Deep-Water Stratigraphic Evolution of the Nanaimo Group, Hornby and Denman Islands, British Columbia

University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2016 Deep-Water Stratigraphic Evolution of The Nanaimo Group, Hornby and Denman Islands, British Columbia Bain, Heather Bain, H. (2016). Deep-Water Stratigraphic Evolution of The Nanaimo Group, Hornby and Denman Islands, British Columbia (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/25535 http://hdl.handle.net/11023/3342 master thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Deep-Water Stratigraphic Evolution of The Nanaimo Group, Hornby and Denman Islands, British Columbia by Heather Alexandra Bain A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE GRADUATE PROGRAM IN GEOLOGY AND GEOPHYSICS CALGARY, ALBERTA SEPTEMBER, 2016 © Heather Alexandra Bain 2016 ABSTRACT Deep-water slope strata of the Late Cretaceous Nanaimo Group at Hornby and Denman islands, British Columbia, Canada record evidence for a breadth of submarine channel processes. Detailed observations at the scale of facies and stratigraphic architecture provide criteria for recognition and interpretation of long-lived slope channel systems, emphasizing a disparate relationship between stratigraphic and geomorphic surfaces. The composite submarine channel system deposit documented is 19.5 km wide and 1500 m thick, which formed and filled over ~15 Ma. Facies scale analyses highlight conglomeratic channel fill juxtaposed against thin-bedded out-of-channel deposits. Evidence that the channel system was maintained through a variety of processes over a protracted period includes identification of stratigraphic products that record degradational terraces, cyclic steps, mass transport deposition, nested erosion surfaces, and fine- and coarse-grained channel fill deposits. The thesis establishes the Nanaimo Group as an ideal unit to investigate the record of deep-water sediment transfer through slope channels. ii ACKNOWLEDGEMENTS I would like to recognize and sincerely thank Dr. Stephen Hubbard for his academic and professional guidance over the past couple of years. It’s amazing that one small conversation during an undergraduate geology field school has transpired into one of the best decisions of my life. I am thankful for the various opportunities he has provided including a field excursion to Chile, attending numerous conferences and for his patience through out the work terms I completed. His mentorship has instilled a powerful work ethic, commitment to excellence and a passion for geology that I will take with me through the next phase of my life. Funding for this research was graciously provided by an NSERC Discovery grant to Dr. Stephen Hubbard as well as student funding from the University of Calgary. To my colleagues at the Centre for Applied Basin Studies (CABS) at the University of Calgary including Danny Coutts, Rebecca Englert, Aaron Reimchen, Paul Durkin, Ben Daniels, Nick Zajac, Emma Percy, David Cronkwright, Dillon Newit, Raymond Van, Garrett Quinn and Adam Coderre thank you for your insightful geologic discussions, outdoor adventures and most importantly friendship over the past couple of years. I could not have completed this degree without the unwavering support that I am so grateful to have received in my personal life. To my parents Don and Helen Bain for their constant love and support in any endeavor that I take on and encourage me to continually follow my dreams. To my brother and sister-in-law Brian and Kristine Bain, who have been exceptional role models in academics, lifestyle, and creating a remarkable work-life balance. To my partner and best friend Ian Gray, who endured the stressful moments that develop during a graduate degree and encouraged me with patience and understanding in the pursuit of my passion. To the Gray’s who accepted me into their family and iii constantly supported me throughout my degree. To my amazing best friends Kristen Barton, Kaitlyn Amatto, Rebecca Mayhew and Courtney Leinweber, for their acceptance of numerous geological factoids on the many adventures we have taken and reminded me to take a step back from planning and appreciate the moment. I am forever indebted to the people in my life. iv TABLE OF CONTENTS Abstract ii Acknowledgements iii Table of Contents v List of Figures vii List of Tables viii CHAPTER ONE: INTRODUCTION 1 Project Motivation 1 Nanaimo Basin 3 Stratigraphy – Nanaimo Group 4 Deep-water Gravity Processes 6 Turbulent Flow 6 Liquefied Flow 6 Grain Flow 8 Cohesive Flow 8 Thesis Organization 8 References 9 CHAPTER