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• 191. [Article] Stratigraphy and sedimentation of the Onion Peak area, Clatsop County, Oregon

  Six Tertiary units are exposed in the Onion Peak area near the town of Cannon Beach., Oregon. The units consist of: late Eocene to early Miocene Oswald West mudstones (informal), middle Miocene Astoria ...

  Citation × Citation Citation Abstract Copy Title: Stratigraphy and sedimentation of the Onion Peak area, Clatsop County, Oregon Author: Smith, Thomas N. Six Tertiary units are exposed in the Onion Peak area near the town of Cannon Beach., Oregon. The units consist of: late Eocene to early Miocene Oswald West mudstones (informal), middle Miocene Astoria Formation (Angora Peak sandstone and Silver Point mudstone members.-informal), middle Miocene basalts of intrusive and extrusive Depoe Bay Basalt, and intrusive Cape Foulweather Basalt. Beach sands, Pleistocene marine terraces, and stream alluvium unconformably overlie these Tertiary units. The Oswald West mudstones consist of more than 1600 feet of well-bedded, burrowed, tuffaceou siltstones and mudstones with sub ordinate tuff and glauconitic sandstone beds. Foraminiferal and trace fossil evidence suggest that these mudstones were deposited in marine waters of upper bathyal depths. The overlying 1700-foot thick Astoria Formation is divided into two informal mappable members: the 1100-foot thick Angora Peak sandstone and the 600-foot thick Silver Point mudstone (proposed informally in this study). The Angora Peak sandstone member is composed of several hundred feet of thickly laminated feldspathic sandstones with local cross-bedded lithic conglomerates and carbonaceous siltstones. The overlying Silver Point mudstone member consists of rhythmically interbedded mudstones and graded turbidite sandstones, overlain by bedded mudstones, thin siltstones, and local conglomerate lenses. Conglomerate clast lithologies and heavy mineral suites of the Silver Point and Angora. Peak members are similar to the sediment carried by the Columbia River today and may be an ancient deposit of that river system. The provenances for these strata were pre-Miocene andesitic and dacitic rocks of the western Cascades, the Coast Range Eocene Tillamook basalts, and plutonic, metamorphic, and sedimentary contributions from eastern Oregon and Washington, Idaho, Montana, and Canada, Channel fluvial sandstones, conglomerates, and well-bedded shallow marine sandstones of the Angora Peak member, probably interfingering with interbedded, deeper marine (600 feet-outer shelf) mudstones and turbidite sndstones of the Silver Point member, are interpreted to have been deposited near the mouth of a river, adjacent to the ocean as a delta. Dikes, sills, peperites, and irregular intrusive bodies of middle Miocene Depoe Bay Basalt intruded Oswald West mudstones and the Astoria Formation. These aphanitic to finely crystalline equigranular basaltic intrusives locally fed over 2000 feet of palagonitized pillow lavas and basaltic breccias which now form the highest peaks in the area. The intrusives locally penecontemporaneously deformed the Astoria strata into a series of large-scale soft sediment deformation folds and sedimentary breccias. Cape Foulweather Basalt intrudes all sedimentary units and cuts the Depoe Bay Basalts. The basalt is recognized by sparse, large plagioclase phenocrysts. The area is cut by several east-west and north-south trending high angle faults with up to 500 feet displacement A large north-south syncline in the central part of the thesis area delineates a structural and depositional basin. A smaller north-plunging anticline is present near the coast. Recent landslides in the Silver Point member have been particularly destructive along the coast and inland; they have been caused by wave, stream action, and by man over-steepening unstable slopes. Crushed basalt quarry rock and potential petroleum reservoirs in the Angora Peak sandstones in stratigraphic and structural tra traps, particularly in nearby offshore areas, are the main geological economic resources of the area. Title: Stratigraphy and sedimentation of the Onion Peak area, Clatsop County, Oregon Author: Smith, Thomas N. Six Tertiary units are exposed in the Onion Peak area near the town of Cannon Beach., Oregon. The units consist of: late Eocene to early Miocene Oswald West mudstones (informal), middle Miocene Astoria Formation (Angora Peak sandstone and Silver Point mudstone members.-informal), middle Miocene basalts of intrusive and extrusive Depoe Bay Basalt, and intrusive Cape Foulweather Basalt. Beach sands, Pleistocene marine terraces, and stream alluvium unconformably overlie these Tertiary units. The Oswald West mudstones consist of more than 1600 feet of well-bedded, burrowed, tuffaceou siltstones and mudstones with sub ordinate tuff and glauconitic sandstone beds. Foraminiferal and trace fossil evidence suggest that these mudstones were deposited in marine waters of upper bathyal depths. The overlying 1700-foot thick Astoria Formation is divided into two informal mappable members: the 1100-foot thick Angora Peak sandstone and the 600-foot thick Silver Point mudstone (proposed informally in this study). The Angora Peak sandstone member is composed of several hundred feet of thickly laminated feldspathic sandstones with local cross-bedded lithic conglomerates and carbonaceous siltstones. The overlying Silver Point mudstone member consists of rhythmically interbedded mudstones and graded turbidite sandstones, overlain by bedded mudstones, thin siltstones, and local conglomerate lenses. Conglomerate clast lithologies and heavy mineral suites of the Silver Point and Angora. Peak members are similar to the sediment carried by the Columbia River today and may be an ancient deposit of that river system. The provenances for these strata were pre-Miocene andesitic and dacitic rocks of the western Cascades, the Coast Range Eocene Tillamook basalts, and plutonic, metamorphic, and sedimentary contributions from eastern Oregon and Washington, Idaho, Montana, and Canada, Channel fluvial sandstones, conglomerates, and well-bedded shallow marine sandstones of the Angora Peak member, probably interfingering with interbedded, deeper marine (600 feet-outer shelf) mudstones and turbidite sndstones of the Silver Point member, are interpreted to have been deposited near the mouth of a river, adjacent to the ocean as a delta. Dikes, sills, peperites, and irregular intrusive bodies of middle Miocene Depoe Bay Basalt intruded Oswald West mudstones and the Astoria Formation. These aphanitic to finely crystalline equigranular basaltic intrusives locally fed over 2000 feet of palagonitized pillow lavas and basaltic breccias which now form the highest peaks in the area. The intrusives locally penecontemporaneously deformed the Astoria strata into a series of large-scale soft sediment deformation folds and sedimentary breccias. Cape Foulweather Basalt intrudes all sedimentary units and cuts the Depoe Bay Basalts. The basalt is recognized by sparse, large plagioclase phenocrysts. The area is cut by several east-west and north-south trending high angle faults with up to 500 feet displacement A large north-south syncline in the central part of the thesis area delineates a structural and depositional basin. A smaller north-plunging anticline is present near the coast. Recent landslides in the Silver Point member have been particularly destructive along the coast and inland; they have been caused by wave, stream action, and by man over-steepening unstable slopes. Crushed basalt quarry rock and potential petroleum reservoirs in the Angora Peak sandstones in stratigraphic and structural tra traps, particularly in nearby offshore areas, are the main geological economic resources of the area. Close

