Silurian and Ordovician Conodont Biostratigraphy of the Moose River Basin and Appalachian Basin

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Silurian and Ordovician conodont biostratigraphy of the Moose River Basin and Appalachian Basin

Dissertation

Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University

By Alyssa Marie Bancroft, M.S.

Graduate Program in the Geological Sciences

The Ohio State University 2014

Dissertation Committee

Dr. William I. Ausich, Advisor

Dr. Matthew R. Saltzman

Dr. Mark A. Kleffner

Dr. Stig M. Bergström

Abstract

A robust chronostratigraphic framework must be created to determine how biotic

events are related to the physical and chemical processes occurring in the ocean-

atmosphere system in the lower Paleozoic Era. The integration of high-resolution

biostratigraphy with high-resolution chemostratigraphy provides the scaffolding

necessary to determine the precise order of events during this interval of Earth’s

history. This study includes three separate manuscripts that integrate biostratigraphic

and chemostratigraphic data to provide better correlation than either tool could on its

own.

The second chapter examines a core from the Moose River Basin in Ontario, Canada

13 and utilizes conodont biostratigraphy and carbon (δ Ccarb) isotope chemostratigraphy

to constrain the relative age and generate a chronostratigraphic framework for

Llandovery (Silurian) strata in this cratonic basin. The integration of conodont

13 biostratigraphy and carbon (δ Ccarb) isotope chemostratigraphy permits rock units that

have been studied for more than a century to be correlated.

13 The third chapter examines conodont biostratigraphic and carbon (δ Ccarb) isotope

chemostratigraphic data from a core on the southeastern margin of the Algonquin Arch

along the distal, northwestern margin of the Appalachian Basin. Data from this study

permits the opportunity to correlate lithostratigraphic nomenclature utilized by the

Ontario Geological Survey (OGS) and United States Geological Survey (USGS), and allows

correlation of these Silurian (Llandovery and Wenlock global series) strata with the

Niagaran Provincial Series.

The fourth chapter examines the conodont fauna in the Appalachian Basin in central

Pennsylvania. The conodont species of this fauna are long-ranging, limiting their utility

for global biostratigraphic correlation. Integration of strontium (87Sr/86Sr) isotope

chemostratigraphy permits chronostratigraphic correlation of this fauna limiting it to

the Middle/Upper Ordovician boundary interval.

These chapters together collectively demonstrate the importance of integrating multiple chronostratigraphic tools. Biostratigraphy can provide a unique answer for relative age, but it is often subject to poor yields or regional endemism.

Chemostratigraphy does not provide a unique answer for relative age determination, but is not susceptible to poor yields or regional endemism. The integration of biostratigraphy and chemostratigraphy is an optimal tool for global chronostratigraphic correlation.

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Dedication

for my parents, Eric and Janelle Bancroft with love

and, to Jackson and Aubriana always remember that the word cannot should never exist in your vocabulary chase your dreams

Acknowledgements

I extend my sincerest gratitude to Lennart Jeppsson and his wife, Ann-Sofi, for opening their home to me. The weeks I spent with you both in Lund, Sweden mean the world to me and I will be forever grateful for that time.

For their mentoring, support, and counseling I would like to thank my committee Stig Bergström, Mark Kleffner, Matthew Saltzman, and most sincerely, my advisor, William Ausich (thank you for your patience and for giving me the freedom to discover and learn!). To Loren Babcock, thank you for your friendship, encouragement, and support!

Much of this work (Chapter Three and Chapter Four) was a collaborative effort with Frank Brunton (Ontario Geological Survey, Sudbury), to whom I am sincerely indebted. Thank you for your support and encouragement during the last eight years!

To my second family, Brad Cramer, Kate Tierney-Cramer, and Norman Williams, I would not have completed this endeavor without your friendship, guidance, patience, endless support and encouragement, I love you!

To Stephen Levas and Steven Goldsmith, thank you for your friendship and support, and for keeping me on my toes!

Thanks to Ryan Albee for being so supportive and for keeping a smile on my face during the last few months!

And, last but not least, to Eric and Janelle Bancroft, without whose endless love, support, and encouragement, I would not have even begun this journey, I love you both, thank you for always standing beside me!

Vita

2000 ...... graduated from Mackinaw City Public High School

2006 ...... Bachelor of Science in Biology and Geology Lake Superior State University

2006 through 2008 ...... Graduate Research Associate School of Earth Sciences The Ohio State University

2008 ...... Master of Science in Geology The Ohio State University

2008 through 2009 ...... Graduate Teaching Associate School of Earth Sciences The Ohio State University

2009 through 2010 ...... National Science Foundation GK-12 Fellow The Ohio State University

2010 through 2012 ...... Graduate Teaching Associate School of Earth Sciences The Ohio State University

2012 through 2014 ...... Instructor School of Physical Sciences Lake Superior State University

Publications

Goldsmith, S.T., Trierweiler, A.M., Welch, S.A., Bancroft, A.M., Von Bargen, J.M., and Carey, A.E. 2013. Transforming a university tradition into a geoscience teaching and learning opportunity for the university community. Journal of Geoscience Education, 61(3):280-290. Abstracts

Jarochowska, E., Munnecke, A., Bancroft, A.M., Kozcowski, W., Ray, D.C., Frisch, K., and 13 Castagner, A. 2014. Preliminary conodont, δ Ccarb, and sequence stratigraphy across the Mulde Event (Homerian, middle Silurian) in the carbonate platform environments of Podolia, Ukraine, and Podlasie Basin, E Poland. Annual Meeting of IGCP 591, Tartu, Estonia, Abstracts and Field Guide, p. 46.

Goldsmith, S.T., Bancroft, A.M., Trierweiler, A.M., Welch, S.A., Von Bargen, J.M., and Carey, A.E. 2012. University tradition becomes a geoscience teaching opportunity. GSA Abstracts with Programs, 44(7):447.

Von Bitter, P.H., Bancroft, A.M., and Purnell, M.A. 2012. The Silurian multielement conodont genus Aldridgeodus Jeppsson in North America. GSA Abstracts with Programs, 44(5):2.

Bancroft, A.M., Kleffner, M.A., and Brunton, F.R. 2011. Silurian conodont biostratigraphy and carbonate carbon isotope stratigraphy of the Eramosa, southwestern Ontario, Canada. Meeting of the International Subcommission of Silurian Stratigraphy and Annual Meeting of IGCP 591, Ludlow, UK. Siluria Revisted: Programme and Abstracts, p. 2.

Leslie, S.A., Saltzman, M.R., Repetski, J.E., Bergström, S.M., Seward, A.M., Bancroft, A.M., Howard, A., and Blessing, R.R. 2011. Conodont biostratigraphy and Sr-isotope stratigraphy across the Knox Beekmantown unconformity in the Central Appalachians. GSA Abstracts with Programs, 43(1):74.

Brunton, F.R., Brintnell, C., Brett, C.E., Jin, J., Bancroft, A.M., and Kleffner, M.A. 2009. Update on Early Silurian stratigraphy of eastern Michigan Basin, Niagara Escarpment, southern Ontario. Canadian Paleontology Conference Proceedings, Number 7, p. 13.

Brunton, F.R., Bancroft, A.M., and Kleffner, M. 2009. Revised early Silurian stratigraphy of eastern Michigan Basin, Niagara Escarpment, southern Ontario. Canadian Paleontology Conference Proceedings, Number 6, pp. 15-16.

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Bancroft, A.M., Kleffner, M.A., and Brunton, F.R. 2008. Silurian conodont biostratigraphy 13 and δ Ccarb stratigraphy of the Eramosa Formation, southwestern Ontario, Canada. GSA Abstracts with Programs, 40(5):22.

Fields of Study

Major Field: Geological Sciences

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Table of Contents

Abstract………………………………………………………………………………………………………………………….ii

Dedication……………………………………………………………………………………………………………………..iv

Acknowledgements...... v

Vita………………………………………………………………………………………………………………………………..vi

List of Figures…………………………………………………………………………………………………….……………x

List of Plates………………………………………………………………………………………………………….……..xii

List of Tables………………………………………………………………………………………………………..………xiii

Chapter 1: Introduction…………………………………………….…………………………………………………..1

Chapter 2: Silurian (Llandovery) biochemostratigraphy of the Moose River Basin……..……………………………………………………………………..…….…………15

Chapter 3: Silurian biochemostratigraphy of the Appalachian Basin……………………………53

Chapter 4: Integrated conodont biostratigraphy and strontium (87Sr/86Sr) chemostratigraphy for the Middle/Upper Ordovician System in central Pennsylvania ………………………………………………………………………………..………………95

References………………………………………………………………………………………………………….………113

List of Figures

Figure 1.1. Faunal diversity shown in relationship to 13 carbon (δ Ccarb) isotope excursions documented in the Ordovician and Silurian systems………………………………………………………………..…8

Figure 1.2. Generalized paleogeographic map illustrating the structural basins and arches of northeastern Laurentia during the Ordovician and Silurian periods…………………………………………………………………………………9

Figure 2.1. Generalized paleogeographic map illustrating the structural basins and arches of the Hudson Platform during the Silurian Period…………………………………………………………………………………………………….……34

Figure 2.2. Lower Paleozoic lithostratigraphy of the Hudson Platform…………………………………..…35

Figure 2.3. Conodont zonation for the Llandovery Series of the Silurian System…………………..….36

Figure 2.4. Llandovery (Silurian) conodont zonation and ranges of selected conodont species……………………………………………………………………………..…..37

Figure 2.5. Chronostratigraphic data from the Victor Mine (V-03-270-AH) core……………………….38

Figure 3.1 Generalized paleogeographic map illustrating the structural features of southwestern Ontario, Canada during the Silurian Period………………………………………………………………………………………………………….72

Figure 3.2. North American Silurian chronostratigraphic terms and lithostratigraphic chart – illustrating the relationships between the USGS and the OGS……………………………………………………………………..……73

Figure 3.3 Silurian (Llandovery and Wenlock) conodont zonation and ranges of selected conodont species………………………………………………………………………………....74

Figure 3.4. Chronostratigraphic data from the Ontario Geological Survey (OGS-DDH6-09) core…………………………………………………………………….…75

Figure 4.1. Generalized paleogeographic map illustrating the Appalachian Basin during the Ordovician Period………………………………………………………………105

Figure 4.2. Conodont zonation for the Ordovician System…………………………………………………….106

Figure 4.3. Combined stratigraphic section for the Roaring Spring and Union Furnace sections, conodont species occurrences, and 87Sr/86Sr curve…………………………………………………………………107

List of Plates

Plate 2.1. Conodonts from the Victor Mine (V-03-270-AH) core……………………………………………….39

Plate 3.1. Conodonts from the Ontario Geological Survey (OGS-DDH6-09) core………..…………….76

Plate 4.1. Conodonts from Roaring Spring and Union Furnace……………………………………….….…..108

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List of Tables

Table 2.1. Silurian chronostratigraphy of the Victor Mine (V-03-270-AH) core in the Moose River Basin, Ontario, Canada……………………………………………………………….………………40

Table 3.1. Silurian chronostratigraphy of the Ontario Geological Survey (OGS-DDH6-09) core along the southeastern flank of the Algonquin Arch on the distal, northern margin of the Appalachian Basin in Ontario, Canada………………………….…77

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Chapter 1: Introduction

Historically, the Ordovician and Silurian Periods were considered to be a time of relative climatic stability during an extended greenhouse interval (Berry and Boucot,

1970), interrupted only by the Hirnantian glaciations (Caputo, 1998; Brenchley et al.,

1994; Grahn and Caputo, 1992; Brenchley et al., 2003). However, research during the last two decades has revealed that this interval was one of the most climatically dynamic episodes in Earth’s history, containing the acme and amelioration of the Early

Paleozoic Ice Age (Frakes et al., 1992; Page et al., 2007). The Ordovician and Silurian can be divided into three stages in the evolutionary development of global marine faunas

(Figure 1.1): the Great Ordovician Biodiversification Event (GOBE) (Webby et al., 2004;

Harper, 2006); the late-Ordovician mass extinction (the second-largest of the five

Phanerozoic mass extinctions) (Barnes, 1986; Rong and Chen, 1986; Rong and Harper,

1988; Barnes et al., 1995; Sheehan, 2001a); and the early Silurian post-extinction recovery (Rong and Harper, 1999). The Paleozoic Evolutionary Fauna and the pattern of marine life in the Ordovician and Silurian oceans were established by these faunal changes (Sheehan, 2001b).

The primary objective for this dissertation research is to address and establish a chronostratigraphic framework to further enable future interpretation of how these

biotic events are related to the physical and chemical processes occurring in the ocean

and atmosphere during the Ordovician and Silurian and how these influences are

reflected at the taxonomic level. In order to understand the cause-and-effect

relationships of global planetary change during the Early Paleozoic, these physical,

chemical, and biological events need to be precisely correlated. High-resolution

conodont biostratigraphy, directly integrated with high-resolution carbonate carbon

13 (δ Ccarb) isotope stratigraphy (biochemostratigraphy), provides the chronostratigraphic framework necessary to determine the relationship between the physical and chemical processes that occurred in the ocean-atmosphere system during the Early Paleozoic.

This integrated investigation of the Early Paleozoic Ice Age can also help provide an

analogue for modern global environmental change.

Chronostratigraphy

The use of marine carbonates that preserve the primary marine isotopic signature for

13 carbonate carbon (δ Ccarb) isotope stratigraphy (Munnecke et al., 1997; Bickert et al.,

1997) is a well-established method for correlating Paleozoic strata (Saltzman, 2005;

13 Kaljo and Martma, 2006). Twelve major positive carbonate carbon (δ Ccarb) isotope

excursions serve as chronostratigraphic markers for the Ordovician (Bergström et al.,

2007, 2009, 2010) and Silurian (Cramer et al., 2011) Periods (Figure 1.1). When the

13 signatures of these carbonate carbon (δ Ccarb) isotope excursions are integrated with equally high-resolution biostratigraphy, the Ordovician can be subdivided into twenty

time slices (Bergström et al., 2009), and the Silurian can be subdivided into twenty-four

time slices (Cramer et al., 2011) (Figure 1.1).

Conodont zonation of the Ordovician and Silurian periods has undergone significant

revision in the last forty years, greatly improving the biostratigraphic resolution for this

Early Paleozoic interval. The conodont fauna of the Ordovician was distributed in two

major biogeographic provinces: the North American Midcontinent Province (warm-

water, shallow seas, extending 30° north and south of the equator) and the North

Atlantic Province (cold-water, deep seas, extending poleward from 30° to 40° latitude)

(Sweet and Bergström, 1974, 1976). The early Silurian marked the diminution of provinciality, and conodont faunas during this period were more cosmopolitan than endemic. The highest resolution conodont biostratigraphic zonation for the Early

Paleozoic has been completed on strata from the paleocontinent Baltica (Jeppsson et al., 1995; Jeppsson, 1997; Jeppsson and Aldridge, 2000; Jeppsson and Calner, 2003;

Jeppsson et al., 2006; Männik, 1998, 2007a, 2007b). Yet, with the exception of Anticosti

Island (Munnecke and Männik, 2009), the Early Paleozoic strata in northeastern

Laurentia have not been thoroughly examined since the biozonation was revised, and these conodont faunas need to be re-examined.

