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Extending the Applications of Tephrochronology in Northwestern North America University of Alberta Extending the applications of tephrochronology in Northwestern North America by HayleyAnn Dunning A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science Department of Earth and Atmospheric Sciences ©HayleyAnn Dunning Fall 2011 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. 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The author retains copyright L'auteur conserve la propriete du droit d'auteur ownership and moral rights in this et des droits moraux qui protege cette these. Ni thesis. Neither the thesis nor la these ni des extraits substantiels de celle-ci substantial extracts from it may be ne doivent etre imprimes ou autrement printed or otherwise reproduced reproduits sans son autorisation. without the author's permission. In compliance with the Canadian Conformement a la loi canadienne sur la Privacy Act some supporting forms protection de la vie privee, quelques may have been removed from this formulaires secondaires ont ete enleves de thesis. cette these. While these forms may be included Bien que ces formulaires aient inclus dans in the document page count, their la pagination, il n'y aura aucun contenu removal does not represent any loss manquant. of content from the thesis. 1+1 Canada ABSTRACT Major-element geochemistry, stratigraphy and Bayesian statistical age modeling are combined with the aim of integrating paleoclimate records. The goal is to create a tephrochronological framework for northwestern North America. The coastal region of southeastern Alaska is explored through a terrestrial peat core and a marine core. The widespread Mount Edgecumbe dacite (MEd) is identified in both cores. The age of the MEd is modeled between 13,270 -13,050 cal yrs BP. This date is used to estimate the marine reservoir for this area; approximately 320 - 810 years. Four sulphate peaks from the PR Col ice core from Mt Logan are investigated for associated cryptotephras. The expected tephras are found for White River East and Aniakchak events, and possible correlations are found for White River North and Hayes Tephra Set H events. The PR Col age model for these tephras is tested against terrestrial age estimations, and shows good agreement. TABLE OF CONTENTS CHAPTER 1 - INTRODUCTION 1.1 Introduction 1 1.2 References 6 CHAPTER 2 - METHODOLOGY 2.1 Introduction 11 2.2 Preparation techniques 12 2.2.1 Macrotephra 12 2.2.2 Cryptotephra 13 2.3 Electron microprobe analysis 15 2.3.1 Calibration 15 2.3.2 Conditions for analysis 17 2.4 Data analysis 18 2.4.1 Correcting for offset and drift 18 2.4.2 Normalization 19 2.4.3 Identifying contaminants 20 2.5 Correlations 20 2.6 Bayesian age modeling 22 2.7 Sediment cores 24 2.7.1 PSequencing 24 2.7.2 Bacon 25 2.7.3 Comparison 25 2.8 Single tephra ages 26 2.8.1 Phase model 26 2.8.2 Equals model 27 2.9 Outlier analysis 28 2.10 Conclusions 29 2.11 References 43 CHAPTER 3 - CORRELATING THE TERRESTRIAL AND MARINE RECORD OF THE MOUNT EDGECUMBE VOLCANIC FIELD 3.1 Introduction 48 3.2 Regional setting 50 3.3 Methods 51 3.3.1 Column Point 51 3.3.2 Lower Sitka Sound 52 3.3.3 Microprobe analysis 53 3.3.4 Age determination 53 3.4 Tephra characterization 54 3.5 Correlations 56 3.6 Core ages 58 3.7 MEd age 61 3.8 Marine reservoir estimation 62 3.9 Discussion and conclusions 64 3.10 References 73 CHAPTER 4 - TEPHROCHRONOLOGY OF THE PROSPECTOR RUSSELL COL ICE CORE, MOUNTT LOGAN 4.1 Introduction 78 4.2 PR Col sampling and geochemical analysis 81 4.2.1 White River Ash 83 4.2.2 Aniakchak 85 4.2.3 Hayes Tephra Set H 86 4.3 Bayesian statistical age modeling 87 4.3.1 White River Ash 89 4.3.2 Aniakchak 90 4.3.3 Hayes Tephra Set H 91 4.4 Discussion 91 4.4.1 White River Ash 92 4.4.2 Aniakchak 93 4.4.3 Hayes Tephra Set H 94 4.5 Conclusions 95 4.6 References 115 CHAPTER 5 - CONCLUSIONS 5.1 Conclusions 124 5.2 Further study 125 5.3 References 126 APPENDIX 6.1 Glass data 127 6.2 OxCal codes 168 LIST OF TABLES Table 2.1 Paradox Lake core chronology 36 Table 2.2 PSequencing and Bacon results 39 Table 2.3 Dates for the Fisher-Funk Phase model 39 Table 2.4 Cores for the Kaguyak Equals model 41 Table 3.1 Geochemistry of investigated tephras 69 Table 3.2 Preliminary Similarity Coefficient matches 70 Table 3.3 Radiocarbon dates for Column Point core 72 Table 3.4 Modeled tephra dates 72 Table 3.5 Dates for MEd Phase model 73 Table 4.1 PR Col target depths and ages 100 Table 4.2 Dates for all Phase models 107 Table 4.3 Core dates for Hayes Tephra Set H Equals model 108 LIST OF FIGURES Fig 1.1 Locations of tephra deposits 5 Fig 2.1 Mounting procedure for macrotephra 31 Fig 2.2 Mounting procedure for cryptotephra 32 Fig 2.3 Example of improvement by polishing 33 Fig 2.4 Example of normalization of tephra data 33 Fig 2.5 Example of geochemical difference in similar Similarity Coefficients 34 Fig 2.6 Radiocarbon calibration curve issues 35 Fig 2.7 Paradox Lake P_Sequencing output 37 Fig 2.8 Paradox Lake Bacon output 38 Fig 2.9 Fisher-Funk Phase model output 40 Fig 2.10 Kaguyak Equals model output 42 Fig 3.1 Locations map of MEVF and study sites 66 Fig 3.2 Column Point core 66 Fig 3.3 Lower Sitka Sound core 67 Fig 3.4 TAS plot of tephra data 68 Fig 3.5 Tephra data against Type I and II fields 68 Fig 3.6 Comparison of tephra data to MEd reference 71 Fig 4.1 Location map of target tephra deposits 97 Fig 4.2 PR Col core chemical data 98 Fig 4.3 ECM and sulphate plots for target events 99 Fig 4.4 Mounting procedure for cryptotephra 101 Fig 4.5 Geochemical bivariate plots of suspected WRE sections 102 Fig 4.6 Geochemical bivariate plots of suspected WRN sections 103 Fig 4.7 Geochemical bivariate plots of suspected Anaikchak sections 104 Fig 4.8 Geochemical bivariate plots of suspected Hayes Tephra Set H sections 105 Fig 4.9 Location map for Hayes sites visited 106 Fig 4.10 Nenana site photograph 106 Fig 4.11 Wiggle-match output for WRE tree stump 109 Fig 4.12 OxCal output for WRE Phase model 110 Fig 4.13 OxCal output for WRN Phase model Ill Fig 4.14 OxCal output for final Anaikchak Phase model 112 Fig 4.15 OxCal output for final Hayes Tephra Set H Equals model 113 CHAPTER 1 - INTRODUCTION 1.1 Introduction Each explosive volcanic eruption creates a unique ash layer, or tephra, which can be fingerprinted based on its distinctive mineralogy, geochemistry and stratigraphic properties. Where a tephra occurs as a consistent stratigraphic layer (i.e. not reworked), it can be considered as marking a single point in time, or isochron. Tephrostratigraphy can then connect sedimentary sequences in different places based on the presence of the tephra. Associated age data, whether relative or absolute (e.g. radiocarbon, lake varves), can then be applied to all locations where the tephra is present. Records that have been linked in this way may be diverse, ranging from paleoenvironmental and archaeological reconstructions, to records of eruptive history for improved hazard assessment. The combination of geochemical and chronological data can form interlinked tephrochronological frameworks across environmentally distinct regions, and such networks have been created, for example, in western Europe (e.g. Davies et al., 2002; Boygle, 2004; Mortensen et al., 2005); Japan, (e.g. Suzuki, 1996; Machida, 1999); and New Zealand (e.g. Shane et al., 1995; Shane, 2000; Carter et al., 2004; Alloway et al., 2007). The unglaciated area of Yukon and Alaska, collectively termed eastern Beringia, has undergone many climatological, ecological and archaeological changes in the past 20,000 years, and developing a robust tephrochronological framework for the area 1 would help to accurately date some of the changes.
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