Ministry of Economic Affairs, Adm. of Mines, Belgian Geological Survey Special volume “ Aachen 1986" Annales de ta Société géologique de Belgique, T. 109 - 1986, pp. 27-42 A vril 1 98 6

REVIEW OF LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES MODELS AS APPLIED TO THE ARDENNE SHELF

by

Roland DREESEN 1, Charles A. SANDBERG 2 & Willi ZIEGLER 3

(11 figures)

ABSTRACT. - The history of Upper Devonian to Lower Carboniferous conodont biostratigraphy and ecostra- tigraphy is briefly reviewed w ith special emphasis on application to the Belgian shelf environments. During the past decade several conodont biofacies models have been proposed which are successfully applied to Upper Devonian and Lower Carboniferous deposits in the Western United States and in Northwestern Europe.

RESUME. - L'historique de la biostratigraphie et de l'écostratigraphie basées sur les Conodontes du Dévonien supérieur et du Carbonifère inférieur est brièvement revue en mettant l'accent sur les applications au milieu de plate­ forme en Belgique. Dans la dernière décade, plusieurs modèles de biofaciès à conodontes ont été proposés. Ils ont été appliqués avec succès aux roches sédimentaires du Dévonien supérieur et du Carbonifère inférieur des Etats-Unis et du Nord- Ouest de l'Europe.

INTRODUCTION This Palmato/epis-based revision of the upper part of the standard Late Devonian zonation provided not only The West German Late Devonian conodont zo­ an autochronologic sequence, but also a zonal sequence nation (Ziegler, 1962) proved to be recognizable not that is based mainly on pelagic taxa. The pelagic affinity only in Western Europe but also worldwide. This of Palmatolepis was, and still is, a major problem in reco­ standard Late Devonian conodont zonation was success­ gnizing the standard conodont zones within shallow- fully applied as an excellent biostratigraphic tool, marine and nearshore environments, such as those of the subdividing the approximately 15 million years of the Frasnian and Famennian Ardennes shelf settings. Late Devonian into 28 zones. Many detailed studies Likewise, the Siphonodella zonation proposed by updated, revised, and completed the standard zonation Sandberg, Ziegler and others (1978) and the post- (Ziegler, 1966, 1969, 1971; in Klapper & Ziegler, Siphonodella zonation proposed by Lane, Sandberg 1979; Sandberg & Ziegler, 1973, 1979; Ziegler, Klapper & Ziegler (1980) have proven useful in pelagic and hemi- & Johnson, 1976; Ziegler, Sandberg & Austin, 1974), pelagic facies of Europe and North America, and have thus while improving the understanding of taxonomy and become the worldwide standard zonation for the early evolutionary pattern of key platform conodont genera part of the Early Carboniferous (Early Mississippiana such as Palmatolepis, Ancyrognathus, Ancyrodella, Consequently, the use of Sandberg, Ziegler and others Scaphignathus, Bispathodus and Polygnathus. Following (1978), and Lane, Sandberg & Ziegler (1980) provide Weddige & Ziegler's (1979) autochronologic concept - a worldwide succession of 38 conodont zones from the that is, all geologic time ideally is represented by the base of the Frasnian into the early Visean. taxa and the morphotypes of only one taxonomic group and their continuous evolution - Ziegler & Sandberg 1 INIEB, rue du Chéra, B-4000 Liège, Belgium. (1984) revised the upper part of the standard Late 2 U.S. Geological Survey, Box 25046, Denver Federal Center, Devonian conodont zonation to replace the former Denver, Colorado 80225, U.S.A. velifer, styriacus and costatus zonal groups, which had 3 Forschungsinstitut Senckenberg, Senckenberganlage 25. been based primarily on genera other than Palmatolepis. D-6000 Frankfurt am Main 1, Federal Republic of Germany. 28 Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

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CARBONIFEROUS SULCATA

DEVONIAN LOWER PROTOGN. FAUNA

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Figure 1. - Range chart of important Late Famennian conodont species in Belgium Shaded area represents conodont zones not yet recognized on the Ardenne shelf (unfavourable facies). Spot samples from this unfavourable facies yield conodonts typical of Scaphignathid and Pandorinellid biofacies (see further). LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 29