Study Area

Global paleogeography of the Ordovician and Silurian periods was characterized by a distribution of several continents at low latitudes (Laurentia, Baltica, Siberia); the supercontinent Gondwana extended from equatorial latitudes to the South Pole; and a

vast polar ocean existed in the northern hemisphere (Munnecke et al., 2010). During

this interval sea-level was higher than any other time in the Paleozoic Era, and extensive

epicontinental seas were widely distributed across the continents (Haq and Schutter,

2008). The primary goal for this project is to construct a high-resolution biochemostratigraphic data set for two major basins on the northeastern margin of the paleocontinent Laurentia: the Appalachian Basin and the Moose River Basin (Figure

1.2).

During the Ordovician and Silurian periods these basins were located south of the equator, between 0°S and 30°S latitude. The Algonquin Arch acted as a structural barrier between the eastern foreland Appalachian Basin and the western intracratonic

Michigan Basin (Johnson et al., 1992), and the Fraserdale Arch acted as a structural barrier between the Michigan Basin and the Moose River Basin to the north (Norris,

1993a, 1993b). Similarities in the facies and faunas indicate that these basins were connected at various intervals during the Early Paleozoic.

Samples were collected from outcrop and core for both conodont biostratigraphy

13 and for carbonate carbon (δ Ccarb) isotope chemostratigraphy. Generating an

integrated high-resolution biochemostratigraphic data set for the Ordovician and

Silurian strata in these basins not only permits a more accurate age determination and regional correlation for these Early Paleozoic strata in northeastern Laurentia, but also facilitates the construction of a more robust global chronostratigraphic framework for this interval in Earth’s history.

Significance

The manuscripts presented herein demonstrate the utility of integrated high- resolution biochemostratigraphy in producing the chronostratigraphic framework necessary to confidently correlate the Ordovician and Silurian strata in the Moose River

Basin and Appalachian basins in northeastern Laurentia to other sections globally. By establishing a chronostratigraphic framework for this interval in Earth’s history it will be possible to begin to determine how the physical and chemical processes occurring in the ocean-atmosphere system influenced the three major biotic events of the Early

Paleozoic (the Great Ordovician Biodiversification Event, the end-Ordovician mass

extinction, and the early Silurian post-extinction recovery), and how these changes

affected the evolutionary development of marine faunas. This interval in Earth’s history

is integral to our understanding of global changes associated with modern climate – the

Early Paleozoic Ice Age is an analogue of similar conditions in a world where

anthropogenic influences were not a factor.

Biostratigraphy is a robust method for chronostratigraphic correlation. However, the

resolution for conodont biostratigraphy is limited by the number of specimens that can

be collected from any given thickness of strata and by endemism of conodont faunas.

Processing conodont samples using refined standard techniques (Jeppsson et al., 1985;

Jeppsson, 1987; Jeppsson and Anehus, 1995, 1999) significantly improves conodont

element yields (specimens per kilogram of sample), enhancing biostratigraphic

resolution and the ability to correlate lithostratigraphic units. The integration of non-

13 biostratigraphic chronostratigraphic tools, specifically carbonate carbon (δ Ccarb)

isotope chemostratigraphy and strontium (87Sr/86Sr) isotope chemostratigraphy, with

conodont biostratigraphy further improves chronostratigraphic resolution.

This document is divided into three chapters (not including Chapter One:

Introduction) dealing with the biochemostratigraphy of two basins in northeastern

Laurentia: the Appalachian Basin and the Moose River Basin. Each chapter represents a

stand-alone manuscript (in preparation for submission). A brief summary of each of

these chapters is discussed below.

Chapter 2

The second chapter examines a core from the Moose River Basin in Ontario, Canada

13 and utilizes conodont biostratigraphy and carbon (δ Ccarb) isotope chemostratigraphy

to constrain the relative age and generate a chronostratigraphic framework for

Llandovery (Silurian) strata in this cratonic basin. The integration of conodont

13 biostratigraphy and carbon (δ Ccarb) isotope chemostratigraphy permits rock units that

have been studied for more than a century to be correlated globally.

Chapter 3

13 The third chapter examines conodont biostratigraphic and carbon (δ Ccarb) isotope

chemostratigraphic data from a core on the southeastern margin of the Algonquin Arch

along the distal, northwestern margin of the Appalachian Basin. Data from this study

permits the opportunity to correlate lithostratigraphic nomenclature utilized by the

Ontario Geological Survey (OGS) and United States Geological Survey (USGS), and allows

correlation of these Silurian (Llandovery and Wenlock series) strata with the Niagaran

Provincial Series.

Chapter 4

The fourth chapter examines the conodont fauna in the Appalachian Basin in central

Pennsylvania. The conodont species of this fauna are long-ranging, limiting their utility

for global biostratigraphic correlation. Integration of strontium (87Sr/86Sr) isotope

chemostratigraphy permits chronostratigraphic correlation of this fauna limiting it to

the Middle/Upper Ordovician boundary interval.

Figures

13 Figure 1.1. Faunal diversity shown in relationship to carbonate carbon (δ Ccarb) isotope excursions documented in the Ordovician and Silurian systems. International subdivisions of the Ordovician and Silurian systems 13 and series dates from Gradstein et al. (2012) with stage slices and carbonate carbon (δ Ccarb) isotope data for the Ordovician from Bergström et al. (2009) and the Silurian from Cramer et al. (2011). Diversity of Cambrian, Paleozoic, and Modern marine evolutionary faunas for the Ordovician and Silurian from Sepkoski (2005) are shown in relation to the Great Ordovician Biodiversification Event (GOBE), the end- Ordovician mass extinction, and the early Silurian post-extinction recovery. 8

Figure 1.2. Generalized paleogeographic map illustrating the structural basins and arches of northeastern Laurentia during the Ordovician and Silurian periods. The localities sampled for both conodont biostratigraphy 13 and carbonate carbon (δ Ccarb) isotope stratigraphy are shown ( ): from the Appalachian Basin in central Pennsylvania, the New Enterprise Quarry at Roaring Spring and the Union Furnace roadcut (Route 453); from the Moose River Basin in northern Ontario, the Victor Mine (V-03-270-AH) core; and from the Ontario Geological Survey (OGS-DDH-6-09) core along the southeastern flank of the Algonquin Arch along the distal, northern margin of the Appalachian Basin in Ontario, Canada (map modified from Norris, 1993a, 1993b). 9

References

Barnes, C.R. 1986. The faunal extinction event near the Ordovician-Silurian boundary: A climatically induced crisis. In Global bio-events: A critical approach. Edited by O.H. Walliser. Lecture Notes in Earth Sciences, 8, Springer-Verlag, Berlin, Germany, pp. 121-126.

Barnes, C.R., Fortey, R.A., and Williams, H. 1995. The pattern of global bio-events during the Ordovician Period. In Global Events and Event Stratigraphy in the Phanerozoic. Edited by O.H. Walliser, pp. 139-172.

Bergström, S.M., Chen, X., Gutiérrez-Marco, J.C., and Dronov, A. 2009. The new chronostratigraphic classification of the Ordovician System and its relations to major regional series and stages and to δ13C chemostratigraphy. Lethaia, 42(1):97-107.

Berry, W.B.N. and Boucot, A.J. 1970. Correlation of the North American Silurian rocks. Geological Society of America, Special Paper 102, 289 pp.

Bickert, T., Pätzold, J. Samtleben, C., and Munnecke, A. 1997. Paleoenvironmental changes in the Silurian indicated by stable isotopes in brachiopod shells from Gotland, Sweden. Geochimica et Cosmochimica Acta, 61(13):2717-2730.

Brenchley, P.J., Carden, G.A., Hints, L., Kaljo, D., Marshall, J.D., Martma, T., Meidla, T., and Nõlvak, J. 2003. High-resolution stable isotope stratigraphy of Upper Ordovician sequences: Constraints on the timing of bioevents and environmental changes associated with mass extinction and glaciations. Geological Society of America, Bulletin, 115(1):89-104.

Brenchley, P.J., Marshall, J.D., Carden, G.A.F., Robertson, D.B.R., Long, D.G.F., Meidla, T., Hints, L., and Anderson, T.F. 1994. Bathymetric and isotopic evidence for a short-lived Late Ordovician glaciations in a greenhouse period. Geology, 22(4):295-298.

Caputo, M.V. 1998. Ordovician-Silurian glaciations and global sea-level changes. In Silurian Cycles: Linkages of dynamic stratigraphy with atmospheric, oceanic, and tectonic changes. Edited by E. Landing and M.E. Johnson. New York State Museum Bulletin 491, pp. 15-25.

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., and Saltzman, M.R. 2011. Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and δ13C chemostratigraphy. Lethaia, 44(2):185-202. 10

Frakes, L.A., Francis, J.E., and Syktus, J.I. 1992. Climate modes of the Phanerozoic. Cambridge University Press, Cambridge, 274 pp.

Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M. 2012. The Geologic Time Scale 2012. Elsevier, 1176 pp.

Grahn, Y.G. and Caputo, M.V. 1992. Early Silurian glaciations in Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology, 99(1-2):9-15.

Haq, B.U. and Schutter, S.R. 2008. A chronology of Paleozoic sea-level changes. Science, 322(5898):64-68.

Harper, D.A.T. 2006. The Ordovician biodiversification: Setting an agenda for marine life. Palaeogeography, Palaeoclimatology, Palaeoecology, 232(2-4):148-166.

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

Jeppsson, L. 1987. Some thoughts about future improvements in conodont extraction methods. In Conodonts: Investigative techniques and applications. Edited by R.L. Austin. Ellis Horwood Ltd., Chichester, England, pp. 35, 45-51, 52, 53.

Jeppsson, L. and Aldridge, R.J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London, 157(6):1137-1148.

Jeppsson, L. and Anehus, R. 1999. The optimal acetate buffered acetic acid technique for extracting phosphatic fossils. Journal of Paleontology, 73(5):964-972.

Jeppsson, L. and Anehus, R. 1995. A buffered formic acid technique for conodont extraction. Journal of Paleontology, 69(4):790-794.

Jeppsson, L. and Calner, M. 2003. The Silurian Mulde Event and a scenario for secundo- secundo events. Transactions of the Royal Society of Edinburgh: Earth Sciences, 93(2):109-114.

Jeppsson, L., Aldridge, R.J., and Dorning, K.J. 1995. Wenlock (Silurian) oceanic episodes and events. Journal of the Geological Society, London, 152(3):487-489.

Jeppsson, L., Eriksson, M.E., and Calner, M. 2006. A latest Llandovery to latest Ludlow high-resolution biostratigraphy based on the Silurian of Gotland—A summary. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):109-114. 11

Jeppsson, L., Fredholm, D., and Mattiasson, B. 1985. Acetic acid and phosphatic fossils— A warning. Journal of Paleontology, 59(4):952-956.

Johnson, M.D., Armstrong, D.K., Sanford, B.V., Telford, P.G., and Rutka, M.A., 1992. Paleozoic and Mesozoic geology of Ontario. In geology of Ontario. Edited by P.C. Thurston, H.R. Williams, R.H. Sutcliffe, and G.M. Stott. Ontario Geological Survey, Special Volume 4(2), pp. 907-1008.

Kaljo, D. and Martma, T. 2006. Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):123-129.

Männik, P. 2007a. An updated Telychian (late Llandovery, Silurian) conodont zonation based on Baltic faunas. Lethaia, 40(1):45-60.

Männik, P. 2007b. Recent developments in the upper Ordovician and lower Silurian conodont biostratigraphy in Estonia. Estonian Journal of Earth Sciences, 5(1):35-46.

Männik, P. 1998. Evolution and taxonomy of the Silurian conodont Pterospathodus. Palaeontology, 41(5):1001-1050.

Munnecke, A. and Männik, P. 2009. New biostratigraphic and chemostratigraphic data from the Chicotte Formation (Llandovery) on Anticosti Island (Québec, Canada). Estonian Journal of Earth Science, 58(3):159-169.

Munnecke, A., Calner, M., Harper, D.A.T., and Servais, T. 2010. Ordovician and Silurian sea water chemistry, sea level, and climate: A synopsis. Palaeogeography, Palaeoclimatology, Palaeoecology, 296(3-4):389-413.

Munnecke, A., Westphal, H., Reijmer, J.J.G., and Samtleben, C. 1997. Microspar development during early marine burial diagenesis: A comparison of Pliocene carbonates from the Bahamas with Silurian limestones from Gotland (Sweden). Sedimentology, 44(6):977-990.

Norris, A.W. 1993a. Hudson Platform – Introduction, Chapter 7. In Sedimentary Cover of the Craton in Canada. Edited by D.F. Stott and J.D. Aitken. Geological Survey of Canada, Geology of Canada 5, pp. 643-651.

Norris, A.W. 1993b. Hudson Platform – Geology, Chapter 8. In Sedimentary Cover of the Craton in Canada. Edited by D.F. Stott and J.D. Aitken. Geological Survey of Canada, Geology of Canada 5, pp. 653-700.

Page, A., Zalasiewicz, J., Williams, M., and Popov, L. 2007. Were transgressive black shales a negative feedback modulating glacioeustasy in the Early Paleozoic Icehouse? In Deep-time perspectives on climate change: Marrying the signal from computer models and biological proxies. Edited by M. Williams. A.M. Haywood, F.J. Gregory, and D.N. Schmidt. Special Publication of the Geological Society of London, The Micropalaeontological Society, pp. 123-156.

Rong, J.-Y. and Chen, X. 1986. A big event of latest Ordovician in China. In Global bio- events: A critical approach. Edited by O.H. Walliser. Lecture Notes in Earth Sciences, 8, Springer-Verlag, Berlin, Germany, pp. 127-131.

Rong, J.-Y. and Harper, D.A.T. 1988. A global synthesis of the latest Ordovician Hirnantian brachiopod faunas. Transactions of the Royal Society of Edinburgh: Earth Sciences, 79:383-402.

Rong, J.-Y. and Harper, D.A.T. 1999. Brachiopod survival and recovery from the latest Ordovician mass extinctions in South China. Geological Journal, 34(4):321-348.

Saltzman, M.R. 2005. Phosphorus, nitrogen, and the redox evolution of the Paleozoic oceans. Geology, 33(7):573-576.

Sepkoski, J.J. 1995. The Ordovician radiations: Diversification and extinction shown by global genus-level taxonomic data. In Ordovician Odyssey: Short Papers for the Seventh International Symposium on the Ordovician System. Edited by J.D. Cooper, M.L. Droser, and S.C. Finney. Pacific Section SEPM, Fullerton, California, USA, pp. 393- 396.

