Silurian conodont biostratigraphy of the east-central Appalachian Basin (eastern USA): Re-examination of the C.T. Helfrich Collection


Authors: Bancroft AM, Cramer BD

Published in: Bulletin of Geosciences, volume 95, issue 1; pages: 1 - 22; Received 15 February 2019; Accepted in revised form 10 December 2019; Online 7 February 2020

Keywords: Appalachian Basin, Wenlock, Ludlow, Pridoli, conodont biostratigraphy, global zonation, Helfrich collection,

full text (PDF, 7.73 MB)

Export to RIS



The conodont biozonation for the Silurian succession in the Appalachian Basin was established by C.T. Helfrich nearly half a century ago. Herein, we re-examined and updated the taxonomy of the conodont fauna and the consequent biozonation of the upper Rose Hill, Mifflintown, Wills Creek, and lower Tonoloway formations in the east-central Appalachian Basin. While these strata span the upper Telychian Stage (Llandovery Series) to the upper Pridoli Series, a major stratigraphic gap representing most of the Ludlow Series (from the lower part of the Gorstian to the upper part of the Ludfordian stages) was identified. The new conodont biozonation consists of: the Pterospathodus amorphognathoides amorphognathoides Zonal Group, an Unzoned Interval of the Sheinwoodian Stage, the Kockelella walliseri Zonal Group, the Ozarkodina bicornuta Zone, an Unzoned Interval of the Homerian Stage, the Ozarkodina bohemica Interval Zone, the Ozarkodina crispa Zone, and the Ozarkodina eosteinhornensis sensu lato Interval Zone. This refined biozonation permits enhanced global correlation of the Silurian within the east-central Appalachian Basin.


Aldridge, R.J. 1972. Llandovery conodonts from the Welsh Borderland. Bulletin of the British Museum (Natural History) Geology 22, 125-231.

Aldridge, R.J. 1975. The Silurian conodont Ozarkodina sagitta and its value in correlation. Palaeontology 18(2), 323-332.

Aldridge, R.J. 1985. Conodonts of the Silurian System from the British Isles, 68-92. In Higgins, A.C. & Austin, R.L. (eds) A stratigraphical index of conodonts. Ellis Horwood Ltd., Chichester, England.

Aldridge, R.J. & Schönlaub, H.P. 1989. Conodonts, 264-267. In Holland, C.H. & Bassett, M.G. (eds) A global standard for the Silurian System. National Museum of Wales Geological Series No. 9. Cardiff.

Aldridge, R.J. & von Bitter, P. 2009. The Pander Society: a brief history at Forty (1967-2007). Palaeontographica Americana 62, 11-21.

Barrick, J.E. & Klapper, G. 1976. Multielement (late Llandoverian-Wenlockian) conodonts of the Clarita Formation, Arbuckle Mountains, Oklahoma, and phylogeny of Kockelella. Geologica et Palaeontologica 10, 59-100.

Berry, W.B.N. & Boucot, A.J. 1970. Correlation of the North American Silurian rocks. Geological Society of America Special Paper 102, 1-289.View article

Bischoff, G.C.O. 1986. Early and middle Silurian conodonts from Midwestern New South Wales. Courier Forschungsinstitut Senckenberg 89, 1-337.

Branson, E.B. & Mehl, M.G. 1933. Conodonts from the Bainbridge (Silurian) of Missouri, Conodont Studies Number 1. The University of Missiouri Studies: A Quarterly of Research 8, 39-52.

Brett, C.E., Tepper, D.H., Goodman, W.M., Loduca, S.T. & Eckert, B.-Y. 1995. Revised stratigraphy and correlation of the Niagaran Provincial Series (Medina, Clinton and Lockport Groups) in the type area of western New York. United States Geological Survey Bulletin 2086, 1-66.