On the other hand, extensive shallow-water, near­ differing in salinity, bottom sediments, aeration, and shore to restricted-marine environments characterize other environmental factors. most o f the "classical" Dinantian shelf areas in Belgium Finally, a ninth biofacies, the anthognathid (IX) and the British Isles, so that the pelagic Siphonodella biofacies, was recognized to occur in a hypersaline en­ zonation is somewhat difficult, locally even impossible, vironment of the Upper postera Zone in Utah (Sandberg to apply. Therefore, European conodont workers have & Dreesen, 1983, 1984). These authors also changed proposed local (conodont assemblage) zones for the the notation icriodid to "ic rio d id ", because true tcrio- Dinantian based on mixed, often shallow-water, cono­ dus died out in the early Famennian and later " Icrio- dont biofacies, using environmentally restricted genera dus" were really triple-row Pelekysgnathus that inha­ such as Clydagnathus, Patrognathus, Mestognathus, bited shallower habitats than true leriodus. which provide a tool for local intrabasinal correlations Sandberg & Gutschick (1984) proposed a new (Rhodes, Austin & Druce, 1969; Austin, 1973, 1974; conodont biofacies model for the Early Mississippian Groessens, 1974). anchora!is-latus Zone in the Western United States, which revised, updated, and improved earlier versions by Sandberg & Gutschick (1979) and Gutschick & BIOFACIES Sandberg (19 83 ). Seven Mississippian conodont bio­ facies are recognized and named after the one or two The concept of a conodont paleoecology, invol­ conodont platform genera that form the bulk of faunas ving different,distinctive, and coeval conodont biofacies, in each paleotectonic setting : has been slow to develop. Nevertheless, during the past I. Bispathodid biofacies (starved basin); decade serious attempts have been made in conodont II. Scaliognathid-doliognathid biofacies (foreslope ecostratigraphy and several conodont biofacies models toe and starved basin); have been proposed, especially for the Late Devonian III. Gnathodid-pseudopolygnathid biofacies (fore­ and Early Carboniferous. Apparently, environmental slope); factors other than a simple stratification of Iiving- depth zones (the Seddon-Sweet ecologie model, 1971) IV. Eotaphrid biofacies (carbonate-platform margin, are required. These factors also become more influen­ shelfedge); tial in increasingly shallower waters, where many spe­ V. Hindeodid biofacies (outer platform); cialized ecologie niches become segregated and loca­ VI. Pandorinellinid biofacies (inner platform and lized by different depositional environments and by tidal lagoon); greatly varying water salinities, currents, circulations, V II. Mestognathid biofacies (tidal lagoon and sabkha). and temperatures. Sandberg (1976) recognized five conodont bio­ Shallow-water conodonts are regarded to have facies based on percentages o f platform genera at many had their own evolution within their habitat. Sandberg sections within paleotectonic and paleoecologic recons­ & Ziegler (1979) believed that the common root that tructions of the former Upper styriacus (now Lower gave rise to the development of those specialized asym­ expansa) Zone in the Western United States. In a shore­ metric forms was Pandorinellina insita (Stauffer), ward direction, these are the biofacies, which are ty p i­ which is known to occur first within the basal Frasnian. fied by the abundance ratios of characteristic forms, Succeeding forms (P. cf. insita) gave rise during the and which occupy linear belts paralleling the former Famennian to Scaphignathus, Patrognathus, and Cly­ coastline : dagnathus. Recently, the recognition of differences in habitats, I. Palmatolepid-bispathodid biofacies (continental apparatuses, and ranges of Late Devonian leriodus, slope and rise) ; "leriodus ", and Pelekysgnathus has lead to a refinement II. Palmatolepid-polygnathid biofacies (shallow to of their biofacies interpretations and to the construction moderately deep water on the continental shelf); of an alternate icriodontid zonation (Sandberg & Dree­ III. Polygnathid-icriodid biofacies (moderately shallow sen, 1984). This shallow-water zonation is related to water on the outer cratonic platform) ; the mainly Palmatolepis-based standard zonation (for IV. Polygnathid-pelekysgnathid biofacies (shallow wa­ pelagic biofacies) by the usage o f stragglers (conodonts ter of normal salinity on the inner craton) ; living or deposited outside their optimum habitat). V. Clydagnathid biofacies (very shallow, brackish to Studies of the Frasnian to early Famennian foreslope normally saline, perhaps hypersaline, water on mudmound tracts of Belgium and of the partly contem­ offshore banks and in associated lagoons). poraneous basinal Kellwasser Limestones of West Ger­ many have provided evidence of close association of Sandberg & Ziegler (1979) recognized that three nearshore and pelagic biofacies at different water depths other biofacies - the scaphignathid (VI), pandorinellinid and mixtures of their faunas (due to downslope trans­ (V II), and patrognathid (V III) biofacies - were also pre­ port) that closely integrate ranges of icriodontids and sent within the same linear belt in nearshore settings those of key species and subspecies of the standard comparable to that of the clydagnathid biofacies, but Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

Figure 2. - Reprint from Ziegler and Sandberg, 1984, fig. 1 LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 31

zonation. In the original bathymetric setting, downslope schick, 1984) : Bispathodus and Polygnathus communis transport of mound talus and slope deposits as debris communis were ubiquitous, euryhaline dwellers of the flows and turbidites episodically mixed conodonts of euphotic zone. Scaliognathus and Doliognathus were the shallower polygnathid-'' icriodid " biofacies with mesopelagic nektonic dwellers of the dysphotic and those of the nearby, deeper palmatolepid-polygnathid aphotic zones. Bactrognathus was a nektonic slope biofacies. Moreover, occasional upslope stragglers date dweller. Gnathodus and Pseudopolygnathus were even some of the purer polygnathid-''icriodid " faunas. nektöbenthic slope dwellers whose habitats bottomed Similarly, the mixing of biofacies-controlled genera out seaward against the dysaerobic zone. Eotaphrus within the regressive megasequence of the Belgian Fa­ was a dweller of well-aerated shallow water of the upper mennian has been explained as the result of sedimento- foreslope and platform margin. The favored habitat logic processes such as tidal currents and storm surges for Hindeodus would have been the outer platform, (Dreesen & Thorez, 1980; Dreesen, 1984; Sandberg & whereas Pandorinellina is interpreted as an inner-plat­ Dreesen, 1984). form dweller above wave base and Mestognathus is inter­ As a result of these ecostratigraphic studies, dif­ preted mainly as a hypersaline lagoonal dweller. ferences in the normal or optimal distribution or sup­ Besides their value as accurate biostratigraphic posed habitat of some important platform conodonts correlation tools and as facies indicators, conodonts have became obvious. A t the same time, differences in first proved to be very useful in dating stratigraphie events. occurrences of key species of pelagic conodonts w ith Although the short length and importance of biostrati­ respect to the standard conodont zonations could now graphic zones in portraying geologic history have long be explained as the result of differences in biofacies. been recognized, conodont-based timespans have only Palmatolepis is interpreted as an offshore or pelagic recently been applied to paleogeographic reconstructions genus. Pelekysgnathus (both single-row species and by Sandberg & Poole (1977), Sandberg & Gutschick triple-row “leriodus" ) is interpreted to be a nekto- (1 9 8 0 ), and Sandberg and others (1983). An average benthic, nearshore genus that lived primarly in the timespan of about 0.5 m.y. for Late Devonian conodont euphotic zone and at water depths so shallow that its zones was obtained by dividing a radiometric timespan habitat was controlled by bottom conditions, leriodus of 13-15 m.y. for the Late Devonian by 28 conodont is interpreted to be an euphotic genus that lived in most zones. The authors argued for the approximately equal environments, including pelagic, during the early Late length of Late Devonian conodont zonal timespans on Devonian (Frasnian) but died out during the early Fa­ the basis of steady, rapid evolution of a single phylo­ mennian. The distribution of Polygnathus is more genetic lineage in favorable tropical environments. A complex; representatives of the P. nodocostatus group slightly longer timespan of about 1.3 m.y. for Early occur in more offshore and/or deeper water, whereas Carboniferous conodont zones was calculated by Sand­ those of the P. semicostatus group occur in more near­ berg & Gutschick (1979) and revised to about 1.5 by shore and/or shallower water. The P. communis group Sandberg (1980). preferred the highest (nearsurface or euphotic) part of Using this methodology, Middle Devonian to Late the water column. Late Devonian species of the asym­ Mississippian eustatic changes and epeirogenic events metric genera Clydagnathus, Patrognathus, Pandorinel- that influenced them were dated in millions of years lina, and Scaphignathus lived principally in shallow before or after the time of the Devonian-Carboniferous nearshore or restricted-marine water, in relation to boundary by means of a biostratigraphic time scale bottom conditions. Bispathodus (including morpholo­ based on conodont zones (Sandberg and others, 1983; gically similar platform genera such as Branmehla and Johnson and others, 1985). Similarly, a maximum Mehlina) occurs abundantly in pelagic, far-offshore time span of about 0.5 to 1 m.y. has been calculated settings, but it is equally common in the most nearshore for the hiatus or nondepositional event preceeding or settings. This group is interpreted to have lived in the accompanying the formation of oolitic ironstones on euphotic zone in the highest part of the water column. the Ardennes shelf during the early and early late Fa­ Thus it occurs widely, independent of bottom condi­ mennian (Dreesen, 1982, 1984). tions, in all but the most nearshore, restricted bio­ facies (Sandberg, 1979; Gutschick & Sandberg, 1983). The distribution pattern and biofacies affinities of some LATE FAMENNIAN CONODONT ZONATION other Late Devonian platform conodont genera such as Polylophodonta, Nothognathella, Pseudopolygnathus Ziegler's (1962) standard conodont zonation for and Protognathodus, are less clear and require further the Late Devonian remains virtually unchanged; it has detailed investigation. withstood critical testing because it was based on a Habitats of Dinantian platform conodonts have condensed sequence of hemipelagic limestones that also been interpreted from their distributions, associa­ were deposited in a moderately deep-water setting on tions, and abundances in different paleotectonic settings submarine rises. The zonation did not suffer from during the anchoralis-latus Zone in Utah and adjacent overlaps and gaps in the ranges of species, as might parts of the Western United States (Sandberg & Gut­ have occurred had it been pieced together from several 32 Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

