1.2. DESCRIPTIONS
1.2.1. Fépin Formation - FEP
Authors:Dumont, 1848; Meilliez, 1984; Meilliez & Blieck, 1994a.
Description: Conglomeratic formation made up of rudites and arenites as major constituants with sandstones, siltstones, shales and breccias as interbeds. Depositional environments are either fluviatile or tidal marine. The formation is interpreted as a positive megasequence corresponding to the Lower Devonian transgression on the Ardennnes. The lowermost layers unconformably rest on the folded Lower Paleozoic basement. The top of the series is placed where the sandstones are passing upwards to the shales of the Mondrepuis Formation.
Stratotypes: The Fépin Fm was first described at an old quarry W of Fépin (France). However, the only place where the series is complete is the Lahonri quarry, S of Couvin.
Area: Mainly known from the northern flank ofthe Rocroi Massif and the SW flank of the Stavelot Massif.
Thickness:Very variable: 20 to > 40 m at Lahonri quarry, 5 to > 70 m at Fépin, 20 to > 300 m at Dochamps.
Age: Lochkovian (R subzone of the MN Oppel Miospore Biozone) on the northern flank of the Rocroi Massif. However, at Muno, in the southern part of the Neufchâteau Synclinorium, Godefroid (1995a) has identified a brachiopod (Dayia shirleyi) of Silurian (Pridolian) agein the lower part of the Mondrepuis Fm, overlying the Fépin conglomerate (there also named "Linchamps conglomerate"). In the northern part of the Neufchâteau Synclinorium, South of the Stavelot Massif, at Gdoumont, Godefroid & Cravatte (1999) have confirmed the Pridolian age of the Gdoumont sandstone overlying the Quarreux conglomerate (3 to 5 m thick) resting unconformably on the Cambro-Ordovician basement. This means that the Fépin Fm is very diachronous from south to north, with ages ranging from Silurian (Pridolian) to Lochkovian.
Remarks: The rocks, which unconformably rest on the Cambro-Silurian basement, generally start with a conglomerate. In some cases, this conglomerate is not thick enough to be considered as a distinct formation (e.g. base of the Marteau and Fooz Formations).
1.2.2. Mondrepuis Formation - MON
Authors: Thorent, 1839; Mailleux, 1927; Meilliez & Blieck, 1994b; Godefroid, 1995a.
Description: Blauw shales with disseminated quartz grains (detrital or volcanic). Some sandstone layers are interbedded in the first basal meters of the series. The abundance of fossils (lamellibranchs, brachiopods, ostracods, tentaculites, bryozoans, trilobites, crinoids) confirms its marine character.
Stratotype: There isno continuous section atMondrepuis (France). The best section (although much degraded) is situated at Haybes (France), in the Bois du Ridoux.
Area: Southern border of the Dinant Synclinorium and northern part of the Ardenne Anticlinorium.
Thickness: Probably 175 m at the Bois du Ridoux. Thickness and facies change S of Hargnies, due to synsedimentary faults.
Age:Late Pridolian at Muno (occurrence of Dayia shirleyi) - Early Lochkovian (R Subzone of the MN Oppel Miospore Biozone).
1.2.3. Oignies Formation - OIG
Authors: Gosselet & Malaise, 1868; Gosselet, 1880a; Meilliez & Blieck, 1994c.
Description: Formation made up of detrital rocks of red colour. At the bottom, coarse-grained sandstones, with feldspathic lenses, changing upwards to finer-grained rocks (fine-grained sandstones, siltstones, shales). Sedimentological observations indicate an evolution from a marine environment to an exunded alluvial plain.
Stratotype: The best sections are situatedat Fépin (France), at the Moulin de Fétrogne along the Meuse, and N of the meeting of the Meuse and Risdoux rivers.
Area: S flank of the Dinant Synclinorium.
Thickness: < 210 m at the stratotype, 800-1000 m in the Dochamps area.
