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ProQuest Information and Learning 300 North Zeeb Road. Ann Arbor, Ml 48106-1346 USA 800-521-0600 UMI NOTE TO USERS This reproduction is the best copy available. UMI' Interdisciplinary insights into paleoenvironments of the Queen Charlotte Islands/Hecate Strait region by Renée Hetherington B.A., Simon Fraser University, 1981 M B A., University of Western Ontario, 1985 A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY in the Interdisciplinary Degree Program (Geography, and Earth and Ocean Sciences) We accept this thesis as conforming to the required standard Dr. D.J. Smith, Co/Supe^rvisor (Department of Geography) Dr. Barrie, Co-'Supervisor (School of Earth and Ocean Sciences) Dr. R.G.B/Reiadepartmental Member (Department of Biology) Dtj P-Xeller, Departn^ntal Member (Department of Geography) Dr. T.S. James.yOutsi i^i^ber (Geological Survey of Canada) _____________________________________ Dr. L.E. Jackson Jr., External Examiner (Geological Survey of Canada) ® Renée Hetherington, 2002 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. Co-supervisors: Dr. D.J. Smith and Dr. J.V. Barrie ABSTRACT Subsequent to the Last Glacial Maximum (LGM), complex coastal response resulted from deglaciation, eustatic sea-level change, and a relatively thin, flexible lithosphere in the Queen Charlotte Islands (QCI) region of northwestern Canada. Presented here is an interdisciplinary study that combines the methodologies and schools of thought from geology, biology, and geography to address a research problem that spans these disciplines, speciflcally to illustrate the environment, temporal and spatial dimensions of isostatic crustal adjustment and the Late Quaternary coastline o f the northeast Pacific continental shelf. Molluscan distribution, lithology, and published sub­ bottom profiles are used to deduce sea-levels, outline the influence of glacially-induced crustal displacement, and reconstruct the paleoenvironment of the northeast Pacific Late Quaternary coastline, including the absence of ice and the presence of emergent coastal plains. These data are used to ascertain the region's suitability as a home for an early migrating coastal people. A series of paleogeographic maps and isostatic crustal displacement maps chart the sequence of evolving landscapes and display temporal changes in the magnitudes and extent of crustal flexure as a forebulge developed. The wave-length and amplitude of the glacially-induced forebulge supports thermal and refraction modeling of a thin (—25 km thick) lithosphere beneath Queen Charlotte (QC) Sound and Hecate Strait. Glacial ice at least 200 m thicker than present water depth began retreating from Dixon Entrance after 14,000 and prior to 12,640 ‘‘‘C years BP, generating 50 m of uplift in northern Hecate Strait. The position of the forebulge remained essentially constant after 12,750 '^C years BP, implying a fixed ice-front and continued ice presence on the British Columbia (BC) mainland until - 10,000 ‘‘‘C years BP. A 3-dimensional model shows two ice-free terrains emerged: one extended eastward from the QCI, the other developed in QC Sound. By-11,750 '^C years BP a landbridge connected the BC mainland and QCI. Ill Malacological evidence indicates a paucity of Arctic molluscan faima subsequent to glaciation, perhaps a consequence of shallow, narrowed straits, and the presence of ice sheets that interfered with ocean currents. Water temperature, sedimentation rates, turbidity, and photoperiod are factors that limited invertebrate colonization during the Late Pleistocene - Early Holocene. The oldest dated mollusc to colonize QCI region subsequent to LGM wasMacoma nasuta at 13,210 '^C years BP. Once habitat and sea- surface temperatures were conducive, rates of recolonization appear to be limited only by the availability of ocean currents to bring temperate pelagic larvae into the region from outlying areas. Between ~11,000 and 10,000 ‘'*C years BP the appearance of Clinocardium ciliatum and Serripes groenlandicus, concurrent with the disappearance, or significant reduction in number and productivity of temperate intertidal molluscs, indicates the onset of a short interval of cool sea-surface temperatures