to olive green beds of weakly micaceous siltstone and fine-grained sandstone.  Both rocks are feldspathic to arkosic.  They are eventually interbedded with thin shaly intercalations.  The Esneux Fm is often affected by chevron tight folds.  Sedimentary structures are common : planar parallel-laminations, cross-beddings, small load-casts, bioturbations, etc.  Remnants of decalcified fossils (crinoids, brachiopods) are also sometimes abundant.  The arenaceous sediments have been interpreted as subtidal marine deposits.  The transition to the overlying Souverain-Pré Fm is characterized by the occurrence of light grey crinoidic limestone beds in the shales.  Laterally, to the south, the sandstone beds alternate with lenticular layers of siltstones and shales announcing the Aye Fm facies.
The Watissart Mbr has ben introduced, within the Esneux Formation, by Dumoulin (2001, p. 31) to the south of Jeumont in France. It is a marker level which consists of massive quartzitic sandstone; it may reach a thickness of 50 m. The Watissart Mbr occurs at the western end from the north side of the Dinant Synclinorium, close to the French border.
Stratotype: Ourthe valley, railway trench, south of the Esneux railway station.
Area: Namur Synclinorium, north of the Dinant Synclinorium, Vesdre Nappe, Theuw Window.
Thickness: 25 to 150 m in the Vesdre Nappe; 250 m in the Hermeton and Lesse valleys, as well as in the Silenrieux-Walcourt area; 400 m in the Achêne-Leignon area (including the Aye Fm).
Age: Base of the Middle Famennian (Fa2a).  P. rhomboidea and early P. marginifera conodont zones.
4.2.7. Aye Formation - AYE
Authors: Bouckaert et al., 1968; Thorez et al., 1977.
Description: As pointed out by Bouckaert et al. (1968), the Esneux Fm passes laterally in the southern part of the Dinant Synclinorium (i.e. in a more offshore position) to the Aye Fm (former name: Aye shales or schists).  The dominant lithology is that of greenish shale with alternating interbedded greenish argillaceous platy siltstone beds and lenticular (some cm thick) fine-grained sandstones and siltstones.  Bioturbation is important.  Brachiopods accumulations and limestone beds are locally frequent.  The overall paleobathymetry for the Esneux and Aye Fms is that of a subtidal wave-influenced environment.  Cross-bedding structures are related to storm current origin (tempestite).
Stratotype: area of Houyet and Aye.
Area: South of the Dinant Synclinorium; north of the Philippeville Tectonic Unit.
Thickness:  at least 140 m in the Silenrieux area; 220 m in the Hermeton valley.
Age: Base of the Middle Famennian (Fa2a).  P. rhomboideaconodont zone.
4.2.8. Souverain-Pré Formation - SVP
Authors: Mourlon, 1875; Dreesen et al., 1985.
Description: The most representative rocks of the Souverain-Pré Fm (former name: Souverain-Pré “macigno”) are metric-thick layers of nodular limestones with shaly to silty cement.  The nodules are often aligned along the stratification and dissolved, giving rise to cellular alignements, very characteristic of the formation.  Bioclastic character (crinoids, brachiopods, bryozoans) is often marked, especially in the limestone nodules.  Decimetric beds of calcareous sandstones are also interbedded in the limestones.  The Souverain-Pré Fm is interpreted as a “back-reef” facies of crinoidal mud mounds named the Baelen Mbr and described here-after.
In the Dinant Synclinorium, the Souverain-Pré Fm passes laterally, in a more inshore direction, to the Ciney Fm.  At the bottom of the Souverain-Pré Fm, limestone and thin sandstone beds alternate, forming the transition to the underlying Esneux Fm.  The transition zone between the Souverain-Pré and the lateral or overlying Ciney Fm is gradual and characterized by the occurrence of more sandy facies with discrete sedimentary structures.