Sheehan, P.M. 2001a. The late Ordovician mass extinction. Annual review of Earth and Planetary Sciences, 29:331-364.

Sheehan, P.M. 2001b. History of marine biodiversity. Geological Journal, 36(3-4):231-249.

Sweet, W.C. and Bergström, S.M. 1976. Conodont biostratigraphy of the Middle and Upper Ordovician of the United States Midcontinent. In The Ordovician System: Proceedings of a Palaeontological Association Symposium. Edited by M.G. Bassett. Cardiff, University of Wales Press and National Museum of Wales, pp. 121-151.

Sweet, W.C. and Bergström, S.M. 1974. Provincialism exhibited by Ordovician conodont faunas. In Paleogeographic Provinces and Provinciality. Edited by C.A. Ross. Society of Economic Paleontologists and Mineralogists, Special Publication 21, pp. 189-202.

Webby, B.D., Cooper, R.A., Bergström, S.M., and Paris, F. 2004. Stratigraphic framework and time slices. In The Great Ordovician Biodiversification Event. Edited by B.D. Webby, M.L. Droser, F. Paris, F., and I.Percival. 2004. Columbia University Press, New York, pp. 41-47.

Chapter 2: Silurian (Llandovery) biochemostratigraphy of the Moose River Basin

Abstract

The Moose River Basin in Ontario, Canada contains nearly one kilometer of Silurian marine strata. Whereas it has been studied for more than a century, its precise correlation globally has not been constrained. A core (V-03-270-AH) from the Victor

Mine in the Moose River Basin is examined for biostratigraphy of conodonts and

13 carbonate carbon (δ Ccarb) isotope chemostratigraphy to constrain the relative age and generate a detailed chronostratigraphic framework for the strata in the Moose River

Basin. The presence of Icriodella sp., Aspelundia expansa, Ozarkodina gulletensis,

Distomodus staurognathoides, Aspelundia fluegeli fluegeli, Pterospathodus sp.,

Aulacognathus bullatus, and the lower and upper Aeronian positive carbonate carbon

13 (δ Ccarb) isotope excursions permit precise chronostratigraphic correlation of the

Llandovery strata in this cratonic basin.

Introduction

The Hudson Platform, in the central part of the Canadian Shield, consists of two cratonic sedimentary basins: the Hudson Bay Basin and the Moose River Basin separated by a Precambrian basement high, the Cape Henrietta Maria Arch (Patricia

Arch of Nelson and Johnson, 1966) (Sanford et al., 1968). Silurian stratigraphy of the

15 region was summarized by Norris (1993a, 1993b) and Sanford et al. (1993), and the stratigraphy was correlated with other regions across Canada by Norford (1997).

Detailed stratigraphic studies of the Silurian succession in the Hudson Platform include conodont biostratigraphy, brachiopod biostratigraphy, and sequence stratigraphy (Le

Fèvre et al., 1976; Zhang and Barnes, 2007; Jin et al., 1993; Suchy, 1992; Suchy and

Stearn, 1992). However, the relative age and regional lithostratigraphic relationships of these Silurian units have not been constrained precisely.

Historically, the Silurian was considered to be a period of relative climatic stability during a greenhouse interval that was characterized by high global sea-level, stable environmental conditions, and cosmopolitan faunas (Berry and Boucot, 1970).

However, research during the last two decades suggests that the ocean-atmosphere system was highly volatile during this period of Earth’s history, and changes in the global carbon cycle were more frequent during the Silurian than any other period of the

Paleozoic Era. The Llandovery was affected by the last three glacial maxima of the Early

Paleozoic Icehouse: early Aeronian, late Aeronian, and early Telychian (Grahn and

Caputo, 1992; Frakes et al., 1992; Caputo, 1998; Page et al., 2007). In parallel, three

13 positive carbonate carbon (δ Ccarb) isotope excursions have been documented in the

Llandovery, although they are not yet well-constrained globally: early Aeronian, late

Aeronian, and (Valgu) early Telychian (each approximately +2.0‰ change) (Kaljo and

Martma, 2000; Kaljo et al., 2003; Põldvere, 2003; Melchin and Holmden 2006;

Munnecke and Männik, 2009). Significant improvements have been made to Silurian

16 chronostratigraphic correlation in the last decade and integrated biostratigraphy and

13 carbonate carbon (δ Ccarb) isotope stratigraphy (biochemostratigraphy) have created a high-resolution framework enabling Silurian strata to be globally correlated (Cramer et al., 2011).

Geologic Background

Paleogeography

The Hudson Platform (central Canadian Shield) was located in the tropical climate belt during the Silurian Period (Figure 2.1) at low latitudes (between 0°S and 10°S) just south of the equator on the northeastern margin of the paleocontinent Laurentia.

Sediment deposition and faunal distribution during this time were controlled by a northeast-trending Precambrian basement high, the Cape Henrietta Maria Arch (Patricia

Arch of Nelson and Johnson, 1966), which separated two cratonic, sedimentary basins: the Hudson Bay Basin (northwest) and the Moose River Basin (southeast) (Norris,

1993b). The Victor Mine (V-03-270-AH) core is located in the north-central part of the

Moose River Basin, in Ontario, Canada (Figure 2.1).

Chronostratigraphy

The Silurian stratigraphic succession of the Hudson Platform (Savage and Van Tuyl,

1919) consists of the Severn River, Ekwan River, and Attawapiskat formations, in ascending order (Figure 2.2). The Severn River Formation disconformably overlies the

Red Head Rapids Formation, and this disconformity has been interpreted to represent either an interval containing the missing Ordovician-Silurian boundary (Sanford et al.,

1968; Norris and Sanford, 1969; Norford, 1970, 1988; Suchy and Stearn, 1993; Jin et al.,

1993) or an interval of missing lower Llandovery strata (Le Fèvre et al., 1976; Norris,

1993b; Jin et al., 1993). A second disconformity between the Severn River Formation

and overlying Ekwan River Formation has also been recognized, but the extent of the

missing stratigraphic interval has not been constrained (Suchy and Stearn, 1992).

Le Fèvre et al. (1976) proposed four provisional conodont assemblage zones and one

formal conodont zone for the Silurian succession of the Hudson Platform. Zhang and

Barnes (2007) provided the most recent conodont biostratigraphic data for the Hudson

Platform and erected three interval zones and one assemblage zone. During the last

two decades there have been significant revisions to the taxonomy and ranges of

conodonts used for biostratigraphic zonation of the lower Silurian (Figure 2.3), and

these zonations will be used throughout this manuscript (Männik, 1998, 2007a, 2007b).

13 Carbonate carbon (δ Ccarb) isotope chemostratigraphy has become a robust method for high-resolution global correlation of Silurian strata (Melchin et al., 2012). Three

13 positive carbonate carbon (δ Ccarb) isotope excursions have been documented from

Llandovery strata that are useful for global correlation: lower Aeronian, upper

Aeronian, and the lower Telychian (Valgu) excursions. Each of these excursions has

been documented from multiple paleobasins (Kaljo and Martma, 2000; Kaljo et al.,

2003; Põldvere, 2003; Melchin and Holmden 2006; Munnecke and Männik, 2009).

Previously, no chemostratigraphic data were known from the Moose River Basin.

Methods

Silurian strata from the Victor Mine (V-03-270-AH) core (strata in ascending order:

Severn River, Ekwan River, and Attawapiskat formations) in the Moose River Basin in

Ontario, Canada were sampled for conodont biostratigraphy and carbonate carbon

13 (δ Ccarb) isotope chemostratigraphy.

Biostratigraphic Methodology

For nearly one century the acetic acid residue method has been used to extract

conodont elements (carbonate fluorapatite – francolite) from carbonate lithologies

(Graves and Ellison, 1941). Using controlled experiments, Jeppsson determined that most conodont elements were damaged or destroyed using this method and introduced new techniques for conodont extraction that not only enhanced the yield (specimens per kilogram) but also prevented the etching of elements (Jeppsson et al., 1985;

Jeppsson 1987; Jeppsson and Anehus, 1995, 1999). Conodont samples processed in this study (between five hundred grams and two kilograms) utilized these refined standard techniques (Jeppsson et al., 1985; Jeppsson and Anehus, 1995, 1999), which significantly improved element yields and enhanced biostratigraphic resolution and hence the ability

to correlate lithostratigraphic units.

Chemostratigraphic (Stable Isotope) Methodology

13 The primary marine carbon isotopic δ Ccarb signature is well-preserved in marine

carbonates (Munnecke et al., 1997; Bickert et al., 1997; Saltzman and Thomas, 2012),

13 and the utility of carbonate carbon (δ Ccarb) isotope excursions (chemostratigraphy) has

been demonstrated to be a valuable method for global chronostratigraphic correlation

(Saltzman, 2005; Saltzman and Thomas, 2012), especially when combined with equally

high-resolution biostratigraphy (Kaljo et al., 1998; Kaljo et al., 2003; Munnecke et al.,

2003; Calner et al., 2004; Porębska et al., 2004; Cramer et al., 2006a; Cramer et al.,

13 2006b; Kaljo and Martma, 2006; Bergström et al., 2012). All carbonate carbon (δ Ccarb)

isotope samples collected from the Victor Mine (V-03-270-AH) core were micro-drilled

from micritic matrix (Saltzman, 2002) and sent to the University of Kansas W.M. Keck

Paleoenvironmental and Environmental Stable Isotope Laboratory (KPESIL) for analysis.

Samples were measured (20 μg to 80 μg) and heated under vacuum at 200°C for one

hour to release any volatile organic compounds. To dissolve the carbon of calcite,

carbonate powders were reacted under vacuum with three drops of prepared 100%

phosphoric acid for four minutes (or reacted for twelve minutes to dissolve the carbon

of dolomite) at 75°C using a Kiel Carbonate Device III, and the carbon dioxide (CO2)

released was trapped cryogenically and transferred to a Finnigan MAT253 isotope ratio

mass spectrometer for analysis. Data are reported using the per mil (‰) notation relative to the Vienna Pee Dee belemnite (VPDB) standard (Craig, 1957). Precision and calibration of data were monitored through routine analysis of National Bureau of

Standards – NBS-18 and NBS-19 and an internally calibrated calcite standard.

Reproducibility for values obtained was checked by replicate analysis of laboratory standards and typically yield an R2 value of 0.9995 or better.

Results

From the Victor Mine (V-03-270-AH) core in the Moose River Basin, twenty-two samples were collected and processed for conodont biostratigraphy (Jeppsson, 1985,

1987; Jeppson and Anehus, 1995, 1999) and two hundred and thirty-four samples were

13 collected and processed for carbonate carbon (δ Ccarb) isotope stratigraphy at the

University of Kansas (KPESIL). Biostratigraphically useful species include: Icriodella sp. from the Severn River Formation (Plate 2.1, Figure 2.5); Aspelundia expansa from the

Ekwan River Formation (Plate 2.1, Figure 2.5); and Ozarkodina gulletensis, Aspelundia fluegeli fluegeli, Distomodus staurognathoides, Pterospathodus sp., and Aulacognathus bullatus from the Attawapiskat Formation (Plate 2.1, Figure 2.5). Carbonate carbon

13 (δ Ccarb) isotope values within the core varied from -4.7‰ to +3.0‰ with a baseline

near -1.0‰ (Table 2.1, Figure 2.5). The data appear to record three low-magnitude

13 carbonate carbon (δ Ccarb) isotope excursions within the Ekwan River Formation at

approximately 170 m, 150 m, and 135 m, with total magnitude changes of +4.0‰,

+5.0‰, and +3.5‰, respectively.

Discussion

Silurian strata of the Hudson Platform were previously assigned to the Llandovery

Series, but stage designations remained tentative (Le Fèvre et al., 1976; Norris, 1993b;

Norford, 1997; Zhang and Barnes, 2007). The biochemostratigraphic framework

generated by this study, which included integrated conodont biostratigraphy and

13 carbonate carbon (δ Ccarb) isotope stratigraphy for the samples studied from the Victor

Mine (V-03-270-AH) core in the Moose River Basin, further constrains the relative ages and the magnitudes of the disconformities between these units (Figure 2.5). A discussion of each formation in the sampled interval of the core is included below.

Severn River Formation

The Severn River Formation was previously interpreted to disconformably overlie the

Red Head Rapids Formation (Sanford et al., 1968; Norris and Sanford, 1969; Norford,

1970, 1988; Le Fèvre et al., 1976; Suchy and Stearn, 1993; Jin et al., 1993; Norris et al.,

1993b; Zhang and Barnes, 2007). This disconformity was interpreted to represent the

Ordovician-Silurian boundary interval, which was a global sea-level low (e.g. Munnecke et al., 2010). Norford (1997) assigned the Severn River to the Rhuddanian through lower Telychian stages based on the nautiloid cephalopod Dicosorus-Huronia fauna

(Flower and Teichert, 1957; Flower, 1968). This designation is problematic because the

Discosorus-Huronia fauna is of limited utility as a high-resolution biostratigraphic tool.

The recovery of Icriodella sp. from this study potentially permits the Severn River

Formation to be globally correlated. Species of the genus Icriodella Rhodes, 1953 are known globally in the Silurian (Nicoll and Rexroad, 1968; Pollock et al., 1970; Rexroad and Nicoll, 1971; Aldridge, 1972; Aldridge, 1975; Cooper, 1975); however the species of this genus range from the Upper Ordovician Series through the Llandovery Series

(Silurian). Elements of the genus Icriodella recovered from this study have well- preserved anterior processes, but the posterior processes are broken, and as a result species designation within the genus Icriodella for this study is tentative. It is possible

that the Icriodella species recovered from the Severn River Formation could be assigned

to the Distomodus kentuckyensis Zone (Rhuddanian Stage) of Männik (2007b; see Figure

2.4); however, based on conodont elements recovered from the present study, such a

designation is not definitive.

Ekwan River Formation

The Ekwan River Formation was interpreted to disconformably overlie the Severn

River Formation (Suchy and Stearn, 1992) and was assigned to the Telychian Stage by

Norford (1997) based on the presence of the stromatoporoid Pseudolabechia, which

also occurs in the Upper Visby Formation of Gotland, Sweden (Larsson and Stearn,

1986). The base of the Ekwan River Formation within the core cannot be constrained

precisely by this study. However, from the middle and upper portions of the Ekwan

13 River Formation three low-magnitude positive carbonate carbon (δ Ccarb) isotope

excursions are recorded at approximately 170 m, 150 m, and 135 m (total magnitude

changes of +4.0‰, +5.0‰, and +3.5‰, respectively). There is no biostratigraphically

13 useful conodont data associated with the first low-mangitude positive carbon (δ Ccarb)

isotope excursion recorded at approximately 170 m within the core. The second low-

13 magnitude positive carbon (δ Ccarb) isotope excursion recorded at approximately 150 m

within the core occurs within a succession of Ekwan River strata that yields the

conodont Aspelundia expansa. No biostratigraphically useful conodont data is

13 associated with the third low-magnitude positive carbon (δ Ccarb) isotope excursion at

approximately 135 m within the core, however Aspelundia expansa was recovered from

strata just below the excursion and Ozarkodina gulletensis was recovered from strata just above the excursion. Based on the ranges of Aspelundia expansa and Ozarkodina gulletensis (Figure 2.4) it is likely that these three excursions could possibly represent the lower Aeronian, upper Aeronian, and lower Telychian (Valgu) positive carbon

13 (δ Ccarb) isotope excursions, respectively. However, at this time limited conodont

biostratigraphic data (specifically, the lack of the recovery of Pterospathodus eopennatus) prevents any of these excursions from being positively identified. Based on

13 the limited conodont biostratigraphic data and the carbon isotope (δ Ccarb)

chemostratigraphic data from this study, the Ekwan River Formation in this core is most

likely limited to the Aeronian Stage and potentially the lower Telychian Stage (Figure

2.5), but further conodont biostratigraphic data is necessary to definitively determine the stage designation of this lithostratigraphic unit.

