Detailed Lithology and Faunal Occurrence of the Fromelennes Formation in the Type Area (Middle/Upper Givetian, Southern Part of the Dinant Synclinorium, Ardenne)

  • Description lithologique détaillée et distribution faunique de la Formation de Fromelennes dans la région type (Givétien moyen/supérieur, bord sud du synclinorium de Dinant, Ardenne)

DOI : 10.54563/asgn.1274

p. 11-36

Abstracts

The Flohimont and Nichet sections, located in the southern part of the French Ardenne, expose parts of the Fromelennes Formation series (Middle/Upper Givetian - Middle Devonian). This work presents the detailed, bed by bed, stratigraphic columns for the two sections along with data on the macro- and microfauna occurrence and abundance. Characteristic beds and zones are recognized. Correlations between these different sections and the close Cul d’Houille section allow proposing the most complete up to date stratigraphic synthesis for the Fromelennes Formation in the type area.

Les coupes de Flohimont et de Nichet, situées dans la partie méridionale des Ardennes françaises, permettent d’observer différentes séquences de la série sédimentaire de la Formation de Fromelennes (Givétien moyen/supérieur - Dévonien moyen). Ce travail présente les colonnes stratigraphiques détaillées de ces deux coupes ainsi qu’un relevé, banc par banc, de l’abondance des macro- et microfaunes. L’identification de bancs et zones repères permet de corréler entre eux ces différents affleurements et la coupe du Cul d’Houille et de reconstituer ainsi la séquence stratigraphique la plus complète possible à ce jour pour la Formation de Fromelennes dans la région type.

Outline

Text

I. — Introduction

The Fromelennes Formation, firstly recognized along the Meuse river in Ardenne as a carbonated unit by Gosselet (1871) and defined by Errera et al. (1972), has never been completely studied in detail despite the fact that two different reference sections are usually mentioned (Bultynck, 1974; Brice, 1980; Bultynck et al., 1991; Brice & Mistiaen, 2008) : respectively the Flohimont section along the Flohimont- Fromelennes road (D46) and the Cul d'Houille section on the western bank of the Houille stream.

After the detailed work on the Cul d'Houille section (Hubert & Pinte, 2009; Maillet et al., 2010), this paper describes, bed by bed, the lithology and the occurrence and abundance of the main macro- and microfaunas in two other complementary sections : the Flohimont section and the new Nichet section.

Finally, the correlation of the three studied sections, by means of fifteen characteristic beds or zones allow to propose the most complete stratigraphic column for the Fromelennes Formation in its type area.

II. — Stratigraphy

The Givet Group (Errera et al., 1972) is currently divided into 4 formations from the Trois-Fontaines Formation at the base to the Fromelennes Formation at the top (Fig. 1) : the latter is subdivided into three members (Flohimont Member, Moulin Boreux Member and Fort Hulobiet Member) (Bultynck et al., 1991).

According to Bultynck (1974), Cornet (1975), Bultynck et al. (1991), Bultynck (2001), Lacquement et al. (2006) and Maillet et al. (2010), the historical boundary between the Mont d'Haurs Formation and the Fromelennes Formation is defined at the base of the first clayey bed containing brachiopods. We considered this boundary here.

The Fromelennes Formation is usually reported to Upper Givetian (Milhau, 1983; Bultynck et al., 1991). Nevertheless, according to the sub-commission on Devonian Stratigraphy (Becker, 2007; Bultynck & Gouwy, 2008), the Middle/Upper Givetian boundary is fixed at the transition between P. varcus and S. hermanni conodonts zones. Then, the Flohimont Member displaying P. varcus and P. ansatus (Bultynck et al., 1991; Bultynck, 2001; Gouwy & Bultynck, 2003), is consequently referred to Middle Givetian. Defining the beginning of the Upper Givetian, S. hermanni appears 83 meters above the base of the Fromelennes Formation in the Flohimont section, in the second half of the Moulin Boreux Member (Gouwy & Bultynck, 2003).