In the Vesdre Nappe, the Souverain-Pré Fm passes laterally to the east to the Baelen Mbr (former name: Crinoidic Red Marble of Baelen).  This is a reef mud mound forming a heterogenous limestone complex.  The marble s.s. consists of relatively pure fine-grained limestones, occurring in massive beds, rubefied, and frequently interbedded with clearer coarse-grained limestones.  Crinoids, stromatactis and slumps are abundant.  The marble is restricted to the central part of the complex and is surrounded by sandy or argillaceous, nodular limestones, very rich in crinoids, and micaceous, carbonate sandstones.
Stratotype: Ourthe valley, railway trench, Souverain-Pré railway station.
Area: Dinant Synclinorium, Vesdre Nappe, Theux Window.
Thickness: variable : 50 to 120 m in the Dinant area; 80 to 140 m in the Achêne-Leignon area; 120 to 180 m in the Silenrieux area; 80 to 100 m in the Vesdre Nappe.  Baelen Mbr: 20 to 150 m.
Age:  The Souverain-Pré Fm is a diachronous formation of Middle Famennian age (Fa2ab).  At Blaimont, the formation corresponds to the Scaphignathus velifer conodont zone; at Houyet and in the Vesdre nappe, it covers the P. marginifera zone and the lower part of the Sc. velifer zone.  In the Achêne-Leignon area, the formation starts with the P. marginifera zone and covers the base of the Palmatolepis rugosa trachytera zone.  The Baelen Mbr is dated of the Middle Famennian (Fa2a), late P. marginifera zone.
4.2.9. Ciney Formation - CIN
Authors: Thorez et al., 1977; Dreesen & Thorez, 1980.
Description: The Souverain-Pré Fm passes laterally to the north-northeast, i.e. in a more inshore direction, to a more sandy facies defined as the Ciney Fm.  Indeed, the Ciney Fm is essentially made up of fine-grained micaceous sandstones and siltstones with nodular limestone intercalations occurring both to the top and the bottom, and with stratified limestones to the top only.  The series starts with metric to plurimetric-thick bars of fine-grained laminated massif carbonate sandstones containing long flattened dolomitic nodules.  Sandstones surmount them, with carbonate nodules alternating with metric-thick beds of grey siltstones and sandstones taking a yellow ocher or orange brown weathering patina (due to iron dolomitic cement).  The main sedimentary structures are planar parallel laminations, cross-beddings, hummocky cross-beddings and load casts.  Its depositional environment has been defined as distal subtidal.  A Dorinne Mbr is distinguished at the lower part of the formation.
The Ciney Fm wedges out northwards where it disappears between the Esneux and Comblain-la-Tour Fms.
In the geological maps Hastière-Dinant (Delcambre & Pingot, 1993) and Achêne-Leignon (Boulvain et al., 1995), the Ciney Fm comprises all the Famennian rocks overlying the Souverain-Pré Fm.  In the Silenrieux-Walcourt geological map (Dumoulin & Marion, 1997), the Etroeungt Fm was distinguished from the Ciney Fm, although both were represented by the same color, as the poor outcrops of the Etroeungt Fm did not permitted an accurate mapping.
Stratotype: Quarries around Ciney, in the Bocq valley.
Area: Dinant Synclinorium.  The Ciney Fm is well developed in the Dinant area, but is lacking in the Ourthe valley, south of Liège.
Thickness: 200 to 300 m for the Ciney and Etroeungt Fms in the Silenrieux-Walcour area; 250 to 300 m in the Dinant area (including 120 m for the Etroeungt Fm at Hastière); > 300 m in the Rosée borehole.
Age: Upper part of the Middle Famennian (Fa2b).  Sc. veliferand P. trachytera conodont zones.
4.2.10. Comblain-la-Tour Formation - CLT
Authors: Thorez et al., 1977, 1988; Thorez & Dreesen, 1986.
Description: The Comblain-la-Tour Fm is essentially a sandy deposit with arkosic beds, interlayered with thin beds of more clayey micaceous material and occasional crinoidal limestones.  It has been related to an open marine-proximal subtidal depositional environment.  Members are also distinguished : the Poulseur Mbr to the N-NE and the Haversin Mbr to the S-SW.
