LATE PLEISTOCENE GLACIAL AND ENVIRONMENTAL HISTORY OF THE SKAGIT VALLEY, WASHINGTON AND BRITISH COLUMBIA by Jon L. Riedel B.Sc. (Geography and Biology), University ofWisconsin - LaCrosse, 1982 M.Sc. (Geography), University of Wisconsin - Madison, 1987 Licensed Geologist, State ofWashington, since 1998 THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY In the Department of Earth Sciences © Jon L. Riedel 2007 SIMON FRASER UNIVERSITY Summer 2007 All rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission ofthe author. Approval Name: Jon L. Riedel Degree: Doctor ofPhilosophy Title ofThesis: Late Pleistocene Glacial and Environmental History of Skagit Valley, Washington and British Columbia Examining Committee: Chair: Dr. John J. Clague Senior Supervisor Dr. Brent C. Ward Supervisor Dr. Ralph A. Haugerud Supervisor Dr. Rolph Mathewes Internal Examiner Dr. Douglas Clark External Exam iner Date Defended/Approved: II SIMON FRASER UNIVERSITY LIBRARY Declaration of Partial Copyright Licence The author, whose copyright is declared on the title page of this work, has granted to Simon Fraser University the right to lend this thesis, project or extended essay to users of the Simon Fraser University Library, and to make partial or single copies only for such users or in response to a request from the library of any other university, or other educational institution, on its own behalf or for one of its users. The author has further granted permission to Simon Fraser University to keep or make a digital copy for use in its circulating collection (currently available to the public at the "Institutional Repository" link of the SFU Library website <www.lib.sfu.ca> at: <http://ir.lib.sfu.ca/handle/1892/112>) and, without changing the content, to translate the thesis/project or extended essays, if technically possible, to any medium or format for the purpose of preservation of the digital work. The author has further agreed that permission for multiple copying of this work for scholarly purposes may be granted by either the author or the Dean of Graduate Studies. It is understood that copying or publication of this work for financial gain shall not be allowed without the author's written permission. Permission for public performance, or limited permission for private scholarly use, of any multimedia materials forming part of this work, may have been granted by the author. This information may be found on the separately catalogued multimedia material and in the signed Partial Copyright Licence. While licensing SFU to permit the above uses, the author retains copyright in the thesis, project or extended essays, including the right to change the work for subsequent purposes, including editing and publishing the work in whole or in part, and licensing other parties, as the author may desire. The original Partial Copyright Licence attesting to these terms, and signed by this author, may be found in the original bound copy of this work, retained in the Simon Fraser University Archive. Simon Fraser University Library Burnaby,BC,Canada Revised: Summer 2007 Abstract Drainage patterns established in the Tertiary in the North Cascades were reorganized to accommodate southern drainage ofCordilleran Ice Sheet meltwater. Repeated continental glaciation rendered the Skagit an interconnected valley, with meltwater routes opening it to the Fraser and Okanogan watersheds, and linking it to a drainage system around the east margin of the Puget lobe ofthe ice sheet. AIpine glaciers from two major tributaries blocked Skagit valley during the late Wisconsin Evans Creek stade, creating glacial lakes Concrete and Skymo. Organic material from lake sediments provides the first radiometric constraint on the beginning ofthe Evans Creek stade in the Cascades about 25,040 J4C yr BP. Sediments and macrofossils at the Cedar Grove section define two advances ofBaker alpine glaciers during this stade, separated by warmer and wetter climate at 20,310 /4C yr BP. During colder parts ofthe Evans Creek stade macrofossils indicate treeline was as much as 1200 ± 150 m lower than present, which corresponds to a mean July temperature depression ofapproximately 7 ± 1°C. Glacier equilibrium line altitudes (ELA) during the cold periods were depressed 730-970 m below the modem glaciation threshold. Skagit valley alpine glaciers advanced several times to positions 5-10 km below valley heads between 12,200 and 9,975 14C yr BP. ELA depression during these advances vary from 340 ± 100 m to 590 ±75 m, with greater depression in maritime western tributaries. Skagit ELA depression values are about 200 m less than reported for the southern North Cascades during the Sumas stade. The effect ofthe Cordilleran Ice Sheet on precipitation likely caused ELAs to be higher in the Skagit valley than in the southern North Cascades. Keywords: glaciers; late Pleistocene; geochronology; equilibrium line altitude; North Cascades; Skagit valley; moraines; macrofossils iii Dedication ] dedicate this thesis to the many Riedels and Ploens that made it possible. In particular, it is for my