Age: Lochkovian, with a diachronous character. The Oignies Fm is younger to the W (Couvin area, Z Subzone; lower part of the BZ Oppel Miospore Biozone = Lochkovian-Pragian) and older to the E (Arville-Poix St-Hubert area, E of the Rocroi Massif, SibSubzone, MN Oppel Miospore Biozone = Lochkovian).
1.2.4. Saint-Hubert Formation - STH
Authors: Gosselet, 1880a; Mailleux, 1932; Stainier 1994a.
Description: The formations begins above the last green and mottled shales of the Oignies Formation. At the bottom, green shales with some lenticular beds of pale green quartzites. At the top, thick mass of light green quartzites. In between, green shales, frequently cellular, and green or grey green siltstones, sometimes with green, light green or grey green sandstones and quartzites beds. On the plateaus, the quartzites are often bleached or reddened.
Stratotypes: Saint-Hubert, sections along the Lhomme river and the Namur-Arlon railway track. The top is outcropping at the Mirwart railway station.
Area: Southern flank of the Dinant Synclinorium; northern part of the Ardenne Anticlinorium.
Thickness: 400 m in the Couvin area, 500 m in the Meuse valley, 500-700 m in the Dochamps area.
Age: Lochkovian/Pragian. Diachronous character based on miospore zonation. Younger age in the Couvin area, Pèrnelle section (Z Subzone at the bottom; E Subzone at the top, BZ Oppel Miospore Biozone) and older age in the Saint-Hubert area (Sibto Z Subzones, MN to BZ Oppel Miospore Biozones).
1.2.5. Mirwart Formation - MIR
Authors: Hebert, 1855; Stainier, 1994b.
Description: The Mirwart Formation corresponds to the former Anor Formation. However, the lack of a good section in the Anor area has justified the abandon of the Anor name. Furthermore, the name "Mirwart" was already used in the legends of the geological maps at the scale 1:40,000 (published between 1900 and 1909) to describe the upper part of the formation.
At the bottom, the Mirwart Formation begins with greyish green shalesoverlying the quartzites of the St-Hubert Formation. At the top, green quartzites underly the carbonate and fossiliferous beds of the Villé Formation. In between, there are occurrences of thick lenticular masses of green, light blauw, greenish blauw, sometimes white or cream quartzites and sandstones, interbedded in green grey or black shales and siltstones. Sandstones often contain pebbles of black shale. Towards the top, the black shales contain plants remains. In the 100 uppermost meters, the sandstone layers may also contain rare shells.
Stratotypes: Mirwart, sections along the Lhomme river and the Namur-Arlon railway track. Other good section for the upper part at Villé, near La Roche-en-Ardenne.
Area:S and E of the Dinant Synclinorium; Halleux Anticline.
Thickness: 300 m at Couvin, 450 m in the Meuse valley, 600 m at Mirwart, 600 m on the eastern side of the Dinant Synclinorium, > 700 m N at Halleux, 1000 m W of Dochamps.
Age: Lochkovian-Pragian. On the base of miospore zonation, diachronous character from W to E. At Mirwart, top of the Z, E, Po and W Subzones, BZ and PoW Oppel Miospore Biozones (= Lochkovian-Pragian border); at Couvin, in the Pèrnelle valley : PaaSubzone of the PoW Oppel Miospore Biozone (= Pragian). Former Early Siegenian (Sg1) age.
1.2.6. Villé Formation - VIL
Authors: Maillieux & Demanet, 1929; Asselberghs, 1946; Godefroid & Stainier, 1982.
Description:Dark blue shales and slates with intercalations of rust-coloured sandy laminated layers, blue sandstones, often with brown pellicular weathering, and blue carbonate sandstones, often very fossiliferous and strongly weathered at the surface (dissolved; limonitized). Also green and sometimes white sandstones and quartzites. Ripple marks occur frequently at the sandstone layers boundaries.
