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Devonian reefs in Belgium
D E V O N I A N REEFS IN BELGIUM by H.H. TSIEN*, A.N. M O L I R A V I E F F * and E.W. MOLINTJOY**
INTRODUCTION The Devonian of Belgium is situated on the northern boundary of the West-European Hercynian geosyncline towards its western limit. It was deformed, with its Carboniferous cover, by the Hercynian orogeny, and lies discordantly on a Cambro-Silurian basement folded by the Caledonian orogeny. All Devonian rocks crop out along the southern, eastern and northern margins of the Dinant basin, in the Philippeville massif and along the southern and northern belts of The Namur basin. Table 1 shows the stratigraphic relationships of the different sedimentary facies and the stratigraphic correlation of Devonian sequence in Belgium with other localities in Germany and U.S.A. For overviews and summaries of Devonian reefs in Europe see W . Krebs (1974), W . Krebs and E.W, Mountjoy (1972) and J.L. Wilson (1975).
Six types of reefs are recognized on the basis of their morphology and paleogeographic setting (tabl. 2, fig. 1-2). These are barrier reef (R1), patch reef (R2), bioherm complexes (R3A, R3B), biostrome (R4), mud mounds (R5A, R5B) and fringing reef (R6). Most of the reefs (RI, R2, R3 and R4) have developed during relatively stable phases. Other reels (R5 and R6) developed during the transgressive phases (Tsien, 1975, 1977). Recent systematic information on Devonian of Belgium is available in a series of publications by M. Lecompte (1964, 1970), J. Bouckaert and M. Streel (1974), P. Bultynck (1970), P. Bultynck and P. Boonen (1976), M. Coen (1974), M. Coen-Aubert (1974), E. Dricot and H.H. Tsien (1977), M. Errera ~ al. (1972), ]. Godefroid (1968), D. Lacroix (1974), A.N. Mouravieff (1974), ]. Pel (1975), H.H. Tsien (1971, 1979).
* Laboratoire de Pal~ontologie, LIniversit6 de Louvain, 3, place Louis~Pasteur, B - 1348 Louvain-la-Neuve, Belgique. ** Depart. Geol. Sciences, McGill Univ., 3450 University Street, Montreal, PQ Canada H3A 2AF.
Gfiobios, M~m. special 4
p. 17-33, 9 fig., 2 tabl., 1 pl.
Lyon, mai 1980
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A. Relatively stable phase 1. On the stable platform 1. Biostrome (R4) : widespread tabulate or layered reef. 2. Patch reef (R2) : isolated in the restricted carbonate. II. At a shelf or platform margin 3. Barrier reef (R 1) 1II. Within a basin 4. Bioherm complex (R3) a. Type Arche reef (R3A) : vertical then horizontal variation. b. Type Lion reef (R3B) : horizontal variation. B. Transgressive phase IV. In a basin 5. Mud mound (R5) a. Type Neuville reef (R5A) : mainly lamellar corals and algae. b. Type Beauchateau reef (R5B) : mainly fasciculated corals and algae. V. Fringing a landmass 6. Fringing reef (R6).
Tabl. 2 - Types of reefs. Types de r4eifs.
FIELD TRIP I T I N E R A R Y LOCALITY 1 : TAILFER QUARRY AND CLIFF OF TAIL~ FER (fig. 3) (LEcorvlPTE, 1964 ; TSIEN ~ al., 1974 ; TSIEN, 1975, 1977). The rock facies are mainly sublagoonal facies, lagoonal facies, and occasionally reef facies of the Frasnian Belgium reef complex model (fig. 1) and represent sediments on a stable platform. Four lithofacies are present. A. Dark gray or light gray, fine grained limestone beds, mainly mudstone and wackestone; with some parallel algal laminations and fenestral fabrics; Girvanella, Botonminella, Kamaena, calcispheres, Nanicella, Umbenilla are common. Rare micr0stalactite cements and mud cracks are p r e s e n t (pl. 1, fi 9. 1-2). This lithofacies represents the sediments deposited in a restricted shallow environment. B. Argillaceous limestone beds (mainly wackestone and packstone) with detrital Amphipora, or Stachyodes radiata, S. costulata or sometimes Thamnopora boloniensis, Disphyllum or Phacello-
phyllum. Amphipora are broken and were deposited uniformily on the sea bottom. Judging by the fragility of the animal a n d the position or the distribution in the general Frasnian reef model, Amphipora in lithofacies B likely grew in a relatively calm and restricted environment and then was disturbed and broken by storms or periods of high agitation and deposit.ed over a large area. C. Argillaceous limestone with in situ Disphyllure gold[ussi colonies. Two kinds of Disphyllum beds have been found in Belgium. In situ bushy~ like Disphyllura colonies form generally extensive meadows indicating muddy turbulent environments (Tsien, 1971). The erosion and redeposited arrangement of the detrital Disphyllum suggests these may represent storm deposits. D. Organoclastic limestone (packstone and bandst°ne), generally distinctly graded, with large coral fragments (Hexagonaria) and/or mas~ sive stromatoporoids fragments at the base and fine-grained packstones or wackestones with large tabular stromatoporoids at the top of each
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Fig. 1 - Simplified model of a reef complex developed during a relatively stable phase and environmental distribution of the organisms. 1 : littoral facies, only developed localiy in a narrow belt ; 2 : lagoonal facies ; 3 : sublagoonal facies ; 4 : back-reef facies ; 5 : nodular shales ; 6 : slop deposits ; 7 : barren shales, deposited after to the development of reef ;R1 : barrier reef ;R2 : patch reef ;R3 : bioherm complex ;R4 : biostrome.
Mod61e simplifi6 d'un complexe r6cifal d6velopp6 pendant une phase relativement stable et la distribution des faunes et flores. 1 : faci6s littoral, tr~s localis6 ; 2 : faci6s lagunaire ; 3 : faci6s sublagunaire ; 4 : faci6s subr6cifal ; 5 " schistes noduleux ; 6 : "slope deposits" ; 7 : schistes azoi~tues, post6rieurs au d6veloppement des r6cifs ;RI : r6cifbarri6re ;R2 " "patch reef" ;R3 : complexe biohermal ;R4 : biostrome.
bed. V e r y often, the beds have sharp upper and lower boundaries. T h e lower boundaries are irregular and undulatory, probably due to scouring of the underlying sediment by storms (pl. 1, fig. 3). T h e organoclastic limestones of D lithofacies suggest deposition under varying conditions : a. moderately agitated conditions for corals and massive stromatoporoids; b. strongly agitated conditions for broken corals and stromatoporoids; c. the grading of organic fragments suggests a turbid
suspension caused by a storm of short duration; d. encrustation of organic fragments by stromatoporoids and sometimes by thin layered algae indicate calm conditions. A n d whole rock unit is finally stabilized by the large tabular stromatoporoids. Generally the four lithofacies occur in a complete or incomplete cycle. Lithofacies A generally is found at the top of the sequence. The cycle represents gradual restriction beginning with open marine conditions. During periods of relative
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in macroorganisms, whereas during open sea periods, the biostromes or organisms rich beds were being built. In this manner alternating closure and opening of the platform occurred, and, as a consequence different types of carbonate facies and units are superposed, and thus form distinct cycles in the stratigraphic sequence. Llsually each cycle begins with the deeper water lithofacies A. This locality provides an excellent opportunity for paleoecological and sedimentologic observations.