• 192. [Article] The geology of part of the Snake River Canyon and adjacent areas in Northeastern Oregon and Western Idaho

  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 included. A composite stratigraphic section ...

  Citation × Citation Citation Abstract Copy Title: The geology of part of the Snake River Canyon and adjacent areas in Northeastern Oregon and Western Idaho Author: Vallier, Tracy L. (Tracy Lowell), 1936- 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 included. 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 volcaniclastic and volcanic flow rocks. At least four pre -Tertiary intrusive suites occur. Tertiary rocks are Miocene and Pliocene plateau basalts. Quaternary glacial materials 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 pyroclastic 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 gabbro. The Paleozoic rocks were deformed by an orogeny between 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 Triassic (Karnian) age overlies the Permian strata unconformably 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 Conglomerate 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 Pliocene time and covered an old erosion surface. Pliocene - Pleistocene uplift, alpine glaciation, and extensive stream erosion are responsible for the present topography. Title: The geology of part of the Snake River Canyon and adjacent areas in Northeastern Oregon and Western Idaho Author: Vallier, Tracy L. (Tracy Lowell), 1936- 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 included. 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 volcaniclastic and volcanic flow rocks. At least four pre -Tertiary intrusive suites occur. Tertiary rocks are Miocene and Pliocene plateau basalts. Quaternary glacial materials 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 pyroclastic 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 gabbro. The Paleozoic rocks were deformed by an orogeny between 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 Triassic (Karnian) age overlies the Permian strata unconformably 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 Conglomerate 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 Pliocene time and covered an old erosion surface. Pliocene - Pleistocene uplift, alpine glaciation, and extensive stream erosion are responsible for the present topography. Close

• 193. [Article] Lithologic, Climatic, and Biotic vs. Abiotic Controls on Erosion and Landscape Evolution

  The triumvirate of tectonics, lithology, and climate control landscape evolution. This study quantifies how lithologic variation and climate-mediated changes in ecosystems perturb steady state processes ...