Calner, M. & Jeppsson, L. 2003. Carbonate platform evolution and conodont stratigraphy during the middle Silurian Mulde Event, Gotland, Sweden. Geological Magazine 140, 173-203.View article

Carls, P., Slavík, L. & Valenzuela-Ríos, J.I. 2007. Revisions of conodont biostratigraphy across the Silurian-Devonian boundary. Bulletin of Geosciences 82, 145-164.View article

Corradini, C. & Serpagli, E. 1999. A Silurian conodont zonation from late Llandovery to end Pridoli in Sardinia. Bollettino della Societa Paleontologica Italiana 38, 255-273.

Corradini, C., Corriga, M.G., Männik, P. & Schönlaub, H.P. 2015. Revised conodont stratigraphy of the Cellon section (Silurian, Carnic Alps). Lethaia 48, 56-71.View article

Corriga, M.G. & Corradini, C. 2009. Upper Silurian and lower Devonian conodonts from the Monte Cocco II section (Carnic Alps, Italy). Bulletin of Geosciences 84, 155-168.View article

Cramer, B.D., Brett, C.E., Melchin, M.J., Männik, P., Kleffner, M.A., McLaughlin, P.I., Loydell, D.K., Munnecke, A., Jeppsson, L., Corradini, C., Brunton, F.R. & Saltzman, M.R. 2011b. Revised correlation of Silurian Provicial Series of North America with global and regional chronostratigraphic units and δ13Ccarb chemostratigraphy. Lethaia 44, 185-202.View article

Cramer, B.D., Kleffner, M.A., Brett, C.E., McLaughlin, P.I., Jeppsson, L., Munnecke, A. & Samtleben, C. 2010. Paleobiogeography, high-resolution stratigraphy and the future of Paleozoic biostratigraphy: Fine-scale diachroneity of the Wenlock (Silurian) conodont Kockelella walliseri. Palaeogeography, Palaeoclimatology, Palaeoecology 294, 232-241.View article

Cramer, B.D., Munnecke, A., Schofield, D.I., Haase, K.M. & Haase-Schramm, A. 2011a. A revised 87Sr/86Sr curve for the Silurian: Implications for global ocean chemistry and the Silurian timescale. Journal of Geology 119, 335-349.View article

Denkler, K.E. & Harris, A.G. 1988a. Conodont-based determination of the Silurian-Devonian boundary in the Valley and Ridge Province, northern and central Appalachians. United Stated Geological Survey Bulletin 1937, B1-B13.

Denkler, K.E. & Harris, A.G. 1988b. Homeognathodus peniculus (Conodonta), a new earliest Pridolian index species, and the Ludlovian-Pridolian boundary in the central Appalachian Basin. United States Geological Survey Bulletin 1937, C1-C10.

Ettensohn, F.R. & Brett, C.E. 2002. Stratigraphic evidence from the Appalachian Basin for continuation of the Taconic Orogeny into early Silurian time. Physics and Chemistry of the Earth 27, 279-288.View article

Goodman, W.M. & Brett, C.E. 1994. Roles of eustasy and tectonics in development of Silurian stratigraphic architecture of the Appalachian foreland basin, 147-169. In Dennison, J.M. & Ettensohn, F.R. (eds) Tectonic and eustatic controls on sedimentary cycles. Society of Economic and Petroleum Mineralogists, Concepts in sedimentology and paleontology 4.View article

Helfrich, C.T. 1972. Silurian conodonts from the Wills Mountain Anticline, Virginia, West Virginia, and Maryland. 402 pp. Ph.D. thesis, Virginia Polytechnic Institute and State University. Blacksburg, Virginia.

Helfrich, C.T. 1975. Silurian conodonts from the Wills Mountain Anticline, Virginia, West Virginia, and Maryland. Geological Society of America Special Paper 161, 1-82.View article

Helfrich, C.T. 1978. A conodont fauna from the Keyser Limestone of Virginia and West Virginia. Journal of Paleontology 52, 1133-1142.

Helfrich, C.T. 1980. Late Llandovery-early Wenlock conodonts from the upper part of the Rose Hill and basal part of the Mifflintown Formations, Virginia, West Virginia, and Maryland. Journal of Paleontology 54, 557-569.