Figure 1

Figure 1

Standard conodont zonation, chronostratigraphy and lithostratigraphy in the southern border of the Dinant synclinorium.
 
Zonation standard des conodontes, chronostratigraphie et lithostratigraphie pour le bord sud du synclinorium de Dinant.

The Givetian/Frasnian (Middle/Upper Devonian) boun- dary is located inside the Nismes Formation (Casier, 1987; Bultynck et al., 1991; Lacquement et al., 2006). However, this boundary currently tends to be considered as closer to the lithostratigraphical boundary between the Fromelennes Formation and the Nismes Formation (Casier & Préat, 2009).

III. — Studied Sections

The Givet area belongs to the southern border of the Dinant synclinorium (Fig. 2A). Several outcrops expose the carbonated Fromelennes Formation. Three sections have been sampled.

1) Cul d'Houille section

In this section, located on the western bank of the Houille stream (Fig. 2B1), the Fromelennes Formation is about 136 meters-thick (Hubert & Pinte, 2009 emend Maillet et al., 2010). The contacts Mont d'Haurs Formation/Fromelennes Formation and Flohimont Member/Moulin Boreux Member have been recognized (Maillet et al., 2010). The Moulin Boreux Member is visible in an abandoned quarry but the contact between the Moulin Boreux Member and the Fort Hulobiet Member was not identified. The upper part of the Fort Hulobiet Member is lacking.

2) Flohimont section

This section crops out along the road D46, from the north of Flohimont to the south of Fromelennes, on the eastern bank of the Houille stream (Fig. 2B2). The Fromelennes Formation is about 84 meters-thick. The lower contact (Mont d'Haurs Formation/Fromelennes Formation) and the upper contact (Fromelennes Formation/Nismes Formation) are well exposed (Bultynck, 1974; Milhau, 1983). Boundaries between the different members are faulted and unclear.

3) Nichet section

This new section is located in Fromelennes, along the way leading to the Nichet caves (Fig. 2B3). Only the upper half of the Fromelennes Formation and the base of the Nismes Formation were studied. The Fort Hulobiet Member is about 13 meters-thick but all the boundaries are faulted.

Figure 2

Figure 2

Location of the studied sections, A. in the Dinant synclinorium (modified from Bultynck et al., 2001). B. in the Fromelennes area (topographic map of Givet (25,000e), IGN France, https://infoterre.brgm.fr/). 1. Cul d'Houille section; 2. Flohimont section (D46); 3. Nichet section.
 
Localisation des coupes étudiées, A. à la bordure sud du synclinorium de Dinant (modifié d'après Bultynck et al., 2001). B. dans la région de Fromelennes (carte topographique de Givet au 25 000e, IGN France, https://infoterre.brgm.fr/). 1. Coupe du Cul d'Houille ; 2. Coupe de Flohimont (D46) ; 3. Coupe de Nichet.

IV. — Previous Works

Historical review of the Cul d'Houille section works can be found in Hubert & Pinte (2009) emend Maillet et al. (2010).

Few authors studied the Flohimont section. Thus, Coen & Coen-Aubert (1971) described lithological units and macrofauna in the F1a (currently the Flohimont Member). Bultynck (1974) focussed his work on boundaries and conodonts in the upper part of the Mont d'Haurs Formation and the base of the Fromelennes Formation. Cornet (1975) described the reefal organisms (stromatoporoids, rugose and tabulate corals) in the upper part of the Mont d'Haurs Formation. Milhau (1983) was the first one to study ostracodes from the base and the top of the Fromelennes Formation. Coen (1985) studied ostracodes from the lower part of the Flohimont Member. Bultynck (2001) recorded the occurrences of conodonts taxa at the Mont d'Haurs Formation/Fromelennes Formation transition. Boulvain et al. (2009a and b) published sedimentological studies, magnetic susceptibility measurements and provided a synthetic stratigraphic column of the section.

The Nichet section has never been studied.