LU STANDARD CONODONT NEARSHORE GENUS ZONE (PELAGIC BIOFACIES) CONODONT ZONE leriodus

U pper

M iddle U pper Lower U pper M id d le Middle L o w e r U p p e Low er U p p e r L o w e Lo w e r U p perm ost U p p e r 4 MV ll L o w e r -OHL U p p e r U p p e r rhom boidea L o w e r 4 MII. U pper cornutus Middle ? M iddle Low e U p p e r Lower M id d le L o w e r Pelekys­ U p per gnathus U pper

Lower p lan u s L o w e r

.dneyrognathus triangul,

U pper I e nodus LL symmetricus M iddle

L o w e r {>0

L o w e rm ost UNZONED

Figure 3. - Reprint from Sandberg and Dreesen, 1984, fig. 1. Roman numerals 0 -V show zonal positions of seven oolitic ironstone levels of Dreesen (1982).

sections that represented different paleotectonic settings phylogenetic model of Palmatolepis, by range extensions and biofacies. Over the years this standard zonation has bridging former gaps between the records o f some Pal­ undergone some minor changes, additions, and modi­ matolepis taxa, and by further taxonomic revisions of fications. Sandberg & Ziegler (1973) added a Lower some double-rowed Bispathodus taxa. A new zone, Palmatolepis rhomboidea Zone, changed the former the Uppermost Pa. marginifera Zone, was added to the Pa. rhomboidea Zone to Upper Pa. rhomboidea Zone, former Lower and Upper Pa. marginifera Zones, and and changed the name of the Pa. quadrantinodosa Zone replaced the former Lower Sc. velifer Zone. The former to Pa. marginifera Zone. Ziegler, Sandberg & Austin Middle and Upper Sc. velifer Zones are now replaced (1974) monographed the Bispathodus group and chang­ by the new Lower and Upper Pa. trachytera Zones. ed the name of the Spathognathodus costatus Zones to Lower and Upper Pa. postera Zones replace the former Bispathodus costatus Zones. Sandberg, Ziegler and Lower and Middle P. styriacus Zones. The new Pa. others (1978) added a Siphonodella praesulcata Zone, expansa zonal group includes the former Upper P. which partly overlaps and partly extends above the styriacus and the Lower and part of the Middle Bi. B. costatus Zone to the top of the Devonian, and re­ costatus Zones. The three new Siphonodella praesulcata cognized a time-equivalent Protognathodus (or proto- Zones are form ally incorporated in the revised standard gnathodid) biofacies. Late Devonian zonation, rather than being considered The most important change, however, was the part o f an alternate, coeval zonal scheme. recent Palmatolepis-based revision of the upper part of Siphonodella was chosen as a zonal index, al­ the standard Late Devonian Conodont zonation between though it occurs distinctly below the highest ranges of the top of the Upper Pa. marginifera Zone and the the youngest Palmatolepis taxa. In this way, two major earliest Carboniferous Siphonodella sulcata Zone (fig. 2 autochronologic zonal successions were linked to one and Ziegler & Sandberg, 1984). This revision was ne­ another. The Middle praesulcata Zone is less strongly cessary because of biofacies influences on the formal based than the Lower and Upper praesulcata Zones, but zonal scheme-- i.e., usage of shallow-water nominal it bridges the gap between the former Upper costatus species for groups of zones in a supposedly deeper water Zone (Ziegler, 1962, 1971;in Klapper & Ziegler, 1979) pelagic setting. The changes were enabled by a new and the former Lower Protognathodus fauna (Ziegler, LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 33