Stratotype: Villé near La Roche-en-Ardenne.
Area: S and SE sides of the Dinant Synclinorium, up to the Xhoris fault.
Thickness:30 m S of Couvin, 200 m S of Grupont, 200 m at Amonines, 250-300 m in the La Roche-en-Ardenne area.
Age: Although being very rich in fossils (brachiopods, crinoids, lamellibranchs, corals), no marker guide was up to now identified. A Pragian age is inferred, due to the ages attributed to the neighbouring formations. Former Siegenian (Sg2 or S2) age.
1.2.7. La Roche Formation - LAR
Authors: Dewalque, 1874; Asselberghs, 1946; Godefroid & Stainier, 1982.
Description: At the stratotype, from the bottom to the top, the La Roche Formation is made up of:
· 200 m of dark blue slates with thin layers of light blue sandstones or quartzites. Load casts;
· 100 m of dark blue slates and blue grey silty slates with sandy intercalations and 0.1-1 m thick banks of reddish sandstones. Rare fossils;
· 150 m of dark blue slates progressively richer to the top in thin sandy layers and blue green siltstones, sometimes fossiliferous.
Stratotypes: Lower boundary at La Roche-en-Ardenne, along the Hotton road; upper boundary S of Jupille, at the Hodister crossing.
Area:S and SE sides of the Dinant Synclinorium, up to the vicinity of the Xhoris fault.
Thickness: 215 m S of Couvin, 420 m S of Grupont, about 400 m at Amonines, 400 m at the northern flank of the La Roche Syncline increasing to > 800 m at the southern flank of the syncline.
Age: Probably Pragian, due to the age of the neighbouring formations.
Jupille Formation – JUP (introduced June 2009, V. Dumoulin and M. Coen-Aubert)
Authors: Dejonghe et al., 2008; Dejonghe & Hance, 2008.
Description: The Jupille Formation is proposed to better characterize in the High-Ardenne area the rocks occurring between the La Roche (or Villé Formation if the La Roche Formation is not represented) and Pèrnelle Formations. This formation is made up of series of grey, blue grey or greenish grey sandstone layers interbedded in blue grey siltstones and slates similar to those of the La Roche Formation. Locally, the sandstones grade to quartzites. Toolmarks, current ripples, lenticular and oblique or hummocky cross stratifications and load casts are present in the sandstone layers.
In the Ourthe valley, where the new lithostratigraphic unit is introduced, the Jupille Formation overlies the La Roche Formation and it is not possible to distinguish its top from the succeeding Pèrnelle Formation. In the parastratotype of Mirwart (Lomme valley), the Jupille Formation is present between the Villé and Pèrnelle Formations. Indeed, the La Roche Formation passes laterally into the Jupille Formation between Grune and Nassogne (Barchy et al. submitted). According to Marion & Barchy (1999), it is difficult to map separately the Pèrnelle Formation even in the type area of Couvin. Maybe, the Pèrnelle Formation should be reconsidered as a member of the Jupille Formation.
Stratotypes:different outcrops close to the Jupille village in the Ourthe valley, between Hotton and La Roche-en-Ardenne; parastratotype at Mirwart, sections along the Namur-Arlon railway track and the Lomme river.
Area:S and SE sides of the Dinant Synclinorium, up to the vicinity of the Xhoris fault.
Thickness:500 m at Mirwart (Jupille Formation), at least 600 m at Jupille, at least 600 m in the Nisramont area, 150 m at the northern flank of the Halleux Anticline (Jupille and Pèrnelle Formations).
Age:Probably Pragian, due to the age of the neighbouring formations.
1.2.8. Pèrnelle Formation - PER
Author: Godefroid, 1979, 1994.