Hibbard, J. 2000. Docking Carolina: Mid-Paleozoic accretion in the southern Appalachians. Geology 28, 127-130.View article

Horvath, A.L. 1969. Relationships of middle Silurian strata in Ohio and West Virginia. The Ohio Journal of Science 69, 321-342.

Jeppsson, L. 1969. Notes on some Upper Silurian multielement conodonts. GFF 91, 12-24.View article

Jeppsson, L. 1997. A new latest Telychian, Sheinwoodian and early Homerican (early Silurian) standard conodont zonation. Transactions of the Royal Society of Edinburgh: Earth Sciences 88, 91-114.View article

Jeppsson, L. 2005. Conodont-based revisions of the Late Ludfordian on Gotland, Sweden. GFF 127, 273-282.View article

Jeppsson, L. & Aldridge, R.J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London 157, 1137-1148.View article

Jeppsson, L., Aldridge, R.J. & Dorning, K.J. 1995. Wenlock (Silurian) oceanic episodes and events. Journal of the Geological Society, London 152, 487-498.View article

Jeppsson, L., Eriksson, M.E. & Calner, M. 2006. A latest Llandovery to latest Ludlow high-resolution biostratigraphy based on the Silurian of Gotland - a summary. GFF 128, 109-114.View article

Jeppsson, L., Talent, J.A., Mawson, R., Simpson, A.J., Andrew, A.S., Calner, M., Whitford, D.J., Trotter, J.A., Sandström, O. & Caldon, H.-J. 2007. High-resolution Late Silurian correlations between Gotland, Sweden, and the Broken River region, NE Australia: Lithologies, conodonts, and isotopes. Palaeogeography, Palaeoclimatology, Palaeoecology 245, 115-137.View article

Kaljo, D., Einasto, R., Martma, T., Märss, T., Nestor, V. & Viira, V. 2015. A bio-chemostratigraphical test of the synchroneity of biozones in the upper Silurian of Estonia and Latvia with some implications for practical stratigraphy. Estonian Journal of Earth Sciences 64, 267-283.View article

Kleffner, M.A. 1989. A conodont-based Silurian chronostratigraphy. Geological Society of America Bulletin 101, 904-912.View article

Kleffner, M.A. 1995. A conodont- and graptolite-based Silurian chronostratigraphy. SEPM Special Publication 53, 159-176.View article

Kleffner, M.A., Barrick, J.E., Ebert, J.R., Matteson, D.K. & Karlsson, H.R. 2009. Conodont biostratigraphy and δ13C chemostratigraphy, and recognition of Silurian/Devonian boundary in the Cherry Valley, New York region of the Appalachian Basin. Palaeontographica Americana 62, 57-73.

Kozłowski, W. 2015. Eolian dust influx and massive whiting during the kozlowski/Lau Event: carbonate hypersaturation as a possible driver of the mid-Ludfordian Carbon Isotope Excursion. Bulletin of Geosciences 90, 807-840.View article

Männik, P. 1998. Evolution and taxonomy of the Silurian conodont Pterospathodus. Palaeontology 41, 1001-1050.

Männik, P. 2007. An updated Telychian (late Llandovery, Silurian) conodont zonation based on Baltic faunas. Lethaia 40, 45-60.View article

Männik, P., Loydell, D.K., Nestor, V. & Nolvak, J. 2015. Integrated Upper Ordovician - lower Silurian biostratigraphy of the Grötlingbo-1 core section, Sweden. GFF 137, 226-244.View article

Mathieson, D., Mawson, R., Simpson, A.J. & Talent, J.A. 2016. Late Silurian (Ludlow) and Early Devonian (Pragian) conodonts from the Cobar Supergroup, western New South Wales, Australia. Bulletin of Geosciences 91, 583-652.View article