1969) or Protognathodus biofacies (Sandberg, 1979). FAMENNIAN CONODONT BIOFACIES MODELS The upper boundary of the Upper praesulcata Zone, at the entry of Siphonodella sulcata (Huddle), was LOWER EXPANSA ZONE OF WESTERN UNITED STATES proposed to define the lower boundary of the Carboni­ More than 75 widespread measured sections (Sand­ ferous System by the IUGS Working Group on the berg, 1976; Sandberg & Poole, 1977; Sandberg and Devonian-Carboniferous Boundary, meeting in Washing­ others, 1983) have been used for documenting conodont ton, D.C., in May 1979. biofacies and icriodontid distribution within the Lower This Palmatolepls-based upper part of the stan­ expansa (former Upper styriacus) Zone in the Western dard Late Devonian zonation (Ziegler & Sandberg, United States. The conodont biofacies are named for 1984) is applicable mainly to the farthest offshore the one or two predominant platform elements, the in­ biofacies - the palmatolepid-bispathodid and palmato- ferred iiving-depth zones of which best characterize the lepid-polygnathid biofacies. Simultaneously, Sandberg water depths of the particular biofacies. For all biofa- & Dreesen (1984) proposed an alternate icriodontid- cies, the nominate platform genera constitute at least based zonation that comprises only 10 zones as opposed 65 percent of the total population of platform elements. to the 28 zones of the standard zonation (fig. 3). How­ The five biofacies (l-V ) established by Sandberg (1976) ever, this zonation is applicable to the next two shore­ occupy long, relatively narrow belts paralleling a former ward biofacies - the polygnathid-'' icriodid " and poly- east-west coastline in an equatorial region. The bio­ gnathid-pelekysgnathid biofacies - as well as to some facies do not demonstrate any significant longitudinal occurrences of the five most nearshore (restricted- changes in faunas and only slight latitudinal (seaward) marine) biofacies - the scaphignathid, pandorinellinid, ecologie straggling or post-mortem mixing of conodonts patrognathid, clydagnathid, and antognathid biofacies. from one biofacies belt to another. A belt shoreward of Although nearshore conodont zones are equivalent to the inner shelf contains various restricted-marine and from 1.5 to 5.5 standard zones, positions exist where peritidal settings (offshore bars, bays, lagoons, estuaries) nearshore and standard zone boundaries do not coin­ characterized by shallow-water biofacies (V-IX). The cide, so that the nearshore zones might be used to sub­ nine currently recognized biofacies ( I-IX ) are shown in divide the standard zones. figure 5 together with the type of icriodontid fauna Conodonts that lived in the five shallowest bio­ they contain. facies (V -IX ) must have lived in water so shallow that The tw o most seaward biofacies (I, II) lack indi­ they were controlled by bottom conditions and there­ genous icriodontid faunas and contain only simple cones fore could have been nektobenthic. These shallow- (C, K elements) that, because o f their shape and small water biofacies include nearshore and peritidal settings mass, must have been transported seaward by surface suchas bays, estuaries, and lagoons (Western United currents, incapable of carrying the larger, heavier plat­ States) or tidal flats, tidal lagoons and evaporitic lagoons form-(I) elements. The stratigraphie units containing w ith a wide range of salinities (southern Belgium). the various rock types and conodont biofacies are shown The Famennian species of Clydagnathus, Patrognathus, across the bottom of the model (fig. 5). and Scaphignathus evolved from the Pandorinellina stock, members of which are characterized by an asym­ FAMENNIAN REGRESSIVE MEGACYCLE OF BELGIUM metric platform. Most probably these forms gave rise in the Early Carboniferous to other asymmetric form- The Belgian model (fig. 6) differs somewhat fom genera such as Cavusgnathus, Cloghergnathus, and the Western United States model because it does not Mestognathus (Austin, 1976; von Bitter, 1976; Austin depict a single time-slice or zone, but rather a regressive & Davies, 1984). These are apparent homeomorphs of megacycle that passes through five Famennian zonal older Famennian genera that occupied similar nearshore groups from the crepida to postera Zones, progressing to restricted-marine environments. The problematic in a landward direction. This deviation from single­ Scaphignathus ? subserratus (Branson & Mehl) and zone reconstruction was necessary because of erosion Polygnathus ? pseudostrigosus Dreesen and Dusar have of some older offshore lithofacies during the regression been excluded from this group of asymmetric shallow- and because of later regional folding and thrust faulting, water conodonts and assigned to a more offshore genus which make it impossible to find exposures of the Alternognathus by Ziegler & Sandberg (1984). A lter- offshore and nearshore biofacies of any one zone. An­ nognathus has a lower-surface morphology identical to other exception is that biofacies I is called simply pal- that of early species of Siphonodella and may have matolepid biofacies. This change is necessary because given rise to that genus. the genus Bispathodus did not evolve until the margini­ Range of conodont species in terms of the new fera Zone and hence it was'not available as a constituent Famennian zonation are shown in figure 4. of the pelagic faunas of the crepida zone. 34 Roland DREESEN, Charles A. SANDBERG & WIMI ZIEGLER

i ï

—— Sipfi. sulcata Po. inornatus

•—■i i Prtogn. kockeli Po. mogolensis

— Siph. praesulcata Po. delicatulus

Ps. m. rrigonicus Po. hassi

Pa. gr. gonio- Po. extralobatus clymeniae B. ultimus Iziegleri Po. praehassi & ultimus)

B. costatus Po. communis carina

8. aculeatus Po. experplexus

B. jugosus Ps. controversus

Ps. m. marburgensis Po. margaritatus

Ps. brevipennatus Po. marginvolutus Pa. gracilis sigmoidalis Po. obliquicostatus

Pa. r. rugosa Po. homoirregularis

Pa. gr. expansa Po. perplexus

B. bispathodus Po. subitregularis

Pa. gr. manca Po. granulosus

Pa. r. ampla Po. lagoniensis

Po. styriacus Pa. pcrlobata sigmoidea Pa. p. postera Pa. glabra lepta typ. Ps. granulosus Pa. stoppeli

Pa. p. helmsi Pa. m. minuta

Pa r. trachytes Pa. m. schleiria

Se. velifer velifer Pa. gr. gracilis

Pa. p. maxima Pa. k/apperi

Pa. p. grossi Pa. gl. acuta Pa. rugosa ct, ampla Pa. gl pectinata M / Pa. m. utahensis Pa. gl. glabra Pa. m. duplicata Pa. p. schindemiiti Pa. p. sigmoidea Pa. gl. prima Pa. glabra distorta

Pa. q. mtlexoidea

Pa. marginifera marginifera

Figure 4. - Reprint from Ziegler and Sandberg, 1984, figs. 2, 3, 4 LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 35.