  Citation × Citation Citation Abstract Copy Title: Lithologic, Climatic, and Biotic vs. Abiotic Controls on Erosion and Landscape Evolution Author: Marshall, Jill Year: 2015 The triumvirate of tectonics, lithology, and climate control landscape evolution. This study quantifies how lithologic variation and climate-mediated changes in ecosystems perturb steady state processes in the unglaciated, soil-mantled Oregon Coast Range (OCR). I first demonstrate that minor grain-scale differences in rock properties in a seemingly uniform sandstone control differences in rock strength, biotic bedrock-to-soil production efficacy, and erosion rates and influence relief at the watershed scale. I then build on sedimentology, paleoecology, and isotopic-derived paleoerosion data I collected from a new 50 ka sediment archive at Little Lake, OR to explore climate controls on soil production and erosion rates 21 ka across the OCR and spanning 50 ky within a single watershed. In Chapter III, I combine a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction and paleovegetation data to demonstrate that accelerated frost-driven erosion was pervasive across the OCR during the LGM. My findings provide a new framework to quantify how the late Pleistocene affects modern erosion and soil formation rates in unglaciated environments and implies that most landscapes reside in a transient state. In Chapter IV, I document climate-mediated ecosystem influence on erosion rates over 3 climatic intervals. 10Be-derived erosion rates increase 3x (from 0.6 mm/yr to 0.21 mm/yr) as the OCR transitioned from the open forest-dominated marine isotope stage (MIS) climate interval (50-26 ka) into the periglacial subalpine MIS 2 glacial interval (26-13 ka). Measured erosion rates fell by more than half as the subalpine ecosystem gave way to the modern MIS 1 closed canopy Douglas-fir forest. Coupling paleovegetation-derived climate information with core observations I model frost weathering intensity from ~ 43 ka to 21 ka and establish a correspondence with increasing frost weathering intensity and increasing 10Be-derived erosion rates. Utilizing a transient mixing depth and erosion rate model, I am able to broadly replicate measured erosion rates at Little Lake through time. My findings contradict previous work that suggests climate has only weak control on erosion rates. This dissertation includes previously published and unpublished co-authored material. Title: Lithologic, Climatic, and Biotic vs. Abiotic Controls on Erosion and Landscape Evolution Author: Marshall, Jill Year: 2015 The triumvirate of tectonics, lithology, and climate control landscape evolution. This study quantifies how lithologic variation and climate-mediated changes in ecosystems perturb steady state processes in the unglaciated, soil-mantled Oregon Coast Range (OCR). I first demonstrate that minor grain-scale differences in rock properties in a seemingly uniform sandstone control differences in rock strength, biotic bedrock-to-soil production efficacy, and erosion rates and influence relief at the watershed scale. I then build on sedimentology, paleoecology, and isotopic-derived paleoerosion data I collected from a new 50 ka sediment archive at Little Lake, OR to explore climate controls on soil production and erosion rates 21 ka across the OCR and spanning 50 ky within a single watershed. In Chapter III, I combine a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction and paleovegetation data to demonstrate that accelerated frost-driven erosion was pervasive across the OCR during the LGM. My findings provide a new framework to quantify how the late Pleistocene affects modern erosion and soil formation rates in unglaciated environments and implies that most landscapes reside in a transient state. In Chapter IV, I document climate-mediated ecosystem influence on erosion rates over 3 climatic intervals. 10Be-derived erosion rates increase 3x (from 0.6 mm/yr to 0.21 mm/yr) as the OCR transitioned from the open forest-dominated marine isotope stage (MIS) climate interval (50-26 ka) into the periglacial subalpine MIS 2 glacial interval (26-13 ka). Measured erosion rates fell by more than half as the subalpine ecosystem gave way to the modern MIS 1 closed canopy Douglas-fir forest. Coupling paleovegetation-derived climate information with core observations I model frost weathering intensity from ~ 43 ka to 21 ka and establish a correspondence with increasing frost weathering intensity and increasing 10Be-derived erosion rates. Utilizing a transient mixing depth and erosion rate model, I am able to broadly replicate measured erosion rates at Little Lake through time. My findings contradict previous work that suggests climate has only weak control on erosion rates. This dissertation includes previously published and unpublished co-authored material. Close