Attawapiskat Formation

The Attawapiskat Formation was previously interpreted to span the late Telychian

(Llandovery) to early Sheinwoodian (Wenlock) stages based upon nautiloid cephalopod and trilobite faunas (Norford, 1997). Ozarkodina gulletensis was recovered from the base of the Attawapiskat Formation in the present study. This demonstrates that the base of the Attawapiskat Formation in the core correlates to a position no lower than the Upper Pterospathodus eopennatus ssp. n. 2 Subzone of the Telychian Stage and no higher than the Lower Pterospathodus amorphognathoides angulatus Subzone. The assignment of the uppermost Ekwan River Formation in this core combined with base of

the Attawapiskat Formation being limited to the Upper Pterospathodus eopennatus ssp.

n. 2 Subzone indicates that there is likely a disconformity between these two formations

(missing Pterospathodus eopennatus ssp. n. 1 Zone and the Lower Pterospathodus

eopennatus ssp. n. 2 Subzone). This interpretation is further supported by the fact that

Pterospathodus eopennatus was not recovered. Seventy meters above the base of the

Attawapiskat Formation in the core, the presence of Aspelundia fluegeli fluegeli,

Distomodus staurognathoides, Pterospathodus sp., and Aulacognathus bullatus, limit this position of this lithostratigraphic unit to no higher than the Lower Pterospathodus amorphognathoides angulatus Subzone, still within the lower Telychian Stage. The only pterospathodid species that Aulacognathus bullatus co-occurs with is Pterospathodus amorphognathoides angulatus within the Lower Pterospathodus amorphognathoides angulatus Subzone (Männik, 1998, 2007a, 2007b). The co-occurrence of all four of these species limit this interval of the Attawapiskat to the Lower Pterospathodus amorphognathoides angulatus Subzone of Männik (1998, 2007a, 2007b) and the

Telychian Stage. No biostratigraphically useful conodonts were recovered from the upper portion of the Attawapiskat Formation (upper fifty meters) within the core, and as a result the present study cannot constrain the chronostratigraphic correlation of this

13 interval. However, the carbonate carbon (δ Ccarb) isotope values steadily increase up-

section within the Attawapiskat Formation until values reach nearly +3.0‰ at the top of

13 the core. Based on global carbon (δ Ccarb) isotope chemostratigraphic data (Cramer et

al., 2010; Cramer et al., 2011) these values may indicate that the upper part of the

Attawapiskat Formation in the core belongs to the uppermost Telychian Stage.

Regional Correlation

The most recent chronostratigraphic study of the Hudson Platform was completed by

Zhang and Barnes (2007). Their study was based on a series of core and cuttings that ranged from one foot spacing to one hundred and twenty foot spacing, depending on the core studied. The wide spacing and potential for down-hole caving contamination limit the utility of data recovered from the cuttings. A discussion of their findings compared with data from the Victor Mine (V-03-270-AH) core in the Moose River Basin is presented herein.

The Severn River Formation was assigned to the Rhuddanian through lower Telychian stages by Zhang and Barnes (2007) based on the presence of the conodonts Ozarkodina elibata, Kockelella? trifucata, Aspelundia expansa, Aspelundia fluegeli fluegeli,

Distomodus staurognathoides, Pterospathodus eopennatus, Pterospathodus celloni,

Pterospathodus amorphognathoides angulatus, and Aulacognathus bullatus. Based on these occurrences the Severn River Formation was assigned to the Ozarkodina elibata

Interval Zone, Kockelella? trifucata Interval Zone, Distomodus staurognathoides Interval

Zone, and the Pterospathodus celloni—eopennatus Assemblage Zone. The Ozarkodina elibata fauna is provincial and has not been recognized outside North America (Pollock et al., 1970; Le Fèvre et al., 1976; Zhang and Barnes, 2007). Similarly the zone based on the eponymous species has never been used globally. Kockelella? trifurcata has only

been recovered from strata in the Hudson Platform, and its use as a zonal indicator has

not been applied outside the region. Zhang and Barnes (2007) placed the base of the

Distomodus staurognathoides Interval Zone at the first appearance of the nominative

species, which is consistent with Männik (1998, 2007a, 2007b). The base of the

overlying Pterospathodus celloni—eopennatus Assemblage Zone of Zhang and Barnes

(2007) was defined by the first appearance of any of the key species within the assemblage: Pterospathodus celloni, Pterospathodus eopennatus, Pterospathodus

amorphognathoides angulatus, and Aulacognathus bullatus. Männik (1998, 2007a,

2007b) divided this interval into three discrete zones: Pterospathodus eopennatus ssp.

n. 1, Pterospathodus eopennatus ssp. n. 2, and Pterospathodus amorphognathoides

angulatus, the bases of which are defined by their nominative species. Zhang and

Barnes (2007) suggested that the zones of Pterospathodus eopennatus ssp. n. 1,

Pterospathodus eopennatus ssp. n. 2, and Pterospathodus amorphognathoides

angulatus could not be identified in the Hudson Platform due to the inability to separate the Pterospathodus eopennatus Superzone from the Pterospathodus celloni Superzone.

This conclusion was not based on direct co-occurrences of the nominative species but, rather, due to the presence of Pterospathodus eopennatus in a cutting sample from a depth of 777.20 meters to 792.50 meters and of Apsidognathus tuberculatus in core sample from 777.20 meters from the same well, indicating that these two species occur in close proximity. They argued that the first appearance of Apsidognathus tuberculatus is the same as Pterospathodus celloni globally (Zhang and Barnes, 2007). The range of

Apsidognathus tuberculatus has been significantly lowered by Männik (1998, 2007a,

2007b) to the base of Pterospathodus eopennatus spp. n. 1 Zone.

If the occurrences presented by Zhang and Barnes (2007) do not represent down-

hole caving contamination, then the Severn River Formation extends from the

Distomodus kentuckyensis zone through the Pterospathodus amorphognathoides

angulatus Zone, which would represent all of the Rhuddanian Stage, all of the Aeronian

Stage, and the lower third of the Telychian Stage. Undoubtedly, at least some part of

the Severn River Formation is within the Distomodus kentuckyensis zone due to the

recovery of both Distomodus kentuckyensis by Zhang and Barnes (2007) and recovery of

Icriodella sp. in the present study. The assignment of the Severn River to the Aeronian and lower part of the Telychian stages by Zhang and Barnes (2007) is more problematic.

The co-occurrence of Aspelundia expansa, Aspelundia fluegeli fluegeli, Distomodus

staurognathoides, Pterospathodus eopennatus, Pterospathodus celloni, Pterospathodus amorphognathoides angulatus, and Aulacognathus bullatus has not been demonstrated elsewhere. Therefore, these co-occurrences demonstrate that the Severn River

Formation is exceptionally time-transgressive, that the lithostratigraphic identification needs to be revised, that almost every biostratigraphically useful conodont species for the Llandovery needs to have their ranges re-evaluated, or that there was down-hole

caving contamination within the cuttings examined in their study. There are two

parsimonious explanations for these co-occurrences, the first explanation is down-hole

contamination. The second explanation may be the result of differences in the

identification of lithostratigraphic units in the Hudson Platform, the lithostratigraphic

nomenclature used in the Hudson Bay Basin and the Moose River Basin may be

inconsistent between basins. From the limited biostratigraphic data presented in the

present investigation, at least a portion of the Severn River Formation in the Victor Mine

(V-03-270-AH) core in the Moose River Basin must be within the Distmodus

kentuckyensis zone and the Rhuddanian Stage (Figure 2.5). However, the presence of

Pterospathodus eopennatus in a core sample from the Severn River Formation in the

Narwhal O-58 core (Zhang and Barnes, 2007) cannot be explained by down-hole

contamination because it is not a cutting sample and suggests that the Severn River may

extend into the Telychian in some areas of the Hudson Platform. This suggests the

possibility of a lithostratigraphic nomenclatural problem between the Hudson Bay Basin

and Moose River Basin.

The Ekwan River Formation has been assigned to the Telychian Stage by Zhang and

Barnes (2007) based on the presence of Pterospathodus eopennatus, Pterospathodus

celloni, Pterospathodus amorphognathoides angulatus, and Aulacognathus bullatus.

Only Pterospathodus eopennatus was recovered from a core sample, and the elements

of the other species were recovered from cuttings. In the present study the recovery of

Aspelundia expansa combined with three low-magnitude positive carbonate carbon

13 (δ Ccarb) isotope excursions, potentially the lower Aeronian, upper Aeronian, and lower

13 Telychian (Valgu) positive carbon (δ Ccarb) isotope excursions, indicates that the Ekwan

River Formation in the Victor Mine (V-03-270-AH) core is most likely limited to the

Aeronian Stage and potentially the lower Telychian Stage (Figure 2.5). This

interpretation is not entirely consistent with the Pterospathodus eopennatus recovered from a core sample in the lowermost part of the Ekwan River Formation in the Narwhal

O-58 core of Zhang and Barnes (2007). The most parsimonious explanation for the difference in stage-designation for the Ekwan River Formation between Zhang and

Barnes (2007) and the present study may again be the result of differences in the identification of lithostratigraphic units in the Hudson Platform, the lithostratigraphic nomenclature used in the Hudson Bay Basin and the Moose River Basin may be inconsistent between basins.

Zhang and Barnes (2007) assigned the Attawapiskat Formation to the Telychian Stage based on the recovery of Pterospathodus celloni from cuttings only, and as a result

placed this unit within their Pterospathodus celloni–eopennatus Assemblage Zone. This

is consistent with data collected by this study. Ozarkodina gulletensis was recovered at

the base of the Attawapiskat Formation, limiting the base of this unit to no lower than

the Upper Pterospathodus eopennatus ssp. n. 2 Subzone and no higher than the Lower

Pterospathodus amorphognathoides angulatus Subzone. Based on the co-occurrence of

Aspelundia fluegeli fluegeli, Pterospathodus sp., and Aulacognathus bullatus, the middle portion of the Attawapiskat Formation can be assigned to the Lower Pterospathodus amorphognathoides angulatus Subzone.

Further conodont biostratigraphic data could also potentially permit future correlation of the Moose River Basin strata in this core with other Llandovery sections

preserved on the paleocontinent Laurentia. The Jupiter and Chicotte formations of

Anticosti Island yielded the condoonts Pterospathodus eopennatus ssp. n. 1,

Pterospathodus eopennatus ssp. n. 2, and Pterospathodus amorphognathoides

13 angulatus and carbon(δ Ccarb) isotope chemostratigraphic data record the lower

13 Telychian (Valgu) positive carbon (δ Ccarb) isotope excursion (Munnecke and Männik,

2009). The upper portion of the Ekwan River Formation and the Attawapiskat

Formation in the Moose River Basin likely correlates to the upper part of the Jupiter

Formation and the Chicotte Formation of Anticosti Island (Munnecke and Männik,

2009). In the Appalachian Basin, the base of the Attawapiskat Formation likely

correlates to the base of the Williamson Shale or the Estill Shale (Cramer et al., 2011).

13 The lower Aeronian, upper Aeronian, and Telychian (Valgu) positive carbon (δ Ccarb)

isotope excursions have yet to be recovered from the Appalachian Basin, and therefore the Ekwan River Formation cannot be precisely correlated with Appalachian Basin strata

13 (Cramer et al., 2011). The stable carbon (δ Ccarb) isotope curve from the Laketown

Dolostone Formation of the Pancake Range in Nevada (Gouldey et al., 2010) exhibits

13 several low-magnitude carbon (δ Ccarb) isotope excursions, some of which may be the

same isotopic events recorded in the Moose River Basin strata. However, the lack of

biostratigraphic information from the Pancake Range section (Gouldey et al., 2010)

prohibits secondary confirmation of any potential chemostratigraphic correlation

13 between these carbon (δ Ccarb) isotope curves.

Conclusions

The Silurian stratigraphic succession in the Victor Mine (V-03-270-AH) core of the

Moose River Basin in Ontario, Canada preserves at least portions of the Rhuddanian,

Aeronian, and Telychian stages (Figure 2.5). The Severn River Formation is most likely in

part within the Distomodus kentuckyensis Zone of the Rhuddanian Stage. The middle

and upper parts of the Ekwan River Formation likely record the lower Aeronian, upper

13 Aeronian, and lower Telychian (Valgu) positive carbonate carbon (δ Ccarb) isotope

excursions, limiting this unit to the Aeronian Stage and potentially the lower Telychian

Stage. There is a possible disconformity between the Ekwan River and Attawapiskat formations where the Pterospathodus eopennatus ssp. n. 1 Zone and the Lower

Pterospathodus eopennatus ssp. n. 2 Subzone are presumably missing, but futher conodont biostratigraphic data is needed to definitively confirm this. The base of the

Attawapiskat Formation can be assigned to the Upper Pterospathodus eopennatus ssp.

n. 2 Subzone of the Telychian Stage. The overlying 70 m of the Attawapiskat Formation

in the core can be assigned to the Lower Pterospathodus amorphognathoides angulatus

Subzone.

Comparison of the Victor Mine (V-03-270-AH) core of the Moose River Basin with the

cores analyzed by Zhang and Barnes (2007) suggests that the Severn River and Ekwan

River may be significantly diachronous across the Hudson Platform. In particular, the

Severn River Formation appears to include strata from the Rhuddanian through the

lower Telychian within the region (Zhang and Barnes, 2007). Without significant new

32 biostratigraphic and chemostratigraphic data the regional and global correlation of the

Silurian stratigraphy of the Hudson Platform will remain enigmatic. However, this study has begun the process of reevaluating these units and integrating this stratigraphic succession into the global chronostratigraphic framework for the Silurian System.

Acknowledgements

I would like to thank Frank Brunton (Ontario Geological Survey, Sudbury, Canada) and Stephan Kurszlaukis (DeBeers Canada), without who this study would not have been possible. I would also like to thank Brad Cramer (University of Iowa) and Mark Kleffner (The Ohio State University) for their scientific discussions, patience, and help improving this manuscript. This work represents a contribution to the IGCP 591 Project.

