Inferring Bedrock Uplift in the Klamath Mountains Province from River Profile Analysis and Digital Topography
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Inferring bedrock uplift in the Klamath Mountains Province from river profile analysis and digital topography By Timothy Kirt Anderson, B.A., B.S. A Thesis In Geosciences Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for Degree of Masters of Science Approved Dr. Aaron Yoshinobu Chairperson of the Committee Dr. Calvin Barnes Dr. David Leverington Accepted Fred Hartmeister Dean of Graduate School December, 2008 Texas Tech University, Timothy Anderson, December 2008 Acknowledgements I would like to thank my advisor, Dr. Aaron Yoshinobu for the opportunity to work on an exciting project, and am grateful for his enthusiastic approach to science. I would like to thank my committee members, Dr. Cal Barnes and Dr. David Leverington, for their thoughtful reviews of this manuscript. I would like to thank Dr. Jeff Lee and Linda Jones of the Department of Economics and Geography for the role they played in my financial support as a teaching assistant. I would like to acknowledge the Department of Geography and Dr. Yoshinobu for allowing me access to the hardware and software necessary to undertake this research. I would like to thank Dr. Don Elder for providing me with his ‘latest and greatest’ digital data of the Klamath Mountains. Finally, I’d like to thank my friends and family for their understanding, support, encouragement, and willingness to listen to my ideas. ii Texas Tech University, Timothy Anderson, December 2008 Table of Contents Acknowledgements ii Abstract v List of Figures vi List of Acronyms xii Chapter 1. Introduction 1 2. Tectonic Setting of the KMP and its Geologic History 10 2.1. Tectonic Setting 10 2.2. Subduction beneath the Klamath Mountains Province 12 2.3. Geologic Background: Neoproterozoic to Cretaceous 15 2.4. Cenozoic Tectonics of the KMP 24 2.5. Development of the Klamath Peneplain 24 2.6. Cenozoic Paleogeography of the KMP 29 2.7. Late Cenozoic Climate Change 38 3. Analysis of Digital Topography and Klamath Peneplain 39 3.1. Research Methods 39 3.2. Describing KMP Topography 41 3.3. Creation of Klamath Peneplain Surface 54 3.4. Klamath Peneplain Topographic and Landscape Observations 58 3.5. The Klamath Peneplain Interpolation Surface (KPS) 63 3.6. Creation of Erosion and Paleotopography Surfaces 64 3.7. Paleotopography 68 3.8. Calculated Erosion from the Klamath Peneplain Erosion Surface 71 4. River Profile Analysis 78 4.1. Introduction 78 4.2. Historical Background of Longitudinal River Profiles 78 iii Texas Tech University, Timothy Anderson, December 2008 4.3. Modern River Incision Models 81 4.4. Detachment-limited stream power model 82 4.5. River Profile Construction Methods 89 4.6. Rivers in the KMP and Adjacent Regions 94 4.7. Longitudinal River Profiles 95 4.8. Rivers in the Southern Klamath Mountains 97 4.9. Rivers in the Central Klamath Mountains 100 4.10. Rivers in the Siskiyou Mountains 110 4.11. Rivers in the Northern California and Southern Coast Range 117 5. Discussion 178 5.1. Discussion of Origin, Uplift and Erosion of Klamath Peneplain 178 5.2. Volumetric Analysis of Rates and Duration of Uplift and Erosion 182 in KMP 5.3. Evaluation of Miocene and Pliocene Paleotopography 184 5.4. Inferred Faults in the KMP 186 5.5. Rock Uplift and Topographic Evolution based on River Profile 187 Analysis 5.6. Landscape Development and Evaluation of Uplift and Erosion in 192 local KMP 5.7. Uplift Models 211 5.8. Future Tests 223 6. Conclusion 224 Literature Cited 227 Appendix 236 iv Texas Tech University, Timothy Anderson, December 2008 Abstract The Klamath Mountains Province (KMP), northern California/Southern Oregon, is situated at the juncture of the Mendocino Triple Junction, the southern boundary of the Cascades Volcanic Arc and the Juan de Fuca-North America convergent margin, and the western boundary of the Basin and Range province. KMP topography extends from sea level to over 2.5 kilometers of elevation. The mean elevation of the central KMP is greater than one kilometer, defining a regional dome of elevated topography. Surface uplift and rock exhumation have been ongoing since the Late Pliocene. A quasi-planar, regionally-extensive erosional surface termed the Klamath Peneplain (KP) is exposed in coastal regions at/near sea level and at elevations in excess of 2 kilometers more than 100 kilometers inland. Pleistocene marine and non-marine deposits have aggraded on the KP, thus preserving the surface. The geometry of the peneplain and the average amount of uplift and erosion may be calculated by interpolating a westward-dipping surface through the basal peneplain exposures. This assumes the peneplain was continuous over the entire western KMP. Time-averaged long-term uplift