V. — Material and Methods

Sampling of the Cul d'Houille section was made according to the stratigraphic column of Hubert & Pinte (2009) and Maillet et al. (2010). Bed by bed measurements and sampling have been performed in the Flohimont and Nichet sections. More than 250 samples were collected (Tabl. I.).

To extract ostracodes and other calcitic microfossils from the carbonated gangue, we used the well known hot acetolysis method (Milhau, 1983 and 1984; Coen, 1985; Lethiers & Crasquin-Soleau, 1988; Casier & Préat, 2009).

More than 12,000 carapaces, valves and fragments of ostracodes have been collected and identified under binocular lens.

The material and fossils are housed in the collections of the Faculté Libre des Sciences et Technologies (FLST) in Lille.

VI. — Description of the Series

The upper part of the Mont d'Haurs Formation and the Fromelennes Formation are described, from bottom to top, for the Flohimont and Nichet sections. For the Cul d'Houille section, refer to Hubert & Pinte (2009) and Maillet et al. (2010).

1) Flohimont section

In this section, the sedimentary series presents a N70 orientation and a reversed dip of 70°S.

a) The Mont d'Haurs Formation

The described upper part of the Mont d'Haurs Formation is 29.7 meters-thick (beds 969-1000; Annex I).

Bed 969 : 0.25m, calcareous, macrofauna composed of stromatoporoids and tabulate corals. Calcitic bevel-edged base due to a fault.

Bed 970 : 0.80m, sedimentary bias.

Beds 971 to 975 : 3.10m, calcareous, macrofauna composed of some stromatoporoids, rugose and branching tabulate corals (Thamnopora sp.), rare brachiopods and gastropods.

Bed 976 : 1.60m, sedimentary bias.

Beds 977 to 980 : 7.05m, massive, calcareous, macrofauna composed of some laminar stratifications and rare stromatoporoids, tabulate corals and brachiopods.

Bed 981 : 0.45m, nodular, calcareous.

Beds 982 to 985 : 6.15m, thick reef-limestone, providing rugose corals, stromatoporoids and brachiopods (Stringocephalus burtini DEFRANCE, 1827). Poor microfauna with some brachiopods, crinoids, echinoids spines and sponge spicules.

Beds 986 to 987 : 3.75m, massive biostromal unit, with abundant stromatoporoids (Amphiporidae), tabulate corals (Thamnopora sp., Scoliopora sp. and Caliapora sp.), solitary rugose corals, some brachiopods and crinoids. Microfauna mainly composed of brachiopods, gastropods and crinoids.

Beds 988 to 992 : 3.65m, thinner reef-limestones with solitary rugose corals and massive and branching tabulate corals (Crassialveolites sp., Thamnopora sp.) alternating with crinoidal limestones. Common microfossils, particularly ostracodes, brachiopods, crinoids and tentaculitids.

Beds 993 to 1000 : 2.90m, thin crinoidal argillaceous limestones. Very abundant macro- and microfauna with numerous ostracodes, brachiopods, gastropods and crinoids, some reefal organisms, conodonts and trilobites fragments, presence of tentaculitids, perireefal charophyta (Sycidium sp., D. Vachard pers. comm.) and foraminifera.

b) The Fromelennes Formation

The Fromelennes Formation crops out on about 92 meters in this section, compared to about 136 meters in the Cul d'Houille section (Tabl. I), due to numerous faults.

– Flohimont Member (Annex I)

Bed 1001 : 0.45m, incompetent argillaceous limestone showing a brachiopods coquina (1001), accompanied by crinoids. Microfauna well diversified, including charophyta (Sycidium sp.), tentaculitids, gastropods, reefal organisms fragments and very abundant brachiopods, crinoids and ostracodes (Quasillites fromelennensis MILHAU, 1983 as dominant species).

Beds 1002 to 1005 : 2.30m, thin argillaceous crinoidal limestones, rich in brachiopods. Some solitary rugose corals and bioclasts. Well diversified microfauna, with dominant ostracodes, brachiopods and crinoids.