Description: The formation begins with the first massive sandstone bank overlying the siltstones of the La Roche Formation. It finishes with the last thick sandstone bank underlying the shales, siltstones and shelly (and also sometimes carbonate) sandstones of the Pesche Formation. The Pèrnelle formation is mainly made up of massive, green blauw (brownish if weathered) sandstones and quartzitic sandstones, sometimes fossiliferous, separated by thin dark shaly beds. Locally, the thickness of the dark shales and siltstones increases.
Stratotype: Couvin, Pèrnelle pond, old railway tram trench.
Area: S and SE sides of the Dinant Synclinorium.
Thickness: 39 m at the Pèrnelle pond, about 40 m at Jupille, 45 m S of Grupont, about 60 m in the Meuse valley, 150 at the northern flank of the Halleux Anticline, > 600 m in the Nisramont area.
Age: Late Pragian at the stratotype (Su Subzone of the PoW Oppel Miospore Biozone).
1.2.9. Pesche Formation - PES
Authors: Maillieux, 1910; Asselberghs & Maillieux, 1938; Godefroid, 1979.
Description: Grey or blue grey (greenish or brownish by weathering) shales and siltstones with lenses en layers of sandstones, sometimes containing shells. The sandstones can also be argillaceous or with a carbonate cement and become limonitic by weathering.
Stratotype: Couvin, Pèrnelle pond, old railway tram trench.
Area: S and SE sides of the Dinant Synclinorium, up to the area between the Ourthe valley and Villers-Ste-Gertrude.
Thickness: 160 m in the Meuse valley, ±190 m in the Couvin area, ±375 m in the Lesse valley, ±400 m S of Grupont, ±400 m in the Ourthe valley; 700-800 m in the Hodister area.
Age: On the base of three species of Brachyspirifer, the Siegenian (@Pragian) - Emsian boundary was defined in the lower part of the Pesche Fm. Caudicriodus celtibericus was also identified at the base of this formation. In Spain, this conodont species is associated to Polygnathus dehiscens indicating a Lower Emsian age.
1.2.10. Vireux Formation - VIR
Authors: Gosselet, 1864; Godefroid & Stainier, 1988, 1994a.
Description: The Vireux Fm begins with blue grey quartzitic sandstones overlying the shales and siltstones of the Pesche Fm. This formation is mainly made up of thick masses of blue grey or greenish quartzites and sandstones (eventually argillaceous) separated by dark grey or greenish shales and siltstones interbeds. East of Olloy-sur-Viroin and W of Chooz, the shale beds increase. Some sandstone layers contain shells or plants remains. The top of the Vireux Fm is defined below the first red rocks of the Chooz Formation.
Two members are distinguished, respectively from bottom to top:
· the Ecluse Member, in which the grey and blue grey colours are dominant and in which some layers contain fossils (corals, brachiopods, lamellibranchs, trilobites, crinoids);
· the Ruisseau de Deluve Member, in which the argillaceous character of the rock is generally more pronounced, the greenish colour frequent and plant remains present in some levels.
The limit between the two members is defined at the top of the last bank containing macrofossils.
Stratotype: Vireux (France), Montigny quarry, left bank of the Meuse.
Area: S and SE sides of the Dinant Synclinorium, up to the surroundings of the Ourthe valley.
Thickness: > 80 m at Couvin, 120-120 m S of Chooz, 350 m in the Lesse valley, 400 m S of Grupont.
Age: Emsian.
1.2.11. Chooz Formation - CHO
Authors: Gosselet, 1868; Godefroid & Stainier, 1988, 1994b.
Description: Detrital formation essentially characterized by its red or mottled colours. At Vireux, two subunits are distinguished:
· a lower unit (±50 m), which contain argillaceous sandstones or quartzitic sandstones occurring as thick masses separated by red and green, rarely grey, shales and siltstones;
· an upper unit (270-280 m), which is mainly made up of red and green shales and siltstones with intercalations of red or green sandstone lenses or beds which may reach 10-14 m thick.
East of Hampteau, the top of the Chooz Fm is situated at the bottom of the first gravelly or conglomeratic bed of the Hampteau Fm and not at the last red bed as it is the case to the west.