Figures, Plate, and Table

Figure 2.1. Generalized paleogeographic map illustrating the structural basins and arches of the Hudson Platform during the Silurian Period. The locality of the core sampled for both conodont biostratigraphy and 13 carbonate carbon (δ Ccarb) isotope stratigraphy is shown ( ): Victor Mine (V-03-270-AH) core in the Moose River Basin, Ontario, Canada (modified from Norris, 1993b).

Figure 2.2. Lower Paleozoic lithostratigraphy of the Hudson Platform. Chronostratigraphic units for the Ordovician are from Bergström et al. (2007) and chronostratigraphic units for the Silurian are from Cramer et al. (2011). Correlation on the left-side of the diagram is from Norris (1993b), while the correlation on the right-side of the diagram is from Zhang and Barnes (2007).

Figure 2.3. Conodont zonation for the Llandovery Series of the Silurian System. Chronostratigraphy and global conodont zonation from Cramer et al. (2011); Estonian conodont zonation from Männik (2007a, 2007b); and stage dates from Gradstein et al. (2012).

Figure 2.4. Llandovery (Silurian) conodont zonation and ranges of selected conodont species. Conodont zonation and ranges from Männik (2007a, 2007b), stage dates from Gradstein et al. (2012). Horizontal bars at the bottom or top of a species range indicate the first appearance (FAD) and the last appearance (LAD) of that species, respectively. Dashed lines in the range of a species indicate the scattered presence of that species. Ranges of species that extend beyond what is represented in the figure are indicated with an arrow.

Figure 2.5. Chronostratigraphic data from the Victor Mine (V-03-270-AH) core. Lithostratigraphy, conodont 13 biostratigraphy, and carbonate carbon (δ Ccarb) isotope chemostratigraphy (VPDB – Vienna Pee Dee belemnite) from the Victor Mine (V-03-270-AH) core, in the Moose River Basin, Ontario, Canada.

Plate 2.1. Silurian conodonts from the Victor Mine (V-03-270-AH) core. The core is located in the Moose River Basin, Ontario, Canada. All photographs were taken with a light microscope at 31x magnification. 1: Pseudooneotodus tricornis Drygant from 27.55 meters to 28.02 meters within the V-03-270-AH core. 2 and 4: Pterospathodus ramiforms from 64.66 meters to 65.00 meters within the V-03-270-AH core. 3: Ozarkodina sp. (?) from 64.66 meters to 65.00 meters within the V-03-270-AH core. 5, 6, 7, 8, and 9: Aulacognathus bullatus (Nicoll and Rexroad) from 64.66 meters to 65.00 meters within the V-03-270-AH core; 5, 6, and 7 – Pa elements; 8 and 9 – Pb elements. 10: Distomodus staurognathoides (Walliser) from 101.10 meters to 101.43 meters within the V-03-270-AH core. 11: Aspelundia fluegeli fluegeli (Walliser) from 64.66 meters to 65.00 meters within the V-03-270-AH core. 12: Aspelundia expansa Armstrong from 142.26 meters to 142.40 meters within the V-03-270-AH core. 13. Ozarkodina gulletensis Aldridge from 132.85 meters to 133.05 meters within the V-03-270-AH core. 14: Icriodella sp. from 210.80 meters to 211.00 meters within the V-03-270-AH core.

Table 2.1. Silurian chronostratigraphy of the Victor Mine (V-03-270-AH) core in the Moose River Basin, Ontario, Canada.

Table 2.1 (continued)

References

Aldridge, R.J. 1972. Llandovery conodonts from the Welsh Borderland. Bulletin of the British Museum (Natural History) Geology, 22(2):125-231.

Aldridge, R.J. 1975. The stratigraphic distribution of conodonts in the British Silurian. Journal of the Geological Society, London, 131(6):607-618.

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

Barnes, C.R., Norford, B.S., and Jackson, D.E. 1976. Correlation between Canadian Ordovician zonations based on graptolites, conodonts, and benthic macrofossils from key successions. In Ordovician System Symposium. Edited by M.G. Bassett. University of Wales Press and National Museum of Wales, Cardiff, pp. 209-226.

Berry, W.B.N. and Boucot, A.J. 1970. Correlation of the North American Silurian rocks. Geological Society of America, Special Paper 102, 289 pp.

Calner, M., Jeppsson, L., and Munnecke, A. 2004. The Silurian of Gotland – Part 1: Review of the stratigraphic framework, event stratigraphy, and stable carbon and oxygen isotope development. Erlanger Geologische Abhandlungen, Sonderband 5, pp. 113-131.

Cooper, B.J. 1975. Multielement conodonts from the Brassfield Limestone (Silurian) of southern Ohio. Journal of Paleontology, 49(6):984-1008.

Craig, H. 1957. Isotopic standards for carbon and oxygen and correction factors for mass-spectrometric analysis of carbon dioxide. Geochimica et Cosmochimica Acta, 12(1-2):133-149.

Cramer, B.D., Saltzman, M.R., and Kleffner, M.A. 2006a. Spatial and temporal variability 13 in organic carbon burial during global positive carbon isotope δ Ccarb excursions: 13 New insight from high-resolution δ Ccarb stratigraphy from the type area of the Niagaran (Silurian) Provincial Series. Stratigraphy, 2(4):327-340.

Cramer, B.D., Kleffner, M.A., and Saltzman, M.R. 2006b. The late Wenlock Mulde positive carbon isotope excursion in North America. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):85-90.

Flower, R.H. 1968. Silurian cephalopods of the James Bay Lowland, with a revision of the Narthecoceratidae. Geological Survey of Canada, Bulletin 164, 88 pp.

Flower, R.H. and Teichert, C. 1957. The cephalopod Order Discosorida. University of Kansas Paleontological Contributions, Mollusca, Article 6, 144 pp.

Frakes, L.A., Francis, J.E., and Skytus, J.I. 1992. Climate modes of the Phanerozoic. Cambridge University Press, Cambridge, 274 pp.

Gouldey, J., Saltzman, M., Young, S., and Klajo, D. 2010. Strontium and carbon isotope stratigraphy of the Llandovery (Early Silurian): Implications for tectonics and weathering. Palaeogeography, Palaeoclimatology, Palaeoecology, 296(3-4):264-275.

Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M. 2012. The Geologic Time Scale 2012. Elsevier, 1176 pp.

Grahn, Y.G. and Caputo, M.V. 1992. Early Silurian glaciations in Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology, 99(1-2):9-15.

Graves, R.W. and Ellison, S.P. 1941. Ordovician conodonts of the Marathon Basin, Texas. University of Missouri, School of Mines and Metallurgy, Technical Bulletin Series, 14(2):1-26.

Jeppsson, L. 1997. A new latest Telychian, Sheinwoodian, and early Homerian (early Silurian) standard conodont zonation. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88(2):91-114.

Jeppsson, L. and Aldridge, R.J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London, 157(6):1137-1148.

Jeppsson, L. and Anehus, R. 1999. The optimal acetate buffered acetic acid technique for extracting phosphatic fossils. Journal of Paleontology, 73(5):964-972.

Jeppsson, L. and Anehus, R. 1995. A buffered formic acid technique for conodont extraction. Journal of Paleontology, 69(4):790-794.

Jeppsson, L., Aldridge, R.J., and Dorning, K.J. 1995. Wenlock (Silurian) oceanic episodes and events. Journal of the Geological Society, London, 152(3):487-489.

Jeppsson, L., Fredholm, D., and Mattiasson, B. 1985. Acetic acid and phosphatic fossils— A warning. Journal of Paleontology, 59(4):952-956.

Jin, J., Caldwell, W.G.E., and Norford, B.S. 1993. Early Silurian brachiopods and biostratigraphy of the Hudson Bay Lowlands, Manitoba, Ontario, and Québec. Geological Survey of Canada, Bulletin 457, 221 pp.

Johnson, M.D., Armstrong, D.K., Sanford, B.V., Telford, P.G., and Rutka, M.A., 1992. Paleozoic and Mesozoic geology of Ontario. In Geology of Ontario. Edited by P.C. Thurston, H.R. Williams, R.H. Sutcliffe, and G.M. Stott. Ontario Geological Survey, Special Volume 4(2), pp. 907-1008.

Kaljo, D. and Martma, T. 2006. Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):123-129.

Kaljo, D. and Martma, T. 2000. Carbon isotopic composition of Llandovery rocks (East Baltic Silurian) with environmental interpretation. Proceedings of the Estonian Academy of Sciences, Geology, 49(4):267-283.

Kaljo, D., Kiipli, T., and Martma, T. 1998. Correlation of carbon isotope events and environmental cyclicity in the East Baltic Silurian. In Silurian Cycles: Linkages of Dynamic Stratigraphy, with Atmospheric, Oceanic, and Tectonic Changes. Edited by E. Landing and M.E. Johnson. New York State Museum Bulletin 491, pp. 297-312.

Kaljo, D., Martma, T., Männik, P., and Viira, V. 2003. Implications of Gondwana glaciations in the Baltic Late Ordovician and Silurian and a carbon isotopic test of environmental cyclicity. Bulletin de la Société Géologique de France, 174(1):59-66.

Larsson, S.Y. and Stearn, C.W. 1986. Silurian stratigraphy of the Hudson Bay Lowland in Québec. Canadian Journal of Earth Sciences, 23(3):288-299.

Le Fèvre, J., Barnes, C.R., and Tixier, M. 1976. Paleoecology of Late Ordovician and Early Silurian conodontophorids, Hudson Bay Basin. In Conodont Paleoecology. Edited by C.R. Barnes. Geological Association of Canada, Special Paper 15, pp. 69-89.

Männik, P. 2007a. An updated Telychian (late Llandovery, Silurian) conodont zonation based on Baltic faunas. Lethaia, 40(1):45-60.

Männik, P. 2007b. Recent developments in the upper Ordovician and lower Silurian conodont biostratigraphy in Estonia. Estonian Journal of Earth Sciences, 5(1):35-46.

Männik, P. 1998. Evolution and taxonomy of the Silurian conodont Pterospathodus. Palaeontology, 41(5):1001-1050.

Melchin, M.J. and Holmden, C. 2006. Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada: Implications for global correlation and sea-level change. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):173-180.

Melchin, M.J., Sadler, P.M., and Cramer, B.D. 2012. The Silurian Period. In The Geologic Time Scale 2012. Edited by Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M., Elsevier, pp. 525-558.

Munnecke, A., Samtleben, C., and Bickert, T. 2003. The Ireviken Event in the lower Silurian of Gotland, Sweden – Relation to similar Palaeozoic and Proterozoic events. Palaeogeography, Palaeoclimatology, Palaeoecology, 155(1-2):99-124.

Nelson, S.J. and Johnson, R.D. 1966. Geology of Hudson Bay Basin. Bulletin of Canadian Petroleum Geology, 14(4):520-578.

Nicoll, R.S. and 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 Geological Survey Bulletin 40, 73 pp.

Norford, B.S. 1997. Correlation chart and biostratigraphy of the Silurian rocks of Canada. International Union of Geological Sciences, Publication Number 33, 77 pp.

Norford, B.S. 1988. The Ordovician-Silurian boundary in the Rocky Mountains, Arctic Islands, and Hudson Platform, Canada. In A Global Analysis of the Ordovician-Silurian Boundary. Edited by L.R.M. Cocks and R.B. Rickards. Bulletin of the British Museum (Natural History), Geology Series 43, pp. 259-263.

Norford, B.S. 1971. Silurian stratigraphy of northern Manitoba. In Geoscience Studies in Manitoba. Edited by A.C. Turnock. Geological Association of Canada, Special Paper 9, pp. 199-207.

Norford, B.S. 1970. Ordovician and Silurian biostratigraphy of the Sogetpet-Aquitaine Kaskattama Province No. 1 well northern Manitoba. Geological Survey of Canada, Paper 69-8, 36 pp.

Norris, A.W. and Sanford, B.V. 1969. Palaeozoic and Mesozoic geology of Hudson Bay Lowlands. In Earth Science Symposium on Hudson Bay. Edited by P.J. Hood. Geological Survey of Canada Paper, 68-53, pp. 169-205.

Page, A., Zalasiewicz, J., Williams, M., and Popov, L. 2007. Were transgressive black shales a negative feedback modulating glacioeustasy in the Early Paleozoic Icehouse? In Deep-time perspectives on climate change: Marrying the signal from computer models and biological proxies. Edited by M. Williams, A.M. Haywood, F.J. Gregory, and D.N. Schmidt. Special Publication of the Geological Society of London, The Micropalaeontological Society, pp. 123-156.

Põldvere, A. (editor) 2003. Ruhnu (500) Drill Core. Estonian Geological Sections, Bulletin 5, 76 pp.

Pollock, C.A., Rexroad, C.B., and Nicoll, R.S. 1970. Lower Silurian conodonts from northern Michigan and Ontario. Journal of Paleontology, 44(4):734-764.

Porębska, E., Kozłowska-Dawidziuk, A., and Masiak, M. 2004. The lundgreni event in the Silurian of the East European Platform, Poland. Palaeogeography, Palaeoclimatology, Palaeoecology, 213(3-4):271-294.

Rexroad, C.B. and Nicoll, R.S. 1971. Summary of conodont biostratigraphy of the Silurian System of North America. In Symposium on conodont biostratigraphy. Edited by W.C. Sweet and S.M. Bergström. Geological Society of America Memoir 127, pp. 207-225.

Rhodes, F.H.T. 1953. Some British lower Palaeozoic conodont faunas. Philosophical Transactions of the Royal Society of London, Series B (Biological Sciences), 237(647):261-334.

Saltzman, M.R. 2005. Phosphorus, nitrogen, and the redox evolution of the Paleozoic oceans. Geology, 33(7):573-576.

13 Saltzman, M.R. 2002. Carbon isotope δ Ccarb stratigraphy across the Silurian-Devonian transition in North America: Evidence for a perturbation of the global carbon cycle. Palaeogeography, Palaeoclimatology, Palaeoecology, 187(1):83-100.

Saltzman, M.R. and Thomas, E. 2012. Carbon Isotope Stratigraphy. In The Geologic Time Scale 2012. Edited by Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M., Elsevier, pp. 207-232.

Sanford, B.V., Norris, A.W., and Bostock, H.H. 1968. Geology of the Hudson Bay Lowlands (Operation Winisk). Geological Survey of Canada, Paper 67-60, pp. 1-45. Geological Map 17-1967.

Sanford, B.V., Norris, A.W., and Cameron, A.R. 1993. Hudson Platform – Economic geology. In Sedimentary Cover of the Craton in Canada. Edited by D.F. Stott and J.D. Aitken. Geological Survey of Canada, Geology of Canada, Number 5, pp. 701-707.

