Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School 2017 Investigation of Paleoredox Conditions across the Llandovery- Wenlock (Silurian) Boundary: Implications for the Ireviken Extinction Event and Carbon Isotope Excursion Andrew Thomas Kleinberg Follow this and additional works at the DigiNole: FSU's Digital Repository. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES INVESTIGATION OF PALEOREDOX CONDITIONS ACROSS THE LLANDOVERY- WENLOCK (SILURIAN) BOUNDARY: IMPLICATIONS FOR THE IREVIKEN EXTINCTION EVENT AND CARBON ISOTOPE EXCURSION By ANDREW KLEINBERG A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master in Science 2017 Andrew Kleinberg defended this thesis on June 29, 2017. The members of the supervisory committee were: Seth Young Professor Directing Thesis Jeremy Owens Committee Member Angie Knapp Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that this thesis has been approved in accordance with university requirements. ii ACKNOWLEDGMENTS I would like to take the time to thank my thesis advisor, Dr. Seth Young, whose invaluable guidance, patience, and positive encouragement has pushed me well past the precipice of my own capabilities and expectations throughout my Masters career. I am so grateful for the opportunities he has provided me and being given the chance to study my Masters under him. I would also like to take the chance to thank my other committee members: Dr. Jeremy Owens for his equal involvement during my Masters and his light-hearted and humorous, yet engaging and helpful, mentoring approach; and Dr. Angela Knapp for her helpful guidance and providing an oceanographic perspective to this geologic event. Additionally, I could have never of done this without the help of my friends/colleagues Chelsie Bowman and Nevin Kozik whose support and helpfulness throughout my Masters was immeasurably important. I would also like to thank Emily Benayoun, Lance Newman, Adolfo Calero, Claudia Richbourg, and Matt Mcdowell for their help as undergrad assistants during this process. I would also like to thank Burt Wolff of the National High Magnetic Field Laboratory Geochemistry department for his help in running my samples for carbon isotope analysis and Ben Underwood from the Indian State University Stable Isotope Research Laboratory for running my samples for sulfur isotope analysis on their instruments Additionally, I would like to thank the National Geologic Society of America, awarding me with the Charles A. and June R.P. Ross Research Grant, and Southeastern GSA for the partial funding of this project. Finally, I would like to thank my friends and family whose love, support, and encouragement helped me get through some of the harder parts of my Masters. iii TABLE OF CONTENTS List of Tables ................................................................................................................................. vi List of Figures ............................................................................................................................... vii Abstract ........................................................................................................................................ viii 1. INTRODUCTION ......................................................................................................................1 2. GEOLOGIC BACKGROUND ...................................................................................................6 2.1 Early Silurian Climate and Oceans .....................................................................................6 2.2 Depositional Environment, Facies, and Sequence Stratigraphy .........................................9 3. METHODS ...............................................................................................................................11 3.1 Sample Preparation and Extraction ..................................................................................11 3.2 Stable Isotope and I/(Ca+Mg) ..........................................................................................12 4. RESULTS .................................................................................................................................15 4.1 Newsom Roadcut, Nashville, Tennessee ..........................................................................15 4.2 Pete Hanson Creek II, Roberts Mountains, Nevada .........................................................16 5. DISCUSSION ...........................................................................................................................18 5.1 Evaluation of Diagenesis on Primary Geochemical Signatures .......................................19 34 5.2 Mechanism for late Llandovery-early Wenlock δ SCAS Trends: a Global Redox Proxy 21 5.3 Variation in I/(Ca+Mg) records: a Local Redox Proxy ...................................................24 13 13 5.4 Factors Affecting Variability of δ CCarb and δ COrg .......................................................25 5.5 Redox and Environmental Conditions Across the Llandovery-Wenlock Boundary ........26 6. CONCLUSIONS .......................................................................................................................29 APPENDICES ...............................................................................................................................31 A. DATA TABLES .......................................................................................................................31 B. FIGURES AND GRAPHS ........................................................................................................37 References ......................................................................................................................................46 Biographical Sketch .......................................................................................................................55 iv LIST OF TABLES A.1 Geochemical proxy data of Newsom Roadcut field site ..........................................................31 A.2 Geochemical proxy data of Pete Hanson II field site ..............................................................35 v LIST OF FIGURES 13 B.1 Generalized Silurian (Wenlock-Ludlow) δ Ccarb curve with conodont and graptolite biostratigraphy, and new high precision U-Pb radiometric dates [Cramer et al., 2011, 2012, 2015] ....................................................................................................................................... 37 B.2 Timeframe of the Ireviken Carbon Isotope Excursion in relation to Jeppsson (1990) oceanic states, epicontinental stratigraphy, glaciation, and eustatic sea level change [Cramer and Saltzman, 2007]. Detailed biostratigraphy after Calner [2004] and eustatic sea-level curve from Cramer and Saltzman [2005] ..........................................................................................38 B.3 Primo and Secundo state model modified after Jeppsson (1990) and Cramer and Saltzman (2005). Red star marks the Pete Hanson Creek II section and blue marks the Newsom Roadcut section. WSBW stands for Warm Saline Bottom Waters .........................................39 B.4 Geochemical crossplots for evaluation of diagenesis for this study, please note that all 13 18 Newsom Roadcut δ Ccarb and δ Ocarb values are replotted from Cramer and Saltzman (2005, 13 18 13 34 2007). A) Plot of δ Ccarb vs. δ Ocarb. B) Plot of δ COrg vs %TOC. C) Plot of δ SCAS vs 18 18 δ Ocarb. D) Plot of CAS(ppm)% vs δ Ocarb ............................................................................40 B.5 Paleogeographic reconstruction of Laurentia during the middle Silurian ~431 Ma with field sites marked in their respective localities both during this time and in modern day ...............41 B.6 Roberts Mountains Stratigraphic Column with stable carbon and sulfur isotopes and I/Ca+Mg data. The conodont biostratigraphy plotted is from Klapper and Murphy (1975) ...42 B.7 Newsom Roadcut Stratigraphic Column with stable carbon and sulfur isotopes and I/Ca+Mg data. Please note that δ13Ccarb and δ13Corg are replotted from Cramer and Saltzman (2007) and conodont biostratigraphy is from Barrick et al. [1983] .................................................. 43 13 B.8 δ Ccarb isotope data of Pete Hanson Creek II, Roberts Mountains, NV, Banwy River, Wales, 13 13 δ Corg data from Loydell and Frýda (2007), and the Newsom Roadcut, Nashville, TN, δ Corg data from Cramer and Saltzman (2007). Condont and graptolite biostraigraphy done by [Männik and Aldridge, 1989; Jeppsson, 1997; Loydell et al., 1998; Männik, 2007; Rubel et al., 2007; Cramer and Saltzman., 2006a; 2010]. Grey is due to a confusion of graptolite and conodont correlation ................................................................................................................44 B.9 Carbonate Redox Proxies and expected trends during the Ireviken CIE ................................45 vi ABSTRACT The Ireviken extinction event occurred within the early-middle Silurian, spanning the Llandovery-Wenlock boundary, ~431 million years ago and has been proposed to have been initiated at least partly through the transition from late Ordovician- early Silurian icehouse conditions to middle Silurian greenhouse conditions. This extinction, like many of the