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Fault Segmentation Control on Alluvial Fan and Fan

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Fault Segmentation Control on Alluvial Fan and Fan FAULT SEGMENTATION CONTROL ON ALLUVIAL FAN AND FAN DRAINAGE BASIN MORPHOMETRY, LEMHI RANGE, EAST-CENTRAL IDAHO by Christina Grace Carr A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Earth Sciences MONTANA STATE UNIVERSITY Bozeman, Montana April 2011 © COPYRIGHT by Christina Grace Carr 2011 All Rights Reserved ii APPROVAL of a thesis submitted by Christina Grace Carr This thesis has been read by each member of the thesis committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to The Graduate School. Dr. James G. Schmitt Approved for the Department of Earth Sciences Dr. Stephan G. Custer Approved for The Graduate School Dr. Carl A. Fox iii STATEMENT OF PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a master’s degree at Montana State University, I agree that the Library shall make it available to borrowers under rules of the Library. If I have indicated my intention to copyright this thesis by including a copyright notice page, copying is allowable only for scholarly purposes, consistent with “fair use” as prescribed in the U.S. Copyright Law. Requests for permission for extended quotation from or reproduction of this thesis in whole or in parts may be granted only by the copyright holder. Christina Grace Carr April 2011 iv ACKNOWLEDGMENTS Funding was generously provided by the Montana Association of Geographic Information Professionals, the Montana Space Grant Consortium, the Montana State University Earth Sciences Department, the Colorado Scientific Society, the Geological Society of America, the American Association of Petroleum Geologists, ConocoPhillips, ExxonMobil, and Marathon. Discussions with my committee members, Stuart Challender and Steve Custer, as well as with William Locke, Diana Cooksey, Ken Pierce, and Jen Pierce, provided insight into various aspects of the research. David Keto, Megan Selheim, Bobby Boessenecker, and everyone else who lent a listening ear, thank you. Syverine Abrahamson and Travis Naibert – thank you for the fieldwork through trying times. Caitlyn Florentine and Mark Egge – you helped me through the toughest parts of the last several years as well as with the thesis, thank you. Jason Allen, you helped me finally finish this project in so many ways. Thanks for looking at scribbles on scrap paper and seeing progress. Thank you for enduring endless hours of frustration, success, setbacks, and eventual triumph. Finally, thank you to my advisor, Jim Schmitt. I am honored to have been your student. You’ve been supportive, given strong shoves of encouragement, listened, laughed, and mentored my geologic learning and my life for almost a decade. v TABLE OF CONTENTS 1. INTRODUCTION ...........................................................................................................1 Alluvial Fans and Tectonic Signals .................................................................................3 Models of Extensional Basin Evolution and Resulting Stratigraphy...............................5 Segmentation of Normal Faults .......................................................................................9 Tectonically Driven Evolution of the Extensional Footwall as a Sediment Source......12 Alluvial Fan and Drainage Basin Area and Slope Relationships .............................14 Basin Elongation Ratio, Hypsometry, and Melton Ratio .........................................15 Alluvial Fan Processes...................................................................................................18 Axial River Influences on Alluvial Fans ..................................................................19 Study Area and Previous Regional Morphometric Work..............................................21 Hypothesis Questions.....................................................................................................23 2. REGIONAL SETTING (GEOLOGY, TECTONICS, AND CLIMATE).....................26 Structural History...........................................................................................................29 Multiple Phases of Cenozoic Extension in east-central Idaho..................................33 Eocene Metamorphic Core Complex Development ...........................................34 Paleogene Supradetachment Basins....................................................................35 Basin and Range Extension ................................................................................37 Modification by Passage of the Yellowstone Hotspot .......................................39 Regional Stratigraphy ....................................................................................................39 Lemhi Alluvial Fans .................................................................................................40 Quaternary Faulting and the Intermountain Seismic Belt..............................................44 Quaternary Seismicity of the Lemhi and Surrounding Ranges ................................44 The 1983 Borah Peak Earthquake.............................................................................47 Intermountain Seismic Belt.......................................................................................48 Seismicity and the Idaho National Engineering and Environmental Laboratory .....52 Yellowstone Hotspot and the Snake River Plain ...........................................................53 Climate...........................................................................................................................58 Modern Climate ........................................................................................................58 Pleistocene Glaciations .............................................................................................58 Periods of Fan Deposition and Glacial/Interglacial Cycles ......................................59 Climate-related Changes in Seismicity.....................................................................62 Climate, Tectonics, and Erosion: Coupled Systems with Complex Responses ............63 Previous Work Delineating Fault Segments Along the Lemhi Range ..........................66 Individual Study Descriptions...................................................................................67 Preferred Segmentation Model .................................................................................74 vi TABLE OF CONTENTS – CONTINUED 3. METHODOLOGY ........................................................................................................76 Data Sources and Accuracy ...........................................................................................77 Data Preprocessing.........................................................................................................78 Terrain Analysis and Morphometry...............................................................................82 Basin Delineation......................................................................................................82 Basin Area, Flow Path Length, Elongation Ratio, and Melton Ratio.......................87 Fan Area....................................................................................................................90 Drainage Basin Slope and Fan Slope........................................................................90 Basin Hypsometry.....................................................................................................91 Other Zonal Statistics: Elevation ..............................................................................92 Distance from Segment Boundary............................................................................93 Standard Regressions.....................................................................................................95 4. RESULTS ......................................................................................................................97 General Statistics for Drainage Basin and Fan Areas and Slopes .................................97 Morphometric Parameters and Distance from Fault Segment Boundaries....................98 Fan Area to Drainage Basin Area Ratio ...................................................................98 Drainage Basin Elongation Ratio and Melton Ratio...............................................100 Drainage Basin Hypsometric Integral and Hypsometric Curves............................103 Drainage Basin and Fan Area and Slope Relationships...............................................107 Fan Area and Drainage Basin Area ........................................................................107 Fan Slope and Drainage Basin Area .......................................................................112 Drainage Basin Slope and Drainage Basin Area ....................................................114 5. DISCUSSION..............................................................................................................117 Drainage Basin Area....................................................................................................117 Morphometric Parameters and Distance from Fault Segment Boundaries..................118 Fan Area to Drainage Basin Area Ratio .................................................................119 Drainage Basin Elongation Ratio and Melton Ratio...............................................121 Drainage
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