Savage, T.E. and Van Tuyl, F.M. 1919. Geology and stratigraphy of the area of Paleozoic rocks in the vicinity of Hudson and James bays. Geological Society of America, Bulletin 30, pp. 339-378.

Suchy, D.R. 1992. Drill core descriptions (field notes), Silurian section on the Hudson Bay platform – A supplement to the Ph.D. Dissertation (Hudson Bay Platform: Silurian sequence stratigraphy and paleoenvironments), McGill University, 108 pp.

Suchy, D.R. and Stearn, C.W. 1992. Lower Silurian sequence stratigraphy and sea-level history of the Hudson Bay Platform. Bulletin of Canadian Petroleum Geology, 40(4):335-355.

Zhang, S. and Barnes, C.R. 2007. Late Ordovician – early Silurian conodont biostratigraphy and thermal maturity, Hudson Bay Basin. Bulletin of Canadian Petroleum Geology, 55(3):179-216.

Chapter 3: Silurian biochemostratigraphy of the Appalachian Basin

Abstract

A four-hundred and sixty foot core from the Ontario Geological Survey (OGS-DDH6-

09) penetrating the Silurian carbonate succession in Ontario, Canada was studied for

13 conodont biostratigraphy and carbonate carbon (δ Ccarb) isotope stratigraphy to

provide improved chronostratigraphic control for these strata. This core was drilled on

the southeastern margin of the Algonquin Arch that separates the cratonic Michigan

Basin from the foreland Appalachian Basin and provides an opportunity to correlate the

lithostratigraphic nomenclature used by the Ontario Geological Survey (OGS) with that

used by the United States Geological Survey (USGS), which have been historically

incongruous. This core contains one of the thickest successions of the Guelph

Formation in the Appalachian Basin and a significant disconformity that appears to have removed upper Sheinwoodian and lower Homerian strata. The recovery of several biostratigraphically useful conodont species as well as the lower Sheinwoodian

13 (Ireviken) and Homerian (Mulde) positive carbonate carbon (δ Ccarb) isotope excursions

allow chronostratigraphic correlation of this core with the Niagaran Provincial Series and

Silurian strata worldwide.

Introduction

The Niagaran Provincial Series in the Niagara region of western New York has been

studied for 150 years and is the type area for the Silurian succession in the United States

(Berry and Boucot, 1970; Brett et al., 1995; Cramer et al., 2011a; Cramer et al., 2011b).

Recent work in the type area of western New York (Brett et al., 1995; Cramer et al.,

2006a; Cramer et al., 2006b; McLaughlin et al., 2008; Cramer et al., 2011a; Cramer et al.,

2011b) significantly revised the global correlation of the Niagaran Provincial Series.

Chronostratigraphic control for Silurian strata in Ontario, Canada is less well-constrained due to poor biostratigraphic information and lithostratigraphic nomenclatural differences across the Niagara River between the United States Geological Survey

(USGS) and the Ontario Geological Survey (OGS). The strata along the Algonquin Arch are critical for understanding the relationship between the Appalachian Basin and the

Michigan Basin during the Silurian Period; however, these problems have prevented a uniform chronostratigraphy for the region.

Due to refined processing techniques (Jeppsson et al., 1985; Jeppsson 1987; Jeppsson and Anehus, 1995, 1999), conodont taxonomy and biostratigraphy have undergone major revisions in the last two decades (Jeppsson, 1997; Männik, 1998, 2007a, 2007b).

As a result, the resolution of Silurian conodont biozonation has increased by an order of magnitude and can be applied globally. This has provided a catalyst for a revolution in the study of biogeochemical events. A series of extinction events during the Silurian

Period (Jaeger, 1959; Jeppsson, 1990, 1998; Jeppsson et al., 2006; Munnecke and

Männik, 2009) are correlative with perturbations in the global carbon cycle, which are

13 recorded as major positive carbonate carbon (δ Ccarb) isotope excursions in marine carbonates (Samtleben et al., 1996; Bickert et al., 1997; Munnecke et al., 1997; Kaljo and Martma, 2006; Cramer et al., 2011a). These combined biogeochemical events provide useful chronostratigraphic markers for high-resolution global correlation of

Silurian strata, particularly when biostratigraphic information is limited. As a result,

13 integrated conodont biostratigraphy and carbonate carbon (δ Ccarb) isotope chemostratigraphy for the Silurian System now provide a high-resolution chronostratigraphic framework for Silurian strata globally (Samtleben et al., 1996;

Jeppsson 1997; Männik, 1998; Jeppsson and Calner 2003; Munnecke et al., 2003; Kaljo and Martma, 2006; Männik, 2007a, 2007b; Cramer et al., 2011a; Cramer et al., 2011b;

Melchin et al., 2012). Herein, an Ontario Geological Survey (OGS-DDH6-09) core from the southeastern margin of the Algonquin Arch (along the distal, northwestern margin of the Appalachian Basin) in Ontario, Canada was sampled for conodont biostratigraphy

13 and carbonate carbon (δ Ccarb) isotope chemostratigraphy to correlate to the Niagaran

13 Provincial Series. The recognition of two major positive carbonate carbon (δ Ccarb) isotope excursions, with limited conodont biostratigraphic data, has helped provide a definitive correlation with the Silurian type area in New York.

Geologic Background

Paleogeography

The province of Ontario, Canada, was located on the northeastern margin of the paleocontinent Laurentia during the Silurian Period, between 10°S and 30°S latitude in the subtropical climate belt (Witzke, 1990). Sediment deposition and faunal distribution

within the cratonic Michigan Basin and the Appalachian Foreland Basin was controlled

by the Algonquin Arch, a northeast-trending Precambrian basement high (Figure 4.1).

The Algonquin Arch was often subaerially exposed during regressive phases of the

Tippecanoe or during Taconic flexural uplift in the early Silurian Period (Ettensohn,

1994; Goodman and Brett, 1994; Ettensohn and Brett, 1998). As a result,

communication was commonly restricted between the Michigan Basin and Appalachian

Basin, and there were abrupt temporal and spatial changes in depositional environments. This is evident in the significant regional variations in sedimentation and fossil content (Brunton, 2009). The Ontario Geological Survey (OGS-DDH6-09) core is located on the southeastern flank of the Algonquin Arch in the distal, northwestern portion of the Appalachian Basin (Figure 3.1). The location of this core (OGS-DDH6-09)

provides the opportunity to further address problems with the lithostratigraphic

nomenclature between the USGS and OGS and the chronostratigraphic correlation of

the Silurian System in eastern North America.

Chronostratigraphy

During the last two decades a high-resolution global chronostratigraphic framework

for the Telychian Stage (Llandovery Series) and Wenlock Series (Sheinwoodian Stage and

Homerian Stage) of the Silurian System has been developed that integrates graptolite

(Koren’ et al., 1996; Loydell, 1998) and conodont biostratigraphy (Jeppsson, 1997;

13 Männik, 1998, 2007a, 2007b) with carbonate carbon (δ Ccarb) isotope

chemostratigraphy (Kaljo et al., 2003; Munnecke et al., 2003; Cramer et al., 2006a;

Cramer et al., 2006b; Kaljo and Martma, 2006; Melchin and Holmden, 2006). This has

enabled the precise correlation of certain Silurian intervals at a resolution finer than the

stage-level (Cramer et al., 2010).

During the last 150 years, the Silurian succession in North America has been divided into various regional series (Alexandrian, Niagaran, and Cayugan – Figure 3.2) hindering

global correlation of these units (Berry and Boucot, 1970; Brett et al., 1995; Norford,

1997; Cramer et al., 2011a). Recent revisions to the biostratigraphic and

chronostratigraphic framework of the Niagaran Provincial Series from the Niagara

region of western New York demonstrated that the correlation of the Silurian System in

North America needs to be reexamined (Brett et al., 1995; Cramer et al., 2006a; Cramer

et al., 2006b; McLaughlin et al., 2008; Cramer et al., 2010; Cramer et al., 2011a).

Historically, the Alexandrian Series spanned an interval from the base of the Silurian

to the middle of the Llandovery Series. Recent revisions to the Ordovician System

demonstrated that the Alexandrian Series (original type area located in the American

mid-continent in southwestern Illinois and southeastern Missouri) crossed a systemic

boundary and spanned an interval from the Hirnantian Stage to the Aeronian Stage

(Bergström et al., 2006; Bergström et al., 2009) and as a result, the term Alexandrian

Series was abandoned and the Cincinnatian Series was extended to the top of the

Ordovician System (Bergström et al., 2009). The Alexandrian Series was rendered

obsolete within the Silurian System due to revisions in the type area in the Niagara

region of western New York (Brett et al., 1995), which extended the Niagaran Series

down to the base of the Silurian System.

The Niagaran Series was redefined by Brett et al. (1995) to include all Silurian strata

below the Salina Group and was thought to include all of the Llandovery Series, all of the

Wenlock Series, and most of the Ludlow Series. The Medina, Clinton, and Lockport groups are all included within the Niagaran Series, and at present only the base of the

Lockport can be precisely correlated globally (Cramer et al., 2011a).

The Medina Group represents the first major sea-level transgression after the Late

Ordovician glacial maximum and overlies the Cherokee Unconformity (Brett et al.,

1995). Unlike the rest of the Silurian succession in the Appalachian Basin, the Medina

Group consists predominantly of clastic lithologies (Johnson et al., 1992; Brett et al.,

1995). In Ontario, units that are equivalent to the Medina Group are classified within

the Cataract Group (Johnson et al., 1992). The Medina Group in western New York

includes, in ascending order stratigraphically, the Whirlpool, Power Glen, Devils Hole,

Grimsby, Thorold, Cambria, and Kodak formations (Brett et al., 1995) and in

southwestern Ontario, the Cataract Group includes the Whirlpool, Manitoulin, and

Cabot Head formations (Johnson et al., 1992).

The Clinton Group in western New York and southwestern Ontario includes, in

ascending order stratigraphically, the Neahga, Reynales, Merriton (upper part of the

Fossil Hill Formation in Ontario, Brunton, 2009), Williamson, Rockway, Irondequoit,

Rochester (Lions Head Formation in Ontario, Brunton 2009), and Decew formations.

The Neahga and Reynales formations were assigned to the Aeronian Stage (Brett et al.,

1995), and this chronostratigraphic designation is further supported by the recovery of

the conodont Pranognathus tenuis from the upper part of the Neahga Formation and

throughout the Reynales Formation in western New York (Kleffner 2004). The base of

the Telychian Stage lies at a position between the top of the Reynales Formation and

the base of the Merritton Formation (Kleffner, 2004). However, from western New York

to southwestern Ontario, the Reynales and Neahga formations are successively

truncated westward into Ontario, and the base of the Merritton Formation overlies this

disconformity (Johnson et al., 1992; Brett et al., 1995). At the type section of the

Williamson Formation in Rochester, New York, the graptolite Stimulograptus

clintonensis and the conodont Pterospathodus amorphognathoides angulatus were found to co-occur (Loydell et al., 2007). Stimulograptus clintonensis is not known to range into the Pterospathodus amorphognathoides angulatus Zone elsewhere in the world, and as a result, a stage determination for the Williamson Formation was not reached by Loydell et al., 2007. Chitinozoan distribution in the Williamson Formation

(Verniers et al., 2012), combined with the recovery of the conodont Pterospathodus amorphognathoides angulatus (Loydell et al., 2007), provided the evidence necessary to designate the Williamson Formation to the Telychian Stage (Verniers et al., 2012). The base of the Wenlock Series is located within, or at the top of, the Rockway Formation

(Cramer et al., 2006a; Cramer et al., 2010), however, the precise position of the base of the Wenlock Series has not yet been determined (Cramer et al., 2011a). In western New

York the Irondequoit, Rochester, and Decew formations record the lower portion of the

13 lower Sheinwoodian (Ireviken) positive carbonate carbon (δ Ccarb) isotope excursion

and, therefore, are within the lower half of the Sheinwoodian Stage (Cramer et al.,

2006a; Cramer et al., 2011a). However, in southwestern Ontario the Irondequoit

Formation is equivalent to the Irondequoit Formation in western New York, the Lions

Head Formation is equivalent to the Rochester Formation, and the Decew Formation is

not preserved (Figure 3.2).

The Lockport Group in western New York and southwestern Ontario includes, in ascending order stratigraphically, the Gasport, Goat Island, Eramosa, and Guelph

formations (Brett et al., 1995; Brunton, 2009; Cramer et al., 2011).

Biochemostratigraphic data from the type area of the Niagaran Series (Cramer et al.,

2006a; Cramer et al., 2011a) place the base of the Gasport Formation and, therefore, the base of the Lockport Group, within the middle part of the Sheinwoodian Stage. The

13 descending limb of the lower Sheinwoodian (Ireviken) positive carbon (δ Ccarb) isotope

excursion occurs within the Goat Island Formation and reaches baseline values within

the lower part of the Eramosa Formation (Cramer et al., 2006a). The conodont

Kockelella ortus ortus was recovered from the Eramosa Formation, indicating that this

unit can be chronostratigraphically correlated to the upper part of the Sheinwoodian

Stage (Bancroft, 2008). The base of the Homerian Stage likely correlates to a position

within the lower part of the Guelph Formation (Cramer et al., 2011a). The Silurian

lithostratigraphic nomenclature of the Ontario Geological Survey (Figure 3.2) will be

used throughout the remainder of this manuscript, unless otherwise noted.

Methods

Silurian strata from the Ontario Geological Survey (OGS-DDH6-09) core (strata in

ascending order: Cabot Head, Fossil Hill/Merritton, Rockway, Irondequoit, Lions Head

(Rochester), Gasport, Goat Island, Eramosa, and Guelph formations) on the

southeastern flank of the Algonquin Arch in the distal, northwestern portion of the

Appalachian Basin, were sampled for conodont biostratigraphy and carbonate carbon

13 (δ Ccarb) isotope chemostratigraphy. This core (OGS-DDH6-09) is housed at the Ontario

Geological Survey, in Sudbury, Ontario, Canada.

Biostratigraphic Methodology

Using controlled experiments Jeppsson (Jeppsson et al., 1985; Jeppsson 1987;

Jeppsson and Anehus, 1995, 1999) revolutionized the techniques used for extracting

conodont elements (carbonate fluorapatite – francolite) from carbonate lithologies. For

nearly one century the acetic acid residue method (Graves and Ellison, 1941) damaged

or destroyed conodont elements during processing. Buffering the acetic (limestone –

Jeppsson and Anehus, 1999) or formic (dolostone – Jeppsson and Anehus, 1995) acid solution, to an optimum pH and calcium ion [Ca2+] concentration enhances yields

(conodont elements per kilogram of sample) by preserving elements during dissolution

and preventing etching of the conodont elements. Conodont samples from the Ontario

Geological Survey (OGS-DDH6-09) core (between five hundred grams and two kilograms) were processed using these refined standard techniques (Jeppsson and

Anehus, 1995).