Stratotype: Ourthe valley, old quarry of Comblain-la-Tour.
Area: Dinant Synclinorium.
Thickness: ±150 m at Comblain-la-Tour.
Age: Upper part of the Middle Famennian (Fa2b).  Sc. velifer and P. trachytera conodont zones in the Hamoir-Ferrière area.
4.2.11. Montfort Formation - MFT
Authors: Davreux, 1833; Mourlon, 1875; Thorez et al., 1977.
Description:  The Monfort Fm (former names: Montfort assise, Montfort “psammites” or paving sandstone of Monfort) is made up of micaceous, dark grey bluish, sometimes nearly black by weathering, thick (up to 5 m) sandstone beds, practically without any shaly intercalations.  Locally, at the top, the rocks take a maroon (“lie de vin” in french) color, especially in the Vesdre Nappe.  Plant debris are abundant.  The Monfort Fm represents a sand barrier complex.  It was subdived by Thorez et al. (1977) into three members, respectively from bottom to top :
1.     the Bon-Mariage Mbr : forebarrier environment, with rhythmic deposits of a typical tidal-flat environment, with subtidal, intertidal and occasionally supratidal environments;
2.     the La Gombe Mbr : sand barrier environment itself, virtually barren of limestone or calcareous sediment; the rocks are higly sandy, arkosic, and organized in at least one meter thick beds, exhibiting a systematic reverse grading; clay material occurs occasionnaly interlayered within the sandy beds;
3.     and the Barse Member : back-barrier environment with typical lagoon-evaporitic (sabkha) sedimentary deposits.  The carbonate material is always a “primary” dolomite, without any fossil content.
Stratotype: Ourthe valley, railway trench, 1700 m south of the Esneux railway station.
Area: Part of the Namur Synclinorium, Dinant Synclinorium, Vesdre Nappe, Theux Window.
Thickness: 170 m in the Dinant Synclinorium of which 150 m in the Ourthe valley; ±350 m for both the Monfort and Evieux Fm in the Vesdre Nappe.
Age: Middle (Fa2b) to Upper (Fa2c) Famennian.  Late Sc. velifer, Polygnathus styriacus, Palmatolepis perlobata postera, early Palmatolepis gracilis expansa conodont zones.
4.2.12. Evieux Formation - EVX
Authors: Mourlon, 1875; Thorez et al., 1977.
Description: The Evieux Fm (former names: Evieux “assise”, or Evieux “psammites”) consists of a complex of shales and argillaceous, sometimes very micaceous sandstones, with towards the top, subordinate carbonate sandstones often decalcified.  Plant debris are very abundant.  The Evieux Fm was subdived by Thorez et al. (1977) into three members, from bottom to top:
1.     the Royseux Mbr, with arenaceous red beds, related to sabkhas, interlayered with supratidal evaporitic dolomites;
2.     the Fontin Mbr, with dolomites containing sublagoonal ostracods and oncolithic micrites;
3.     and the Crupet Mbr, with “continental” red beds.
Area: Namur and Dinant synclinoria, Vesdre Nappe, Theux Window.
Thickness: 120-200 m in the Dinant Synclinorium (200 m in the Ourthe valley).
Age: Upper (Fa2c) to Uppermost (Fa2d) Famennian. Upper P. styriacus, lower to middle Bispathodus costatus, and P. expansa conodont zones.
4.2.13. Beverire Formation - BEV
Authors: Thorez et al., 1977, 1978; Thorez & Dreesen, 1986.
Description: The Beverire Fm faces but overlap somewhat both the Montfort and Evieux Fms within a southern, more offshore, position.  This formation appears to have been deposited as a rhythmically organized succession of high-interdital to supratidal sediments.  Most of the limestones are micritic.
Area: The Beverire Fm is well developed in the southern part of the Ourthe valley and seems to be restricted to this area.
