Conodonts from the Davidsville Group, northeastern ...

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the Canadian Western Cordillera (sensu Nelson et al. 1964; Wheeler 1966; Nelson 1970) and would paleontologically identify eugeosynclinal strata at least as old as Ordovician.' To date, the oldest fossils found in the Intermontane Belt are in the Shoemaker Creek area near Keremeos, some 125 km (80mi) to the south, where corals, stromatoporoids, brachiopods, and microfossils have variously been dated as Late Silurian or Devonian (Pedder in Read and Okulitch 1977) or Silurian (Mamet in Read and Okulitch 1977). Present thinking among Western Cordilleran geologists tends toward placing the Chapperon Group in the Late Paleozoic. Okulitch (A. V. Okulitch, persona1 communication, 1979) considers that it may be questionably Mississippian. Although an Ordovician dating is at odds with this thinking, the presumed stratigraphic position with respect to the underlying or possibly coeval Cambro-Ordovician Eagle Bay Formation does allow the possibility of a Late Ordovician age. Acknowledgments The author wishes to thank A. V. Okulitchfor his very helpful comments and criticisms, and B. E. B. Cameron for his attempts at conodont analysis. E. R. Nelson helped in the field when the outcrop was revisited in 1978. J. P. M. Syvitski and D. A. 'Recently, late Middle Ordovician graptolites have been found at the base of the Black Stuart Formation in the Cariboo Mountains. However, this unit is considered to belong more likely with the miogeosynclinal than the eugeosynclinal facies (A. V. Okulitch, persona1 communication, 1979).

Johnston aided in petrographic analysis and X-ray diffraction of rock samples. A. E. Oldershaw examined the fossil structure and commented upon its organic origin. Field and laboratory work was supported by grants from the National Research Council of Canada. J ONES , A. G. 1959. Vernon map area, British Columbia. Geological Survey of Canada, Memoir 296. M ONGER , J. W. H. 1977. Upper Paleozoic rocks of the western Canadian Cordillera and their bearing on Cordilleran evolution. Canadian Journal of Earth Sciences, 14, pp. 1832-1859. N ELSON , S. J. 1963. Ordovician paleontology of northern Hudson Bay Lowland. Geological Society of America, Memoir 90. 1970. The face of time. Alberta Society of Petroleum Geologists. 1975. Paleontological field guides, northern Canada and Alaska. Bulletin of Canadian Petroleum Geology, 23, pp. 428-683, PIS. 1-71. R. G. 1964. N ELSON , S. J., GLAISTER, R. P., and MCCROSSAN, Introduction. In Geological history of western Canada. Edited b y R. G. McCrossan et al. Alberta Society of Petroleum Geologists, pp. 1-13. O KULITCH , A. V., and CAMERON, B. E. B. 1976. stratigraphic revisions of the Nicola. Cache Creek, and Mount Ida Groups, based on conodont collections from the western margin of the Shuswap Metamorphic Complex, south-central British Columbia. Canadian Journal of Earth Sciences, 13, pp. 44-53. READ,P. B., and O KULITCH , A. V. 1977. The Triassic unconformity of south-central British Columbia. Canadian Journal of Earth Sciences, 14, pp. 606-638. READ,P. B., and W HEELER , J. 0. 1977. Lardeau (west half) map area. Geological Survey of Canada, Open File 432. W HEELER , J. 0 . 1966. Eastern tectonic belt of Western Cordillera in British Columbia. In Tectonic history and mineral deposits of the Western Cordillera. Edited b y W. G. Stevenson et al. Canadian Institute of Mining and Metallurgy, Symposium, Special Volume 8, pp. 27-45.

