Optical Dating of Stabilized Parabolic Dunes, Savary Island, British Columbia
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Optical dating of stabilized parabolic dunes, Savary Island, British Columbia by Libby Biln Bachelor of Science, University of the Fraser Valley, 2014 Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Earth Sciences Faculty of Science © Libby Biln SIMON FRASER UNIVERSITY Summer 2017 Copyright in this work rests with the author. Please ensure that any reproduction or re-use is done in accordance with the relevant national copyright legislation. Approval Name: Libby Biln Degree: Master of Science Title: Optical dating of stabilized parabolic dunes, Savary Island, British Columbia Examining Committee: Chair: Dirk Kirste Associate Professor Brent Ward Senior Supervisor Professor Olav Lian Supervisor Adjunct Professor John Clague Committee Member Professor Emeritus Ian J. Walker Committee member Professor, Arizona State University Stephen A. Wolfe External Examiner Natural Resources Canada Geological Survey of Canada Date Defended/Approved: June 13, 2017 ii Abstract Research has shown that the south coast of British Columbia (BC) has experienced changes in relative sea level and climate since deglaciation (~15 ka ago); however, there has been little study of the landscape’s response to these changes. On Savary Island, in the Strait of Georgia, there exist large parabolic dunes that are unique to the region. These dunes are stabilized, supporting mature forest growing in well- developed soil, and they contain eroded palaeosols indicating that their formation was punctuated by periods of episodic stabilization and soil formation. Optical ages from K- feldspar indicate that dune formation began prior to 7.69 ± 0.71 ka and stabilized by about 5.47 ± 0.36 ka ago when relative sea level lowering was slowing and climate was becoming cooler and moister. Periods of landscape stability during dune formation were brief, probably lasting only a few hundred years. Keywords: Parabolic sand dunes; optical dating; postglacial landscape change; radiocarbon dating; Coastal British Columbia; relative sea level change iii Dedication Firstly, I would like to dedicate this work to my loving and supportive parents. You have always pushed me to be the best version of myself, supporting me in everything I do. Thank you for understanding the importance of a good education and encouraging me to pursue my passions. Secondly, this work would not have been possible without the support of my husband, Alec. You have been by my side throughout this entire journey, listening to my crazy OSL talk, putting up with my field-work absences, dealing with my frequent break downs, and editing my poor grammar. Your intense work ethic has encouraged me to push myself to new levels and get the most out of every day. I could not have accomplished this feat without you, I am beyond grateful. ♥ iv Acknowledgements This work would not have been possible without the help, guidance and support of Dr. Olav Lian. His patience in teaching me the complicated nuances of research and optical dating are invaluable. I am very grateful to Dr. Brent Ward for taking me on as a masters student and allowing me to work with ‘black magic’. Your constructive criticism has helped me grow as researcher. I am also indebted to Dr. John Clague for allowing me to build on his initial findings and providing guidance in the realm of Quaternary sciences. Thanks are also due to Dr. Ian Walker for his insight into coastal processes and dune dynamics. Your advice has helped me to become a more well-rounded scientist. I am very grateful to Liz Webster from the Savary Island Land trust for introducing me to Savary Island, showing me the trails and letting us stay in her beautiful cabin. Many thanks to the external examiner, Dr. Stephen Wolfe, whose comments and advice greatly improved this thesis. This work would not have been possible without the financial support of the Hakai Institute and Tula Foundation, notably Eric Peterson and Christina Munck. Many thanks for supporting Science on the coastal margin and in the Discovery Islands. A big thank-you to Dr. Christina Neudorf who taught me the ways of analysing luminescence data, more than once, and answered my never ending questions in record breaking time. Your insight and expertise greatly assisted this research and I would not have optical ages without you. I would also like to acknowledge Dr. Paul Sanborn from the University of Northern British Columbia who provided soil science expertise and advice in the field and throughout this thesis. Additionally, Dr. Brian Menounos and Rob Vogt from the UNBC Lidar research group for facilitating lidar acquisition. Thanks to Derek Heathfield for his assistance with lidar processing. To my Luminescence Dating Lab mates, Jordan Bryce and Travis Gingerich, thank you for all of your help in the field and laboratory, you made the ‘Bat-cave’ exciting. To my fellow grad students, thanks for keeping my graduate work caffeinated, full of punny moments, dance parties, and good conversation, it would not have been the same without you: Carie-Ann, Snowy and Patt. A big thanks to everyone who helped me in the v field, and finally, to all the friends and family who have encouraged and supported me throughout this journey, your interest in what I do means the world. vi Table of Contents Approval ...........................................................................................................................ii Abstract ...........................................................................................................................iii Dedication ...................................................................................................................... iv Acknowledgements ......................................................................................................... v Table of Contents .......................................................................................................... vii List of Tables ................................................................................................................... x List of Figures................................................................................................................. xi Chapter 1. Introduction ............................................................................................. 1 1.1. Study area: location, access and general character ................................................ 2 1.2. Regional overview .................................................................................................. 4 1.2.1. Geology ..................................................................................................... 4 1.2.2. Climate and vegetation .............................................................................. 4 1.2.3. Coastal environment and conditions .......................................................... 7 1.2.4. Quaternary history ..................................................................................... 8 Late Quaternary history ........................................................................................... 8 Olympia Interstade............................................................................................. 8 Fraser Glaciation ............................................................................................... 9 Postglacial period ............................................................................................ 11 Glacial and postglacial climate ............................................................................... 12 Sea level history ..................................................................................................... 13 1.2.5. Savary Island lithostratigraphy and previous research ............................. 15 1.3. Thesis objectives and rationale ............................................................................. 16 1.4. Thesis format ........................................................................................................ 17 Chapter 2. Methods.................................................................................................. 18 2.1. Pedology .............................................................................................................. 18 2.2. Radiocarbon dating .............................................................................................. 19 2.3. Lidar analysis ....................................................................................................... 20 2.4. Optical dating ....................................................................................................... 20 2.4.1. Sample collection and preparation ........................................................... 22 2.4.2. Estimating the equivalent dose (De) ......................................................... 24 2.4.3. Estimating the environmental dose rate ................................................... 28 2.4.4. Anomalous fading .................................................................................... 30 2.5. Grain size analysis ............................................................................................... 31 2.5.1. Palaeowind speed calculation .................................................................. 32 Chapter 3. Results ................................................................................................... 35 3.1. Introduction ..........................................................................................................