• 194. [Article] Late Quaternary and Holocene Paleoecology of Interior Mesic Forests of Northern Idaho

  The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest ...

  Citation × Citation Citation Abstract Copy Title: Late Quaternary and Holocene Paleoecology of Interior Mesic Forests of Northern Idaho Author: Herring, Erin Year: 2014 The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within the inland disjunction survived the glacial periods of the Pleistocene, or whether they were more recently dispersed from coastal populations. To see if the dominant tree taxa of the mesic forests today could have persisted in a refugium south of the large ice sheets, four sediment cores were used to reconstruct the vegetation and climate history of the region. A nearly continuous record of pollen and sediment composition (biogenic silica and inorganic and organic matter) over the last ca. 120,000 years provides evidence of a dynamic ecosystem. Over a long timescale, the slow shifts in vegetation are attributed to the changes in climate. During the last interglacial period, the region was warmer and drier with a Pinus dominated mixed conifer forest. Approximately 71,000 years ago, a Pseudotsuga/Larix forest became established in the area as a response to the increased available moisture. As climate cooled and glaciers expanded the Pinus and Picea forest was the dominant vegetation type until ca. 40,000 years ago. The environment during the Last Glacial Maximum (LGM) was so harsh that no vegetation record was recorded. After the LGM, climate warmed, enabling a Pinus and Picea forest to establish and persist until the Holocene. The mesic taxa that dominate the modern forests did not arrive in northern Idaho until the mid- to late-Holocene. The recent arrival of the dominant tree species, Thuja plicata and Tsuga mertensiana, suggests that they likely did not persist in a refugium during the last glaciation. Instead, these species recently dispersed from coastal populations, but expansion into their interior distributions was likely limited by both climate and species competition in already established forests. During the late-Quaternary, the deposition of thick tephra layers (>20 cm) from the eruptions of Glacier Peak (ca. 13,400 years ago) and Mt. Mazama (ca. 7,600 years ago) also facilitated an abrupt and persistent change in vegetation in northern Idaho. Title: Late Quaternary and Holocene Paleoecology of Interior Mesic Forests of Northern Idaho Author: Herring, Erin Year: 2014 The mesic forests distributed within the Rocky Mountains of northern Idaho are unique because many species contained within the forest are separated from their main distribution along the Pacific Northwest coast. It remains unclear whether most species within the inland disjunction survived the glacial periods of the Pleistocene, or whether they were more recently dispersed from coastal populations. To see if the dominant tree taxa of the mesic forests today could have persisted in a refugium south of the large ice sheets, four sediment cores were used to reconstruct the vegetation and climate history of the region. A nearly continuous record of pollen and sediment composition (biogenic silica and inorganic and organic matter) over the last ca. 120,000 years provides evidence of a dynamic ecosystem. Over a long timescale, the slow shifts in vegetation are attributed to the changes in climate. During the last interglacial period, the region was warmer and drier with a Pinus dominated mixed conifer forest. Approximately 71,000 years ago, a Pseudotsuga/Larix forest became established in the area as a response to the increased available moisture. As climate cooled and glaciers expanded the Pinus and Picea forest was the dominant vegetation type until ca. 40,000 years ago. The environment during the Last Glacial Maximum (LGM) was so harsh that no vegetation record was recorded. After the LGM, climate warmed, enabling a Pinus and Picea forest to establish and persist until the Holocene. The mesic taxa that dominate the modern forests did not arrive in northern Idaho until the mid- to late-Holocene. The recent arrival of the dominant tree species, Thuja plicata and Tsuga mertensiana, suggests that they likely did not persist in a refugium during the last glaciation. Instead, these species recently dispersed from coastal populations, but expansion into their interior distributions was likely limited by both climate and species competition in already established forests. During the late-Quaternary, the deposition of thick tephra layers (>20 cm) from the eruptions of Glacier Peak (ca. 13,400 years ago) and Mt. Mazama (ca. 7,600 years ago) also facilitated an abrupt and persistent change in vegetation in northern Idaho. Close

• 195. [Article] Structure and stratigraphy of the Argenta area, Beaverhead County, Montana

  The thesis area comprises 53 square miles located in Beaverhead County, Montana, and includes the Argenta mining district. Sedimentary and igneous rocks of the area range in age from Precambrian to Recent. ...