mother, Bernice Ploen Riedel, whose journey through life has been far more difficult than mine. Through the great depression, World War 11 , and a long illness, she has taught me lessons of love, humiIity, and perseverance. IV Acknowledgements Few people reach their goals without the support and guidance ofothers. This research would not have been possible without the patient, informed supervision ofmy senior advisor, Dr. John 1. Clague. His encouragement led me to attempt and stick with this project while continuing with a full-time job and raising a family. Juggling these three large, slippery balls would not have been possible without the support ofmy partner and my employer. My wife, Sarah Welch, supported this effort from the very beginning and provided assistance with editing and preparation ofthe final document. I extend thanks to Bruce Freet, Jack Oelfke, and Bill Paleck for allowing me to maintain my career with the National Park Service while in a Ph.D. program. I also want to thank the other members ofmy supervisory committee, Dr. Brent Ward of Simon Fraser University and Dr. Ralph Haugerud ofthe U.S. Geological Survey. I am fortunate to have been associated with such excellent geologists and people. Many other geologists contributed to the success ofthis project, including Dr. Rowland Tabor, Dr. Kevin Scott, Dr. Johannes Koch, Dr. John Stone, and Dave Tucker. I am grateful to Dr. Linda Brubaker, Alecia Spooner, and Alice Telka for identification ofmacrofossils. Alice, in particular, has done a tremendous amount ofwork in support ofthis research. I acknowledge the staffofthe Department ofEarth Sciences and the Office ofGraduate Studies for their support and patience. In particular, I want to thank Tarja Vaisanen, Glenda Pauls, Wendy Bourke, and Matt Plotnikoff. Field assistance was provided by friends, family, and colleagues, including my brother Tom Riedel, brother-in-law Dan Goska, Jeanna Wenger, Mike Larrabee, Stephen Dorsch, Rob Burrows, Dan Heidal, and Bob Mierendorf. Mike, Jeannie, and Steve also patiently assisted me in the use ofgeographic information systems. Funding for this project came from several sources, including Simon Fraser University, the Natural Sciences Engineering and Research Council ofCanada, the Skagit Environmental Endowment Commission, and the U.S. National Park Service. v Table ofContents Approval ii Abstract iii Ded ica tion iv Acknowledgements v Table ofContents vi List ofFigures viii List ofTables xi Chapter 1: Introduction 1 Chapter 2: Geomorphology ofa Cordilleran ice sheet drainage network through breached divides in the North Cascades mountains ofWashington and British Columbia 5 Abstract 5 Introduction 6 Pre-glacial drainage patterns 7 Methods 9 Results 11 Discussion 15 Conclusion 21 Acknowledgements 22 Figures 23 Tables 35 Reference List 36 Chapter 3: Chronology and extent ofEvans Creek stade alpine glaciation in Skagit valley, Washington 40 Abstract 40 Introduction 41 Late Pleistocene setting 41 Methods 42 Stratigraphy 43 Discussion 48 Conclusions 54 Acknowledgements 54 Figures 56 Tables 69 Reference List 73 VI Appendices 77 Chapter 4: Paleoecology of Skagit valley, Washington, during the Evans Creek stade 80 Abstract 80 Introduction 81 Modern climate and forest ecology 81 Methods 83 Glacial Lake Skymo assemblages 85 Glacial Lake Concrete assemblages 89 Discussion 92 Conclusions 97 Acknowledgements 99 Figures 100 Tables 109 Reference List 118 Appendix 122 Chapter 5: Equilibrium line altitudes ofalpine glaciers during the Fraser Glaciation in Skagit valley, Wasbington 127 Abstract 127 Introduction 128 Methods 128 Results 131 Discussion 133 Conclusions 139 Acknowledgements 140 Figures 141 Tables 153 Reference List 155 Appendices 159 Cbapter 6: Syntbesis 170 Figures 173 General Bibliograpby 175 VII List ofFigures Figure 2-1. Drainage pattern and major faults ofthe Skagit region 23 Figure 2-2. Breached divides ofthe Skagit region 24 Figure 2-3. Skagit River drainage connectivity 25 Figure 2-4. Process-form model illustrating the geomorphic effects ofCordilleran Ice Sheet drainage across the North Cascades crest.. 26 Figure 2-5. View northeast over the breached divide at Hozomeen Pass into Similkameen valley 27 Figure 2-6. Topographic cross-section along the modern North Cascades crest showing locations ofbreached divides and proglaciallake and outlet elevations 28 Figure 2-7. Drainage pattern and divide changes in the upper Skagit River watershed 29 Figure 2-8. Drainage pattern and divide changes in the upper Lightning Creek area 30 Figure 2-9. The Lightning Creek fan in Skagit valley 31 Figure 2-10. Drainage pattern and divide changes in the upper Lost River area 32 Figure 2-11. Shaded relief image of Skagit Gorge 33 Figure 2-12. Schematic diagram of drainage pattern and divide changes in the Skagit River watershed 34 Figure 3-1. Digital elevation model ofthe Pacific Northwest showing locations ofearly Fraser Glaciation stratigraphic sites 56 Figure 3-2. Early Fraser Glaciation lithostratigraphic and chronostratigraphic units in the Pacific Northwest 57 Figure 3-3.