Stratotype: old quarries at Comblain-au-Pont, left bank of the Ourthe river.  These are however either banked up or in a private property.
Thickness: ±90 m in the stratotype area.
Age: Upper (Fa2c) to Uppermost (Fa2d) Famennian.  Upper P. styriacus, lower to middle B. costatus and P. expansa conodont zones.
4.2.14. Etroeungt Formation - ETR
Authors: Gosselet, 1857; Barrois, 1913; Conil & Lys, 1980.
Description: The Etroeungt Fm is made up of of several dm- to several m-thick beds of green shales and siltstones interbedded with argillaceous or carbonate, micaceous sandstones, often of yellow brown color.  Interbedded nodular or lenticular beds of carbonate, often crinoidic, are also frequent.  Three lithological units may be distinguished, respectively from bottom to top : a shale dominant unit, a sandstone dominant unit and a carbonate dominant unit (the latter corresponding to the Etroeungt Limestone s.s.).
Former names: Etroeungt zone or “assise”; Etroeungt limestone; Etroeungt Limestones and Shales.
Stratotype: Parcq quarry, Etroeungt, near Avesnes (N of France).
Area: Dinant Synclinorium.
Thickness: 120 m at Hastière and Yves-Gomezée; 200 m at Walcourt.
Age: Uppermost Famennian (Strunian, Fa2d-Tn1a).  Biostratigraphical correlations between miospores and conodonts due to Maziane et al. (1999) indicate that the base of the Retispora lepitophyta-Knoxisporites literatus miospore biozone is correlated with the middle or late P. expansa conodont biozone and the base of the Retispora lepidophyta-Indotriadites explanatus microspore biozone with the early to middle Siphonodella praesulcata conodont biozone.
Remark: The Comblain-au-Pont Fm (formerly, Comblain-au-Pont zone or “sous-assise”) is a synonym to characterize the same formation in Belgium, when moving eastwards.
4.2.15. Comblain-au-Pont Formation - CLP
Authors: Dufrenoy & de Beaumont, 1841-1848.
Eastwards time-equivalent in Belgium of the Etroeugnt Formation.  The Comblain-au-Pont “assise” was systematically represented in the various geological maps at the scale 1:40,000 published in the 1900s and situated east of the Samson valley.
4.2.16. Dolhain Formation - DOL
Authors: Laloux et al., 1996.
Description: The Dolhain Fm is characterized by 3 biostromal carbonate units, rich in fossils, interbedded within olive green micaceous shales and siltstones with thin sandy laminae.  The uppermost biostrome is the thickest and contain abundant stromatoporoids (lamellar and globular), rugose corals (Palaeosmillia aquisgranensis, Campophyllum flexuosum) and tabular corals (Syringopora, Yavorskia).
Stratotype: Dolhain area, especially the section of the Trauty street at Dison.
Area: Vesdre Nappe, Theux Window.
Thickness: Total thickness : 30-40 m.  The lowermost biostrome is ± 0.5 m thick; the middle biostrome, ± 2 m thick; the uppermost biostrome, 20-25 m thick.
Age: Uppermost Famennian (Strunian, foram Df3 subzone).
4.2.17. Samme Formation - SAM
Authors:Doremus & Hennebert, 1995.
Description: The Samme Fm is subdivided into three members, respectively from bottom to top :
1.     the Bois de La Rocq Mbr : conglomerates, red and green sandstones, red shales to the bottom; sandstones with dolomitic cement to the top;
2.     the Feluy Mbr : mainly limestones, sometimes oolitic, dolostones and less abundant sandstones;
3.     and the Mévergnies Mbr : sandstones , often dolomitic, with shaly intercalations.
Stratotype:Samme valley.
Area: western part of the northern limb of the Namur Synclinorium.
Thickness: 65 to 100 m.
Age: Bois de La Rocq Mbr: Strunian; upper part, Hastarian.  Feluy and Mévergnies Mbrs: Hastarian.