coincident with the Younger Dryas cooling event. Five molluscan species: Macoma incongrua, Musculus taylori (cf), Mytilimeria nuttallii, Tellina nucidoides, Mytilus edulis/Mytilus trossulus previously categorized as possessing a Recent geologic range were collected in sediments dating older than 10,000 '‘*C years BP. Fossil mollusc shells indicate edible intertidal biomass densities well within commercially harvested levels on southern Moresby Island by 8,800 ‘■‘C years BP, and on northern Graham Island by 8,990 "C years BP. The presence and productivity of nutritious intertidal molluscs indicates the QCI region had a suitable climate, possessed open ocean conditions, and provided subsistence resources for potential early humans subsequent to at least 13,210 '“‘C years BP. Three- dimensional modeling shows subaerially exposed land that could have been inhabited by plants, animals, including coastal-migrating early humans. Early coastlines that have not been drowned, and which may harbour early archaeological sites, are identified along the western and northern coasts of QCI and the BC mainland. IV Examiners: Dr. D.J. Smith, Co-Supervisor (Department of Geography) D rJW . Barrie, Co-Supervisor (School of Earth and Ocean Sciences) Dr. R G B. Reid, Departmental Member (Department of Biology) Dr. P. Keller, Departmental Member (Department of Geography) Dr. T.S. James, Outside Member (Geological Survey of Canada) Dr. L.E. Jackson Jr., Extm al Examiner (Geological Survey of Canada) TABLE OF CONTENTS ABSTRACT ii TABLE OF CONTENTS v LIST OF TABLES and TABLE APPENDICES viii LIST OF FIGURES x ACKNOWLEDGMENTS xiv DEDICATIONS xvii CHAPTER 1 : Introduction I Objectives 8 Methodologies 8 Thesis structure 9 Context Location of study area 11 Geology and geophysics 11 Wisconsinan glacio-isostatic effects 12 Oceanography Sea-surface temperature, salinity, tides, 15 waves, winds, and currents Circulation and zoogeographic distribution 16 Molluscs as a subsistence resource 16 An Interdisciplinary perspective 18 References 19 CHAPTER 2: Paleogeography, glacially-induced crustal displacement, and Late Quaternary coastlines on the continental shelf of British Columbia, Canada Abstract 26 Introduction 27 Geological and physiographic setting 30 Materials and Methods Collecting methods 35 Dating methods 41 Relative sea-level, eustatic sea-level, and crustal displacement 42 Geostatistical interpolation 49 Shell taphonomy 52 Results Relative sea-level observations 53 Paleoenvironmental results 59 13.750 to 14,250 '"C years BP 59 12.750 to 13,250 '^C years BP 62 VI 12.250 to 12,750 '^C years BP 64 11.250 to 11,750 '^C years BP 65 10.750 to 11,250 "C years BP 67 10.250 to 10,750 '-"C years BP 69 9.750 to 10,250 '^C years BP 72 8.750 to 9,750 '"C years BP 75 Discussion Forebulge position, shape and amplitude through time 78 Paleogeography and paleoenvironment 82 Conclusion 83 References 85 CHAPTER 3: Malacological insights into the marine ecology and changing climate of the Late Pleistocene - Early Holocene northeastern Pacific Abstract 93 Introduction 94 Context Geology 97 Present sea-surface temperature and salinity in QCI and 99 the Canadian Arctic QCI tide, wave, wind patterns, and currents 100 QCI circulation and zoogeographic distribution 101 Materials and methods Collecting methods 103 Dating methods 110 Shellfish biomass 110 Shell taphonomy 111 Intertidal assemblages 112 Results Molluscan species identified 112 Timing of recolonization and oldest mollusc shells found 113 Paleofaunistic zones 115 Biomass quantification 115 Discussion Environment 126 Timing of recolonization 128 Geological range of molluscs 130 Younger Dryas 130 Biomass 132 References 135 Appendix Table A 1 141 Appendix Table A2 142 Appendix Table A3 143 vu Appendix Table A4 146 CHAPTER 4: Queen Charlotte Islands paleogeography and the Americas’ first humans Introduction 148 Materials, Methods, and shellfish biomass 151 Results Sea-level change and crustal displacement 156 Ice extent 156 Paleogeographic reconstructions 157 Paleoenvironment and Younger Dryas 159 Edible resources and productivity of the intertidal zone 159 Early human dispersal routes 160 Potential archaeological site locations 161 References 163 Appendix Table A 1 166 CHAPTER