Chemostratigraphic (Stable Isotope) Methodology

The use of marine carbonates that preserve the primary marine carbon isotopic

13 δ Ccarb signature (Bickert et al., 1997; Munnecke et al., 1997; Saltzman and Thomas,

2012) is a well-established method for global chronostratigraphic correlation (Saltzman,

2005), especially when integrated with equally high-resolution biostratigraphy (Kaljo et

al., 1998; Kaljo et al., 2003; Munnecke et al., 2003; Calner et al., 2004; Porębska et al.,

2004; Cramer et al., 2006a; Cramer et al., 2006b; Kaljo and Martma, 2006). All

13 carbonate carbon (δ Ccarb) isotope samples collected from the Ontario Geological

Survey (OGS-DDH6-09) core were micro-drilled from micritic matrix (Saltzman, 2002)

and sent to the University of Kansas W.M. Keck Paleoenvironmental and Environmental

Stable Isotope Laboratory (KPESIL) for analysis. Samples were measured (20 μg to 80

μg) and heated under vacuum at 200°C for one hour to release any volatile organic compounds. To dissolve the carbon of calcite, carbonate powders were reacted under vacuum with three drops of prepared 100% phosphoric acid for four minutes (or reacted

for twelve minutes to dissolve the carbon of dolomite) at 75°C using a Kiel Carbonate

Device III, and the carbon dioxide (CO2) released was trapped cryogenically and

transferred to a Finnigan MAT253 isotope ratio mass spectrometer for analysis. Data

are reported using the per mil (‰) notation relative to the Vienna Pee Dee belemnite

(VPDB) standard (Craig, 1957). Precision and calibration of data were monitored

through routine analysis of National Bureau of Standards – NBS-18 and NBS-19 and an

internally calibrated calcite standard. Reproducibility for values obtained was checked

by replicate analysis of laboratory standards and typically yield an R2 value of 0.9995 or

better.

Results

From the Ontario Geological Survey (OGS-DDH6-09) core on the southeastern flank of

the Algonquin Arch in the distal northwestern portion of the Appalachian Basin, thirty-

two samples were collected and processed for conodont biostratigraphy (Jeppsson,

1985, 1987; Jeppson and Anehus, 1995, 1999) and four hundred and seventy-four

13 samples were collected and processed for carbonate carbon (δ Ccarb) isotope

stratigraphy at the University of Kansas (KPESIL). Conodont yields from the sampled

intervals were exceptionally low, and few biostratigraphically useful conodonts were

recovered. From the Cabot Head Formation a robust fauna of Icriodella was recovered

(Plate 3.1, Figure 3.4). The remainder of the core yielded little to no biostratigraphically

useful conodont data. However, within the Wellington Member of the Guelph

Formation a single conodont element was recovered that has affinities to the

Ozarkodina lineage of sagitta rhenana, sagitta sagitta, bohemica longa, and bohemica

bohemica. Definitive diagnosis of this element was prevented because it was a poorly

preserved single specimen, and the distal end of the element was broken. The work of

Lennart Jeppsson has illustrated that high-resolution conodont biostratigraphic zonation

in the Silurian can be best accomplished via collections of adequate size. Sample sizes for this study (core samples ranging from five hundred grams to two kilograms), compounded by lithology, hampered element yield, resulting in a lack of adequate biostratigraphic control.

13 Carbonate carbon (δ Ccarb) isotope values are exceptionally high throughout the

core with values ranging from -1.72‰ to +5.59‰ (Table 3.2, Figure 3.4). Carbon

13 (δ Ccarb) isotope values are greater than +4.0‰ from the base of the Irondequoit

Formation through the top of the Eramosa Formation. Values remain near +4.0‰

through the lower half of the Wellington Member of the Guelph Formation, before a

small negative shift of 1.0‰ in the middle of the Wellington Member. Isotope values

rise back to +4.0‰ in the upper part of the Wellington Member before a steady decline

from +4.0‰ to +0.0‰ over the next 225 feet near the top of the Hanlon Member of the

Guelph Formation. The topmost isotope sample from this core, within the Hanlon

Member of the Guelph Formation records a value of +4.83‰.

Discussion

The Cataract Group is poorly represented within the Ontario Geological Survey (OGS-

DDH6-09) core. Based on the recovery of Icriodella sp. (Plate 3.1) from the Cabot Head

Formation this lithostratigraphic unit can potentially be globally correlated. Species of the genus Icriodella Rhodes, 1953 range from the Upper Ordovician Series through the

Llandovery Series (Silurian) and species of the genus are known globally in the Silurian

(Nicoll and Rexroad, 1968; Pollock et al., 1970; Rexroad and Nicoll, 1971; Aldridge, 1972;

Aldridge, 1975; Cooper, 1975). Elements of the genus Icriodella recovered from this study have well-preserved anterior processes, but the posterior processes are broken, and as a result species designation within the genus Icriodella from this study is tentative. It is likely that the Icriodella fauna recovered from the Cabot Head Formation in the present study correlate to the Icriodella fauna described by Pollock, Rexroad, and

Nicoll (1970) from the Cabot Head Formation in northern Michigan and Ontario. Thus, it is possible that the Icriodella fauna recovered from the Cabot Head Formation in the core are within the Distomodus kentuckyensis Zone and can be assigned to the

Rhuddanian Stage of the Llandovery Series; however, based on conodont elements recovered from the present study, such a designation is not definitive. The remainder of the Llandovery Series within the core is represented by the Fossil Hill and Rockway

formations, demonstrating that there are only fifteen feet of Llandovery strata within

the core (Figure 3.4).

The Irondequoit, Lions Head, Gasport, Goat Island, and Eramosa formations record

13 elevated carbon (δ Ccarb) isotope values indicative of the lower Sheinwoodian (Ireviken)

13 positive carbon (δ Ccarb) isotope excursion, and therefore, these units can be constrained to the lower part of the Sheinwoodian Stage (Figure 3.4). Based on the

presence of the Ireviken Excursion, these strata correlate with the Irondequoit,

Rochester, Decew, Gasport, Goat Island, and Eramosa formations in the type area of

western New York. Stratigraphic control from the Eramosa down within the core is well-

constrained, however precise chronostratigraphic correlation for the remainder of the

13 core (Guelph Formation) is problematic. Carbon (δ Ccarb) isotopic values within the

Guelph Formation remain high, but there is no biostratigraphic control to differentiate

13 between the Ireviken and Mulde positive carbon (δ Ccarb) isotope excursions. As a

result, there are several possible interpretations for the chronostratigraphic correlation

of the Guelph Formation in the core.

13 The global Wenlock standard carbon (δ Ccarb) isotope curve (Cramer et al., 2011a;

13 Melchin et al., 2012) contains two positive carbon (δ Ccarb) isotope excursions, the

lower Sheinwoodian (Ireviken) excursion and the Homerian (Mulde) excursion. The

13 lower Sheinwoodian (Ireviken) positive carbon (δ Ccarb) isotope excursion is a single- peaked event (Samtleben et al., 1996; Bickert et al., 1997; Kaljo and Martma, 2006;

Cramer et al., 2011a), the upper Sheinwoodian and lower Homerian typically record baseline values (Cramer et al., 2011a), and the middle and upper Homerian (Mulde)

positive isotope excursion, is a double-peaked event with a return to baseline values

between each peak (Corfield et al., 1992; Cramer et al., 2006b; Cramer et al., 2011a).

Therefore, a complete Wenlock succession would be expected to record two intervals of

13 elevated carbon (δ Ccarb) isotopic values with three discrete peaks (Cramer et al.,

2011a).

Based on previous stratigraphic correlations, the Guelph Formation was expected to

lie within the Homerian Stage (Cramer et al., 2011a) and as a result, this

lithostratigraphic unit within the core was expected to record the Homerian (Mulde)

13 positive carbon (δ Ccarb) isotope excursion. However, isotopic values are elevated

throughout the entire core with no discernable mid-Wenlock baseline. There are four

possible interpretations for the elevated isotopic record contained in the core and each

is discussed below.

13 1) The carbon (δ Ccarb) isotope data within the core represents only the Ireviken

13 positive carbon (δ Ccarb) isotope excursion, and if this is the case, there are two potential explanations. The core is located along the southwestern flank of the

Algonquin Arch, and the Guelph Formation in the core is one of the thickest successions of this lithostratigraphic unit recorded in the Appalachian Basin. It is possible that the strata identified as the Guelph Formation in the core may actually be the Gasport, Goat

Island, or Eramosa formations, which would require reexamination of strata previously identified as the Guelph Formation in this study. However, misidentification of this stratigraphic interval is highly unlikely due to the recovery of extensive drill cores and regional lithostratigraphic correlation done by the OGS during the last decade.

Another possible explanation for the presence of the Ireviken Excursion in the Guelph

Formation is that this unit is diachronous from western New York to southwestern

Ontario. In western New York the Guelph Formation lies within the lower Homerian

Stage. If the Guelph Formation in southwestern Ontario contains the Ireviken Excursion

then this lithostratigraphic unit would have to extend down to the middle Sheinwoodian

Stage. To test this hypothesis extensive biochemostratigraphic data from a series of

cores between southwestern Ontario and western New York would be necessary, because the chronostratigraphic data (specifically, the conodont biostratigraphic data)

recovered from this core alone are insufficient to address this hypothesis.

13 The remaining explanations all imply that the mid-Wenlock carbon (δ Ccarb) isotopic

baseline has been removed and that the data recovered in the core represent both the

13 lower Sheinwoodian (Ireviken) and Homerian (Mulde) positive carbon (δ Ccarb) isotope

excursions. These interpretations are supported by the presence of a regional sharp

erosional basal contact between the Guelph Formation and the underlying Eramosa or

Goat Island formations (Brunton, 2009). This regional disconformity has been well-

documented in southwestern Ontario (Brunton, 2009). The differences between the

following explanations center on how much of the Mulde excursion has been preserved

above this regional disconformity.

13 2) The carbon (δ Ccarb) isotopic data recovered in the core represent the Ireviken

Excursion and both peaks of the Mulde Excursion. In this interpretation the first peak of

the Mulde Excursion is recorded within the lower Wellington Member of the Guelph

Formation, the drop in values between the two peaks of the excursion is recorded

within the middle Wellington Member. The second peak of the Mulde Excursion occurs

within the upper Wellington Member and values steadily decline through the Hanlon

Member of the Guelph Formation. However, there are two features of the isotope

curve in the core that render this interpretation unlikely.

First, there is no return to baseline values within the isotopic data, and the drop

within the middle Wellington Member is only 1‰ and does not approach baseline

values for the Mulde Excursion. In most sections that contain both peaks of the Mulde

Excursion worldwide the drop between the two peaks approaches the values before and

after the excursion (Corfield et al., 1992; Cramer et al., 2006a; Kaljo and Martma, 2006;

Cramer et al., 2012). The magnitude of the drop between the two peaks in the isotopic

data in this core is of smaller magnitude than expected if this were the entirety of the

Mulde Excursion. More importantly, if this core records the entire Mulde Excursion, the

elevated values at the very top of the core are difficult to explain.

13 Globally, above the Homerian (Mulde) positive carbon (δ Ccarb) isotope excursion

13 there are two positive carbon (δ Ccarb) isotope excursions in the Ludlow Series, a low-

amplitude (+1.0‰) excursion at the base of the Ludfordian Stage known as the Linde

Excursion and a large-magnitude (+8.0‰) excursion in the middle and upper part of the

Ludfordian Stage, known as the Lau Excursion (Cramer et al., 2011a). If the core records

the entirety of the Mulde Excursion, then the elevated isotopic values at the top of the core in the Hanlon Member of the Guelph Formation must represent either the Linde

Excursion or the Lau Excursion. This interpretation is problematic because it would require a significant disconformity within the Hanlon Member, in which the entire

Gorstian Stage is missing, and there is no stratigraphic evidence of such an unconformity either within the core or regionally. Furthermore, the isotopic values are exceptionally high to represent the Linde Excursion. If this were to represent the onset of the Lau

Excursion, the Gorstian Stage and the lower portion of the Ludfordian Stage would be missing; and based on current knowledge, the Ludfordian Stage should be well-within the Salina Group (Johnson et al., 1992; Brett et al., 1995; Brunton, 2009; Cramer et al.,

13 2011a). As a result, it is highly unlikely that the carbon (δ Ccarb) isotopic data within the

13 core records both peaks of the Homerian (Mulde) positive carbon (δ Ccarb) isotope excursion.

13 3) The carbon (δ Ccarb) isotope data within the core may represent the Ireviken

Excursion and the second peak of the Mulde Excursion. In this scenario, the first peak of the Mulde Excursion was removed by the regional disconformity between the Eramosa

Formation and overlying Guelph Formation. This interpretation is unlikely because it

13 suffers from the same difficulty to explain the elevated carbon (δ Ccarb) isotopic values at the top of the core in the Hanlon Member of the Guelph Formation.

4) The carbon isotope data within the core may represent the Ireviken Excursion and the first peak of the Mulde Excursion. In this interpretation, the mid-Wenlock baseline and ascending limb of the first peak of the Mulde Excursion are removed by the regional disconformity between the Eramosa Formation and the overlying Guelph Formation.

The entirety of the first peak of the Mulde Excursion is preserved, including the descending limb of the first peak, and the elevated isotopic values at the top of the core in the Hanlon Member of the Guelph Formation would represent the ascending limb of

69 the second peak. Whereas this is the most parsimonious explanation for the data at the top of the core, this interpretation cannot explain the small drop (1.0‰) in isotopic values in the middle part of the Wellington Member of the Guelph Formation.

Based on the evidence listed above, interpretation number four appears to be most likely, because this interpretation requires the least chronostratigraphic revision, avoids the requirement of significant lithostratigraphic diachroneity, includes the smallest amount of disconformable removal of stratigraphic section, is most in line with present regional chronostratigraphy, and can best explain the isotopic data at the top of the core. To fully evaluate these hypotheses, however, significant additional biostratigraphic data must be obtained.

Conclusions

The Silurian stratigraphic succession from the Ontario Geological Survey (OGS-DDH6-

09) core studied preserves a only a small portion of the Llandovery Series and portions of the Wenlock Series. The Cabot Head Formation can be constrained to the

Rhuddanian Stage within the Distmodus kentuckyensis Zone due to the presence of

Icriodella sp. Biostratigraphic control of the strata above this position within the core was not possible due to extraordinarily poor conodont yields. However, the carbon

13 (δ Ccarb) isotope chemostratigraphic data provides important constraints for this

13 succession within the core. The lower Sheinwoodian (Ireviken) positive carbon (δ Ccarb)

13 isotope excursion and a portion of the Homerian (Mulde) positive carbon (δ Ccarb) isotope excursion appear to be recorded within the core. The Irondequoit, Lions Head,

Gasport, Goat Island, and Eramosa formations record the Ireviken Excursion and can be

correlated to the North American regional type series. The Wellington and Hanlon

members of the Guelph Formation record elevated carbon isotope values likely

13 indicative of the first peak of the Homerian (Mulde) positive carbon (δ Ccarb) isotope

excursion. However, due to poor conodont element yields from samples processed

from this core, precise chronostratigraphic correlation of the Guelph Formation cannot

be accomplished.

