The Geology of Part of the Snake River Canyon and Adjacent Areas in Northeastern Oregon and Western Idaho
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AN ABSTRACT OF THE THESIS OF Tracy Lowell Vallier for the Ph.D. in Geology (Name) (Degree) (Major) Date thesis is presented May 1, 1967 Title THE GEOLOGY OF PART OF THE SNAKE RIVER CANYON AND ADJACENT AREAS IN NORTHEAXERN OREGON AND WESTERN IDAHO Abstract approved Redacted for Privacy (Major professor) The mapped area lies between the Wallowa Mountains of northeastern Oregon and the Seven Devils Mountains of western Idaho. Part of the Snake River canyon is in- cluded. A composite stratigraphic section includes at least 30,000 feet of strata. Pre- Tertiary and Tertiary strata are separated by a profound unconformity. Pre -Tertiary layered rocks are mostly Permian and Triassic volcani- clastic and volcanic flow rocks. At least four pre -Ter- tiary intrusive suites occur. Tertiary rocks are Miocene and Pliocene plateau basalts. Quaternary glacial materi- als and stream deposits locally mantle the older rocks. Permian ( ?) rocks of the Windy Ridge Formation are the oldest rocks and consist of 2,000 to 3,000 feet of keratophyre, quartz keratophyre, and keratophric pyro- clastic rocks. Unconformably ( ?) overlying the Windy Ridge Formation are 8,000 to 10,000 feet of volcaniclastic rocks and minor volcanic flow rocks of the Hunsaker Creek Formation of Middle Permian (Leonardian and Wordian) age. Spilitic flow rocks of the Kleinschmidt Volcanics are interlayered with and in part overlie the Hunsaker Creek Formation and comprise a sequence about 2,000 to 3,000 feet thick. The Paleozoic layered rocks were intruded by the Holbrook - Irondyke intrusives, composed of keratophyre porphyry, quartz keratophyre porphyry, diabase, and gab- bro. The Paleozoic rocks were deformed by an orogeny be- tween Middle Permian and Middle Triassic time. Plutonic rocks (Oxbow Complex) of gabbro, quartz diorite, diorite, and albite granite were intruded during Early Triassic (7) time. Movements along the Oxbow -Cuprum shear zone occurred during and after the intrusions. Middle Triassic (Ladinian) spilitic flow rocks and volcaniclastic rocks of the Grassy Ridge Formation overlie the older rocks with angular unconformity. Thicknesses are 3,000 to 4,000 feet in the northeast part of the map area; no rocks of the Grassy Ridge Formation are exposed in the southwest part. The Imnaha Formation of Late Tri- assic (Karnian) age overlies the Permian strata uncon- formably near Fish Lake in the western part of the area. The Doyle Creek Formation of Late Triassic (Karnian) age conformably overlies the Grassy Ridge Formation in the Snake River and Imnaha River canyons and may interfinger with the Imnaha Formation east of Fish Lake. The Doyle Creek Formation ranges in thickness from 3,000 to 5,000 feet and includes two members - the Ashby Creek Conglom- erate and the Piedmont Point Member. The Martin Bridge Formation, represented by 1,750 feet of Late Triassic (Norian) limestone, conformably overlies the Doyle Creek Formation. At least two intrusive events apparently occurred during the Jurassic Period. The Jurassic ( ?) intrusives, were emplaced before regional metamorphism and consist of hypabyssal dikes and sills of diorite, quartz diorite, and dacite and andesite porphyries. Subsequently, the Upper ( ?) Jurassic intrusives were emplaced during a late stage of regional metamorphism and are represented by small stocks of gabbro, norite, quartz diorite, and gran - odiorite porphyry. A major orogeny during Middle and Late ( ?) Jurassic time deformed the rocks. Regional metamorphism produced mineral assemblages characteristic of the greenschist facies. Columbia River Basalt, 2,000 to 3,000 feet thick, erupted from fissures during late Miocene and early Plio- cene time and covered an old erosion surface. Pliocene - Pleistocene uplift, alpine glaciation, and extensive stream erosion are responsible for the present topography. THE GEOLOGY OF PART OF THE SNAKE RIVER CANYON AND ADJACENT AREAS IN NORTHEASTERN OREGON AND WESTERN IDAHO by TRACY LOWELL VALLIER A THESIS submitted to OREGON STATE UNIVERSITY in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY June 1967 APPROVED: Redacted for Privacy Professor of the Department of Geology In Charge of Major Redacted for Privacy Chairman of the Department of Geology Redacted for Privacy Dean of Graduate School Date thesis is presented May 1, 1967 Typed by Trudie Vallier ACKNOWLEDGEMENTS The writer is especially grateful for the guidance, manuscript criticism, and constant encouragement given by his major professor, Dr. W.H. Taubeneck. Sincere appreci- ation is also extended to Dr. W.C. Barnes for field visits and for valuable suggestions during manuscript prepara- tion. In addition, the writer is grateful for the inter- est of