Conodonts from the Davidsville Group, northeastern Newfoundland SVEND STOUGE Minera1 Development Division, Newfoundland Department of Mines and Energy, P.O. Box 4750, St. John's, N j d . , Canada A1C5ï7 Received May 7, 1979 Revision accepted October 12, 1979

Conodonts from the basal part of the Davidsville Group, Botwood Zone of Newfoundland, are assigned a late Llanvim to early Llandeilo age. Other fossil groups suggest a time range of Llanvirn to early Caradoc, and the conodonts are in accordance with the previous datings. The conodont fauna is contemporaneous with that of Cobbs Arm Limestone, central Newfoundland, and no major difference between the two faunas exists. On attribue aux conodontes de la partie basale du groupe de Davidsville, dans la zone de Botwood à Terre-Neuve, un âge qui correspond à la fin du Llanvimien ou au début du Llandeilien. Selon Can. J. Earth Sci., 17,268-272 (1980)

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d'autres groupes de fossiles, l'intervalle de temps irait du Llanvirnien au début du Caradocien et les conodontes s'accorderaient bien avec les datations antérieures. La faune de conodontes est contemporaine de celle du calcaire de Cobbs A m , dans la partie centrale de Terre-Neuve, et il n'existe pas de différences majeures entre les deux faunes. [Traduit par le journal]


Introduction The Davidsville Group is located in the Botwood Zone (Williams et al. 1974) of the Newfoundland Appalachians. The group forms a long northeastsouthwest trending outcrop belt in east-central Newfoundland. It is reported to unconformably overlie the Gander Group at Gander Lake (Kennedy and McGonigal 1972; Kennedy 1975); however, this contact is interpreted as being conformable north of Weir's Pond (Currie and Pajari 1977; Currie et al. 1979) (Fig. 1 ) . The Davidsville Group is characterized by volcaniclastic, clastic sedimentary, and volcanic rocks cut by intrusive granitoid bodies of Devonian age (Bell et al. 1977). The sediments have been interpreted as turbidites, olistostromes, and mass flow deposits (Pickerill et al. 1978). The time span of the Davidsville Group is not known, though its upper part has yielded a Nemagraptus gracilis Zone fauna (Jenness 1958, 1963; Anderson and Williams 1970) or Dicranograptus clingani Zone fauna (Bergstrom et al. 1974) from the Gander Lake area. Jenness (1963) recovered brachiopods of mainly Caradocian age, whereas McKerrow and Cocks (1977) reported on brachiopods, which combined with a fragmenta1 trilobite, indicated an Arenig or Llanvirn age. The overall aspect of the shelly fauna shows an affinity with faunas from Europe. Trace fossils have been observed by Pickerill et al. (1978). A preliminary report on conodonts from the Davidsville Group (Stouge 1979) of Upper Llanvirn to Lower Llandei10 age (Blackwood 1978) supplements the previously reported paleontological data. This note presents a more detailed report on conodont faunas recently recovered from the Davidsville Group, the Middle Ordovician age of which is in accordance with current knowledge of the age of the Davidsville Group. The conodonts show similar affinities to shelly faunas, but the similarity of the Davidsville conodont fauna to the Cobbs Arm fauna of New World Island, central Newfoundland (Fig. l), contrasts with the current interpretation of an important faunal provincial boundary separating the two areas (McKerrow and Cocks 1977).

The Conodont Fauna Two fossiliferous limestone localities occur at

the base of the Davidsville Group at Weir's Pond (Jenness 1958). Conodonts have been recovered from these dark grey limestones (Blackwood 1978; Stouge 1979). This site is approximately 40km northeast (Fig. 1) of the previously reported graptolite locality within the Davidsville Group (Bergstrom et al. 1974). The carbonates Vary from grey calcilutite to calcarenite with bioclasts of crinoids, brachiopods, and gastropods. Inarticulate brachiopods have been found in the acid residues (R. B. Neuman, persona1 communication, 1978). These carbonates are comparable with Cobbs Arm Limestone of New World Island, central Newfoundland. About 10 kg of rock were dissolved in acetic acid (15%) and the residue contained conodont elements. Over 400 specimens were recovered although some samples were barren. The preservation of the fauna varies from fragmentary to well preserved. Al1 the specimens are black in color which is the color alteration index (CAI) (Epstein et al. 1977) of 5, indicating a heating of the host strata from 300°C to approximately 400°C. Most of the elements allow an identification to the generic level, and specific identification of much of the material is possible (Table 1). The fauna is predominantly of North Atlantic Faunal Province affinity, indicative of oceanic environments (Bames and Fghræus 1975). Bergstrom (1971) established a conodont zonation for Middle and Upper Ordovician of this faunal province, that is closely tied to the standard graptolite zonation (Fig. 2). Most samples yielded key species of Pygodus and Eoplacognathus, which allow a precise age determination. The fauna from both localities includes P. serrus, P. sp. cf. P. anserinus (elements with a weakly developed fourth denticle row), Eoplacognathus lindstroemi, E. robustus, Prioniodus sp. cf. P. variabilis, and Periodon aculeatus. The four latter forms dominate the fauna. The remainder of the fauna is comprised mainly of species of simple cone genera. Pygodus serrus, Eoplacognathus lindstroemi, E . robustus are characteristic of the two upper subzones ofthe P. serrus Zone (Bergstrom 1971; Fig. 2). P. sp. cf. P . anserinus is transitional between P. serrus and P. anserinus. Prioniodus prevariabilis evolved into P. variabilis in the middle part of the