This study provides additional support for the correlation of the Lions Head

Formation of southwestern Ontario with the Rochester and Decew formations of

western New York. Whereas potential misidentification and miscorrelation of the

Guelph Formation between southwestern Ontario and western New York cannot be

ruled out by this study, the data recovered from this core appear to support the regional

disconformity between the Guelph Formation and the underlying Eramosa and Goat

Island formations. The most parsimonious explanation for the data from this core

suggests that the Guelph Formation belongs to part of the Homerian Stage and records

13 a portion of the Homerian (Mulde) positive carbon (δ Ccarb) isotope excursion.

Additional high-resolution biostratigraphic data is required to constrain this lithostratigraphic unit further.

Acknowledgements

I would like to thank Frank Bruton (Ontario Geological Survey in Sudbury, Ontario, Canada), without who this work would not have been possible. I would also like to thank Brad Cramer (University of Iowa) and Mark Kleffner (The Ohio State University) for their scientific discussions, patience, and help improving this manuscript. This work represents a contribution to the IGCP 591 Project.

Figures, Plate, and Table

Figure 3.1. Generalized paleogeographic map illustrating the structural features of southwestern Ontario, Canada during the Silurian Period. The Algonquin Arch separates the cratonic Michigan Basin and foreland Appalachian Basin (modified from Johnson et al., 1992). The locality of the core sampled for both 13 conodont biostratigraphy and carbonate carbon (δ Ccarb) isotope stratigraphy is shown ( ): Ontario Geological Survey (OGS-DDH-6-09) core along the southeastern flank of the Algonquin Arch along the distal, northwestern margin of the Appalachian Basin in Ontario, Canada.

Figure 3.2. North American Silurian chronostratigraphic terms and lithostratigraphic chart – illustrating the relationships between the USGS and the OGS. Panel A. Chronostratigraphic chart modified from Cramer et al. (2011) illustrating the global series and stages of the Silurian (far left column) and the relationship between the North American Silurian chronostratigraphic terms in use by the USGS (middle column) and the OGS (far right column). The USGS column is from Brett et al. (1995), the Llandovery-Wenlock portion of the OGS column is from Brunton (2009), and the Ludlow-Pridoli portion of the OGS column is from Johnson et al. (1992), using Norford (1997) and Brunton (2009). Panel B. Lithostratigraphic chart illustrating the relationship between North American lithostratigraphic terms in use by the USGS and the OGS. The USGS column (left) is from Brett et al. (1995) and the OGS column (right) is from Brunton (2009). USGS – United States Geological Survey. OGS – Ontario Geological Survey.

Figure 3.3. Silurian (Llandovery and Wenlock) conodont zonation and ranges of selected conodont species. Conodont zonation and ranges after Jeppsson (1997), Jeppsson et al. (2006), Männik (2007a, 2007b), and Cramer et al. (2010). Stage dates from Gradstein et al. (2012). Horizontal bars at the bottom or top of a species range indicate the first appearance (FAD) and the last appearance (LAD) of that species, respectively. Dashed lines in the range of a species indicate the scattered presence of that species. Ranges of species that extend beyond what is represented in the figure are indicated with an arrow.

Figure 3.4. Chronostratigraphic data from the Ontario Geological Survey (OGS-DDH6-09) core. Lithostratigraphy, 13 conodont biostratigraphy, and carbonate carbon (δ Ccarb) isotope chemostratigraphy (VPDB – Vienna Pee Dee belemnite) from the Ontario Geological Survey (OGS-DDH6-09) core. The core is located along the southeastern flank of the Algonquin Arch on the distal, northwestern margin of the Appalachian Basin in Ontario, Canada. Samples that yielded conodonts with no biostratigraphic utility are marked with an ‘x’ along the right-side of the lithostratigraphic column (species of the genus Panderodus).

Plate 3.1. Silurian conodonts from the Ontario Geological Survey (OGS-DDH6-09) core. The core is located along the southeastern flank of the Algonquin Arch on the distal, northwestern margin of the Appalachian Basin in Ontario, Canada. All photographs were taken with a light microscope at 31x magnification. 1: Ozarkodina sp. (affinities to the Ozarkodina lineage of sagitta rhenana, sagitta sagitta, bohemica longa, and bohemica bohemica) from 266’06” to 267’02” within the OGS-DDH6-09 core. 2: Panderodus sp. from 266’06” to 267’02” within the OGS-DDH6-09 core. 3, 4, 5, and 6: Icriodella sp. from 457’06” to 457’08” within the OGS-DDH6-09 core.

Table 3.1 Silurian chronostratigraphy of the Ontario Geological Survey (OGS-DDH6-09) core along the southeastern flank of the Algonquin Arch on the distal, northwestern margin of the Appalachian Basin in Ontario, Canada.

Table 3.1 (continued)

References

Aldridge, R.J. 1975. The stratigraphic distribution of conodonts in the British Silurian. Journal of the Geological Society, London, 131(6):607-618.

Aldridge, R.J. 1972. Llandovery conodonts from the Welsh Borderland. Bulletin of the British Museum (Natural History) Geology, 22(2):125-231.

Bancroft, A.M. 2008. Silurian conodont biostratigraphy and carbonate carbon isotope stratigraphy of the Eramosa of southwestern Ontario, Canada. Unpublished MS Thesis. The Ohio State University, Columbus, 45 pp.

Bergström, S.M., Saltzman, M.R., and Schmitz, B. 2006. First record of the Hirnantian 13 (Upper Ordovician) δ Ccarb excursion in the North American Midcontinent and its regional implications. Geological Magazine, 143(5):657-678.

Bergström, S.M., Chen, X., Gutiérrez-Marco, J.C., and Dronov, A. 2009. The new chronostratigraphic classification of the Ordovician System and its relations to major 13 regional series and stages and to δ Ccarb chemostratigraphy, Lethaia, 42(1):97-107.

Berry, W.B.N. and Boucot, A.J. 1970. Correlation of the North American Silurian rocks. Geological Society of America, Special Paper 102, 289 pp.

Brett, C.E., Tepper, D.H., Goodman, W.M., LoDuca, S.T., and 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. Report: B 2086, 66 pp.

Brunton, F.R. 2009. Update of revisions to Early Silurian stratigraphy of Niagara Escarpment: Integration of sequence stratigraphy/sedimentology/hydrogeology to delineate hydrogeologic units. In Summary of field work and other activities 2009, pp. 25-1-25-20. Ontario Geological Survey, Open File Report 6240.

Cooper, B.J. 1975. Multielement conodonts from the Brassfield Limestone (Silurian) of southern Ohio. Journal of Paleontology, 49(6):984-1008.

Corfield, R.M., Siveter, D.J. Cartlidge, J.E., and McKerrow, W.S. 1992. Carbon isotope excursion near the Wenlock-Ludow (Silurian) boundary in the Anglo-Welsh area. Geology, 20(4):371-374.

Craig, H. 1957. Isotopic standards for carbon and oxygen and correction factors for mass-spectrometric analysis of carbon dioxide. Geochimica et Cosmochimica Acta, 12(1-2):133-149.

Cramer, B.D., Condon, D.J., Söderlund, U., Marshall, C., Worton, G.J., Thomas, A.T., Calner, M., Ray, D.C., Perrier, V., Boomer, I., Patchett, P.J., and Jeppsson, L. 2012. U- Pb (zircon) age constraints on the timing and duration of Wenlock (Silurian) paleocommunity collapse and recovery during the “Big Crisis”. GSA Bulletin, 124(11-12):1841-1857.

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., and Saltzman, M.R. 2011a. Revised correlation of Silurian Provincial Series of North America with global and regional chronostratigraphic units and δ13C chemostratigraphy. Lethaia, 44(2):185-202.

Cramer, B.D., Davies, J.R., Ray, D.C., Thomas, A.T., and Cherns, L. 2011b. Siluria revisited: An introduction. In Siluria revisited: A field guide. Edited by D.C. Ray. 2011 International Subcommission on Silurian Stratigraphy Meeting and IGCP 591 Annual Meeting, Ludlow, England, pp. 6-27.

Cramer, B.D., Loydell, D.K., Samtleben, C., Munnecke, A., Kaljo, D., Männik, P., Martma, T., Jeppsson, L., Kleffner, M.A., Barrick, J.E., Johnson, C.A., Emsbo, P., Joachimski, M.M., Bickert, T., and Saltzman, M.R. 2010. Testing the limits of Paleozoic chronostratigraphic correlation via high-resolution (<500,000 yrs) integrated 13 conodont, graptolite, and carbon isotope (δ Ccarb) biochemostratigraphy across the Llandovery-Wenlock (Silurian) boundary: Is a unified Phanerozoic timescale achievable? Geological Society of America Bulletin, 122(9-10):1700-1716.

Ettensohn, F.R. 1994. Tectonic control on formation and cyclicity of major Appalachian unconformities and associated stratigraphic sequences. In Tectonic and eustatic controls on sedimentary cycles. Edited by J.M. Dennison and F.R. Ettensohn. SEPM Concepts in Sedimentology and Paleontology #4, pp. 217-242.

Ettensohn, F.R. and Brett, C.E. 1998. Tectonic components in Silurian cyclicity: Examples from the Appalachian Basin and global implications. In Silurian cycles: Linkages of dynamic stratigraphy with atmospheric, oceanic, and tectonic changes (James Hall Centennial Volume). Edited by E. Landing and M.E. Johnson. New York State Museum Bulletin 491, pp. 145-162.

Frakes, L.A., Francis, J.E., and Skytus, J.I. 1992. Climate modes of the Phanerozoic. Cambridge University Press, Cambridge, 274 pp.

Goodman, W.M. and Brett, C.E. 1994. Roles of eustasy and tectonics in development of Silurian stratigraphic architecture of the Appalachian foreland basin. In Tectonic and eustatic controls on sedimentary cycles. Edited by J.M. Dennison and F.R. Ettensohn. SEPM Concepts in Sedimentology and Paleontology #4, pp. 147-169.

Gradstein, F.M., Ogg, J.G., Schmitz, M.D., and Ogg, G.M. 2012. The Geologic Time Scale 2012. Elsevier, 1176 pp.

Grahn, Y.G. and Caputo, M.V. 1992. Early Silurian glaciations in Brazil. Palaeogeography, Palaeoclimatology, Palaeoecology, 99(1-2):9-15.

Graves, R.W. and Ellison, S.P. 1941. Ordovician conodonts of the Marathon Basin, Texas. University of Missouri, School of Mines and Metallurgy, Technical Bulletin Series, 14(2):1-26.

Jaeger, H. 1959. Graptolithen und stratigraphie des jungsten Thuringer Silurs. Abhandlungen Akademie Wissenschaften Berlin, Klasse Chemie, Geologie und Biologie 2, 197 pp.

Jeppsson, L. 1998. Silurian oceanic events: Summary of general characteristics. In Silurian cycles: Linkages of dynamic stratigraphy with atmospheric, oceanic, and tectonic changes (James Hall Centennial Volume). Edited by E. Landing and M.E. Johnson. New York State Museum Bulletin 491, pp. 239-257.

Jeppsson, L. 1997. A new latest Telychian, Sheinwoodian, and early Homerian (early Silurian) standard conodont zonation. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88(2):91-114.

Jeppsson, L. 1990. An oceanic model for lithological and faunal changes tested on the Silurian record. Journal of the Geological Society of London, 147(4):663-674.

Jeppsson, L. and Aldridge, R.J. 2000. Ludlow (late Silurian) oceanic episodes and events. Journal of the Geological Society, London, 157(6):1137-1148.

Jeppsson, L. and Anehus, R. 1999. The optimal acetate buffered acetic acid technique for extracting phosphatic fossils. Journal of Paleontology, 73(5):964-972.

Jeppsson, L. and Anehus, R. 1995. A buffered formic acid technique for conodont extraction. Journal of Paleontology, 69(4):790-794.

Jeppsson, L. and Calner, M. 2003. The Silurian Mulde Event and a scenario for secundo- secundo events. Transactions of the Royal Society of Edinburgh: Earth Sciences, 93(2):109-114.

Jeppsson, L., Aldridge, R.J., and Dorning, K.J. 1995. Wenlock (Silurian) oceanic episodes and events. Journal of the Geological Society, London, 152(3):487-489.

Jeppsson, L., Fredholm, D., and Mattiasson, B. 1985. Acetic acid and phosphatic fossils— A warning. Journal of Paleontology, 59(4):952-956.

Kaljo, D. and Martma, T. 2006. Application of carbon isotope stratigraphy to dating the Baltic Silurian rocks. GFF (Geologiska Föreningens I Stockholm Förhandlingar), 128(2):123-129.

Kleffner, M.A. 2004. Lower Silurian Medina and Clinton Groups of the Niagara region. Geological Association of Canada – Mineralogical Association of Canada Meeting 2004. Brock Universty, St. Catherines, Ontario – Pander Society Field Trip, pp. 1-5.

Kleffner, M. 1994. Conodont biostratigraphy and depositional history of strata comprising the Niagran sequence (Silurian) in the northern part of the Cincinnati Arch region, west-central Ohio, and evolution of Kockelella walliseri (Helfrich). Journal of Paleontology, 68(1):141-153.

Koren’, T.N., Lenz, A.C., Loydell, D.K., Melchin, M.J., Štorch, P., and Teller, L. 1996. Generalized graptolite zonal sequence defining Silurian time intervals for global paleogeographic studies. Lethaia, 29(1):59-60.

Loydell, D.K. 1998. Early Silurian sea-level changes. Geological Magazine, 135(4):447-471.

Loydell, D.K., Kleffner, M.A., Mullins, G.L., Butcher, A., Matteson, D.K., and Ebert, J.R. 2007. The lower Williamson Shale (Silurian) of New York: A biostratigraphic enigma. Geological Magazine, 144(2):225-234.

Männik, P. 2007a. An updated Telychian (late Llandovery, Silurian) conodont zonation based on Baltic faunas. Lethaia, 40(1):45-60.

Männik, P. 2007b. Recent developments in the upper Ordovician and lower Silurian conodont biostratigraphy in Estonia. Estonian Journal of Earth Sciences, 5(1):35-46.

Männik, P. 1998. Evolution and taxonomy of the Silurian conodont Pterospathodus. Palaeontology, 41(5):1001-1050.

McLaughlin, P.I., Cramer, B.D., Brett, C.E., and Kleffner, M.A. 2008. Silurian high- resolution stratigraphy on the Cincinnati Arch: Progress on recalibrating the layer- cake. In From the Cincinnati Arch to the Illinois Basin: Geological field excursions along the Ohio River Valley. Edited by A.H. Maria and R.C. Counts. Geological Society of America Field Guide 12, pp. 119-180.