stability, on a stable platform, the organisms could construct very extended reefs and form a true reef cover which is called a biostrome (R4). Towards the end of the development of this extensive biostrome, the organisms could only grow freely at the margin of the biostrome, towards the open sea and there formed a barrier reef (R1). This barrier reef at certain times isolated (closed) platform waters from the open sea to form a restricted environment behind the barrier. At other times through the combined interplay of seafloor subsidence, regional climate, sedimentation, and growth of organisms, slightly deeper waters occurred above the barrier reef allowing normal sea water to cover the platform: this alternating change from normal marine agitated conditions to very shallow restricted conditions caused the variations observed in lithofacies and biofacies. Periods of restriction correspond to the deposition of fine limestones that are rich in algae and poor
LOCALITY SENZEILLE
2: BEALICHATEALI ( f i g . 4) ( T s I E N ,
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The morphology of the Beauchgteau mud-mound (Bioherm) is domal (fig. 4). The massive wackestone and micritic carbonates of the mound interfinger with the surrounding shales and interbedded
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Fig. 2 - Simplified model of a reef complex developed during a transgressive phase and environmental distribution of the organisms. 1 : littoral facies ; 2 : shaly limestones , 3 : nodular limestones ; 4 { nodular shales ; 5 : pelagic
limestones ; 6 : pelagic shales ; 7 : shales ; R5 : mud mounds ; R6 : fringing reef. Mod61e simplifi6 d'un eomplexe r6eifal d6velopp6 pendant une phase transgressive et la distribution des faunes et des flores. 1 : faci6s littoral ; 2 : calcaires argileux ; 3 : calcaires noduleux ; 4 : schistes noduleux ; 5 : calcaires p61agiques'; 6 : schistes p61agiques ; 7 : schistes ; R5 : "mud mounds" ; R6 : r6cif frangeant.
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shales and nodular limestones especially in the upper part. This interfingering is better shown at the abandoned quarry at Neuville. There apparently has been some slippage along the contact between the carbonate mound and the surrounding shales, but this is thought to have occurred rather early and is partially at least the result of differ rential compaction. The lower part of the mud mound consists primarily of lime mudstones and wackestones, with pockets and stringers of cri~ noidal and brachiopod packstones or grainstones. Branching coral colonies are commonly broken and overturned. Globular or thick lamellar colonies of Phillipsastrea and Alveolites are also common. Soft sediment deformation, apparently the result of slumping occurs in the lower central part of quarry face. Some areas may also have been stablized by sponges. The origin of the areas near the base of micrite and wackestone containing small irregular cavities is unknown. Renalcis and lime mud occur among the branching corals may have formed protect areas where lime mud accumulated and probably was either washed in or is produced in situ, and was partially stabilized by Renalcis. Alternatively some of the lime mud may
represent a micrite cement and forms a suitable substrate on which renalcids were attached. M a n y Alveolites and Phillipsastrea are buried by muddy sediments and only the highest part of the animal could move the sediments away showing autocleaning effect and consequently could continue to survie (fi 9. 5 and pl. 1, fi9. 4). The corals in 9eneral form irregular areas or masses of disturbed colonies that occur with layers and masses containing varying amounts of bryozoa; Rothpletzella, and renalcid micrites. Bryozoa and Rot hpletzella alternate and seem to encrust each other : Renalcis is restricted to the micrite facies. The upper part of the mound is, however, different. It consists mainly of mudstones and wackestones. The fauna and flora, for the most part, consist of algae (mainly Renalcis), lameUar Phillipsastrea and Alveolites. Branching corals are absent. Globular forms change to lamellar forms from bottom to top suggesting that the water depth increased. Finally the mud mound was drowned or overwhelmed by rapid deposition of terrigenous muds. These can be also demonstrated by the distinct contact which overlying fine dark shales of the Matagne Formation.
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LOCALITY 3 : CROISETTES QUARRY (R5A), VODEC~E (fi9. 5 and 6) (LEcoMPTE, 1964 ; TSlE,L 1977). The mud mound has a more or less domal shape, with a rather sharp fault contact with the surroundin 9 shales. Some contacts have slickensides and su99est slippage durin 9 compaction and structural movements. At the upper and lateral margins of this bioherm, several stages of 9co petal fillings with different inclinations in sponges (pl. 1, fi 9. 5) and cavities. This su99ests that the flanks of the mound were tilted durin 9 deposition and some of the adjacent cavities filled after tiltin 9. This can be also shown by the 9rowth form of Phillipsastrea near by (pl. 1, fi9. 6). The fauna and flora are common to most of the Frasnian mud mounds, and consist in large part of Alveolites, Phillipsastrea, stromatactis, Rothpletzella, Girv'anella, Frutexites and Epiphyton. The main part of the mud mound has been quarried. But this quarry still provides an excellent opportunity to study the paleoecology and distribution of algae and corals and the nature of stromatactis by examinin 9 the huge blocks at the quarry entrance. Frutexites and an algae (new 9en. 1) occur in cavities of the mud mound and are characterized by iron-oxide deposition suggestin 9 these algae could be heterotrophic or partially heterotrophic (Tsien, 1979). In several cases they can b e 0bserved growing from both sides of a cavity (pl. 1,
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ecologic. At the base of the stromatactis zone, the stromatactis are lamellar, thin and regularly layered (pl. 1, fig. 7) ; they are small irregular flowers in the lower part of the zone (pl. 1, fig. 8). They become large irregular flowers in the middle part (pl. 1, fig. 9). At the upper part, they become again small irregular flowers in form. Their forms are comparable with those of stromatoporoids, tabulate corals (especially Alveolites) and Phillipsastrea (fi 9. 6). The presence of micrite, encrusting algae (Rot,hpletzella), lamellar Alveolites and PhiI!ipsastrea and bryozoans indicate calm conditions. However. broken skeletal materials suggest rather agitated conditions. Thus deposition probably took place largely below wave base, with the mound occasionally buildin 0 up into the zone of wave action. LOCALITY 4: FONDRY DES CHIENS (R2), NISMES (fi 9. 7) (TsIEN, 1975, 1977). At Fondry des Chiens, Nismes very near Couvin is a 96od Lower Givetian section (fi 9. 7) showin 9 the development of a probable isolated organic patch reef on the shelf. This patch reef is built entirely by large irregular shaped stromatoporoids and some corals and surrounded by mostly sublagoonal and lagoonal dark 9ray micritic limestones.
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Stromatactis occupy an important part of the" reef and show variations in form that may be
From bottom to top, the sequence is: 1. 30 m (I, fig. 7) : crinoidal stratified grainstones.
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Fig. 6 - Ecological variations of I. Alveolites ; 1I. Phillipsastrea ;III. Stromatoporoids ; IV. Stromatactis. In many cases, their forms are comparable ;I 1, III 1 and IV 1 ;I 2, II 2, III 2 and 1V 2 ;I 4, II 4, IV 4, etc. Variations 6cologiques chez I. Alveolites ; II. Phillipsastrea ;III. les stromatoporoitles ; IV. Stromatactis. Dans beaucoup de cas, leurs formes sont comparables : I 1, III 1 and IV 1 ; I 2, II 2, III 2 and IV 2 ; 1 4, II 4, IV 4, etc. 2. 20 m (II, fig. 7) : crinoidal stratified grainstones with tabular stromatoporoids. 3. 60 m (III, fig. 7) : reel [acies ; rather pure thick, crinoidal grainstones containing large irregular massive stromatoporoids. N o micrite has been found in the matrix. O n l y slight vertical variations occur in the reef facies with some layers
of corals and tabular stromatoporoids. Algae are absent in the stromatoporoids 9rainstone facies ; but some encrusting Rothpletzella occur in the tabular stromatoporoids layers. Ecologically, this patch reef probably commenced development in clear calm waters below wave base. This can be shown by the important deve-
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noids and tabular stromatoporoids more abundant near the margins at the eastern side of the quarry. This suggests that the northwest side is probably windward and the eastern side leeward. Algae
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Fig. 7 - Section showing the development of a patch reef, Lower Givetian Nismes, near Couvin. 1 : stromatoporoids ; 2 : dendroid stromatoporoids ; 3 : dendroid tabulate coral ; 4 : tabular stromatoporoids ; 5 : massive rugose coral ; 6 : crinoids ; 7 : massive tabulate coral ; 8 : dendroid rugose coral. Coupe montrant le d4veloppement d'un patchreef, Giv4tien inf6rieur, pros de Couvin. 1 : stromatoporoRles ; 2 stromatoporoides dendroides ; 3 : corail tabul6 dendroide ; 4 : stromatoporoides tabulaires ; 5 : corail rugueux massif ; 6 : crinofiles ; 7 : corail tabul6 massif ; 8 : corail rugueux dendroiide.
