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Amino Acid Racemization of Planktonic Foraminifera

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Amino Acid Racemization of Planktonic Foraminifera AMINO ACID RACEMIZATION OF PLANKTONIC FORAMINIFERA: PRETREATMENT EFFECTS AND TEMPERATURE RECONSTRUCTIONS by Emily Watson A thesis submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Master of Science in Marine Studies Spring 2019 © 2019 Emily Watson All Rights Reserved AMINO ACID RACEMIZATION OF PLANKTONIC FORAMINIFERA: PRETREATMENT EFFECTS AND TEMPERATURE RECONSTRUCTIONS by Emily Watson Approved: __________________________________________________________ Katharina Billups, Ph.D. Professor in charge of thesis on behalf of the Advisory Committee Approved: __________________________________________________________ Mark Moline, Ph.D. Chair of the Department of Marine Science and Policy Approved: __________________________________________________________ Estella Atekwana, Ph.D. Dean of the College of Earth, Ocean, and Environment Approved: __________________________________________________________ Douglas J. Doren, Ph.D. Interim Vice Provost for Graduate and Professional Education ACKNOWLEDGMENTS Very special thanks to my M.S. advisor Dr. Katharina Billups for providing me with this amazing opportunity and giving me her utmost support. Her willingness to give her time so generously has been indispensable during my Masters. She is my ultimate scientific role model. I am grateful for my collaborators from Northern Arizona University, Dr. Darrell Kaufman and Katherine Whitacre, who taught me the cleaning methods for this project and opened up their lab to me in January 2018. I would like to express my appreciation to Dr. Kaufman for his valuable and constructive suggestions during the planning and development of this research work. Data provided by Katherine was very valuable. I would also like to thank Dr. Doug Miller, and Dr. Andrew Wozniak, Dr. John Wehmiller from the University of Delaware for their assistance with this project. Dr. Wozniak has been an important part of my committee, especially from the organic chemistry side of things. Dr. Miller gave advice on the development of the statistical tests used in this study. Input from Dr. John Wehmiller (Emeritus) was especially appreciated as he is well-known in the field of amino acid geochronology. I wish to acknowledge funding of this research and first thank the donors of the Petroleum Research Fund (PRF #56964-ND), administered by the American Chemical Society ACS. I also wish to acknowledge the School of Marine Science and Policy at the University of Delaware for their continued support and travel funding over the past 2 years. iii Nobody has been more important to me in the pursuit of this project than my friends and family. I would like to thank my parents, whose love and guidance are with me in whatever I pursue. Most importantly, I wish to thank my loving husband, TJ, who has provided me unending support and encouragement through this journey. I also would like to make a quick shout-out to my lab mates, Maoli Vizcaíno and Emily Kaiser, who always bring a positive atmosphere to the lab and plenty of laughs. iv TABLE OF CONTENTS LIST OF TABLES ....................................................................................................... vii LIST OF FIGURES ....................................................................................................... ix ABSTRACT ................................................................................................................. xiv Chapter 1 INTRODUCTION .............................................................................................. 1 2 BACKGROUND ................................................................................................ 5 2.1 Amino Acid Racemization (AAR)............................................................. 5 2.2 Application of Amino Acid Racemization ................................................ 7 2.2.1 Amino Acid Geochronology .......................................................... 7 2.2.2 Amino Acid Thermometry ........................................................... 10 2.3 Amino Acid Racemization Kinetics ........................................................ 12 2.4 Determination of the EDT ....................................................................... 14 2.5 Pretreatment Methods .............................................................................. 16 3 RESEARCH STRATEGY ................................................................................ 19 3.1 Site Selection and Modern Hydrography ................................................. 19 3.2 Species Selection ..................................................................................... 22 3.3 Sampling Strategy .................................................................................... 24 3.4 Analytical Methods .................................................................................. 28 3.4.1 Foraminiferal Picking .................................................................. 28 3.4.2 Pretreatment Methods .................................................................. 28 3.4.2.1 Non-bleached Method ................................................... 28 3.4.2.2 Bleached Method .......................................................... 29 3.4.3 Analysis on HPLC ....................................................................... 29 3.4.4 Radiocarbon Dating ..................................................................... 30 4 COMPARISON OF 14C AGES AND PUBLISHED STRATIGRAPHY ........ 32 5 PRETREATMENT ANALYSIS ...................................................................... 37 v 5.1 Effect of Bleaching on the Subsample Rejection Rate ............................ 37 5.2 Effect of Bleaching on the Concentration of Amino Acids ..................... 40 5.3 Effect of Bleaching on the D/L Ratios by Species .................................. 44 5.4 Effect of Bleaching on the Variability of D/L Ratios of Subsamples within a Sample ....................................................................................... 53 5.5 Effect of Bleaching on Species Differences in D/L ................................. 56 5.6 Down-Core Trend .................................................................................... 63 5.7 Discussion of Pretreatment Analyses ....................................................... 65 5.8 Summary .................................................................................................. 67 6 APPLICATION TO PALEOTHERMOMETRY ............................................. 69 6.1 Determination of the Effective Diagenetic Temperatures ....................... 69 6.2 Paleotemperature Uncertainties and Trend Selection .............................. 78 6.3 Temperature Histories .............................................................................. 83 6.4 Paleoceanographic Implications .............................................................. 84 6.4.1 Comparison with Other Records of Bottom Water Temperature 84 6.4.2 Deep Water Circulation ............................................................... 86 6.5 Summary .................................................................................................. 88 7 CONCLUSION ................................................................................................. 91 REFERENCES ............................................................................................................. 94 Appendix A SUPPLEMENTARY TABLES AND FIGURES ........................................... 107 vi LIST OF TABLES Table 1. Site information for ODP Cores 1056D, 1059A, and 1062B from the Blake-Bahama Outer Ridge. .................................................................... 21 Table 2. Summary of interval, depth in core, and stratigraphic age for sites used in this study. Stratigraphic ages for Holocene and down-core samples are 18 determined from %CaCO3 orbitally tuned (Grützner et al. 2002) and δ O stratigraphy (Hagen and Keigwin 2002; Billups et al. 2004), respectively.26 14 18 Table 3. Rapid C age measurements compared to δ O (Hagen and Keigwin 2002; Billups et al. 2004) and %CaCO3 orbitally tuned (Grützner et al. 2002) age models. .................................................................................... 36 Table 4. Percent of subsamples rejected. The species in red show higher rejection rates in the bleached samples than unbleached samples. Data used to determine the subsample rejection rate are shown in Table A2. ............. 39 Table 5. Mean D/L values for the unbleached (unbl) and bleached (bl) treatments with the statistical results of Welch’s independent t-tests. ...................... 51 Table 6. Results of two-way replicated ANOVA models to determine the effects of the different pretreatments on the D/L ratios. ..................................... 52 Table 7. Average sample variability (coefficient of variation, CV) in Holocene and down-core sites for both pretreatments (unbleached = unbl and bleached = bl). Data used to calculate the average variability are shown in Table A6. ............................................................................................. 55 Table 8. Results of Welch’s independent t-tests to determine the species effects on the D/L ratios. .......................................................................................... 61 Table 9. Effective diagenetic temperatures (EDTs) and uncertainties in °C derived from amino acid paleothermometry of P. obliquiloculata and G. truncatulinoides for 2000 m (Site 1056) and 3000 m (Site
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