Table I

Section Cul d'Houille Flohimont (D46) Nichet Synthetic stratigraphical column
Fromelennes Fm. thickness 136.00m 92.20m 23.75m 140.00m
Flohimont Mb. 29.60m 12.15m - 29.60m
Moulin Boreux Mb. 84.80m 64.60m Only 11.05m sampled, more about 25.00m 84.80m
Fort Hulobiet Mb. 21.60m 15.45m 12.70m 25.60m
Number of samples 122 121 15 258
Number of ostracodes 7.100 4.900 350 12.350

Data synthesis for the Fromelennes Formation.
 
Synthèse des données pour la Formation de Fromelennes.

Bed 1006 : 0.70m, incompetent bioclastic siltstone, showing a plate-splitting. Microfauna mainly composed of brachiopods, crinoids and tentaculitids.

Beds 1007 to 1013 : 2.15m, bioclastic to crinoidal argillaceous limestones with brachiopods, some trilobites and tabulate corals. Abundant microfauna, with numerous ostracodes, brachiopods, crinoids and tentaculitids, some reefal organisms, trilobites and conodonts fragments, foraminifera (Parathurammina sp.), gastropods, echinoids spines and sponges spicules.

Bed 1014 : 1.10m, sedimentary bias.

Bed 1015 : 0.20m, calcareous. Poor microfauna.

Bed 1016 : 0.75m, sedimentary bias.

Bed 1017 : 0.30m, nodular, calcareous. Common microfauna providing ostracodes, echinoids spines, rare brachiopods and reefal organisms fragments.

Bed 1018 : 0.65m, sedimentary bias.

Bed 1019 to 1026 : 3.55m, nodular calcareous unit, with abundant small trilobites exuviae (Dechenella sp., C. Crônier pers. comm.) and brachiopods. Very abundant crinoids in the lower part. Some solitary rugose corals, branching and massive tabulate (Thamnopora sp., Alveolitidae) at the top. Bed 1023 particularly rich in gastropods. Well-diversified microfauna, with abundant ostracodes, brachiopods and trilobites fragments.

Bed 1027 : 15m, sedimentary bias. In comparison with the close Cul d'Houille section (Hubert & Pinte, 2009 ; Maillet et al., 2010), most of the Flohimont Member is missing, due to a fault.

– Moulin Boreux Member (Annex I)

Beds 1028 to 1038 : 6.45m, decimeters-thick dark thin- grained limestones, with some bioclasts, crinoids and rare stromatoporoids. Microfauna displaying abundant gastropods, some ostracodes, crinoids, algae, rare brachiopods and reefal organisms fragments.

Bed 1039 : 2.50m, sedimentary bias.

Bed 1040 : 0.25m, thin, argillaceous, with some bioclasts and brachiopods valves. Microfauna providing abundant ostracodes and some brachiopods, gastropods, reefal organisms fragments, sponges spicules, charophyta and foraminifera.

Beds 1041 to 1042 : 2.75m, massive biostromal limestones, providing stromatoporoids and solitary rugose corals.

Beds 1043 to 1044 : 0.40m, thin, calcareous, with rare crinoids.

Beds 1045 to 1046 : 4.40m, massive thin-grained limestones, with some bioclasts and brachiopods valves. Poor microfauna with rare ostracodes, crinoids and algae.

Bed 1047 : 1.00m, sedimentary bias.

Beds 1048 to 1050 : 3.65m, massive thin-grained limestones. Bed 1049 is biostromal, with stromatoporoids and solitary rugose corals.

Beds 1051 to 1061 : 7.70m, decimeters to meters-thick limestones, showing some brachiopods valves and rare crinoids, bioclasts and small solitary rugose corals. Poor microfauna.

Beds 1062 to 1065 : 4.35m, massive biostromal limetones, providing abundant stromatoporoids, some solitary rugose corals, rare tabulate corals fragments and crinoids. Bed 1065 especially rich in large globular stromatoporoids. Poor microfauna.