lopment of crinoids. Crinoidal grainstones suggest the presence of very agitated condition which terminated the development of crinoids. The main part of the reef was built in clear, agitated, shal~ low waters. This locality provides an excellent opportunity to study the effect of depth or turbulence on the growth forms of stromatoporoids in different environments. LOCALITY 5: LION QUARRY (R3B), FRASNES-LI~SCOUVIN (fig. 8) (LEcoMPTE, t 9 6 4 ; MOURAVIEFF, 1974 ; TSIEN, 1975, 1977). This reef occurs on argillaceous stratified limestones. This type of bioherm complex is not entirely constructed by massive stromatoporoids and corms as would previously be assumed. T h e association Of the organisms in the r e e f differs from place to place. Lion quarry (fig. 8) shows only a part of the reef. T h e North quarry at Frasnes-l~s~ Couvin west of L i o n quarry and the Lhoist quarry at Rochefort show other parts of the bioherm complex of this type. Limestones of this bioherm complex are rather pure (up to 90 % of CaCO3), with stromatoporoids and corals more abundant at the margins at the northwest side and with cri~
are abundant in the central part of the bioherm complex. Their irregular distribution were probably influenced by local ecological condit.ions in the lagoon of the reef. Algae facies are generally associated with fenestral limestones and mudstones, and algal-laminated sediments which appear to reflect sedimentation in relatively calm, shallow water of lagoonal facies. Epiphyton and Renalcis form very important masses (at least 2 m in diameter). Successive encrustations of thin laminar stromatoporoids by Rothpletzetla straelenii, nonskeletal algae or bryozoans are very common. In the central lagoon, fragment.s of stromatoporoids and corals are generally encrusted by Rothpletzetla and Girvanella. Undulating algal-laminated sediments and small irregular stromatolites are common in the lagoon. Also large areas of micritic limestones without m a n y fossils are common in the lagoon. Bedding is massive and the various facies are not easy to recognize. T h e off-reef facies and the surrounding shales have undergone considerable compaction (up to 74 % compare with the reef of the same level). T h e entrance of the quarry provides an excellent opportunity to view the relationships between the reef and the surrounding shales. This type of reef was burried by barren shales. From paleogeographic and paleoecologic studies, the clays in the barren shales probably came from the South and were deposited after to the development of reef.
LOCALITY 6: ARCHE QUARRY (R3A), FRASNESLES~COLIVIN(fig. 9)(LEcoMPTE, 1964 ; TSIEN, 1975, 1977). Along the section of the quarry, the following succession of units occur (fig. 9)" Substrata: nodular shales and limestones with Alveolites, Disphyllum and Macgeea. Important in situ Disphyllum bush like colonies occur under the bioherm complex. Reef itself : the following zones can be observed.
I. Basal part: the initial part of the Arche reef consists of a dark argillaceous micritic limestones with Disphyllum colonies; about 2 m thick.
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Fig. 8 - Lion Quarry, Lower Frasnian, Frasnes-les-Couvin. 1 : massive s t r o m a t o p o r o i d s ; 2 : tabular s t r o m a t o p o r o i d s ; 3 : d e n d r o i d s t r o m a t o p o r o i d s ; 4 : Alveolites ; 5 : dendroid tabulate coral ; 6 : Hexagonaria ; 7 : d e n d r o i d rugose coral ; 8 : solitary rugose coral ; 9 : bryozoans ; 10 : crinoids ; 11 : b r a c h i o p o d s ; 12 : nautiloids ; 13 : algae ; 14 : Renalcis ; 15 : Rothpletzella ; 16 : algal " o o z e " ; 17 : stromatolitic laminations ; 18 : s t r o m a t o l i t e ; a : fenestral fabrics ; b : micrite ; c : calcarenite ; d : nautiloids in the karst solution cavity ; e : karst solution cavities ; f : slope deposit ;g : nodular limestones ; h : nodular shales ; i : shales.
Carri~re du Lion. Frasnien inf6rieur. Frasnesdes-Couvin. 1 : s t r o m a t o p o r o i d e s massifs ; 2 : s t r o m a t o p o r o i d e s tabulaires ; 3 : s t r o m a t o p o r o i d e s dendroides ; 4 : Alveolites; 5 : corail tabul~ d e n d r o i d e ; 6 : Hexagonaria ; 7 : corail rugueux dendroii~e ; 8 : corail rugueux solitaire ; 9 : bryozoaires ; 10 : crinoides ; 11 : brachiopodes ; 12 : nautiloides ; 13 : algues ; 14 :Renalcis ;15 :Rothpletzella ; 16 : " o o z e " algaire ; 17 : laminations stroihatolitiques ; 18 : stromatolites ; a : "fenestral fabrics" ; b : micrite ; c : calcar~nite ; d : nautiloi~les d a m des cavit6s karstiques ; e : cavit6s de dissolution karstique ; f : d~p6ts de pente ; g : calcaire nodulaire ; h : schistes nodulaires ; i : schistes.
II. L o w e r part: t h e l o w e r p a r t o f t h e A r c h e r e e f ( a b o u t 32 m ) c o n s i s t s o f a p i n k t o r e d d i s h colored m/critic limestone mainly with a coral fauna together with algae and abundant stromatactis. A l s o t h e r e is a l o c a l a c c u m u l a t i o n o f b e a u tiful Receptaculites (pl. 1, fig. l l ) . T h i s p a r t o f the bioherm complex forms a mud mound (type
R5). I I I . Middle p a r t : t h e m i d d l e p a r t c o n s i s t s of a gray packstones, grainstones and wackestones c o n t a i n i n g b r a c h i o p o d s , Alveolites a n d t a b u l a r st r o m a t o p o r o i d s .
I V . Upper part : t h e u p p e r p a r t is c h a r a c t e r i z e d by massive stromatoporoids in f l r a i n s t o n e s a n d p a c k s t o n e s a s s o c i a t e d w i t h b r a c h i o p o d s in l o c a l concentrations. M . L e c o m p t e (196"t) i n t e r p r e t e d t h e s e s t a g e s as f o l l o w s : I a n d II z o n e s - - the <> z o n e ; I I I - - t h e s u b t u r b u l e n t z o n e ; a n d I V -- the turbulent zone. We consider stages I and II to r e p r e s e n t a s e m i - t u r b u l e n t e n v i r o n m e n t a n d s t a g e s I I I a n d I V to b e p r o g r e s s i v e l y m o r e t u r bulent environments on the basis of the types of fossils a n d l i t h o f a c i e s .
29
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Fig. 9 - Arche Quarrysection, Lower Frasnian, Frasnes-les-Couvin. I : basal part, II : lower part, I I I : middle part ; IV : upper part. 1 : massive stromatoporoids ; 2 : tabular stromatoporoids ;3 : lamellar Alveolites ; 4 :Disphyllum ;5 : stromatactis ;6 :Receptaculites ;7 : brachiopods ; 8 : Macgeea ; 9 : ostracods ; 10 : crinoids ; 11 : Algae ; 12 : Thamnopora. Coupe de la carri6re de l'Arehe. Frasnien inf6rieur. Frasnes-les-Couvin. I : partie basale ; II : partie inf6rieure ; I I I : pattie mgyenne ; IV : pattie sup6rieure ; 1 : stromatoporoi~les massifs ; 2 : stromatoporoities tabulaires ; 3 : Alveolites lamellaires ; 4 : Disphyllum ; 5 : Stromatactis ; 6 : Receptaculites ; 7 : brachiopodes ; 8 : Macgeea ; 9 : ostracodes ; 10 : crinoides ; 11 : algues ; 12 : Thamnopora.
