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Reconstruction of the Late Pleistocene and Holocene Geomorphology of Northwest Calvert Island

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Reconstruction of the Late Pleistocene and Holocene Geomorphology of Northwest Calvert Island Reconstruction of the Late Pleistocene and Holocene geomorphology of northwest Calvert Island, British Columbia by Jordan Blair Reglin Eamer B.Sc. (honours with distinction), University of Victoria, 2010 M.Sc., University of Victoria, 2012 A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY In the Department of Geography © Jordan Blair Reglin Eamer, 2017 University of Victoria All rights reserved. This dissertation may not be reproduced in whole or in part, by photocopying or other means, without the permission of the author. ii Reconstruction of the Late Pleistocene and Holocene geomorphology of northwest Calvert Island, British Columbia by Jordan Blair Reglin Eamer B.Sc. (honours with distinction), University of Victoria, 2010 M.Sc., University of Victoria, 2012 Supervisory committee: Dr. I.J. Walker, Co-Supervisor Department of Geography, University of Victoria Dr. O.B. Lian, Co-Supervisor Department of Geography, University of Victoria Dr. J.J. Clague, Member Department of Geography, University of Victoria Dr. D.H. Shugar, Outside Member School of Interdisciplinary Arts and Sciences, University of Washington Tacoma iii Abstract This dissertation presents results from a multi-year interdisciplinary study of the Late Quaternary geomorphic history of northwest Calvert Island, British Columbia, Canada. There is a considerable knowledge gap in the region pertaining to Cordilleran ice cover and extent as well as landscape response to a uniquely stable relative sea-level history. The objective of this study was to reconstruct this regional landscape response to deglaciation including post-LGM ice cover and extent, relative sea-level changes, coastal landform development, and climate and ecological variance. Methods used to inform this reconstruction included airborne lidar, aerial photography interpretation, sedimentary stratigraphy and detailed sedimentology of samples from shovel pits and lake cores, surficial geology and geomorphic mapping, palaeoecological examinations, and the development of a geochronology using radiocarbon and optical dating. To assist with landscape reconstruction, a new method was developed and used to differentiate littoral and aeolian sands in sediment samples that range in age from Mid to Late Holocene by using modern reference samples. The method utilized a standard optical microscope paired with freely available software (ImageJ) to characterize grain shape parameters. The method was tested on nearly 6,000 sand grains from samples of known and hypothesized depositional settings and was able to correctly identify the depositional setting for 76% of the samples. After testing, the method was used to differentiate littoral and aeolian sands in a number of shovel pit, exposure, and core sediment samples to give context to stratigraphic and geomorphic interpretations. A short-lived Late Pleistocene re-advance of Cordilleran ice occurred in the study area, with radiocarbon ages indicating ice advanced to, and then retreated from, the western edge of Calvert Island between 14.2 and 13.8 ka cal BP, respectively. Sedimentological and palaeoecological information that suggests a cold climate and advancing/retreating glacier as well as lidar remote sensing and field- based geomorphic mapping of moraines in the region provide evidence of the re-advance. After ice retreated from the area, a broad suite of geomorphic landforms developed, including flood plains, iv aeolian dunes, beaches, spits, marshes, and tombolos. Coastal reworking was extensive, with progradation rates greater than 1 m a-1 occurring in some locations during the Late Holocene. These data provide the first evidence of a re-advance of the retreating ice sheet margin on the central coast of British Columbia, contribute an important methodology to advance Quaternary reconstructions, and give a unique account of the geomorphic development of a Pacific Northwest coastline that experienced little relative sea-level change over the Late Pleistocene and Holocene. Results help fill a spatial and temporal gap in the landscape history of British Columbia and have implications for climate and sea- level reconstructions, early human migration patterns, and the palaeoenvironment of an understudied area of the Pacific Northwest coast of North America. v Contents Supervisory committee ................................................................................................................................. ii Abstract ........................................................................................................................................................ iii Contents ........................................................................................................................................................ v Table of figures .......................................................................................................................................... viii Table of tables .............................................................................................................................................. xi Table of appendices .................................................................................................................................... xii Acknowledgements .....................................................................................................................................xiii 1. Introduction .......................................................................................................................................... 1 1.1. Investigating the central coast of British Columbia, Canada: a unique opportunity to better understand the Late Quaternary landscape of the west coast of North America.................................... 1 1.2. Research context ........................................................................................................................... 3 1.2.1. The Cordilleran Ice Sheet in the Late Pleistocene – dynamics and legacy ............................ 3 1.2.2. Sea level changes following deglaciation in coastal British Columbia ................................... 7 1.2.3. Tectonic regime of coastal British Columbia ......................................................................... 9 1.3. Dissertation structure and conventions ...................................................................................... 11 2. A glacial re-advance during retreat of the Cordilleran Ice Sheet, British Columbia central coast ...... 13 2.1. Abstract ....................................................................................................................................... 13 2.2. Introduction ................................................................................................................................. 14 2.3. Study area .................................................................................................................................... 18 2.4. Methods and data ....................................................................................................................... 19 2.4.1. Geomorphology and geography of surficial deposits .......................................................... 19 2.4.2. Stratigraphy and geochronology ......................................................................................... 20 2.4.3. Macrofossils ......................................................................................................................... 23 2.5. Results ......................................................................................................................................... 23 2.5.1. Lithostratigrahic units – descriptions and chronology ........................................................ 23 2.5.2. Macrofossils - unit 2 ............................................................................................................. 27 2.6. Discussion .................................................................................................................................... 29 vi 2.6.1. Unit interpretation ............................................................................................................... 29 2.6.2. Section interpretation and evidence for glacial advance and retreat ................................. 32 2.6.3. Palaeoclimatic interpretation in a regional context ............................................................ 33 2.6.4. Relation to other post-LGM advances in BC and possible mechanisms for ice advance .... 34 2.7. Conclusions .................................................................................................................................. 37 3. Distinguishing depositional setting for sandy deposits in coastal landscapes using grain shape ....... 38 3.1. Abstract ....................................................................................................................................... 38 3.2. Introduction ................................................................................................................................. 39 3.3. Study area .................................................................................................................................... 40 3.4. Methodology ............................................................................................................................... 43 3.4.1. Sample collection ................................................................................................................
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