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1 Davtdsville C r o u p ,

2 Gander Group.

F

Fossils

FIG.1. Location map. Fossil localities mentioned in the text are labelled F. The new conodont localities from Weir's Pond are underlined.

Pygodus anserinus Zone (Bergstrorn 1971). The species recovered from the Davidsville Group indicate a tirne range within the upper two subzones of P. serrus Zone and into the lower P. anserinus Zone. This corresponds to Glyptograptus teretiusculus graptolite Zone, which is Late Llanvirn or Earl y Llandeilian (Middle Ordovician) (Fig. 2). In terrns of North Arnerican stages it correlates with Chazyan. Discussion McKerrow and Cocks (1977) placed the suture marking the closure of the Iapetus Ocean along the Reach Fault through central Newfoundland. They believed that this suture should have serious irnplications on the distribution of faunas and faunal provincialisrn. In this context, it is interesting to compare the Davidsville fauna with the Cobbs Arrn fauna, as the two localities would be situated on either side of the supposed Iapetus suture. As rnentioned above, the Davidsville fauna is

very sirnilar, even at species level to that of Cobbs Arrn Lirnestone (Bergstrorn et al. 1974) (Table 1). The principal differences are the presence of Appalachignathus and Belodina in the Cobbs Arm Lirnestone, and their absence from the Davidsville Group. The Davidsville fauna includes the Pygodus serrus/P. anserinus zona1 boundary, which lies within the Cobbs Arrn Lirnestone and equivalents in the Appalachians (Bergstrom et al. 1974). Both faunas belong within the North Atlantic Faunal Province. The Cobbs Arm fauna, situated to the West of the proposed major province boundary, and the new data frorn Davidsville Group, on the east side of this line, do not reflect any major differences across the suture of McKerrow and Cocks (1977). Thus, their proposed boundary rnay not be as significant as they surmised since it did not have any effect on the conodontophorid (Le., the conodont-bearing animal).

BRITISH SERIES

BRITISH GRAPTOLITE ZONES

NORTH ATLANTIC CONODONT ZONES

SUBZONES

AMORPHOGNATHUS TVAERENSIS

CARADOCIAN NEMAGRAPTUS GRACILIS

PYGOWS ANSERINUS


LLANDEILIAN

PRIONIODUS VARIABILIS

--- - - - -

UPPER LOWER

- - - - - - -GLYPTOGRAPTUS

EOPLACOGN ATHUS LlNDSTROEMl

TERETIUSCULUS PYGOWS SER RUS

EOPLACOGNATHUS ROBUSTUS

------

zSt&$ --- - - - - - - -- - -

EOPLACOGNATHUS RECLINATUS LLANVlRNlAN

D

I

~

~

o

~

EOPLACOGNATHUS FOLIACEUS

F IG . 2. Correlation of the conodont fauna from the Davidsville Group and Cobbs Arm Limestone with the conodont and graptolite zonations and with the British series (Bergstrom 1971; Bergstrom et al. 1974).

