1.4. Bedrock Geology
Total Page:16
File Type:pdf, Size:1020Kb
Quaternary Geology in Part of the McLeod Lake Map-Area (NTS 093J), Central British Columbia by David A. Sacco B.A. (Hons.), University of the Fraser Valley, 2008 Thesis Submitted In Partial Fulfillment of the Requirements for the Degree of Master of Science in the Department of Earth Sciences Faculty of Science David A. Sacco 2012 SIMON FRASER UNIVERSITY Fall 2012 Approval Name: David A. Sacco Degree: Master of Science Title of Thesis: Quaternary geology in part of the McLeod Lake map-area (NTS 093J), central British Columbia Examining Committee: Chair: Dr. Dan Gibson Associate Professor Dr. Brent Ward Senior Supervisor Associate Professor Dr. John Clague Supervisor Professor Dr. Olav Lian Supervisor Adjunct Professor Dr. Alain Plouffe External Examiner Research Scientist, Geological Survey of Canada Date Defended/Approved: November 2, 2012 ii Partial Copyright License iii Abstract The Quaternary geology in part of the McLeod Lake map-area was studied through the production and analysis of 1:50 000-scale terrain maps and the examination of stratigraphic exposures and landforms. The surficial geology is dominated by thick, streamlined till that thins where relief is high. Glaciofluvial outwash and ice-contact deposits occur throughout the area and extensive glaciolacustrine deposits blanket low- lying regions. The glacial stratigraphic record spans the Fraser Glaciation and is represented by a sequence of advance glaciolacustrine sediments, till and retreat glaciolacustrine and glaciofluvial sediments. Ice initially flowed into the study area from the northwest and retreated before the arrival of ice from the west and south. Ice-flow during the glacial maximum was northeast and transitioned to the east during deglaciation. Ground penetrating radar suggests that post-glacial aeolian activity was brief. Optical dating on K-feldspar from aeolian material suggests this activity occurred around 9.35 ± 0.64, 9.94 ± 0.77 and 13.3 ± 1 ka and provides minimum ages for ice retreat. Keywords: McLeod Lake map-area; terrain mapping; Quaternary stratigraphy; ice- flow history; optical dating; ground penetrating radar iv Acknowledgements I would like to first express my deep gratitude to my supervisor Dr. Brent Ward. His valuable and constructive suggestions and sincerity helped form this project and were instrumental in my development as a researcher. A special thank you to my committee members, John Clague and Olav Lian, and external examiner, Alain Plouffe, whose thorough edits and thoughtful discussions greatly improved the quality of this thesis. I would like to acknowledge the guidance provided by Denny Maynard and Marten Geertsema during the mapping and fieldwork. Thanks to all of my friends, family and colleagues who provided support and encouragement throughout this project. I would also like to thank all of those who assisted me in the field, the staff from the Luminescence Laboratory at the University of the Fraser Valley, and the GIS technicians at Chartwell Resources and Geoscience BC. Generous funding for this project was provided by Geoscience BC. v Table of Contents Approval .......................................................................................................................... ii Partial Copyright License ............................................................................................... iii Abstract .......................................................................................................................... iv Acknowledgements ......................................................................................................... v Table of Contents ........................................................................................................... vi List of Tables ................................................................................................................. viii List of Figures................................................................................................................. ix 1. Introduction .......................................................................................................... 1 1.1. Location and access ............................................................................................... 2 1.2. Physiography .......................................................................................................... 2 1.3. Climate and vegetation ........................................................................................... 4 1.4. Bedrock geology ..................................................................................................... 6 1.5. Thesis objectives .................................................................................................... 7 2. Regional stratigraphic framework ....................................................................... 9 2.1. Development of the glacial concept in central British Columbia .............................. 9 2.2. Regional stratigraphy ............................................................................................ 12 2.2.1. Central Interior Plateau ............................................................................. 17 2.2.2. Northern Interior Plateau ........................................................................... 19 2.2.3. Northern Rocky Mountain Trench and Omineca Mountains ...................... 23 2.3. Regional glacial history ......................................................................................... 25 2.3.1. A pre-Fraser glaciation .............................................................................. 25 2.3.2. Fraser Glaciation ....................................................................................... 25 3. Terrain mapping ................................................................................................. 32 3.1. Methods ............................................................................................................... 32 3.2. Composite terrain symbols ................................................................................... 33 3.2.1. Surficial material ....................................................................................... 34 3.2.2. Surface expression ................................................................................... 36 3.2.3. Geomorphological process........................................................................ 37 3.3. Map legend .......................................................................................................... 37 3.3.1. Map unit descriptions and genesis ............................................................ 38 3.3.2. Onsite symbols ......................................................................................... 49 3.4. Landforms ............................................................................................................ 49 3.4.1. Striations ................................................................................................... 49 3.4.2. Streamlined macroforms ........................................................................... 50 3.4.3. Eskers ....................................................................................................... 52 3.4.4. Ice-stagnation landforms ........................................................................... 53 3.4.5. Meltwater channels ................................................................................... 54 3.4.6. Aeolian landforms ..................................................................................... 57 3.5. Summary of surficial geology ................................................................................ 58 vi 4. Ground penetrating radar survey and optical dating of aeolian landforms ............................................................................................................ 61 4.1. Ground penetrating radar ..................................................................................... 61 4.1.1. Study locations .......................................................................................... 62 4.1.2. Data collection .......................................................................................... 62 4.1.3. GPR processing ........................................................................................ 66 4.1.4. Results and interpretations........................................................................ 67 4.1.5. Summary of GPR ...................................................................................... 73 4.2. Optical dating ....................................................................................................... 74 4.2.1. Sample collection and preparation ............................................................ 75 4.2.2. Environmental dose rate determination ..................................................... 77 4.2.3. Equivalent dose determination .................................................................. 78 4.2.4. Optical ages and discussion ...................................................................... 83 4.3. Conclusions .......................................................................................................... 85 5. Glacial history ..................................................................................................... 87 5.1. Methods ............................................................................................................... 87 5.2. Quaternary stratigraphy