Stratotype: For the lower limit, Vireux (France), Mont Vireux quarry; for the upper limit, Vireux-Mazée road, W of the crossing with the Givet road.
Area: S and SE flanks of the Dinant Synclinorium.
Thickness: 320-330 m.
Age: Emsian.
1.2.12. Hierges Formation - HIE
Authors: Sauvage & Buvignier; 1842; de Dorlodot, 1901; Godefroid & Stainier, 1994c.
Description:The formation is divided into two members, from bottom to top:
· The Bois Chession Member: ±20 m of argillaceous or quartzitic sandstones, locally fossiliferous, forming two or three units separated by one or two grey or green grey shale units with fossiliferous beds. The Bois Chession Mbr generally begins with 2.5-2.5 m of alternating thin argillaceous sandstones and shales beds. Towards the E, from Tellin, conglomerates and gravelly sandstones are interbedded in the sandstones.
· The Barrage Member: 300-310 m of shale and siltstones, locally with carbonate cement, containing numerous fossiliferous calcareous sandstone banks and sandstone beds with or without shells. From Grupont, a sandstone unit appears in the upper part of the Barrage Mbr. Its thickness increases from Grupont to Marche-en-Famenne, reaching 160-170 m S of Hargimont. The sandstone beds with calcareous cement also increase and fossils are very abundant in some places.
The top of the Hierges Fm is below the first massive shelly limestone bed of the overlying St-Joseph Fm.
Stratotypes: There is no section at Hierges covering the entire formation. Stratotypes for the lower limit are situated at Vireux (France), and for the upper limit, at Nismes (St Joseph locality).
Area: S and SE flanks of the Dinant Synclinorium, up to the Hampteau area.
Thickness: 320-330 m at Hierges.
Age: Traditionally in Belgium, the top of the Hierges Fm was considered as the top of the Emsian (thus, also as the top of the Lower Devonian). Since 1985, the Lower Devonian-Middle Devonian boundary defined by the International Subcommission on the Devonian Stratigraphy corresponds to the occurrence of the Polygnathus costatus partitus conodont. This limit is situated stratigraphically higher, in the Eau Noire Fm. The icriodid conodont assemblage (Latericriodus cf. beckmanni, Icriodus culicellus culicellus, I. corniger ancestralis, I. fusiformis and I.rectirostratus) found in the Hierges Fm covers the Polygnathus laticostatus and P. serotinus biozones. Arduspirifer arduennensis, Brachyspirifer mixtus and Paraspirifer sandbergeri are brachiopods occurring a little above the lower limit of the formation. Paraspirifer praecurssor is a brachipod occurring in the upper part of the formation.
1.2.13. Hampteau Formation - HAM
Authors: Gosselet, 1873; Asselberghs, 1946; Stainier, 1994c.
Description: The Hampteau Fm starts with the occurrence of gravelly or conglomeratic sandstones overlying the red, green and mottled detrital rocks of the Chooz Fm. The rocks are characterized by thick masses of sandstones, coarse-grained to gravelly sandstones with disseminated quartz and sandstone pebbles and conglomerate banks alternating with shales and siltstones. The top of the formation is placed at the last red and green bank underlying the grey shales and siltstones, quickly carbonate bearing, of the St-Joseph Fm. The colour is very variable: red, green, often mottled or greyish green. Some banks contain fossils. The Hampteau Fm is divided into two members, respectively from bottom to top:
· The Hamoûle Member (141 m thick at Hampteau), in which the sandstones contain crinoids and brachiopods. A thin sandy layer is rich in ostracods;
· The Chaieneu Member (432 m at Hampteau), in which pebbles are more abundant within the sandstone beds, conglomerates more frequent and fossils represented by plant remains. A thick level of red shale with burrows is situated close to the bottom.
The boundary between the two members is fixed at the last thick bank with macrofauna.