BIBLIOGRAPHY
BOUC::aERT J. ~ STREEL M . ( 1 9 7 4 ) . -
Guidebook.
Intern. Slim p. Belg. Micropaleont. Limits, N a mur, S e p t e m b e r 1974. BULTYNC: P. ( 1 9 7 0 ) . R6vision s t r a t i g r a p h i q u e et pal6ontologique de la c o u p e - t y p e du C o u v i nien. Mdm. Inst. Gdo,l. Univ. Lorrvain, t. X X V I , 150 p., 39 pl. BULTYNC:< P. ~ BOONEN P. (1976). - - C o n o d o n t e s des F o r m a t i o n s de Rouillon, de C l a m i n f o r g e et de N ~ v r e m e n t - M ~ s o d 4 v o n i e n du B o r d nord du synclinorium de D i n a n t . Ann. Soc. G4ol. Belg., Bruxelles, t. 99, p. 't81-509. CoRN M . (197zt). - - Le F r a s n i e n de la b o r d u r e orientale du Bassin de Dinant. Ann. Soc. G~ol. Belg., Bruxelles, t. 97, fasc. 1, p. 67-103. COEN-AUBERT M . (1974). --- Le G i v e t i e n et le F r a s n i e n du M a s s i f de la V e s d r e . Acacl. Roy.
Belg., Bruxelles, Mdm. CI. Sc., t. X V I I I , fasc. 2, 1't6 p., 10 pl. DmCOT E. 6 T s 1 ~ H . H . (1977). - - Le n o m du g e n r e Ro~hpletzella W o o d 1948 (algue calcaire p a l e o z o i q u e ) est 14gitime et correct. Mdm. Inst. Gdol. Louvain, t. 29, p. 231-240. E R R E ~ M., M a M r V B. O SaRTrNA~R P. (1973). - Le calcaire de G i v e t et le G i v e t i e n ~ Givet. Bull. Inst. roy. Sci. Nat. Belg., Bruxelles (1972), 48, n ° 1, 59 p. GODrFROrD J. (1968). - - C o n t r i b u t i o n ~ l ' e t u d e du C o u v i n i e n entre W e l l i n et ]emelle (Bord s u d du Bassin de D i n a n t ) . Acad. roll. Belg., Bruxelles, Mdm. CI. Sc., 2 ° s~r. X V I I , 3, p. 1-87, 11 pl. KREBS W . (1973). - - D e v o n i a n c a r b o n a t e c o m plexes of C e n t r a l E u r o p e . In L a p o r t e E . F . (ed.) R e e f s in T i m e a n d Space, Selected E x a m p l e s from the Recent and Ancient. Soc. E c o n . Paleont. Mineral., T u l s a , Spec. publ. 18, p. 155-208.
--
KREBS W . & MOUNTrOY E . W . (1972). - - Comparison of central European and W e s t e r n Canad/an Devonian reef complexes. 24th Intern. Geol. Congr., Sect. 6, p. 206-309. LACROIX D. (1974). - - Sur la stratigraphie du M~sod6vonien et du Frasnien sud du Synclinorium de Namur. Ann. Soc. G~ol. Belg., Bruxelles, t. 97, p. 11-21.
VI" Congr~s international de s&timentologie HoUande-Belgique, 1964.
LECOMPTE M. ( 1 9 6 4 ) . -
Excursions C-D. Trois volumes: note pr~limi~ naire, 27 p., livret-guide, 49 p., figures, 33 pl. LECOMPTE M. (1970). - - Die Rifle im Devon der Ardennen und ihre bildungs bedingungen. Geolog. ~ Palaeont., Marburg, 4 , p. 25-71. MOURAVIEFF A.N. (1974). - - Excursion F, in Bouckaert ]. & Streel M. (ed.). Guidebook, Int~ern. Syrup. Belg. Micropaleont. Limits, Namur, September 1974. PEL ]. (1975). - - Etude s~dimentologique et stratigraphique du Givetien synclinorium de Dinant, de Givet h Liege. Coll. Pub. Sc. App., kiniv. Liege, n ° 53.
30
--
Tslm,r H.H. (1971). - - The Middle and kipper Devonian Reef-Complexes fo Belgium. Petrol. Geol. Taiwan, Taipei, 8, p, 119-173. Tslm'q H.H. (1975). - - Introduction to the Devonian reef development in Belgium. In : Conil et a/. Second Intern. Symp. Fossil Corals and Reefs, Guidebook Excursion C (Nord de la France et Belgique). Serv. G~ol. Belgique, Bruxelles, p. 3-43. TSIEN H.H. (1977). - - Morphology and development of Devonian reefs and reef complexes in Belgium. Proceed. Third Intern. Coral Reel Sgmp., p. 191-200. TSInN H.H. (1979). - - Paleoecology of Algalbearing facies in the Devonian (Couvinian to Frasnian) reef Complexes of Belgium. Paleogeog., Palaeoclim., Palaeoecol., Amsterdam, 27, p. 103-127. Tsm~q H.H. DRICOT E., MOHRAVIEFF A.N. ,& BOUCKAERT ]. (1973). - - Le Frasnien de la coupe de Tailfer. Serv. G~ol. Belg. Pro[. Paper, Bruxelles, n o 11. WILSON ].L. (1975). - - Carbonate facies in geologic history. Springer-Verlag ed., New York. 471 p.
PLATE
-
3 2
-
PLATE
1
Fig. 1 - Microstalactite, Tailfer quarry, Fr 1, Tailfer. Fig. 2 - Mud cracks, Tailfer quarry, Fr 1, Tailfer. Fig. 3 - Figure showing the biostrome bed is distinctly graded with large coral and stromatoporoids fragments at the base and the fine-grained packstones or wackestones with large tabular stromatoporoids at the top o f each unit. The bed has sharp, irregular and undulatory upper and lower limits. Fig. 4 - Showing autoclearing during the life o f a. Phillipsastrea, b. Stromatactis. Fig. 5 - Showing several stages o f geopetal fillings with different inclinations in sponges and cavities. Fig. 6 - Showing the growth form and the growth direction of a Phillipsastrea near by the geopetal fillings of figure 5. Fig. 7-9 - Stromatactis zone. 7 : stromatactis of basal part ; they are lamellar, thin and regularly layered ; 8 : stromatactis of lower part, small irregular flowers ; 9 : stromatactis o f middle part, large irregular flowers. Fig. 10 - Frutexites and new gen. 1 occur in cavities and can be observed growing from both sides o f the cavity. Fig. 11 - Showing local accumulation o f beautiful Receptaculites.
Fig. 1 - Microstalactite, Carri6re de Tailfer, Fr 1, Tailfer. Fig. 2 - Mud-cracks, Carri~re de Tailfer, Fr 1, Tailfer. Fig. 3 - Figure montrant le granoclassement net du banc biostromal avec de grands fragments de coraux et de stromatoporoides h la base et des packstones ou wackestones h grains fins contenant de grands stromatoporoides tabulaires au sommet. Le banc a des limites inf6rieure et sup6rieure bien marqu6es, irr6guli~res, ondul6es. Fig. 4 - Auto-nettoyage pendant la vie de a. Phillipsastrea, b. Stromatactis. Fig. 5 - Diverses 6tapes de remplissage g6op6tal, ~t diverses inclinaisons, dans des 6ponges et des cavit6s. Fig. 6 - Forme et direction de croissance d'un Phillipsastrea ~ proximit6 du remplissage g6op6tal de la figure 5. Fig. 7-9 - Zone h stromatactis. 7 : stromatactis de la partie basale ; ils sont lamellaires, minces et r6guli~rement rubann6s ; 8 : stromatactis de la zone inf6rieure : petits fleurages irr6guliers ; 9 : stromatactis de la zone moyenne : grands fleurages irr6guliers. Fig. 10 - Frutexites et nov. gen. 1 se rencontrent dans des cavit6s et on peut observer leur croissance qui d6bute des deux c6t6s de la cavit6. Fig. 11 - Accumulation locale de beaux Receptaculites.