The Belgian model shows that the paleoecologic interpretations of icriodontids established in the Western United States are indeed applicable to a totally different sedimentary regime in which coarse clastic rocks predo­ minate over carbonate rocks. It also provides a detailed depiction of the diverse microenvironments of the two innermost biofacies belts, those containing biofacies IV and biofacies V-IX, in the Western United States. In the most nearshore settings-tidal lagoon and sabkha- scaphignathid biofacies (VI) and pandorinellinid bio­ S. ziegleri facies (VIII) were found in the postera Zone. This in­ S. peterseni nermost biofacies belt has not been thoroughly investi­ Clyd. ormistoni gated to ascertain whether it might also contain bio­ S. velifer lepta facies V, VII, and IX. Mixed conodont biofacies are S. velifer velifer very frequent, and they result from various sedimen- Alternognathus regularis tologic processes, such as storm surges, tidal currents, A. beulensis debris flows (fluxoturbidites), and short-term trans­ Br. suprema gressée pulses (related to synsedirhentary tectonics). Br. fissilis A special sedimentological and biostratigraphical B. stabilis M2 feature of the Famennian Ardennes shelf is the occur­ B. stabilis M3 rence of oolitic ironstone levels, the stratigraphie posi­ Br. bohtenana tion of which is shown in fig. 3. These event-stratigra- B. stabilis Mi phical marker beds represent condensed deposits which Br. inornata can be traced over several tens of kilometers on the Br. werneri shelf in both the D inant and Vesdre Synclinoria (see M. strigosa fig. 6).

Figure 4 (continued)

VARIOUS CONTI­ PALEOTECTONIC SLOPE SHELF RESTRICTED MARINE LAND NENTAL AND SETTING RISE PERITIDAL SETTINGS

31 Clydagnathid I n TSL CONODONT HI 37t S c a p h ig n a th id Palmatolepid- Palmatolepid- Polygnathid Polygnathid- BIOFACIES 3ZE Patrognathid bispathodid polygnathid ic rio d id ” pelekysgnathid (I -IX ) VIII Pandorinellinid 3X Antognathid

ICRIODONTID T r ip le ­ Both types of S in g le -ro w ro w Simple cones (transported) FAUNA Pelek y s. Pelekysgnathus Pelekysgnathus

REPRESENTATIVE SOL MWZ - RQ EGL

SECTION

0 EUPHOTIC

QQ DVSPHOTIC -Palmatolepis (PELAGIC) 0 A PHOT íe Micrite with s ENVIRONMENTAL terbedded encrmite siltstone, RECONSTRUCTION sandstone, ter bed de d e ne ri nit and supratidal ; OXYGEN MINIMUM (OM)------care dolom ite dstone ®oL _ asm

Radiol aria Chert Mudstone mudsto R O C K T Y P E S and chert concret

WOOD­ LEATHAM FM. UPPER MEMBER OF OURAY LOWER PART OF ST RATI GRAPHIC SLAVEN RUFF LEATHAM PINYON PEAK CHERT LIMESTONE CHAFFEE GROUP UNIT FM. MBR. OF LIMESTONE PILOT SH.

Figure 5. - Reprint from Sandberg and Dreesen, 1984, fig. 4 36 Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

OFFSHORE NEARSHORE 'BACKSHORE’

PALEOTECTONIC £ Z < < MUDDY SANDY , û Ui , o I * CD Z SETTING OUTER INNER £ < 0 ü 2 < £ £ CD SHELF SHELF < o 9 1} < e i? < S 3 m S h IL (D h _l (/) O CL

n M is: S,3Zffl,? CONODONT Palmatolepid Palmatolepid- Polygn.- Polygnathld- Scaphignathid, BIOFACIES polygnathld "icriodld” pelekysgnathid pandorinellinid, +? n . i i L .i. Triple-row Both types of I Si nqle-row T ICRIODONTID Rare iBoth types of Pelekysgnathus X T , i ,X, l i n , , i ■ , I Pelekys- , Pelekysgnathus i Pelekys- 1 U N K N O W N leriodus 1 (transported) i I _ƒ ® - , I FAUNA j______'______^ '______gnathus ¡ (indigenous) I gnathus ______

ENVIRONMENTAL

RECONSTRUCTION Algal-crinoidal mudmou nd Supratidal dolomite Sandy shale and shaly sand _ Micrite Anhydrite "o Calcareous stormlayers ^ d) Sí ® O — Redbeds J) Mudstone Coquinas T> ROCK TYPES Nodular limestone Oolitic ironstones d) Coquinas £ Oolitic ironstones 5 E MONFORT EVIEUX c FM. FM. SOUVERAIN^ lii Ld STRATIGRAPHIC FAMENNE mo: (0 o: PRE FM. iCOMBLAIN- < 5 m £ CD UNIT SHALE / L A -T O U R 0 5 < 5 E S N E U X FM. / FM. O m

ZONAL INTERVAL crepida rhomboidea marginijera trachy ter a postera

Figure 6. - Reprint from Sandberg and Dreesen, 1984, fig. 8

EARLY CARBONIFEROUS (EARLY MISSISSIPPIAN) CONODONT ZONATION CONODONT ZONE SERIES DCB A Siphonodella-based standard conodont zonation OR BIOFACIES v. m .y. for the earliest Mississippian was provisionally proposed + 1 8 — Gnathodus texanus by Sandberg & Ziegler (1976) and later formalized by (Lower part) 3 Sandberg, Ziegler and others (1978). This zonation was +15- -ts a> later combined with the standard zonation of Lane, Scaliognathus anchoralis — -§ o « 2 Sandberg & Ziegler (1980) for the higher part of the Doliognathus latus S+ o + 12- Early Mississippian. The combined standard zonation is U pper £§ in shown on figure 7. This zonation is based primarily z Gnathodus typicus < L o w e r on the first occurrences of species of Siphonodella O- ? - +9- a. that in most cases are the nominal species of zones Siphonodella isosticha— cp +7.5 (fig. 8). The base of the Mississippian in North A m e­ CP CP U pper Siphonodella crenulata rica and the base of the Carboniferous worldwide can CP be defined in offshore marine sequences within the -+6 L ow er Siphonodella crenulata Siphonodella phylogeny by the evolutionary change cc ■+S (O LU c +4.5 - a a) from S. praesulcata to S. sulcata at the base of the 5 ct, o Siphonodella sandbergi I ra sulcata Zone. The top of the Siphonodella zonation is O +3- o defined by the last occurrence of the genus. This ex­ in Upper tinction marks the top of the Kinderhookian in North Siphonodella duplicata America and an important biostratigraphic break world­ Lower <3 a. wide. Fortuitously, this extinction occurred almost +1.5- simultaneously with the evolution of a new gnathodid Siphonodella sulcata species, G. typicus, from G. delicatus.