  Citation × Citation Citation Abstract Copy Title: Structure and stratigraphy of the Argenta area, Beaverhead County, Montana Author: Hobbs, Billy Bob The thesis area comprises 53 square miles located in Beaverhead County, Montana, and includes the Argenta mining district. Sedimentary and igneous rocks of the area range in age from Precambrian to Recent. The aggregate thickness of the sedimentary rocks is approximately 13,500 feet. The only systems not represented are Ordovician and Silurian. The oldest sedimentary rocks consist of Late Precambrian shallow marine and nonmarine subarkose, argillite, and ortho-quartzite of the Belt Supergroup. These strata are divided into three informal map units. The Paleozoic sedimentary rocks that overlie the Belt strata were deposited in a marine and in part nonmarine environment. The Cambrian system is represented by the Late Cambrian Hasmark Formation, succeeded disconformably by the Late Devonian Jefferson Dolomite and Three Forks Formation. Overlying the Three Forks is a thick sequence of Early to Late Mississippian limestones which were separated into the Lodgepole Formation and Mission Canyon Limestone. The Amsden Formation of Late Mississippian to Early Pennsylvanian age overlies the Mission Canyon with probable disconformity. The Pennsylvanian Quadrant Formation conformably succeeds the Amsden. The Permian Phosphoria Formation is considered to disconformably(?) overlie the Quadrant Formation. Mesozoic strata were deposited in continental and marine environments. The marine Dinwoody Formation of Early Triassic age is disconformably succeeded by the Late Jurassic continental Morrison Formation. The dominantly continental Early Cretaceous Kootenai Formation overlies the Morrison Formation with a gradational and arbitrarily located boundary. Marine strata of the Colorado Group (?) of Early and Late Cretaceous age overlie the Kootenai Formation with probable disconformity. Rocks representing the Tertiary System are dominantly igneous. The Argenta Stock and related plutons consist of quartz monzonite, granodiorite, and latite porphyry of probable Middle or Late Eocene age. The Argenta Stock is a composite pluton comprising quartz monzonite and quartz monzonite porphyry. Lithic welded tuff and an olivine basalt flow of possible Eocene-Oligocene age are found only in the northwest part of the area. Rhyolitic vitric tuff discomformably overlain by a limestone-pebble conglomerate, both of probable Miocene age, are present only in the eastern part of the area. Quaternary strata in the area include both glacial and fluvial deposits. Pleistocene glaciers, representing at least three glacial stades, produced a glacial trough with valley-in-valley profile, and left moraines in the northwest part of the area. Resulting outwash deposits are found in terraces above the present Rattlesnake Creek drainage. Quaternary landslide and alluvial deposits are locally present. The Laramide Orogeny has produced a complex series of folds and faults which locally trend anomalously northeast-southwest. The main structural features are the Kelly Thrust and the Argenta Anticline. Horizontal compression from the west and northwest produced a series of dominantly northeast-plunging anticlines and synclines broken by steep faults in addition to the major structures. Title: Structure and stratigraphy of the Argenta area, Beaverhead County, Montana Author: Hobbs, Billy Bob The thesis area comprises 53 square miles located in Beaverhead County, Montana, and includes the Argenta mining district. Sedimentary and igneous rocks of the area range in age from Precambrian to Recent. The aggregate thickness of the sedimentary rocks is approximately 13,500 feet. The only systems not represented are Ordovician and Silurian. The oldest sedimentary rocks consist of Late Precambrian shallow marine and nonmarine subarkose, argillite, and ortho-quartzite of the Belt Supergroup. These strata are divided into three informal map units. The Paleozoic sedimentary rocks that overlie the Belt strata were deposited in a marine and in part nonmarine environment. The Cambrian system is represented by the Late Cambrian Hasmark Formation, succeeded disconformably by the Late Devonian Jefferson Dolomite and Three Forks Formation. Overlying the Three Forks is a thick sequence of Early to Late Mississippian limestones which were separated into the Lodgepole Formation and Mission Canyon Limestone. The Amsden Formation of Late Mississippian to Early Pennsylvanian age overlies the Mission Canyon with probable disconformity. The Pennsylvanian Quadrant Formation conformably succeeds the Amsden. The Permian Phosphoria Formation is considered to disconformably(?) overlie the Quadrant Formation. Mesozoic strata were deposited in continental and marine environments. The marine Dinwoody Formation of Early Triassic age is disconformably succeeded by the Late Jurassic continental Morrison Formation. The dominantly continental Early Cretaceous Kootenai Formation overlies the Morrison Formation with a gradational and arbitrarily located boundary. Marine strata of the Colorado Group (?) of Early and Late Cretaceous age overlie the Kootenai Formation with probable disconformity. Rocks representing the Tertiary System are dominantly igneous. The Argenta Stock and related plutons consist of quartz monzonite, granodiorite, and latite porphyry of probable Middle or Late Eocene age. The Argenta Stock is a composite pluton comprising quartz monzonite and quartz monzonite porphyry. Lithic welded tuff and an olivine basalt flow of possible Eocene-Oligocene age are found only in the northwest part of the area. Rhyolitic vitric tuff discomformably overlain by a limestone-pebble conglomerate, both of probable Miocene age, are present only in the eastern part of the area. Quaternary strata in the area include both glacial and fluvial deposits. Pleistocene glaciers, representing at least three glacial stades, produced a glacial trough with valley-in-valley profile, and left moraines in the northwest part of the area. Resulting outwash deposits are found in terraces above the present Rattlesnake Creek drainage. Quaternary landslide and alluvial deposits are locally present. The Laramide Orogeny has produced a complex series of folds and faults which locally trend anomalously northeast-southwest. The main structural features are the Kelly Thrust and the Argenta Anticline. Horizontal compression from the west and northwest produced a series of dominantly northeast-plunging anticlines and synclines broken by steep faults in addition to the major structures. Close