G6obios M6m. sp6cial 4
PI. 1 H.H. Tsien, A.N. Mouravieff and E.W. Mountjoy
INTRODUCTION The Devonian of Belgium is situated on the northern boundary of the West-European Hercynian geosyncline towards its western limit. It was deformed, with its Carboniferous cover, by the Hercynian orogeny, and lies discordantly on a Cambro-Silurian basement folded by the Caledonian orogeny. All Devonian rocks crop out along the southern, eastern and northern margins of the Dinant basin, in the Philippeville massif and along the southern and northern belts of The Namur basin. Table 1 shows the stratigraphic relationships of the different sedimentary facies and the stratigraphic correlation of Devonian sequence in Belgium with other localities in Germany and U.S.A. For overviews and summaries of Devonian reefs in Europe see W . Krebs (1974), W . Krebs and E.W, Mountjoy (1972) and J.L. Wilson (1975).
Six types of reefs are recognized on the basis of their morphology and paleogeographic setting (tabl. 2, fig. 1-2). These are barrier reef (R1), patch reef (R2), bioherm complexes (R3A, R3B), biostrome (R4), mud mounds (R5A, R5B) and fringing reef (R6). Most of the reefs (RI, R2, R3 and R4) have developed during relatively stable phases. Other reels (R5 and R6) developed during the transgressive phases (Tsien, 1975, 1977). Recent systematic information on Devonian of Belgium is available in a series of publications by M. Lecompte (1964, 1970), J. Bouckaert and M. Streel (1974), P. Bultynck (1970), P. Bultynck and P. Boonen (1976), M. Coen (1974), M. Coen-Aubert (1974), E. Dricot and H.H. Tsien (1977), M. Errera ~ al. (1972), ]. Godefroid (1968), D. Lacroix (1974), A.N. Mouravieff (1974), ]. Pel (1975), H.H. Tsien (1971, 1979).
* Laboratoire de Pal~ontologie, LIniversit6 de Louvain, 3, place Louis~Pasteur, B - 1348 Louvain-la-Neuve, Belgique. ** Depart. Geol. Sciences, McGill Univ., 3450 University Street, Montreal, PQ Canada H3A 2AF.
Gfiobios, M~m. special 4
p. 17-33, 9 fig., 2 tabl., 1 pl.
Lyon, mai 1980
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A. Relatively stable phase 1. On the stable platform 1. Biostrome (R4) : widespread tabulate or layered reef. 2. Patch reef (R2) : isolated in the restricted carbonate. II. At a shelf or platform margin 3. Barrier reef (R 1) 1II. Within a basin 4. Bioherm complex (R3) a. Type Arche reef (R3A) : vertical then horizontal variation. b. Type Lion reef (R3B) : horizontal variation. B. Transgressive phase IV. In a basin 5. Mud mound (R5) a. Type Neuville reef (R5A) : mainly lamellar corals and algae. b. Type Beauchateau reef (R5B) : mainly fasciculated corals and algae. V. Fringing a landmass 6. Fringing reef (R6).
Tabl. 2 - Types of reefs. Types de r4eifs.
FIELD TRIP I T I N E R A R Y LOCALITY 1 : TAILFER QUARRY AND CLIFF OF TAIL~ FER (fig. 3) (LEcorvlPTE, 1964 ; TSIEN ~ al., 1974 ; TSIEN, 1975, 1977). The rock facies are mainly sublagoonal facies, lagoonal facies, and occasionally reef facies of the Frasnian Belgium reef complex model (fig. 1) and represent sediments on a stable platform. Four lithofacies are present. A. Dark gray or light gray, fine grained limestone beds, mainly mudstone and wackestone; with some parallel algal laminations and fenestral fabrics; Girvanella, Botonminella, Kamaena, calcispheres, Nanicella, Umbenilla are common. Rare micr0stalactite cements and mud cracks are p r e s e n t (pl. 1, fi 9. 1-2). This lithofacies represents the sediments deposited in a restricted shallow environment. B. Argillaceous limestone beds (mainly wackestone and packstone) with detrital Amphipora, or Stachyodes radiata, S. costulata or sometimes Thamnopora boloniensis, Disphyllum or Phacello-
phyllum. Amphipora are broken and were deposited uniformily on the sea bottom. Judging by the fragility of the animal a n d the position or the distribution in the general Frasnian reef model, Amphipora in lithofacies B likely grew in a relatively calm and restricted environment and then was disturbed and broken by storms or periods of high agitation and deposit.ed over a large area. C. Argillaceous limestone with in situ Disphyllure gold[ussi colonies. Two kinds of Disphyllum beds have been found in Belgium. In situ bushy~ like Disphyllura colonies form generally extensive meadows indicating muddy turbulent environments (Tsien, 1971). The erosion and redeposited arrangement of the detrital Disphyllum suggests these may represent storm deposits. D. Organoclastic limestone (packstone and bandst°ne), generally distinctly graded, with large coral fragments (Hexagonaria) and/or mas~ sive stromatoporoids fragments at the base and fine-grained packstones or wackestones with large tabular stromatoporoids at the top of each
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Fig. 1 - Simplified model of a reef complex developed during a relatively stable phase and environmental distribution of the organisms. 1 : littoral facies, only developed localiy in a narrow belt ; 2 : lagoonal facies ; 3 : sublagoonal facies ; 4 : back-reef facies ; 5 : nodular shales ; 6 : slop deposits ; 7 : barren shales, deposited after to the development of reef ;R1 : barrier reef ;R2 : patch reef ;R3 : bioherm complex ;R4 : biostrome.
Mod61e simplifi6 d'un complexe r6cifal d6velopp6 pendant une phase relativement stable et la distribution des faunes et flores. 1 : faci6s littoral, tr~s localis6 ; 2 : faci6s lagunaire ; 3 : faci6s sublagunaire ; 4 : faci6s subr6cifal ; 5 " schistes noduleux ; 6 : "slope deposits" ; 7 : schistes azoi~tues, post6rieurs au d6veloppement des r6cifs ;RI : r6cifbarri6re ;R2 " "patch reef" ;R3 : complexe biohermal ;R4 : biostrome.
bed. V e r y often, the beds have sharp upper and lower boundaries. T h e lower boundaries are irregular and undulatory, probably due to scouring of the underlying sediment by storms (pl. 1, fig. 3). T h e organoclastic limestones of D lithofacies suggest deposition under varying conditions : a. moderately agitated conditions for corals and massive stromatoporoids; b. strongly agitated conditions for broken corals and stromatoporoids; c. the grading of organic fragments suggests a turbid
suspension caused by a storm of short duration; d. encrustation of organic fragments by stromatoporoids and sometimes by thin layered algae indicate calm conditions. A n d whole rock unit is finally stabilized by the large tabular stromatoporoids. Generally the four lithofacies occur in a complete or incomplete cycle. Lithofacies A generally is found at the top of the sequence. The cycle represents gradual restriction beginning with open marine conditions. During periods of relative
--
21 - -
in macroorganisms, whereas during open sea periods, the biostromes or organisms rich beds were being built. In this manner alternating closure and opening of the platform occurred, and, as a consequence different types of carbonate facies and units are superposed, and thus form distinct cycles in the stratigraphic sequence. Llsually each cycle begins with the deeper water lithofacies A. This locality provides an excellent opportunity for paleoecological and sedimentologic observations.
stability, on a stable platform, the organisms could construct very extended reefs and form a true reef cover which is called a biostrome (R4). Towards the end of the development of this extensive biostrome, the organisms could only grow freely at the margin of the biostrome, towards the open sea and there formed a barrier reef (R1). This barrier reef at certain times isolated (closed) platform waters from the open sea to form a restricted environment behind the barrier. At other times through the combined interplay of seafloor subsidence, regional climate, sedimentation, and growth of organisms, slightly deeper waters occurred above the barrier reef allowing normal sea water to cover the platform: this alternating change from normal marine agitated conditions to very shallow restricted conditions caused the variations observed in lithofacies and biofacies. Periods of restriction correspond to the deposition of fine limestones that are rich in algae and poor
LOCALITY SENZEILLE
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Fig. 4 - Beaueh~iteauQuarry. Carri6re de Beaueh~iteau.