TABLE 1. Conodont species from the Davidsville Group a t Weir's Pond

Multi-element species

Davids- Cobbs ville Arm

Acodus? mutatus (Branson and Mehl) Appalachignathus delicatulus Bergstrom et al. Belodella sp. cf. B. nevadensis (Ethington and Schumacher) Belodina sp. Cornuodus sp. cf. C. longibasis (Lindstrom) Drepanoistodus sp. Drepanoistodus? venustus (Stauffer) Erraticodon? sp. Eoplacognathus lindstroemi Hamar Eoplacognathus robustus (Bergstrom) Panderodus sp. cf. P. gracilis (Branson and Mehl) Periodon aculeatus Hadding Prioniodus prevariabilis Fihræus Prioniodus sp. cf. P. variabilis Bergstrom Prioniodus variabilis Bergstrom Protopanderodus robustus (Hadding) Protopanderodus variocostatus (Sweet and Bergstrom) Pygodus anserinus Lamont and Lindstrom Pygodus sp. cf. P. anserinus L. and L. Pygodus serrus (Hadding) Spinodus spinatus ( ~ a d d i n ~ ) Strachanognathus parvus Rhodes ~ a l l i s e r o d u sethingtoni (Fahræus) Walliserodus sp. Nov. gen. sp. 1 Bergstrom, Riva and Kay Nov. gen. sp. cf. N. gen. flexuosus (Barnes and Poplawski) N OTE: The fauna of the Cobbs A m Limestone, central Newfoundland, is listed for comparison.

Acknowledgements This paper has been published with the permission of the Director, Mineral Development Division, Newfoundland Department of Mines and Energy. F. Blackwood, Minera1 Development Division, has provided samples and offered constructive criticism. J. Hibbard and S. P. Colman-Sadd read earlier drafts of the manuscript. Doreen Peavy typed the manuscript. C. R. Barnes, University of Waterloo, and R. K. Pickerill, University of New Brunswick, reviewed the manuscript. A NDERSON , F.D., and WILLIAMS, H. 1970. Gander Lake (west halo. Geological Survey of Canada, Map 1195A. BARNES,C. R., and FAHRKUS,L. E. 1975. Provinces, communities, and the proposed nektobenthic habit of Ordovician conodonthophorids. Lethaia, 8, pp. 133-149. BELL, K., BLENKINSOP, J., and S TRONG , D. F. 1977. The geochronology of some granitic bodies from eastern Newfoundland and its bearing on Appalachian evolution. Canadian Journal of Earth Sciences, 14, pp. 456-476. BERGSTROM, S. M. 1971. Conodont biostratigraphy of the Middle and Upper Ordovician of Europe and eastern North America. In Symposium on conodont biostratigraphy. Edited by W. C. Sweet and S. M. Bergstrom. Geological Society of America, Memoir 127, pp. 83-161. BERGSTROM, S. M., RIVA, J., and K A Y , M. 1974. Significance of conodonts, graptolites, and shelly faunas from the Ordovician of western and north-central Newfoundland. Canadian Journal of Earth Sciences, 11, pp. 1625-1660. B LACKWOOD , R. F. 1978. Northeastern Gander Zone, Newfoundland. In Report of activities for 1977. Edited by R. V . Gibbons. Newfoundland Department of Mines and.Energy, -. Development Report 78-1' pp. 72-79. C URRIE , K. L., and PAJARI,G . E., J R . 1977. Igneous and