Beds 1066 to 1074 : 10.75m, massive meters-thick thin- grained limestones. Bed 1067 yielding some solitary rugose corals.

Bed 1075 : 3.30m, massive bioclastic limestone, with some globular stromatoporoids.

Beds 1076 to 1077 : 3.40m, thick limestones showing clayey seals, the latter with rugose corals.

Beds 1078 to 1080 : 2.05m, massive limestones alternating with thin argillaceous beds, showing rare crinoids. Very rare microfauna.

Bed 1081 : 0.25m, very nodular, irregular brown siltstone, with a conglomeratic appearance and containing rare badly- preserved rugose corals fragments.

Beds 1082 to 1085 : 1.60m, thin-grained limestones, with iron oxides, rare crinoids, rugose corals and bioclasts.

Beds 1086 to 1089 : 5.25m, massive reef-limestones, with rugose corals and globular stromatoporoids and rare tabulate corals fragments.

Beds 1090 to 1095 : 4.55m, decimeters to meter-thick thin-grained limetones, with iron oxides, rare bioclasts and some solitary rugose corals, especially in bed 1095.

Bed 1096 : 17.00m, sedimentary bias.

– Fort Hulobiet Member (Annex I)

Beds 1097 to 1101 : 1.50m, calcareous, sometimes nodular, with some brachiopods and bioclasts. Microfauna well diversified at the base of this unit. Abundant ostracodes, with Cavellina rhenana KRÖMMELBEIN, 1954 as dominant species.

Bed 1102 : 0.70m, sedimentary bias.

Bed 1103 : 0.40m, thin argillaceous limestone, providing abundant small gastropods.

Bed 1104 : 1.00m, sedimentary bias.

Beds 1105 to 1107 : 0.60m, competent reef-limestones, showing a bevel surface with striated calcite due to a fault. Very abundant tabulate (Thamnopora sp., Crassialveolites sp.) and rugose corals (particularly Disphyllum virgatum HINDE, 1890). Abundant and diversified ostracodes.

Beds 1108 to 1111 : 0.65m, nodular argillaceous limestones. Microfauna essentially yielding foraminifera and algae (Umbellidae).

Beds 1112 to 1116 : 1.50m, competent limestones unit, sometimes slightly dolomitic, with massive and branching tabulate corals and abundant solitary rugose corals. Bed 1114 particularly rich in Disphyllum virgatum HINDE, 1890.

Beds 1117 to 1122 : 1.00m, thin argillaceous dolomitic limestones, with some rugose corals, brachiopods, bivalves, bioclasts and crinoids. Common microfauna with abundant ostracodes.

Beds 1123 to 1124 : 0.50m, siltstones, with very abundant rugose corals, some crinoids and bioclasts. Bed 1124 very rich in disphyllids. Microfauna mainly composed of ostracodes, brachiopods, echinoids spines and foraminifera.

Beds 1125 to 1128 : 1.20m, competent bioclastic limestones. Very rare macrofossils. Common microfauna with abundant ostracodes.

Beds 1129 to 1130 : 0.65m, siltstones, very poor in fauna.

Bed 1131 : 0.15m, thin dolomitic limestone, with brachiopods and bivalves.

Beds 1132 to 1148 : 3.40m, thin-grained limestones, with rare macrofossils. Microfauna mainly composed of ostracodes, brachiopods and echinoderms fragments and foraminifera. Beds 1149 to 1153 : 2.20m, nodular limestones unit, rich in brachiopods. Abundant microfauna, mainly with well-diversified ostracodes, brachiopods, echinoderms fragments, foraminifera (Nanicella sp., D. Vachard pers. comm.) and tentaculitids.

c) The Nismes Formation

Beds 1154 to 1166 : 4.75m, incompetent brown siltstones, with abundant huge brachiopods (Spiriferids, Atrypids…), belonging to the “zone des monstres” (Gosselet, 1871; Errera et al., 1972).