shales and nodular limestones especially in the upper part. This interfingering is better shown at the abandoned quarry at Neuville. There apparently has been some slippage along the contact between the carbonate mound and the surrounding shales, but this is thought to have occurred rather early and is partially at least the result of differ rential compaction. The lower part of the mud mound consists primarily of lime mudstones and wackestones, with pockets and stringers of cri~ noidal and brachiopod packstones or grainstones. Branching coral colonies are commonly broken and overturned. Globular or thick lamellar colonies of Phillipsastrea and Alveolites are also common. Soft sediment deformation, apparently the result of slumping occurs in the lower central part of quarry face. Some areas may also have been stablized by sponges. The origin of the areas near the base of micrite and wackestone containing small irregular cavities is unknown. Renalcis and lime mud occur among the branching corals may have formed protect areas where lime mud accumulated and probably was either washed in or is produced in situ, and was partially stabilized by Renalcis. Alternatively some of the lime mud may
represent a micrite cement and forms a suitable substrate on which renalcids were attached. M a n y Alveolites and Phillipsastrea are buried by muddy sediments and only the highest part of the animal could move the sediments away showing autocleaning effect and consequently could continue to survie (fi 9. 5 and pl. 1, fi9. 4). The corals in 9eneral form irregular areas or masses of disturbed colonies that occur with layers and masses containing varying amounts of bryozoa; Rothpletzella, and renalcid micrites. Bryozoa and Rot hpletzella alternate and seem to encrust each other : Renalcis is restricted to the micrite facies. The upper part of the mound is, however, different. It consists mainly of mudstones and wackestones. The fauna and flora, for the most part, consist of algae (mainly Renalcis), lameUar Phillipsastrea and Alveolites. Branching corals are absent. Globular forms change to lamellar forms from bottom to top suggesting that the water depth increased. Finally the mud mound was drowned or overwhelmed by rapid deposition of terrigenous muds. These can be also demonstrated by the distinct contact which overlying fine dark shales of the Matagne Formation.
m
25
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..
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il Fig. 5 - Showing autocleaning effect during the life of : I. Stromatactis ; II Phillipsastrea ; III. Alveo-
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lites. Effet d'autonettoyage pendant la vie de : I. Stromatactis ; II. Phillipsastrea ; III. Alveolites.
LOCALITY 3 : CROISETTES QUARRY (R5A), VODEC~E (fi9. 5 and 6) (LEcoMPTE, 1964 ; TSlE,L 1977). The mud mound has a more or less domal shape, with a rather sharp fault contact with the surroundin 9 shales. Some contacts have slickensides and su99est slippage durin 9 compaction and structural movements. At the upper and lateral margins of this bioherm, several stages of 9co petal fillings with different inclinations in sponges (pl. 1, fi 9. 5) and cavities. This su99ests that the flanks of the mound were tilted durin 9 deposition and some of the adjacent cavities filled after tiltin 9. This can be also shown by the 9rowth form of Phillipsastrea near by (pl. 1, fi9. 6). The fauna and flora are common to most of the Frasnian mud mounds, and consist in large part of Alveolites, Phillipsastrea, stromatactis, Rothpletzella, Girv'anella, Frutexites and Epiphyton. The main part of the mud mound has been quarried. But this quarry still provides an excellent opportunity to study the paleoecology and distribution of algae and corals and the nature of stromatactis by examinin 9 the huge blocks at the quarry entrance. Frutexites and an algae (new 9en. 1) occur in cavities of the mud mound and are characterized by iron-oxide deposition suggestin 9 these algae could be heterotrophic or partially heterotrophic (Tsien, 1979). In several cases they can b e 0bserved growing from both sides of a cavity (pl. 1,
fig.
ecologic. At the base of the stromatactis zone, the stromatactis are lamellar, thin and regularly layered (pl. 1, fig. 7) ; they are small irregular flowers in the lower part of the zone (pl. 1, fig. 8). They become large irregular flowers in the middle part (pl. 1, fig. 9). At the upper part, they become again small irregular flowers in form. Their forms are comparable with those of stromatoporoids, tabulate corals (especially Alveolites) and Phillipsastrea (fi 9. 6). The presence of micrite, encrusting algae (Rot,hpletzella), lamellar Alveolites and PhiI!ipsastrea and bryozoans indicate calm conditions. However. broken skeletal materials suggest rather agitated conditions. Thus deposition probably took place largely below wave base, with the mound occasionally buildin 0 up into the zone of wave action. LOCALITY 4: FONDRY DES CHIENS (R2), NISMES (fi 9. 7) (TsIEN, 1975, 1977). At Fondry des Chiens, Nismes very near Couvin is a 96od Lower Givetian section (fi 9. 7) showin 9 the development of a probable isolated organic patch reef on the shelf. This patch reef is built entirely by large irregular shaped stromatoporoids and some corals and surrounded by mostly sublagoonal and lagoonal dark 9ray micritic limestones.
10).
Stromatactis occupy an important part of the" reef and show variations in form that may be
From bottom to top, the sequence is: 1. 30 m (I, fig. 7) : crinoidal stratified grainstones.
- -
2 6
II
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.
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.
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.
.
.
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Fig. 6 - Ecological variations of I. Alveolites ; 1I. Phillipsastrea ;III. Stromatoporoids ; IV. Stromatactis. In many cases, their forms are comparable ;I 1, III 1 and IV 1 ;I 2, II 2, III 2 and 1V 2 ;I 4, II 4, IV 4, etc. Variations 6cologiques chez I. Alveolites ; II. Phillipsastrea ;III. les stromatoporoitles ; IV. Stromatactis. Dans beaucoup de cas, leurs formes sont comparables : I 1, III 1 and IV 1 ; I 2, II 2, III 2 and IV 2 ; 1 4, II 4, IV 4, etc. 2. 20 m (II, fig. 7) : crinoidal stratified grainstones with tabular stromatoporoids. 3. 60 m (III, fig. 7) : reel [acies ; rather pure thick, crinoidal grainstones containing large irregular massive stromatoporoids. N o micrite has been found in the matrix. O n l y slight vertical variations occur in the reef facies with some layers
of corals and tabular stromatoporoids. Algae are absent in the stromatoporoids 9rainstone facies ; but some encrusting Rothpletzella occur in the tabular stromatoporoids layers. Ecologically, this patch reef probably commenced development in clear calm waters below wave base. This can be shown by the important deve-
--
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27
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i
(Renalcis, Epiphyton, Rothpletzella, Girvanella)
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CorGi
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noids and tabular stromatoporoids more abundant near the margins at the eastern side of the quarry. This suggests that the northwest side is probably windward and the eastern side leeward. Algae
~4
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|8
H.H. TSIEN lg'/g
Fig. 7 - Section showing the development of a patch reef, Lower Givetian Nismes, near Couvin. 1 : stromatoporoids ; 2 : dendroid stromatoporoids ; 3 : dendroid tabulate coral ; 4 : tabular stromatoporoids ; 5 : massive rugose coral ; 6 : crinoids ; 7 : massive tabulate coral ; 8 : dendroid rugose coral. Coupe montrant le d4veloppement d'un patchreef, Giv4tien inf6rieur, pros de Couvin. 1 : stromatoporoRles ; 2 stromatoporoides dendroides ; 3 : corail tabul6 dendroide ; 4 : stromatoporoides tabulaires ; 5 : corail rugueux massif ; 6 : crinofiles ; 7 : corail tabul6 massif ; 8 : corail rugueux dendroiide.