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metamorphic rocks between Rocky Bay and Ragged HarLake and Davidsville Groups of northeastern Newfoundland: bour, northeastern Newfoundland. Report of Activities, Part new 'data and geotectonic implications. Canadian Journal of Earth Sciences, 9, pp. 453-459. A. Geological Suwey of Canada, Paper 77-lA, pp. 341-345. C URRIE , K. L., Pajari, G. E., J R ., and P ICKERILL , R. K. 1979. MCKERROW, W. S., and COCKS,L. R. M. 1977. The location of Tectonostratigraphic problems in the Carmanville area, the Iapetus Ocean suture in Newfoundland. Canadian Journal northeastern Newfoundland. Current Research, Part A. Geoof Earth Sciences, 14, pp. 488-495. logical Suwey of Canada, Paper 79-lA, pp. 71-76. P ICKERILL , R. K., P AJARI , G. E., J R ., C URRIE , K. L., and E P ~ T E I NA., G., EPSTEIN, F. B., and H ARRIS , L. 1977. C O ~ O - B ERGER , A. R. 1978. Carmanville map area, Newfoundland, dont colour alteration - an index to organic metamorphism. the northeastern end of the Appalachians. Current Research, United States Geological Survey, Professional Paper 995, pp. Part A. Geological Survey of Canada, Paper 78-lA, pp. 209-216. 1-27. J ENNESS , S. E. 1958. Geology of the lower Gander River ulSTOUGE,S. 1979. Conodonts from Davidsville Group of the trabasic belt. Geological Suwey of Newfoundland, Report 11. Botwood Zone. Newfoundland. In Report of activities for 58 p. 1978. Edited by R. V . Gibbons. ~ewfoundlandDepartment of 1963. Terra Nova and Bonavista map-areas, NewMines and Energy, Mineral Development Division, Report 79-1, pp. 43-44. foundland. Geological Suwey of Canada, Memoir 327. 184 p. K ENNEDY , M. J. 1975. Repetitive orogeny in the northwestern WILLIAMS, H., K ENNEDY , M. J., and NEALE,E. R. W. 1974. Appalachians - new plate models based upon Newfoundland The northwestward termination of the Appalachian Orogen. examples. Tectonophysics, 28, pp. 39-87. Zn The ocean basins and margins, 2. ~ d i t e d A. b ~E. M. ~ a i r n M. H. 1972. The Gander K ENNEDY , M. J., and MCGONICAL, and F. G. Stehli. Pienum Press, New York, NY, pp. 70-123.

Borings in solitary rugose corals of the Selkirk Member, Red River Formation (late Middle or Upper Ordovician), southern Manitoba ROBERT J. ELIAS Department of Earth Sciences, University of Manitoba, Winnipeg, Man., Canada R3T 2N2 Received June 25,1979 Revision accepted November 1, 1979 Borings occur in solitary rugose corals from the Selkirk Member of the late Middle or Upper Ordovician Red River Formation in southern Manitoba. They are assigned to Dicfyoporus garsonensis n. ichnosp., which was produced by algae, and Trypanites weisei Magdefrau 1932, made by spionid polychaete annelids. Most, and possibly all, boring occurred while the host corals were alive and in life position. The location and relative abundance of borings support interpretations that unattached curved solitary corals lay with the convex cardinal side in the sediment and the concave counter side facing upward during life, whereas straight conical forms were oriented upright in the sediment. These ichnospecies suggest that host corals lived in very shallow marine environments. On retrouve des perforations dans des coraux rugueux solitaires du membre de Selkirk de la formation de Red River datant de la fin de l'ordovicien moyen à supérieur dans le sud du Manitoba. On les attribue à Diciyoporus garsonensis n. ichnosp., qui était produit par des algues, et à Trypanites weisei Magdefrau 1932, produits par des annélides spionides polychètes. Toute ou la plus grande partie de la perforation s'est faite lorsque le corail hôte était vivant et en position vitale. La localisation et l'abondance relative des perforations supportent les interprétations selon lesquelles les coraux solitaires courbés non ancrés reposaient, lorsque vivants, avec leur côté cardinal convexe dans le sédiment et leur côté concave opposé faisant face vers le haut, alors que les formes coniques droites étaient orientées verticalement dans le sédiment. Ces ichnoespèces suggèrent que les coraux hôtes vivaient en milieux marins très peu profonds. [Traduit par le journal] Can. J. Earth Sci., 17,272-277 (1980)

Introduction Solitary rugose corals from the Selkirk Member of the late Middle or Upper Ordovician Red River Formation in southern Manitoba are described by

Elias (in press). The specimens were collected in quarries at Garson, 55 km northeast of Winnipeg. The lowest level in the quarries is 6 m above the base of the member, and a section 8 m thick is

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