Stratotype: SE of Hampteau, along the road to La Roche-en-Ardenne.
Area: E side of the Dinant Synclinorium, from Hampteau up to the vicinity of the Xhoris fault.
Thickness: The thicknessdecreases to the N :573 m at Hampteau; 360 m in the Aisne valley; 250 m at La Roche à Frène; 45 m at Fagnoul, near the Xhoris fault.
Age: Upper Emsian (Arduspirifer arduennensis) for the Hamoûle Member. Emsian/Eifelian boundary or Eifelian for the Chaieneu Member (Pro-Vel Subzones of the AP Oppel Spore biozonation).
1.2.14. Marteau Formation - MAR
Author: Gosselet, 1888; Dejonghe, Hance & Steemans, 1994a.
Description: In the Marteau stratotype, the formation unconformably rests on the Caledonian (Salmian) basement and is overlaid by the sandstones and quartzites of the Bois d'Ausse Fm. At the bottom, occur a conglomerate of 1.5 m thick at Eupen, increasing S of Eupen and in the Amblève valley (Quarreux Member, locally > 10 m thick). These rocks are overlaid by maroon (red) and mottled siltstones and argillaceous fine-grained sandstones, alternating with green, olive or mottled argillaceous sandstones. The maroon (red) colour is widely dominant. Carbonate nodules are concentrated in some beds and responsible for a cellular structure if dissolved. Light-coloured quartzite banks, sometimes gravely, occur in the lower part. In the Gileppe valley, there are coarse-grained to conglomerate bearing kaolinitic sandstones.
Stratotype: Theux Window, Marteau locality, along the Spa-Pépinster railway.
Area: W and N flanks of the Stavelot Massif.
Thickness: 163 m at Eupen.
Age: Lochkovian (Ma-GSubzones of the MN Oppel Miospore Biozonation in the Vesdre Nappe; R subzone in the Theux Window pointing out to an older age to the S than to the N).
1.2.15. Fooz Formation - FOO
Authors: Gosselet, 1873, 1888; Dejonghe, Hance & Steemans al., 1994b.
Description: In the stratotype of Dave, the Fooz Formation unconformably rests on Silurian shales. The formation starts with 1.5 m of conglomerate overlaid by 11.7 m of coarse-grained sandstones locally kaolinitic form the Dave Member. Olive green siltstones and micaceous sandstones surmount it. A frequent cellular structure is due to the dissolution of carbonate nodules. At the top, the Fooz Fm contain a few meters of maroon (red) and mottled siltstones and sandstones. The top of the formation is defined below the first meter-thick blue grey or light beige quartzite bank of the Bois d'Ausse Fm.
Stratotypes: Fooz, left bank of the Meuse. Dave, Bois de Dave, along the Ruisseau des Chevreuils.
Area: N of the Dinant Synclinorium and in the Vesdre Nappe.
Thickness: 150-200 m at the N side of the Dinant Synclinorium. 193 m at Dave (13.2 m for the Dave Member).
Age: Upper Lochkovian(Sia-bSubzones of the MN Oppel Miospore Biozonation).
1.2.16. Bois d'Ausse Formation - BAU
Authors: d'Omalius d'Halloy, 1868; Asselberghs, 1946; Dejonghe, Hance & Steemans, 1994c.
Description: The lower limit is placed at the first grey, blue grey or light-coloured quartzite bank overlying the green siltstones and sandstones of the Fooz Fm. The upper limit is situated below the red rocks of the overlying Acoz Fm. In the Treko valley, three members are distinguished, respectively from bottom to top:
· The Bôlia Member (50 m) : grey or beige quartzites with cross-stratification;
· The Tréko Member (20 m) : alternating siltstones and green argillaceous sandstones;
· The Masuis Member (30 m): lenticular beige grey quartzite banks with rust-coloured spots and thin grey shale intercalations. In some levels, occurrence of shale pebbles and plants remains.