As in the case of the Palmatolepis-based standard

Late Devonian conodont zonation, the Siphonodella- Figure 7. - Reprint from Sandberg, Gutschick, Johnson, based zonation is applicable mainly to open-marine. Poole and Sando, 1983, fig. 4 LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 37

Siphonodella ABORAL SI DE

DEPRESSED ZONE KEEL PSEUDOKEEL KEEL KEEL

isosticha -

UPPER c re n u la ta

LOWER c ren u lata

sandbergi

UPPER cooperi MORPHOTYPE 1 d u p lic a ta

LO W E R RAPIDLY EVOLVING STOCK d u p lic a ta

s u lc a ta

praesulcata

Figure 8. - Reprint from Sandberg, Ziegler, Leuteritz and Brill, 1978, fig. 1 38 Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

offshore, pelagic to hemipelagic settings, although BASINAL FAUNAS SHELF FAUNAS STAGES stragglers can be found in more nearshore, shallow- Paragnathodus nodosus BRIGANTIAN marine environments. The pelagic affinity of Siphono­ Gnathodus bilineatus della made it necessary to distinguish a pelagic (basinal) ASBIAN Siphonodella biofacies and a nearshore Patrognathus- Cavusgnathus - Pandorinellina biofacies (Sandberg & Gutschick, 1983). G Apatognathus pseudosem/glaber- HOLKERIAN Earlier studies (Sandberg, Ziegler and others, . 1978) revealed the existence of a Protognathodus fauna or ARUNDI AN biofacies, as a time-equivalent fauna of the earliest G commutatus Taphrognathus Siphonodella Zone. However, recent investigations Cloghergnathus (Lane, Sandberg & Ziegler, 1980) demonstrated that G homopunctatus CHADIAN Protognathodus is widely distributed and that its paleo- Mestognathus beckmanni ecologic controls are not yet established; Protognatho­ S. anchoralis S anchoralis dus has been found in nearshore (lagoonal), moderately Polygnathus mehli - deep to deep offshore, and lower-slope settings. D bouckaerh Within the type Dinantian carbonate^shelf rocks Gnathodus delicatus Polygnathus of Belgium and the British Isles, the Siphonodella- communis canna based standard zonation cannot be applied. This is be­ Pseudopolygnathus Lower " ? ^ cause of the persistence of shallow to extremely shallow multistriatus S crenulata COURCEYAN water over very broad areas of the shelf during most of ? Bispathodus - the Dinantian. Austin & Davies (1984) suggested that S. lo b a ta Pseudopolygnathus ? lack of competition in unfavorable shallow-water envi­ Siphonodella - S. duplicata P. inornatus ronments resulted in the success of long-ranging species. S. sandbergi Polygnathus Therefore, correlations based on these species are only spicatus of local relevance. Siphonodella sulcata P variabilis - A clear distinction exists in time-equivalent rocks B plumulus ■ between the early Dinantian (Tournaisian) conodonts of the shelf environment, characterized by the presence of Figure 9. - Reprint from Austin and Davies, 1984, fig. 21. Clydagnathus and Patrognathus, and those of the basinal Summary of principal conodonts found in basinal and shelf environment, which contain Siphonodella and Proto­ faunas of the British Dinantian. The shelf faunas are particularly gnathodus. In practice, different conodont assemblage prone to facies control and some species, including Patrognathus zones (from mixed conodont biofacies) are used for variabilis and Polygnathus inornatus are much longer ranging than this chart would seem to imply. Other long ranging forms, local correlations (fig. 9), although the authors are aware such as Clydagnathus, are not shown on this figure. The sequence of the fact that some, if not all, o f the faunal changes of shelf faunas shown, therefore, should not be used for correla­ reflect changing lithofacies rather than evolutionary tion purposes. In particular, knowledge of Chadian-Asbian shelf lineages of conodonts. faunas is especially limited.

A similar approach (a " multi-biofacies" conodont assemblage zonal scheme) has been applied to the Bel­ gian Dinantian by Groessens (1 9 74 ); this scheme is shown in figure 10. Three acrozones and nine sub­ zones were defined by Groessens w ithin the lower D i­ coincide with the main sedimentary phases of theWaul- nantian (Tournaisian) of Belgium. The lowest or Sipho­ sortian reefs and their proximal off-reef equivalents in nodella Zone groups several of the Siphonodella-based Belgium (Lees and others, 1977). Consequently, great standard zones and reflects an impoverished, mono­ care should be exercised in using conodont assemblage- tonous (shallow-water) conodont fauna. The base of zonal boundaries as time lines in paleogeographic re­ the next acrozone, the Polygnathus communis carina constructions. Zone, corresponds to the base of the Lower Gnathodus typicus Zone of Lane, Sandberg & Ziegler (1980).