lopment of crinoids. Crinoidal grainstones suggest the presence of very agitated condition which terminated the development of crinoids. The main part of the reef was built in clear, agitated, shal~ low waters. This locality provides an excellent opportunity to study the effect of depth or turbulence on the growth forms of stromatoporoids in different environments. LOCALITY 5: LION QUARRY (R3B), FRASNES-LI~SCOUVIN (fig. 8) (LEcoMPTE, t 9 6 4 ; MOURAVIEFF, 1974 ; TSIEN, 1975, 1977). This reef occurs on argillaceous stratified limestones. This type of bioherm complex is not entirely constructed by massive stromatoporoids and corms as would previously be assumed. T h e association Of the organisms in the r e e f differs from place to place. Lion quarry (fig. 8) shows only a part of the reef. T h e North quarry at Frasnes-l~s~ Couvin west of L i o n quarry and the Lhoist quarry at Rochefort show other parts of the bioherm complex of this type. Limestones of this bioherm complex are rather pure (up to 90 % of CaCO3), with stromatoporoids and corals more abundant at the margins at the northwest side and with cri~
are abundant in the central part of the bioherm complex. Their irregular distribution were probably influenced by local ecological condit.ions in the lagoon of the reef. Algae facies are generally associated with fenestral limestones and mudstones, and algal-laminated sediments which appear to reflect sedimentation in relatively calm, shallow water of lagoonal facies. Epiphyton and Renalcis form very important masses (at least 2 m in diameter). Successive encrustations of thin laminar stromatoporoids by Rothpletzetla straelenii, nonskeletal algae or bryozoans are very common. In the central lagoon, fragment.s of stromatoporoids and corals are generally encrusted by Rothpletzetla and Girvanella. Undulating algal-laminated sediments and small irregular stromatolites are common in the lagoon. Also large areas of micritic limestones without m a n y fossils are common in the lagoon. Bedding is massive and the various facies are not easy to recognize. T h e off-reef facies and the surrounding shales have undergone considerable compaction (up to 74 % compare with the reef of the same level). T h e entrance of the quarry provides an excellent opportunity to view the relationships between the reef and the surrounding shales. This type of reef was burried by barren shales. From paleogeographic and paleoecologic studies, the clays in the barren shales probably came from the South and were deposited after to the development of reef.
LOCALITY 6: ARCHE QUARRY (R3A), FRASNESLES~COLIVIN(fig. 9)(LEcoMPTE, 1964 ; TSIEN, 1975, 1977). Along the section of the quarry, the following succession of units occur (fig. 9)" Substrata: nodular shales and limestones with Alveolites, Disphyllum and Macgeea. Important in situ Disphyllum bush like colonies occur under the bioherm complex. Reef itself : the following zones can be observed.
I. Basal part: the initial part of the Arche reef consists of a dark argillaceous micritic limestones with Disphyllum colonies; about 2 m thick.
--
28
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Fig. 8 - Lion Quarry, Lower Frasnian, Frasnes-les-Couvin. 1 : massive s t r o m a t o p o r o i d s ; 2 : tabular s t r o m a t o p o r o i d s ; 3 : d e n d r o i d s t r o m a t o p o r o i d s ; 4 : Alveolites ; 5 : dendroid tabulate coral ; 6 : Hexagonaria ; 7 : d e n d r o i d rugose coral ; 8 : solitary rugose coral ; 9 : bryozoans ; 10 : crinoids ; 11 : b r a c h i o p o d s ; 12 : nautiloids ; 13 : algae ; 14 : Renalcis ; 15 : Rothpletzella ; 16 : algal " o o z e " ; 17 : stromatolitic laminations ; 18 : s t r o m a t o l i t e ; a : fenestral fabrics ; b : micrite ; c : calcarenite ; d : nautiloids in the karst solution cavity ; e : karst solution cavities ; f : slope deposit ;g : nodular limestones ; h : nodular shales ; i : shales.
Carri~re du Lion. Frasnien inf6rieur. Frasnesdes-Couvin. 1 : s t r o m a t o p o r o i d e s massifs ; 2 : s t r o m a t o p o r o i d e s tabulaires ; 3 : s t r o m a t o p o r o i d e s dendroides ; 4 : Alveolites; 5 : corail tabul~ d e n d r o i d e ; 6 : Hexagonaria ; 7 : corail rugueux dendroii~e ; 8 : corail rugueux solitaire ; 9 : bryozoaires ; 10 : crinoides ; 11 : brachiopodes ; 12 : nautiloides ; 13 : algues ; 14 :Renalcis ;15 :Rothpletzella ; 16 : " o o z e " algaire ; 17 : laminations stroihatolitiques ; 18 : stromatolites ; a : "fenestral fabrics" ; b : micrite ; c : calcar~nite ; d : nautiloi~les d a m des cavit6s karstiques ; e : cavit6s de dissolution karstique ; f : d~p6ts de pente ; g : calcaire nodulaire ; h : schistes nodulaires ; i : schistes.
II. L o w e r part: t h e l o w e r p a r t o f t h e A r c h e r e e f ( a b o u t 32 m ) c o n s i s t s o f a p i n k t o r e d d i s h colored m/critic limestone mainly with a coral fauna together with algae and abundant stromatactis. A l s o t h e r e is a l o c a l a c c u m u l a t i o n o f b e a u tiful Receptaculites (pl. 1, fig. l l ) . T h i s p a r t o f the bioherm complex forms a mud mound (type
R5). I I I . Middle p a r t : t h e m i d d l e p a r t c o n s i s t s of a gray packstones, grainstones and wackestones c o n t a i n i n g b r a c h i o p o d s , Alveolites a n d t a b u l a r st r o m a t o p o r o i d s .
I V . Upper part : t h e u p p e r p a r t is c h a r a c t e r i z e d by massive stromatoporoids in f l r a i n s t o n e s a n d p a c k s t o n e s a s s o c i a t e d w i t h b r a c h i o p o d s in l o c a l concentrations. M . L e c o m p t e (196"t) i n t e r p r e t e d t h e s e s t a g e s as f o l l o w s : I a n d II z o n e s - - the <> z o n e ; I I I - - t h e s u b t u r b u l e n t z o n e ; a n d I V -- the turbulent zone. We consider stages I and II to r e p r e s e n t a s e m i - t u r b u l e n t e n v i r o n m e n t a n d s t a g e s I I I a n d I V to b e p r o g r e s s i v e l y m o r e t u r bulent environments on the basis of the types of fossils a n d l i t h o f a c i e s .
29
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~1
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46
II
E) 7
III
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o10
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IV
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H.H.TSIEN197g
Fig. 9 - Arche Quarrysection, Lower Frasnian, Frasnes-les-Couvin. I : basal part, II : lower part, I I I : middle part ; IV : upper part. 1 : massive stromatoporoids ; 2 : tabular stromatoporoids ;3 : lamellar Alveolites ; 4 :Disphyllum ;5 : stromatactis ;6 :Receptaculites ;7 : brachiopods ; 8 : Macgeea ; 9 : ostracods ; 10 : crinoids ; 11 : Algae ; 12 : Thamnopora. Coupe de la carri6re de l'Arehe. Frasnien inf6rieur. Frasnes-les-Couvin. I : partie basale ; II : partie inf6rieure ; I I I : pattie mgyenne ; IV : pattie sup6rieure ; 1 : stromatoporoi~les massifs ; 2 : stromatoporoities tabulaires ; 3 : Alveolites lamellaires ; 4 : Disphyllum ; 5 : Stromatactis ; 6 : Receptaculites ; 7 : brachiopodes ; 8 : Macgeea ; 9 : ostracodes ; 10 : crinoides ; 11 : algues ; 12 : Thamnopora.
BIBLIOGRAPHY
BOUC::aERT J. ~ STREEL M . ( 1 9 7 4 ) . -
Guidebook.