2) Nichet section

In this section, the sedimentary series present a mean N40 orientation and a reversed dip of 70°S.

a) The Fromelennes Formation

The lower part of the Fromelennes Formation (Flohimont Member and base of the Moulin Boreux Member) is not exposed, hidden by the access to the Nichet cave. Only the upper part of the formation can be observed on a few tens of meters, of which about 23 meters were sampled for this study. We especially focussed on the boundary between the Moulin Boreux and the Fort Hulobiet members.

– Moulin Boreux Member (Annex II)

About 25 meters of thick dolomitic limestone beds, belonging to this member, could be observed below the following described series.

Bed 86 : 1.00m, massive meter-thick grey reef-limestone, very rich in stromatoporoids. Some rugose corals. Bed identical to the stromatoporoid wall in the Cul d'Houille quarry (bed 136 in Hubert & Pinte, 2009).

Beds 87 to 89 : 0.35m, thin nodular very bioclastic limestones, with some rugose corals.

Beds 90 to 99 : 5.20m, bioclastic limestones alternating with reef-limestones, with some crinoids, rugose corals and stromatoporoids.

Bed 100 : 1.25m, massive reef-limestone, with some stromatoporoids. Bed analogous to the bed 165 in the Cul d'Houille section (Hubert & Pinte, 2009).

2.00m, sedimentary bias.

Beds 101 to 102 : 0.45m, thin bioclastic, slightly dolomitic limestones, providing a monospecific ostracodes fauna (Cryptophyllus sp.3 sensu Magne, 1964).

0.80m, sedimentary bias.

– Fort Hulobiet Member (Annex II)

Beds 103 to 105 : 0.60m, very calcitic limestones, with striated calcite and iron oxides. Change into the orientation of the series (N50), putting forward a fault.

Beds 106 to 108 : 0.95m, thin dark dolomitic and bioclastic limestones, with iron oxides, some dislocated brachiopods valves and rugose corals. Abundant ostracodes.

6,00m, sedimentary bias.

Bed 109 : 0.50m, argillaceous limestone, rich in small gastropods.

0,50m, sedimentary bias.

Beds 110 to 111 : 0.85m, dolomitic limestones, rich in gastropods. Microfauna mainly composed of ostracodes, gastropods and algae (Umbellidae). Change in the orientation of the series (N40) and bed 110 with a bevel-edged base and striated calcite due to a fault. Presence of a reworked globular stromatoporoid in this bed.

Bed 112 : 0.40m, bioclastic argillaceous limestone. Rare microfauna.

0,50m, sedimentary bias.

Bed 113 : 0.50m, competent limestone, with abundant rugose corals, branching and massive tabulate corals (Thamnopora sp., Crassialveolites sp.), some brachiopods and bioclasts. Very abundant Disphyllum virgatum HINDE, 1890, comparable to the bed 1114 in the Flohimont section. Common microfauna.

Beds 114 to 115 : 0.90m, bioclastic limestones, with brachiopods and some tabulate corals. Microfossils quite rare, with some ostracodes and algae (Umbellidae).

1,00m, sedimentary bias.

b) The Nismes Formation (Annex II)

Bed 116 and above : 2.15m, incompetent brown siltstones alternating with brown argillaceous limestones, with huge brachiopods (Spiriferids, Atrypids…). Unit similar to the beds cropping out in the Flohimont section and belonging to the “zone des monstres” (Gosselet, 1871; Errera et al., 1972).

VII. — Correlations

Lithology, macrofossils, ostracode populations and associated microfauna contents allow recognizing fifteen characteristic beds or zones. Then, fine correlations between the three complementary studied sections (Fig. 3) provide an almost complete 140 meters-thick sedimentary series for the Fromelennes Formation in the Givet area.