TWO: STRATIGRAPHIC EVOLUTION OF A LONG-LIVED SUBMARINE CHANNEL SYSTEM IN THE LATE CRETACEOUS NANAIMO GROUP, BRITISH COLUMBIA, CANADA 13 Introduction 13 Study Area and Geologic Setting 16 Methodology 20 Lithofacies Results 22 Stratigraphic Results 22 Cedar District Formation 25 De Courcy Formation 29 Northumberland Formation 30 Geoffrey Formation 31 Spray Formation 34 Gabriola Formation 38 Nanaimo Group Depositional Setting Interpretation 39 Discussion: The Origins of Conduit-bounding Stratigraphic Surfaces 43 Conclusions 49 References 50 CHAPTER THREE: OUTCROP EVIDENCE FOR PROTRACTED SEDIMENT TRANSFER INA COMPOSITE SUBMARINE CHANNEL MARGIN DEPOSIT, HORNBY ISLAND, CANADA 60 Introduction 60 Background Geology and Study Area 62 Methodology 64 Architectural Elements 66 v Third-order Architectural Elements 68 Fourth-order Architectural Elements 71 Fifth-order Architectural Elements 78 Discussion: Evidence for Knickpoint Erosion in Deep-water Outcrops 81 Conclusions 84 References 85 CHAPTER FOUR: CONCLUSIONS AND FUTURE WORK 92 Future Work 94 References 97 APPENDIX 100 vi LIST OF FIGURES Figure 1.1 - Strait of Georgia Regional Study Area 2 Figure 1.2 - Deep-water Gravity Flow Processes 7 Figure 2.1 - Evolutionary models of conduit stratigraphy 15 Figure 2.2 – Map of Study Area 16 Figure 2.3 – Stratigraphic Chart of the Nanaimo Group 17 Figure 2.4 – Geological Map of Hornby and Denman islands 19 Figure 2.5 – Maps of Paleoflow and Injection Rose Diagrams 21 Figure 2.6 – Lithofacies of the Nanaimo Group 26 Figure 2.7 – Sedimentological Characteristics of the Cedar District Formation 27 Figure 2.8 – Stratigraphic Sections of the Nanaimo Group 28 Figure 2.9 – Sedimentological Characteristics of the Northumberland and Geoffrey Formations 32 Figure 2.10 – Submarine Channel Fill, Geoffrey Formation 33 Figure 2.11 – Sedimentological Characteristics of the Spray and Gabriola Formations 36 Figure 2.12 – Cross-Section of Channel System 40 Figure 2.13 – Lateral Facies Transitions From Channelform Axes to Margin 42 Figure 2.14 – Modern Analog 44 Figure 2.15 – Depositional Evolution of the Nanaimo Group Channel Evolution 47 Figure 3.1 – Stratigraphic Architectural Elements 60 Figure 3.2 – Map of Study Area 61 Figure 3.3 – Stratigraphic Chart of the Nanaimo Group 63 Figure 3.4 – Background Geology 64 Figure 3.5 – Geology Map of Downes Point 65 Figure 3.6 – Overview of Architectural Elements Classification 67 Figure 3.7 – Cross Section of Downes Point 68 Figure 3.8 – Photos of Third-Order Architectural Elements 69 Figure 3.9 – Photos of Fourth-Order Architectural Elements 75 Figure 3.10 – Schematic Block Diagram 79 Figure 3.11 – Knickpoint Morphology 83 Figure 4.1 – Modern Submarine Canyons 95 vii LIST OF TABLES Table - 2.1 Lithofacies 23 Table - 3.1 Third-order Elements 70 Table - 4.1 Canyon size related to respective river input 96 viii CHAPTER ONE: INTRODUCTION PROJECT MOTIVATION Deep-water submarine channel systems are important conduits for immense volumes of sediment from continental margins to the deep ocean (Mutti and Normark, 1987; Kolla et al., 2001; Deptuck et al., 2003; Mayall et al., 2006; Covault et al., 2012; Sylvester et al., 2012). Deep-water environments are diverse and complex, but unlike other depositional environments the processes that govern sediment dispersal are rarely observed (Sumner and Paull, 2014). Continental slopes are commonly inaccessible or inhospitable for the observation of gravity flows as they distribute sediment tens to hundreds of kilometers down slope at high velocities. As such, physical models and numerical simulations are utilized to decipher gravity flow processes that produce the stratigraphic products observed in ancient examples at the Earth’s surface (Cartigny et al., 2014; Jackson, 2014; de Leeuw et al., 2016). The Gulf Islands of British Columbia, Canada, contain well-exposed outcrops of a coarse grained submarine conduit, facilitating interpretations of formative high-energy processes that formed the subsequent stratigraphic product (Fig. 1.1 A). The motivation behind this thesis is to: (i) decipher the depositional environment preserved on Hornby and Denman islands (Fig. 1.1); (ii) reconstruct channel evolution and provide insight to paleogeographic interpretations, and (iii) link sedimentological process to the rock record. This was accomplished by conducting a large-scale analysis of outcrops on Hornby and Denman islands, as well as detailed observations at select outcrop locations. Hornby and Denman islands expose a unique outcrop

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