Intern. Slim p. Belg. Micropaleont. Limits, N a mur, S e p t e m b e r 1974. BULTYNC: P. ( 1 9 7 0 ) . R6vision s t r a t i g r a p h i q u e et pal6ontologique de la c o u p e - t y p e du C o u v i nien. Mdm. Inst. Gdo,l. Univ. Lorrvain, t. X X V I , 150 p., 39 pl. BULTYNC:< P. ~ BOONEN P. (1976). - - C o n o d o n t e s des F o r m a t i o n s de Rouillon, de C l a m i n f o r g e et de N ~ v r e m e n t - M ~ s o d 4 v o n i e n du B o r d nord du synclinorium de D i n a n t . Ann. Soc. G4ol. Belg., Bruxelles, t. 99, p. 't81-509. CoRN M . (197zt). - - Le F r a s n i e n de la b o r d u r e orientale du Bassin de Dinant. Ann. Soc. G~ol. Belg., Bruxelles, t. 97, fasc. 1, p. 67-103. COEN-AUBERT M . (1974). --- Le G i v e t i e n et le F r a s n i e n du M a s s i f de la V e s d r e . Acacl. Roy.
Belg., Bruxelles, Mdm. CI. Sc., t. X V I I I , fasc. 2, 1't6 p., 10 pl. DmCOT E. 6 T s 1 ~ H . H . (1977). - - Le n o m du g e n r e Ro~hpletzella W o o d 1948 (algue calcaire p a l e o z o i q u e ) est 14gitime et correct. Mdm. Inst. Gdol. Louvain, t. 29, p. 231-240. E R R E ~ M., M a M r V B. O SaRTrNA~R P. (1973). - Le calcaire de G i v e t et le G i v e t i e n ~ Givet. Bull. Inst. roy. Sci. Nat. Belg., Bruxelles (1972), 48, n ° 1, 59 p. GODrFROrD J. (1968). - - C o n t r i b u t i o n ~ l ' e t u d e du C o u v i n i e n entre W e l l i n et ]emelle (Bord s u d du Bassin de D i n a n t ) . Acad. roll. Belg., Bruxelles, Mdm. CI. Sc., 2 ° s~r. X V I I , 3, p. 1-87, 11 pl. KREBS W . (1973). - - D e v o n i a n c a r b o n a t e c o m plexes of C e n t r a l E u r o p e . In L a p o r t e E . F . (ed.) R e e f s in T i m e a n d Space, Selected E x a m p l e s from the Recent and Ancient. Soc. E c o n . Paleont. Mineral., T u l s a , Spec. publ. 18, p. 155-208.
--
KREBS W . & MOUNTrOY E . W . (1972). - - Comparison of central European and W e s t e r n Canad/an Devonian reef complexes. 24th Intern. Geol. Congr., Sect. 6, p. 206-309. LACROIX D. (1974). - - Sur la stratigraphie du M~sod6vonien et du Frasnien sud du Synclinorium de Namur. Ann. Soc. G~ol. Belg., Bruxelles, t. 97, p. 11-21.
VI" Congr~s international de s&timentologie HoUande-Belgique, 1964.
LECOMPTE M. ( 1 9 6 4 ) . -
Excursions C-D. Trois volumes: note pr~limi~ naire, 27 p., livret-guide, 49 p., figures, 33 pl. LECOMPTE M. (1970). - - Die Rifle im Devon der Ardennen und ihre bildungs bedingungen. Geolog. ~ Palaeont., Marburg, 4 , p. 25-71. MOURAVIEFF A.N. (1974). - - Excursion F, in Bouckaert ]. & Streel M. (ed.). Guidebook, Int~ern. Syrup. Belg. Micropaleont. Limits, Namur, September 1974. PEL ]. (1975). - - Etude s~dimentologique et stratigraphique du Givetien synclinorium de Dinant, de Givet h Liege. Coll. Pub. Sc. App., kiniv. Liege, n ° 53.
30
--
Tslm,r H.H. (1971). - - The Middle and kipper Devonian Reef-Complexes fo Belgium. Petrol. Geol. Taiwan, Taipei, 8, p, 119-173. Tslm'q H.H. (1975). - - Introduction to the Devonian reef development in Belgium. In : Conil et a/. Second Intern. Symp. Fossil Corals and Reefs, Guidebook Excursion C (Nord de la France et Belgique). Serv. G~ol. Belgique, Bruxelles, p. 3-43. TSIEN H.H. (1977). - - Morphology and development of Devonian reefs and reef complexes in Belgium. Proceed. Third Intern. Coral Reel Sgmp., p. 191-200. TSInN H.H. (1979). - - Paleoecology of Algalbearing facies in the Devonian (Couvinian to Frasnian) reef Complexes of Belgium. Paleogeog., Palaeoclim., Palaeoecol., Amsterdam, 27, p. 103-127. Tsm~q H.H. DRICOT E., MOHRAVIEFF A.N. ,& BOUCKAERT ]. (1973). - - Le Frasnien de la coupe de Tailfer. Serv. G~ol. Belg. Pro[. Paper, Bruxelles, n o 11. WILSON ].L. (1975). - - Carbonate facies in geologic history. Springer-Verlag ed., New York. 471 p.
PLATE
-
3 2
-
PLATE
1
Fig. 1 - Microstalactite, Tailfer quarry, Fr 1, Tailfer. Fig. 2 - Mud cracks, Tailfer quarry, Fr 1, Tailfer. Fig. 3 - Figure showing the biostrome bed is distinctly graded with large coral and stromatoporoids fragments at the base and the fine-grained packstones or wackestones with large tabular stromatoporoids at the top o f each unit. The bed has sharp, irregular and undulatory upper and lower limits. Fig. 4 - Showing autoclearing during the life o f a. Phillipsastrea, b. Stromatactis. Fig. 5 - Showing several stages o f geopetal fillings with different inclinations in sponges and cavities. Fig. 6 - Showing the growth form and the growth direction of a Phillipsastrea near by the geopetal fillings of figure 5. Fig. 7-9 - Stromatactis zone. 7 : stromatactis of basal part ; they are lamellar, thin and regularly layered ; 8 : stromatactis of lower part, small irregular flowers ; 9 : stromatactis o f middle part, large irregular flowers. Fig. 10 - Frutexites and new gen. 1 occur in cavities and can be observed growing from both sides o f the cavity. Fig. 11 - Showing local accumulation o f beautiful Receptaculites.
Fig. 1 - Microstalactite, Carri6re de Tailfer, Fr 1, Tailfer. Fig. 2 - Mud-cracks, Carri~re de Tailfer, Fr 1, Tailfer. Fig. 3 - Figure montrant le granoclassement net du banc biostromal avec de grands fragments de coraux et de stromatoporoides h la base et des packstones ou wackestones h grains fins contenant de grands stromatoporoides tabulaires au sommet. Le banc a des limites inf6rieure et sup6rieure bien marqu6es, irr6guli~res, ondul6es. Fig. 4 - Auto-nettoyage pendant la vie de a. Phillipsastrea, b. Stromatactis. Fig. 5 - Diverses 6tapes de remplissage g6op6tal, ~t diverses inclinaisons, dans des 6ponges et des cavit6s. Fig. 6 - Forme et direction de croissance d'un Phillipsastrea ~ proximit6 du remplissage g6op6tal de la figure 5. Fig. 7-9 - Zone h stromatactis. 7 : stromatactis de la partie basale ; ils sont lamellaires, minces et r6guli~rement rubann6s ; 8 : stromatactis de la zone inf6rieure : petits fleurages irr6guliers ; 9 : stromatactis de la zone moyenne : grands fleurages irr6guliers. Fig. 10 - Frutexites et nov. gen. 1 se rencontrent dans des cavit6s et on peut observer leur croissance qui d6bute des deux c6t6s de la cavit6. Fig. 11 - Accumulation locale de beaux Receptaculites.
G6obios M6m. sp6cial 4
PI. 1 H.H. Tsien, A.N. Mouravieff and E.W. Mountjoy