We can recognize the following characteristic beds and zones:

  1. A 3 meters-thick biostrome (reef-limestone), with abundant tabulate and solitary rugose corals, and stromatoporoids (particularly amphiporidae) : Flohimont bed 986 and Cul d'Houille bed 85''.
  2. A brachiopod argillaceous-carbonated coquina bed, at the base of the Fromelennes Formation : Flohimont bed 1001 and Cul d'Houille bed 102''a.
  3. A Quasillites fromelennensis MILHAU, 1983 and Poloniella tertia KROËMMELBEIN, 1953 very rich zone around the Mont d'Haurs Formation/Fromelennes Formation boundary : Flohimont beds 997 to 1026 and Cul d'Houille beds 95” to 108”.
  4. Calcareous beds bearing small trilobites : Flohimont beds 1019 to 1026 and Cul d'Houille beds 103” to 108”.
  5. Two beds bearing gastropods and serpulids (Spirorbis sp.) and also providing Evlanella germanica BECKER, 1964 and Kozlowskiella aff. boloniensis MILHAU, 1983 : Cul d'Houille beds 109''g and 109''h. No equivalence was found in the other sections, but these characteristic beds might be use for basin-wide correlation.
  6. A thick biostrome : Flohimont bed 1041 and Cul d'Houille bed 11.
  7. A biostromal unit with abundant globular stromatoporoids : Flohimont beds 1063 to 1065 and Cul d'Houille beds 53 to 58.
  8. A paleosol bed, already reported by Boulvain et al. (2009a) : Flohimont bed 1081 and Cul d'Houille bed 109.
  9. A one meter-thick biostrome (“stromatoporoids wall”) : Cul d'Houille bed 136 and Nichet bed 86.
  10. Cryptophyllus sp.3 sensu Magne, 1964 almost monospecific beds at the top of the Moulin Boreux Member : Cul d'Houille beds 138 to 165 and Nichet beds 90 to 108.
  11. Few beds with dominant Cavellina rhenana KRÖMMELBEIN, 1954, sometimes in association with Evlanella germanica BECKER, 1954, Cryptophyllus sp.3 sensu Magne, 1964 and Kozlowskiella plana (KUMMEROV, 1953) at the base of the Fort Hulobiet Member : Flohimont beds 1097 to 1103, Cul d'Houille beds 166 to 190, and Nichet beds 109 to 112.
  12. A succession of disphyllids (rugose corals) beds. The first one is rather argillaceous : Cul d'Houille bed 198. The second one is more calcareous : Flohimont bed 1114, Cul d'Houille bed 209 and Nichet bed 113. The third one is again argillaceous : Flohimont bed 1124.
  13. An abundant Cryptophyllus aff. materni BASSLER & KELLET, 1934 bearing unit below the disphyllids calcareous bed : Flohimont beds 1105 to 1113 and Cul d'Houille beds 199 to 208.
  14. Calcareous beds bearing bivalves : Flohimont beds 1117 to 1119 and Cul d'Houille coquina limestone bed 211.
  15. Beds bearing Polyzygia beckmanni beckmanni KRÖMMELBEIN, 1954, at the base of the Nismes Formation (Lethiers, 1974; Milhau, 1983; Casier, 1987; Bultynck et al., 1991; Lethiers & Raymond, 1991; Lacquement et al., 2006) : Flohimont beds 1154 to 1166 and Nichet beds 116 and above.

We can note that Maillet et al. (2010) reported a faunal renewal in the uppermost part of the Mont d'Haurs Formation in the Cul d'Houille section, shyly beginning above the thick biostromal bed 85'' and becoming more distinct from bed 93”. This diversification event, characterized by the appearance of deeper platform faunas, is also clearly discernable in the Flohimont section, beginning above the thick biostromal bed 986 and becoming clearer from bed 992. In relation with a Givetian major transgressive episode (Milhau, 1983; Bultynck et al., 2001), this faunal and sedimentary event should be found beyond the type area, and could be a useful correlation criterion in the Dinant synclinorium.

Figure 3

Figure 3

Correlation of the Flohimont, the Cul d'Houille and the Nichet sections and synthetic stratigraphic column of the Fromelennes Formation in the Givet area.
 
Corrélation des coupes de Flohimont, du Cul d'Houille et de Nichet et colonne stratigraphique composite synthétique de la Formation de Fromelennes dans la région de Givet.