Stratotypes: Bois d'Ausse,Sart-Bernard, Namur-Arlon railway; Vitrival, Treko valley; Dave, Ruisseau des Chevreuils.
Area: N and E sides of the Dinant Synclinorium and in the Vesdre Nappe.
Thickness: 100 m in the Treko valley, 135 m in the Vesdre Nappe, 180 m at Acoz, 360 m in the Meuse valley.
Age: Lochkovian (SibSubzone of the MN Oppel Miospore Biozonation) to Upper Pragian (SuSubzone of the PoW Oppel Miospore Biozonation).
1.2.17. Nonceveux Formation - NON
Authors: Asselberghs, 1946; Monseur, 1959; Hance, Dejonghe & Steemans, 1992.
Description: Detrital formation with strong sequential character. At Nonceveux, 19 sequences for a total thickness of 107.6 m are distinguished. Each sequence is made up of scouring arenaceous rocks at the bottom passing progressively upwards to pelites which are often maroon (red) to the top.
Stratotypes: Nonceveux, right bank of the Amblève; El Fagne locality, Pépinster-Spa railway section.
Area: N of the Dinant Synclinorium, E of Andenne; E of the Dinant Synclinorium, N of the Xhoris fault; Vesdre Nappe, W of Stembert.
Thickness: 102.5 m at Huy, 100 to 120 m at Pépinster, > 107.6 m at Nonceveux.
Age: Diachronic formation from W to E, between Pépinster (Z subzone of the BZ OppelMiospore Biozone = Upper Lochkovian) to Huy (PaaSubzone of the PoW Oppel Miospore Biozone = Pragian).
1.2.18. Solières Formation - SOL
Authors: Maillieux & Demanet, 1929; Hance, Dejonghe & Steemans, 1992
Description:The formation is essentially made up of shales and siltstones with rare sandstones and quartzite interbeds. Colours are grey, blue grey or blue. Light colours may also characterize sandstones and quartzites. Maroon (red) colours are very accessory ones (only a 4 m thick bed of maroon (red) shale occurs at Nonceveux). The bottom of the formation is fixed, at Nonceveux, below a 0.65 m thick quartzite bed overlying the maroon (red) silstones of the 19th sequence of the Nonceveux Fm. The top is below the first maroon (red), green or mottled pelites of the Acoz Fm.
Stratotype: The name is from a small excavation situated at Solières locality, in the Ben-Ahin municipality. A much better stratotype is N of Nonceveux, right bank of the Amblève, along the Remouchamps - Trois-Ponts road.
Area: N of the Dinant Synclinorium, E of Andenne; E of the Dinant Synclinorium, N of the Xhoris fault; in the Vesdre Nappe, W of Stembert.
Thickness: 125 m at Nonceveux, 130 m at Huy.
Age: Lochkovian to Pragian. Diachronic formation with younger ages to the east (Paaand PabSubzones of the PoW Oppel Miospore biozonation at Solières; E to Su Subzones of the BZ to PoW Oppel Miospore Biozonation in the Pépinster area).
1.2.19. Acoz Formation - ACO
Authors: Legend of the geological map of Belgium at the scale 1/40,000, 1892; Asselberghs, 1946; Dejonghe, Hance & Steemans, 1994d.
Description: Detrital rocks mainly of maroon (red) colours characterize the Acoz Fm. The lower boundary is fixed at the first maroon (red) siltstone and argillaceous sandstone layer overlying the quartzites of the Bois d'Ausse Fm. The upper boundary is situated below the sandstones and quartzites of the Wépion Fm. Two members are distinguished at the stratotype, respectively from bottom to top:
· The Bième Member (140 m) : essentially made up of maroon (red) siltstones and shales;
· The Ruisseau d'Hanzinne Member (160 m): containing progressively more maroon (red) sandstones and m to several m-thick layers of quartzites, generally light-coloured in the maroon (red), pinkish, greenish or yellowish shades. Quartzites often contain pebbles of maroon (red) shales.