rates reach a maximum of 0.4mm/yr in the east. The total amount and rate of erosion since formation of the KP may be calculated by subtracting this interpolated surface from modern topography. These time-averaged results indicate that approximately 3850 km 3 of material has been removed since the Pliocene at a rate of 0.00077 km 3/yr. The maximum long-term erosion rate is 0.29 mm/yr (Salmon River). Our maps suggest that less than sixteen percent of western KMP topography existed before the Pliocene. Paleotopography with elevations greater than a v Texas Tech University, Timothy Anderson, December 2008 kilometer must have existed in the eastern KMP at the time of maximum peneplanation. Longitudinal river profiles in the central KMP are 2 to 3 times steeper than those in adjacent areas. River profile knickpoints suggest that the central KMP could be experiencing baselevel fall in some locations. Modern surface uplift and rock exhumation in the KMP may be attributed to one or more of the following; 1) northward migration of the Blanco F.Z., 2) recent duplexing of the Franciscan Complex or other accreted terranes beneath the KMP, 3) development of a serpentine wedge beneath the KMP, and 4) climate driven isostatic rebound. This last interpretation seems most favorable given the spatial correlation between uplift and erosion. vi Texas Tech University, Timothy Anderson, December 2008 List of Figures 1.1 Klamath Mountain Province and Surrounding Regions Topography 8 1.2 Geographic Locations of the KMP and Adjacent Terranes 9 2.1 Tectonics of Northwest USA 12 2.2 Mesozoic Terranes of the KMP 23 2.3 The Klamath Peneplain (from Aalto, 2006) 27 2.4 Paleogeographic Map of Eocene Geology 33 2.5 Paleogeographic Map of Oligocene Geology 34 2.6 Paleogeographic Map of Late Miocene Geology 35 2.7 Paleogeographic Map of Early Pliocene Geology 36 2.8 Paleogeographic Map of Late Pliocene Geology 37 2.9 Paleogeographic Map of Pleistocene Geology 38 2.10 Paleogeographic Map of Late Pleistocene Geology 39 3.1 Elevation of Northern California and Southern Oregon by Latitude 46 and Longitude 3.2 Longitudinal and Latitudinal Relationship between Topography and 47 Precipitation 3.3 Longitudinal Relationship between Topography and Precipitation in 48 Northern Area 3.4 Longitudinal relationship between Topography and Precipitation in 49 Central Area 3.5 Anomalous Topography of the Central Klamath Mountains and 55 Adjacent Areas 3.6 Precipitation and Hillslopes in the Klamath Mountains Province and 56 vii Texas Tech University, Timothy Anderson, December 2008 Adjacent Areas 3.7 Interpolation Surfaces of the Klamath Peneplain Unit 3.8 Distribution 60 of Erosion Remnant Surfaces 3.8 Distribution of Erosional Remnant Surfaces 62 3.9 Geographic Location and Elevation of Individual Erosional Remnant 63 Surfaces 3.10 Slope and Aspect of Erosional Remnant Surfaces 64 3.11 Elevation of Erosional Remnant Surfaces and Topography by Longitude 65 3.12 Interpolation Surface of Erosional Remnant Surface Elevations 68 (Natural Neighbor) 3.13 Modern Topography Vs. Interpolation Surface 70 3.14 Topography Relative to Interpolation Surface 71 3.15 Map of Paleotopography 76 3.16 Map of Calculated Erosion 80 3.17 Map of Calculated Erosion and Rivers 81 4.1 Northern California and Southern Oregon Subbasins 130 4.2 Equilibrium Vs. Non-Equilibrium Streams 131 4.3 Effect of Basin Shape on Hack Gradient 132 4.4 Parameters used in River Profile Analysis (from Wobus et al., 2006) 133 4.5 Channel Concavity Vs. Channel Steepness 134 4.6 River Profile Shapes 135 4.7 Knickpoint Migration 136 4.8 Map of Normalized Channel Steepness of River Segments of the KMP 137 viii Texas Tech University, Timothy Anderson, December 2008 4.9 Map of River Concavity Measurement in the KMP 138 4.10 Major Rivers in the KMP 139 4.11 Upper Eel Subbasin Streams 140 4.12 Middle Eel Subbasin Streams 141 4.13 Lower Eel Subbasin Streams 142 4.14 Longitudinal Profile of Middle Fork Eel River 143 4.15 Longitudinal Profile of Van Duzen River 144 4.16 Mad-Redwood Subbasin Streams 145 4.17 Longitudinal Profile of Redwood Creek 146 4.18 Longitudinal Profile of Mad River 147 4.19 South Fork Trinity Subbasin Streams 148 4.20 Longitudinal Profile of South Fork Trinity River 149 4.21 Trinity Subbasin Streams: Upper Streams 150 4.22 Trinity Subbasin Streams: Central Streams 151 4.23 Trinity Subbasin Streams: Lower Streams 152 4.24 Longitudinal Profile of Coffee Creek (Trinity River Tributary) 153 4.25 Longitudinal Profile of New River (Trinity River Tributary) 154 4.26 Longitudinal Profile of East Fork (Trinity River Tributary) 155 4.27 Longitudinal Profile of Canyon Creek (Trinity River Tributary) 156 4.28 Longitudinal Profile of Trinity River 157 4.29 Salmon Subbasin Streams 158 4.30 Longitudinal Profile Salmon River 159 ix Texas Tech University, Timothy Anderson,