As a result of the newly proposed (Sandberg & EARLY CARBONIFEROUS CONODONT BIOFACIES MODELS Gutschick, 1984) conodont biofacies models and inter­ preted paleoecology of platform conodonts for the Early Mississippian anchoralis-latus Zone, it is quite Sandberg & Gutschick (1979, 1980, 1984) indicated possible that some o f the younger zones and subzones their concept of Osagean and early Meramecian cono­ of the Belgian Dinantian (Groessens, 1974) represent dont distribution with reference to a biofacies model, successive biofacies rather than conodont chronozones. that extends from deep, starved-basin settings to the Moreover, differences in conodont biofacies would shoreline (fig. 11). This Mississippian biofacies scheme explain why conodont assemblage-zonal boundaries is similar to the worldwide Late Devonian biofacies LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 39

DISTRIBUTION DES CONODONTES DANS LE DINANTIEN DE LA BELGIQUE

1974 EGROESSENS

Gnathodus cf commutatus

Gnathodus homopunc latus

Scaliognathus anchoralis

Eotaphrus burlingtonensis

Doliognathus latus

Dollymae bouckaerti

5pathognathodus bultyncki

Spathognathodus cf bultyncki

Dollymae hassi

Siphonodella ZONE

PROTOGNATHODUS FAUNA

MB dess in e sanséchelle

Figure 10. - Reprint from Groessens, 1974, plate 46 Roland DREESEN, Charles A. SANDBERG & Willi ZIEGLER

m

Z O

33

Q. C/)

<0 z

(D O

SQ

o

33 03

03 2 S

LAND

Figure 11.- Reprint from Sandberg and Gutschick, 1984, fig. 14. LATE DEVONIAN AND EARLY CARBONIFEROUS CONODONT BIOSTRATIGRAPHY AND BIOFACIES 41

scheme originally proposed by Sandberg (1976). The DREESEN, R., 1984. Stratigraphie correlation of Famennian names of the seven Mississippian conodont biofacies oolitic ironstones in the Havelange (Dinant basin) and ( l- V II) are in most cases based on the one or two co­ Verviers boreholes (Vesdre massif) (Upper Devonian, nodont genera that form the bulk of the faunas. Belgium). Bull. Soc. belge de Géologie, 93 (1-2) : 197- Although the distribution shown in figure 11 2 1 1 , 1 pi. can be applied to British and Belgian Dinantian cono­ DREESEN, R. & THOREZ, J., 1980. Sedimentary environ­ donts, the model does not extend across the platform. ments, conodont biofacies and paleoecology of the This region is one which is well developed through the Belgian Famennian (Upper Devonian) - an approach. British and Belgian Dinantian. Therefore it might be - Ann. Soc. géol. Belg., 103 : 97-110. possible that additional shallow-platform , protected- GROESSENS, E., 1974. Distribution de conodontes dans le shelf, and restricted-marine biofacies will be added to Dinantien de la Belgique. Belgian Geological Survey, the Sandberg-Gutschick model in the future. International Symposium on Belgian Micropaleontolo­ The presence of extensive oolite shoals on the gical Limits from Emsian to Visean, Namur, September platform, or of shooaling near the margin of the platform 1-10, 1974, pub. 17, 193 p. has a pronounced effect on water depth, local energy GUTSCHICK, R.C. & SANDBERG, C.A., 1983. Mississippian conditions, salinity, and presumably, the supply of continental margins of the conterminous United States, nutrients. Uncertainty concerning both the function in The shelfbreak; critical interface on continental mar­ and affinity of the organisms, which bore the conodont gins. Society of Economic Paleontologists and Minera­ logists, Special Publication 33 : 79-96. elements, makes judgements concerning the distribution of elements within the aerobic or photic zone extremely JOHNSON, J.G., KLAPPER, G. & SANDBERG, C.A., 1985. tentative (Austin & Davies, 1984). Nevertheless, such Devonian eustatic fluctuations in Euramerica. Geological conodont biofacies models and interpreted paleoecology Society of America Bulletin, 96 (5) : 567-587. of platform conodonts are of the greatest importance in KLAPPER, G. & ZIEGLER, W., 1979. Devonian conodont paleogeographic reconstructions. Classical concepts biostratigraphy, in The Devonian system. Special Papers concerning the paleobathymetric evolution of enigmatic in Palaeontology 33 : 199-224, 8 figs. carbonate buildups such as the Waulsortian reefs of LANE, H.R., SANDBERG, C.A. & ZIEGLER, W„ 1980. Taxo­ Belgium may have to be revised, or at least updated, in nomy and phytogeny of some Lower Carboniferous the light of recent conodont paleoecologic models. conodonts and preliminary standard post-Siphonodella zonation. Geológica et Palaeontologica, 14 : 117-164, ACKNOWLEDGEMENTS 10 pis. LEES, A., NOEL, B. & BOUW, P., 1977. The Waulsortian The authors are gratefully indebted to R. Austin, “ reefs" of Belgium; a progress report. Catholic Univer­ R. Davis, the Geological Society of America and E. sity of Louvain, Memoirs of Geologic Institute, 29 : Groessens for permission to reproduce figures 9 and 2 8 9 -3 1 5 . 10 in this review paper. RHODES, F.H.T., AUSTIN, R.L. & DRUCE, E.C., 1969. British R. Dreesen extends particular thanks to the Avonian (Carboniferous) conodont faunas and their value Alexander von Humboldt Foundation (F.R.G.) for in local and intercontinental correlation. British Museum supporting his research project. (Natural History) Bulletin, Geology, supplement no. 5, 313 p., 31 pis

SANDBERG, C.A., 1976. Conodont biofacies of Late Devonian REFERENCES Polygnathus styriacus Zone in western United States, in Barnes, C.R., ed., Conodont paleoecology. Geolo­ AUSTIN, R.L., 1973. Modification of the British Avonian gical Association of Canada Special Paper 15 : 171- conodont zonation and a re-appraisal of European 1 86. Dinantian conodont zonation and correlation. Ann. Soc. géol. Belg., 96 (3) : 523-532. SANDBERG, C.A., 1979. Devonian and Lower Mississippian conodont zonation of the Great Basin and Rocky Moun­ AUSTIN, R.L., 1974. The biostratigraphic distribution of tains, in Sandberg, C.A., and Clark, D.L., eds., Conodont conodonts in Great Britain and the Republic of Ireland. biostratigraphy of the Great Basin and Rocky Moun­ Belgian Geological Survey, International Symposium tains. Brigham Young University Geology Studies, 26 (3): on Belgian Micropaleontological Limits from Emsian to 97-106, 5 figs. Visean, Namur, Sept. 1-10, 1974, pub. 3 : 1-17, 1 pi. SANDBERG, C.A., 1980. Utility of conodonts in determining AUSTIN, R.L., 1976. Evidence from Great Britain and Ireland rates of synorogenic sedimentation and in timing Antler concerning west European Dinantian conodont paleo­ orogenic events, western United States (abs.), in Second ecology, in Barnes, C.R. ed., Conodont paleoecology. European Conodont Symposium - ECOS II; Guidebook, Geological Association of Canada Special Paper 15 : Abstracts : (Australia) Geologische Bundesanstalt Ab­ 2 0 1 -2 2 4 . handlungen 35, p. 209.