This division in two members is questionable at other places and is certainly not valid in the Vesdre Nappe (there, light-coloured quartzites are concentrated at the bottom and not at the top of the formation).
Stratotype: Acoz, Bième and Hanzinne valleys, between the old quarries of the Bois de Châtelet and the Bois d'Acoz.
Area: N and E flanks of the Dinant Synclinorium and in the Vesdre Nappe.
Thickness: 300 m to the W of the Meuse and 400 m to the E. The thickness varies much in the Vesdre Nappe, depending on the erosion level of the Vicht Conglomerate (thickness = 250 m at Eupen, < 50 m at Pépinster, 0 m at Heusy).
Age: Pragian (Su Subzone of the PoW Oppel Miospore Biozonation N and E of the Dinant Synclinorium; Po-W to Su Subzones of the PoW Oppel Miospore Biozonation in the Vesdre Nappe).
1.2.20. Wépion Formation - WEP
Authors:Gosselet, 1888; Stainier, 1994d.
Description:The Wépion Fm begins with the first green quartzitic thick bed overlying the red siltstones and sandstones thin beds of the Acoz Fm. The very bottom of this quartzitic unit is underlined by a conglomerate made up of pebbles of white quartz, green or red sandstone and tourmalinite. The top of the formation is situated below the sandstone and conglomerates with red cement of the Burnot Fm. In between, the Wépion Fm is mainly made up of quartzites and blue grey, blue or greenish argillaceous sandstones. The beds are often lenticular. Thick interbeds of grey, black or mottled shales and siltstones, sometimes containing pebbles often separate sandstone beds. Plant remains and, less frequently, fish remains also occur. Pelitic units may also contain red and green sandstones beds, generally well stratified. To the top, the green sandstones contain more and more pebbles. The siltstone interbeds are cellular and ferruginous. The Wépion Fm is divided into two members, respectively from bottom to top:
· The Grand Ri Member (260 m): blue grey, greenish or reddish sandstones and quartzites, often conglomeratic bearing, forming thick units separated by grey, green or red shales, siltstones and thin sandstone beds.
· The Bois des Collets Member (40 m): green, very coarse-grained and even conglomeratic bearing sandstones. The rocks are cellular and ferruginous (also the green shales interbeds).
Stratotype:Dave and Wépion, Dave quarry, Bois des Collets quarry and surroundings.
Area:N and E flanks of the Dinant Synclinorium, up to the Mormont fault. The Bois des Collets Mbr is observed from Binche to the Fond d'Oxhe.
Thickness:200 m in the Honelle valley, 223 m at Wépion, 280 m at Acoz, 400 m S of Huy.
Age:Emsian (AB Oppel Miospore Biozone).
1.2.21. Burnot Formation - BUR
Authors: d'Omalius d'Halloy, 1839; Gosselet, 1873; Stainier, 1994e.
Description:The Burnot Fm is mainly made up of red, coarse-grained sandstones and conglomerates with frequent tourmalinite pebbles occurring in lenticular beds interlayered with red and, less frequently, green shales. Plant remains may occur in the shales. The lower limit is fixed above the greenish sandstones, locally gravely, of the Wépion Fm; the upper limit is below the red siltstones and shales containing small pebbles of white quartz and crinoids articles belonging to the Rivière Fm.
Stratotype :Profondeville, N of the Burnot valley and surroundings.
Area :N and E flanks of the Dinant Synclinorium, up to the Xhoris fault.
Thickness :200 m in the Honelle valley, 330 m S of Acoz, 535 m in the Meuse valley, 350 m in the Huy area.
Age :Probably Emsian. However, up to now, no biostratigraphical attempts for dating this formation have succeeded. It is not impossible that its upper part is of Eifelian age, as it is the case for the Hampteau Fm which is a lateral equivalent.