McAdams, N.E.B., Cramer, B.D., Bancroft, A.M., Melchin, M.J., Devera, J.A. & Day, J.E. 2019. Integrated δ13Ccarb, conodont, and graptolite Biochemostratigraphy of the Silurian from the Illinois Basin and stratigraphic revision of the Bainbridge Group. GSA Bulletin 131, 335-352.View article

Mergl, M., Frýda, J. & Kubajko, M. 2018. Response of organophosphatic brachiopods to the mid-Ludfordian (late Silurian) carbon isotope excursion and associated extinction events in the Prague Basin (Czech Republic). Bulletin of Geosciences 93, 369-400.View article

Murphy, M.A., Valenzuela-Ríos, J.I. & Carls, P. 2004. On classification of Pridoli (Silurian)-Lochkovian (Devonian) Spathognathodontidae (Conodonts). University of California, Riverside Campus Museum Contribution 6, 1-27.

Nicoll, R.S. & Rexroad, C.B. 1968. Stratigraphy and conodont paleontology of the Salamonie Dolomite and Lee Creek Member of the Brassfield Limestone (Silurian) in southeastern Indiana and adjacent Kentucky. Indiana Department of Natural Resources Geological Survey Bulletin 40, 1-96.

Nowlan, G.S. 1995. Left hand column for correlation charts. Silurian Times 3, 7-8.

Pinet, N. 2016. Far-field effects of Appalachian orogenesis: A view from the craton. Geology 44, 83-86.View article

Pollock, C.A., Rexroad, C.B. & Nicoll, R.S. 1970. Lower Silurian conodonts from northern Michigan and Ontario. Journal of Paleontology 44, 743-764.

Slavík, L. 2014. Revision of the conodont zonation of the Wenlock-Ludlow boundary in the Prague Synform. Estonian Journal of Earth Sciences 63, 305-311.View article

Sullivan, N.B., McLaughlin, P.I., Brett, C.E., Cramer, B.D., Kleffner, M.A., Thomka, J.R. & Emsbo, P. 2016. Sequence boundaries and chronostratigraphic gaps in the Llandovery of Ohio and Kentucky: The record of early Silurian paleoceanographic events in east-central North America. Geosphere 12, 1813-1832.View article

Sweet, W.C. & Bergström, S.M. 1970. The generic concept in conodont taxonomy. North American Paleontological Convention, 1969, Proceedings C, 157-173.

Van Staal, C.R., Zagorevski, A., McNicoll, V.J. & Rogers, N. 2014. Time-transgressive Salinic and Adacian orogenesis, magmatism and Old Red Sandstone sedimentation in Newfoundland. Geoscience Canada 41, 138-164.View article

Viira, V. 1983. Upper Silurian Spathognathodus (Conodonts) from Estonia 41-71. In Klaamann, E. (ed). Palaeontology of early Paleozoic of the East Baltic and Podolia. Academy of Sciences of the Estonian SSR, Institute of Geology. [in Russian with English summary]

Viira, V. & Aldridge, R.J. 1998. Upper Wenlock to Lower Pridoli (Silurian) conodont biostratigraphy of Saaremaa, Estonia, and a correlation with Britain. Journal of Micropalaeontology 17, 33-50.View article

Waid, C.B.T. & Cramer, B.D. 2017a. Global chronostratigraphic correlation of the Llandovery Series (Silurian System) in Iowa, USA, using high-resolution carbon isotope (δ13Ccarb) chemostratigraphy and brachiopod and conodont biostratigraphy. Bulletin of Geosciences 92, 373-390.View article

Waid, C.B.T. & Cramer, B.D. 2017b. Telychian (Llandovery, Silurian) conodonts from the LaPorte City Formation of eastern Iowa, USA (East-Central Iowa Basin) and their implications for global Telychian conodont biostratigraphic correlation. Palaeontologia Electronica 20.2.39A, 1-37.View article

Walliser, O.H. 1964. Conodonten des Silurs. Abhandlungen des Hessischen Landesamtes für Bodenforschung 41, 1-106.