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SANDBERG, C.A. & GUTSCHICK, R.C., 1979. Guide to SANDBERG, C.A. & ZIEGLER, W., 1979. Taxonomy and bio­ conodont biostratigraphy of Upper Devonian and Missis­ facies of important conodonts of Late Devonian styria- sippian rocks along the Wasatch Front and Cordilleran c u s -Zone, United States and Germany. Geológica et Hingeline, Utah, in Sandberg, C.A. & Clark, D.L., eds., Palaeontologica, 13 : 173-212,7 pis. Conodont biostratigraphy of the Great Basin and Rocky SANDBERG, C.A., ZIEGLER, W., LEUTERITZ, K. & BRILL, Mountains. Brigham Young University Geology Studies, S.M., 1978. Phylogeriy, spéciation and zonation of 26 (3) : 107-134, 16 figs. Siphonodella (Conodonta, Upper Devonian and Lower Carboniferous). Newsletters on Stratigraphy, 7 (2) : SANDBERG, C.A. & GUTSCHICK, R.C., 1980. Sedimentation 102-120, 2 figs. and biostratigraphy of Osagean and Meramecian starved basin and foreslope. Western United States, in Fo uch, SEDDON, G. & SWEET, W.C., 1971. An ecologie model for T.D. & Magathan, E.R., eds., Paleozoic paleogeography conodonts. Journal of Paleontology, 45 (5) : 869-880. Symposium 1 : 129-147. VON BITTER, P.H., 1976. Paleoecology and distribution of Windsor Group (Visean-?Early Namurian) conodonts. SANDBERG, C.A. & GUTSCHICK, R.C., 1983. Early Carbo­ Port Hood Island, Nova Scotia, Canada, in Barnes, C.R. niferous biofacies and paleoecologic models. Geological ed., Conodont paleoecology. Geological Association of Society of America Abstracts with Programs, 15 (4) : Canada, Special Paper 15 : 225-241. 2 2 1. WEDDIGE, K. & ZIEGLER, W„ 1979. Evolutionary patterns SANDBERG, C.A. & GUTSCHICK, R.C., 1984. Distribution, in the Middle Devonian conodont genera Polygnathus microfauna and source-rock potential of Mississippian and leriodus. Geológica et Palaeontologica, 13 : 157- Delle Phosphatic Member of Woodman Formation and 164, 3 figs. equivalents, Utah and adjacent States, in W o o d w ard , ZIEGLER, W„ 1962. Taxionomie und Phylogenie Oberdevo­ Jane, Meissner, F.F., and Clayton, J.L., eds., Hydrocarbon nischer Conodonten und ihre stratigraphische Bedeutung. source rocks of the Greater Rocky Mountain region. Hessisches Landesamt Bodenforschung Abhandlungen 38, Denver, Colorado, Rocky Mountain Association of 166 p., 14 pis. Geologists : 135-178, 17 figs., 8 pis. ZIEGLER, W., 1966. Eine Verfeinerung der Conodontenglie- SANDBERG, C.A., GUTSCHICK, R.C., JOHNSON, J.G., derung an der Grenze Mittel-/Oberdevon. Fortschritt POOLE, F.G. & SANDO, W.J., 1983. Middle Devonian Geologie Rheinland und Westfalen, 9 ; 647-676, 4 pis. to Late Mississippian geologic history of the Overthrust ZIEGLER, W., 1969. Eine neue Conodontenfauna aus dem belt region, western United States. Rocky Mountain höchsten Oberdevon. Fortschritt Geologie Rheinland Association of Geologists, Geologic Studies of the Cor­ und Westfalen, 17 : 343-360, 2 pis. dilleran Thrust Belt, 2 : 691-719. ZIEGLER, W., 1971, Conodont stratigraphy of the European SANDBERG, C.A. & POOLE, F.G., 1977. Conodont biostra­ D evo n ian , in Sweet, W.C., and Bergström, S.M., eds., tigraphy and depositional complexes of Upper Devonian Symposium on conodont biostratigraphy. Geological cratonic-platform and continental-shelf rocks in the Society of America, Memoir 127 : 227-284, 6 charts. Western United States, in Murphy, M.A., Berry, W.B.N., ZIEGLER, W., KLAPPER, G. & JOHNSON, J.G., 1976. Rede­ & Sandberg, C.A., eds., Western North America; Devon­ finition and subdivision of the varcus-2.one (Conodonts, ian. California University, Riverside, Campus Museum Middle-?Upper Devonian) in Europe and North America. Contribution, 4 : 144-182. Geológica et Palaeontologica, 10 : 109-132, 4 pis. SANDBERG, C.A. & ZIEGLER, W., 1973. Refinement of stan­ ZIEGLER, W. & SANDBERG, C.A., 1984. Palmatolepis- dard Upper Devonian conodont zonation based on based revision of upper part of standard Late Devonian sections in Nevada and West Germany. Geológica et conodont zonation, in Clark, D.L., ed., Conodont bio­ Palaeontologica, 7 : 97-122, 5 pis. facies and provincialism. Geological Society of America SANDBERG, C.A. & ZIEGLER, W., 1976. Working zonation Special Paper 196 : 179-194, 3 pis., 4 f igs. and refined spéciation of Siphonodella (Conodonta, ZIEGLER, W„ SANDBERG, C.A. & AUSTIN, R.L., 1974. Upper Devonian and Lower Carboniferous). Geologi­ Revision of Bispathodus group (Conodonta) in the cal Society of America Abstracts with Programs, 8 (4) : Upper Devonian and Lower Carboniferous. Geológica 5 0 6 -5 0 7 . et Palaeontologica, 8 : 97-112, 3 pis.