THE SEDIMENT ACCUMULATION RECORD AT GLACIER-FED KINASKAN LAKE: IMPLICATIONS FOR CHANGES IN HOLOCENE HYDROLOGY AND CLIMATE IN THE UPPER ISKUT RIVER WATERSHED, BRITISH COLUMBIA by Monique M. Stewart A thesis submitted in conformity with the requirements for the degree of Masters of Science Graduate Department of Geography University of Toronto © Copyright by Monique M. 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Canada THE SEDIMENT ACCUMULATION RECORD AT GLACIER-FED KINASKAN LAKE: IMPLICATIONS FOR CHANGES IN HOLOCENE HYDROLOGY AND CLIMATE IN THE UPPER ISKUT RIVER WATERSHED, BRITISH COLUMBIA Ms. Monique M. Stewart Masters of Science, Graduate Department of Geography University of Toronto, 2008 ABSTRACT Acoustic sub-bottom profiles, ~5 m vibra-cores and lake hydrology are used to reconstruct the sediment accumulation history in Kinaskan Lake of the Upper Iskut River watershed in north­ western British Columbia. The lake is dominated by turbidity currents in proximal regions, producing well-laminated sediments that accumulate at -4.4 mm/year. Overflows and interflows distribute silt and clay sediments to distal lake areas and accumulation decreases to ~2 mm/year, forming well-defined couplets that are interpreted as varves. Sediment accumulation chronologies cover approximately the last 2000 years (Neoglacial interval) and demonstrate distinct patterns of above-average (or increasing) sediment accumulation thought to be associated with wetter and/or warmer conditions. This high resolution accumulation chronology is compared with lower resolution and longer duration environment histories from nearby lakes. u ACKNOWLEDGEMENTS I wish to acknowledge the support and assistance of numerous people and organizations, including a generous grant from NSERC, without which this project would not have been possible. My thesis defense committee was composed of Dr. Joseph Desloges, Dr. Sarah Finkelstein and Dr. Bill Gough. Dr. Joseph Desloges, my thesis supervisor and instructor, provided direction and guidance in the field (note: this was my first camping experience), in the laboratory and throughout the writing process. I will forever be indebted to Dr. Desloges for offering me this incredible experience. Dr. Finkelstein, my supervisor as a teaching assistance for undergraduate field course GGR 390 and second defense committee member, graciously shared her paleoclimatology laboratory with me, while providing endless motivation. The third committee member, Dr. Gough, an expert in climatology, provided a unique perspective on my research and helped me to finalize this manuscript. Field assistance came from Melanie Grubb (University of Northern British Columbia) and from Margaret Klocker, Park Operator and was appreciated. Assistance in the laboratory results came from several sources. Mircea Pilaf helped open sediment samples. Toni Largo's analysis of 2004 Ekman cores from Kinaskan Lake, provided interesting comparison to the 2006 Ekman results, and both Toni Largo and Nicole Chow offered guidance in GIS applications. In several instances samples needed to be processed in external laboratories. The Geography Department at Queen's University and the Department of Chemical Engineering at the University of Toronto, offered laser particle size analysis. The samples sent to Queen's University were processed under the supervision of Dr. Robert Gilbert. At the University of Toronto, Sam Roshdi trained me on using the laser particle sizer so that I could conduct my own tests. For radiocarbon dates, samples of organic matter were sent to Dr. W.E. Kieser and Dr. R.P. Beukens at the Isotrace Laboratory of the Department of Physics at the University of Toronto. Geological provenance of sediment was determined using the XRF results generated by the laboratory of Dr. Mike Gorton, Department of Geology at