VIII. — Conclusion

The Fromelennes Formation, in its type area, is frequently faulted and the series, whatever the section, always presents numerous sedimentary biases.

The two studied sections, Flohimont and Nichet, in addition to the previously studied Cul d'Houille section, allow identifying, both on macro- and microfaunal criteria, fifteen characteristic beds or zones.

Correlations between the three sections lead to propose a new up to date synthetic stratigraphic column in which the Fromelennes Formation appears, using the same historical boundaries, to be slightly thicker than previously said : 140 meters instead of 135 meters-thick.

Finally, this work, bringing new data on the distribution and abundance of the macro- and microfauna, is a new contribution to the Givetian database of the southern border of the Dinant synclinorium. Adding to previous works (Hubert, 2008a and b; Hubert & Mabille, 2009; Hubert & Pinte, 2009; Maillet et al., 2010) it will be useful for future correlations.

Acknowledgments. — We are especially grateful to P. Deville, B.L.M. Hubert and J.-P. Nicollin (Laboratoire de Paléontologie stratigraphique FLST – ISA) for their support and their advices during this study. We express thanks to C. Crônier and D. Vachard for trilobites and foraminifera identifications. Thanks also to the Fromelennes town council, the O.N.F., the Conservatoire d'Espaces Naturels de Champagne-Ardenne and the Ardennes prefecture for all the sampling authorizations in the “Réserve de la Pointe de Givet”, to M. Vigneron, owner of the Nichet caves, and to the Flohimont residents. Finally, we are thankful to C. Crônier and to R. Gourvennec for their useful comments and critical reviewing of the manuscript.

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Appendix

Annex I

Detailed stratigraphic column of the Flohimont section (lithology and macrofauna, left part) and microfauna distribution (right part). For caption, see Annex I, p.21.
 
Colonne stratigraphique détaillée de la coupe de Flohimont (lithologie et macrofaune, partie gauche) et répartition de la microfaune (partie droite). Voir légende Annexe I, p. 21.

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Annex II

Detailed stratigraphic column of the Nichet section (lithology and macrofauna, left part) and microfauna distribution (right part). For caption, see Annex I, p. 21.
 
Colonne stratigraphique détaillée de la coupe de Nichet (lithologie et macrofaune, partie gauche) et répartition de la microfaune (partie droite). Voir légende Annexe I, p. 21.

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Illustrations

References

Bibliographical reference

Sébastien Maillet, Bruno Milhau and Emilie Pinte, « Detailed Lithology and Faunal Occurrence of the Fromelennes Formation in the Type Area (Middle/Upper Givetian, Southern Part of the Dinant Synclinorium, Ardenne) », Annales de la Société Géologique du Nord, 18 | 2011, 11-36.

Electronic reference

Sébastien Maillet, Bruno Milhau and Emilie Pinte, « Detailed Lithology and Faunal Occurrence of the Fromelennes Formation in the Type Area (Middle/Upper Givetian, Southern Part of the Dinant Synclinorium, Ardenne) », Annales de la Société Géologique du Nord [Online], 18 | 2011, Online since 06 juillet 2022, connection on 23 mai 2024. URL : http://www.peren-revues.fr/annales-sgn/1274

Authors

Sébastien Maillet

Laboratoire de Paléontologie stratigraphique, FLST-ISA, Géosystèmes FRE 3298 CNRS, 41 rue du Port, F-59046 Lille cedex, France. Email : sebastien.maillet@icl-lille.fr

By this author

Bruno Milhau

Laboratoire de Paléontologie stratigraphique, FLST, 41 rue du Port F-59046 Lille cedex, France. E-mail : bruno.milhau@icl-lille.fr

By this author

Emilie Pinte

Laboratoire de Paléontologie stratigraphique, FLST-ISA, Géosystèmes FRE 3298 CNRS, 41 rue du Port, F-59046 Lille cedex, France. Email : emilie.pinte@icl-lille.fr

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