other faculty members in the Department of Geology at Oregon State University, as well as for the use of field and laboratory equipment. Thanks are due Dr. J.V. Byrne and Dr. K.S. Deffeyes of the Department of Oceanography, Oregon State Universi- ty, for assistance in specific sedimentation problems, as well as to Dr. N.J. Silberling and Dr. Francis Stehli for the identification of fossils. Discussions of both local and regional problems with Willis White, Bruce Nolf, Ralph Cannon, Clyde Wetherell, Howard Brooks, Norman Wagner, and Robert Morrison were beneficial. A three- -yeas NDEA Fellowship and a. Terminal Year Fel- lowship from The National Science Foundation permitted the writer to undertake and complete this study. Grants from the Penrose Bequest Fund of the Geological Society of America, the Sigma Xi -RE;A Fund, and the Oregon Depart- ment of Geology and Mineral Industries were helpful in defraying field expenses and in providing equipment. The writer is deeply grateful to his wife Trudie for her patience during all aspects of this study, for her companionship in the field, and for her assistance with the typing and revision of the manuscript. TABLE OF CONTENTS Page INTRODUCTION 1 Location and Accessibility 1 Topography 1 Drainage 3 Climate and Vegetation 5 Purpose of the Investigation 5 Field and Laboratory Procedures 6 Field Procedures 6 Laboratory Procedures 7 Previous Field Work 7 STRATIGRAPHY 9 Classification and Terminology 9 Introduction 9 Volcanic Flow Rocks 9 Clastic Rocks of Volcanic Derivation (Volcaniclastic) 9 Stratigraphic Relationships of the Pre - Tertiary Rocks 13 Introduction 13 Stratigraphic Column in the Seven Devils Region 13 Stratigraphic Column in the Wallowa Mountains 16 Stratigraphic Column in the Thesis Area 20 Windy Ridge Formation 22 Definition, Distribution, and General Character 22 Stratigraphic Relationships and Thickness 24 Lithology and Petrography 26 Conditions of Deposition, Transportation, and Provenance 29 Age and Correlation 30 Hunsaker Creek Formation 30 Definition, Distribution, and General Character 30 Stratigraphic Relationships and Thickness 32 Lithology and Petrography 33 Conditions of Deposition, Transportation, and Provenance 61 Age and Correlation 63 Kleinschmidt Volcanics 66 Definition, Distribution, and General Character 66 Stratigraphic Relationships and Thickness 66 TABLE OF CONTENTS (Continued) Page Lithology and Petrography 68 Conditions of Deposition, Transportation, and Provenance 70 Age and Correlation 71 Grassy Ridge Formation 71 Definition, Distribution, and General Character 71 Stratigraphic Relationships and Thickness 73 Lithology and Petrography 76 Conditions of Deposition, Transportation, and Provenance 85 Age and Correlation 87 Imna.ha Formation: Russel Mountain Member 88 Definition, Distribution, and General Character 88 Stratigraphic Relationships and Thickness 91 Lithology and Petrography 92 Conditions of Deposition, Transportation, and Provenance 98 Age and Correlation 99 Doyle Creek Formation 100 Definition, Distribution, and General Character 100 Stratigraphic Relationships and Thickness 101 Lithology and Petrography 105 Piedmont Point Member 113 Ashby Creek Conglomerate 115 Conditions of Deposition, Transportation, and Provenance 119 Age and Correlation 119 Martin Bridge Formation 120 Definition, Distribution, and General Character 120 Stratigraphic Relationships and Thickness 122 Lithology and Petrography 122 Age and Correlation 124 Conditions of Deposition 125 Columbia River Basalt 127 Definition, Distribution, and General Character 127 Stratigraphic: Relationships and Thickness 128 Lithology and Petrography 128 Age 130 Quaternary Unconsolidated Deposits 130 Glacial Deposits 130 Landslide Debris 131 TABLE OF CONTENTS (Continued) Page Terrace Gravels and Recent Alluvium 131 Volcanic Ash 133 INTRUSIVE UNITS 134 Introduction 134 Paleozoic Intrusives 134 Mafic Dikes in the Windy Ridge Formation 134 Holbrook- Irondyke Intrusives 137 Mesozoic Intrusives 141 The Oxbow Complex 141 153 Jurassic ( ?) Intrusives Upper Jurassic (2) Intrusives 156 Cenozoic Intrusives 165 METAMORPHISM 168 Introduction 168 Dynamic Metamorphism 168 Igneous Metamorphism 169 Regional Metamorphism 170 Albi tizabion 171 Silicification 173 Conditions and Times of Regional Metamorphism 174 STRUCTURAL GEOLOGY 175 Introduction 175 Folds 175 Faults 177 Permian-Triassic [JnconformitV 178 Mesozoic-Tertiary Unconformity 185 Oxbow- Cuprum Shear Zone 185 192 ï ;1a>M(7 RF>1-,OLOC Y Introduction 192 Plateau Region 192 Glacial Features 192 Non -- Glacial Features 194 Canyon Region 195 General Feature 195 198 I :r-e-- :;eerie Erosion Surface The Geomorphic History of the Snake River 199 introduction 199 Summary DI Preceding Studies 199 observations in the Map Area 200 TABLE OF CONTENTS (Continued) Page Origin of the Oxbow 202 Conclusions 204 ECONOMIC