the in University of Toronto. Finally, Gerald Romme and Marcel Fortin provided GIS assistance from their offices in the Map Library at the University of Toronto. Last, but not least, I would like to extend a warm "thank you" to my family; Clayton, Gabriele, Geneve and Ian, for always encouraging me to pursue my dreams, to my overseas partner, Cesar, for his patience, understanding and love, and to all of my wonderful friends. IV TABLE OF CONTENTS Abstract ii Acknowledgements iii Table of Contents v List of Tables ix List of Figures x List of Appendices xiv CHAPTER 1: INTRODUCTION 1 1.1 Introduction 1 1.2 Research Objectives 3 CHAPTER 2: LITERATURE REVIEW 4 2.1 Introduction 4 2.1.1 Pleistocene Glaciations 4 2.1.2 Holocene Climate Conditions and Neo-glaciations 13 2.2 Pro-glacial Lake Sedimentary Archives of Climate Change 19 2.2.1 Geomorphic Controls on Sedimentation 20 2.2.2 Climate Controls on Sedimentation 22 2.2.3 In-lake Patterns of Sedimentation 25 CHAPTER 3: STUDY AREA 35 3.1 Introduction 35 V 3.1.1 Setting 35 3.1.2 Morphology 37 3.1.3 Geology 37 3.1.4 Climate 41 3.1.5 Hydrology 44 3.1.6 Vegetation 48 CHAPTER 4: METHODS 49 4.1 Field Methods 49 4.1.1 Geophysical Methods 49 4.1.2 Sediment Sampling 49 4.1.3 Water Column Profiling 51 4.2 Laboratory Methods 51 4.2.1 Core Preparation 51 4.2.2 Lamina or Bed Thickness Measurements and Dating 51 4.2.3 Loss-on-ignition 52 4.2.4 Grain Size Analysis 53 4.2.5 X-Ray Fluorescence .54 CHAPTER 5: RESULTS 55 5.1 Introduction 55 5.2 Circulation of Kinaskan Lake 55 5.3 Attributes of the Upper Iskut River watershed from Aerial Imagery 59 VI 5.4 Acoustic Record 61 5.4.1 Bathymetry, Sediment Thickness and Character 61 5.5 Sedimentology of Kinaskan Lake ..68 5.5.1 Sediment Structure 68 5.5.2 Organic Content 75 5.5.3 Particle Size 82 5.5.4 X-Ray Fluorescence 86 5.6 Chronology 88 5.6.1 Couplet Counts 88 5.6.2 Radiocarbon Dates 89 CHAPTER 6: DISCUSSION 91 6.1 Introduction 91 6.2 Sedimentation in Kinaskan Lake 91 6.3 Long-term Changes in Lacustrine Sedimentation and Climate Conditions of British Columbia: Contextualizing the Kinaskan Lake Sedimentary Record 97 6.3.1 Selected British Columbia Lakes for comparison of sedimentary records with Kinaskan Lake 98 6.3.2 Long-term Trends in Sedimentation and Climate Conditions of British Columbia 103 CHAPTER7: CONCLUSION Ill 7.1 Summary of Findings Ill Vll 7.1.1 Modern Patterns of Hydrology and Sedimentation Ill 7.1.2 Long-term Sedimentation 112 7.1.3 Sediment Structure and Composition 113 7.1.4 Findings of this Study 115 7.2 Future Directions 117 LITERATURE CITED 118 APPENDICES 128 viii LIST OF TABLES Number Page 4.1a Site characteristics and sample lengths for 2006 cores 50 4.1 b Site characteristics and sample lengths for 2004 cores 50 4.2 Characteristics of samples processed for XRF 54 5.1 Mean couplet thickness of sediments 69 5.2 Loss-on-ignition results for Kinaskan Lake cores 76 5.3 Grain size results for Kinaskan Lake cores 83 5.4 Location and characteristics of granules and pebbles found in core KIN 309 85 5.5 Percent of element or compound composing sediment samples taken from five depths in KIN 311 87 5.6 Total couplet counts in each core .89 5.6 Radiocarbon sample details for Kinaskan Lake 89 5.7 Radiocarbon results for Kinaskan Lake 90 6.1 Sites of the Northern British Columbia lakes chosen for comparison with Kinaskan Lake 97 IX LIST OF FIGURES Number Page 2.1 Map showing the extent of Glacial Lake Stikine 6 2.2 Map showing the pattern of Cordilleran Ice Sheet movement 8 2.3 Map showing reconstruction of Cordilleran Ice Sheet flow 9 2.4 Map showing Cordilleran Ice Sheet flow 10 2.5 Map of major British Columbian physiographic regions 11 2.6 Map showing the location of Skinny Lake, Upper Iskut River watershed 15 2.7 Site specific climate conditions of the Holocene 16 2.8 a & b (a) Timing and duration