• 196. [Article] Subsurface geology of the southeastern Cuyama Valley, southern Coast Ranges, California

  The southeastern Cuyama Valley is located in the southern Coast Ranges, west of Bakersfield, California. Subsurface geologic mapping using data from 62 prospect wells was integrated with surface mapping to ...

  Citation × Citation Citation Abstract Copy Title: Subsurface geology of the southeastern Cuyama Valley, southern Coast Ranges, California Author: Spitz, Herbert M. The southeastern Cuyama Valley is located in the southern Coast Ranges, west of Bakersfield, California. Subsurface geologic mapping using data from 62 prospect wells was integrated with surface mapping to determine the depositional and deformational history of this part of the Neogene Cuyama basin. The northwest-trending Russell fault system was active from late Oligocene to Pliocene time. Deformation along this major wrench system began during deposition of the late Oligocene to early Miocene Soda Lake Shale Member of the Vaqueros Formation and ended prior to deposition of the Plio-Pleistocene Morales Formation. The southern extension of this fault system remains uncertain, but it probably joins the Ozena fault southeast of the South Cuyama oil field. Removal of 16 to 18 miles of right-lateral offset on the Russell fault system restores the Ozena fault to a position directly east of the La Panza fault. These two faults were probably a single fault, designated the La Panza-Ozena fault, which was active, north-side down, during the Oligocene. Nonmarine conglomerates of the Simmler and lower Caliente formations were deposited north of this fault during the Oligocene, prior to the initiation of notion on the Russell fault system. Three major faults of the Cox fault zone on the west and the Lundstrom-Becker and Becker-Heller faults on the east define the margins of the Cox trough, a complex north- to northeast-trending graben north of the Russell fault which was active from Saucesian through Relizian time (early Miocene). The Saltos Shale Member of the Monterey Formation increases in thickness by 3 to 7 times across the margins of the trough. Growth faulting associated with the Cox trough ended prior to deposition of the middle Johnston sand on all faults except the Cox 46-5 fault, which was active through deposition of the Branch Canyon Sandstone. Post-Pliocene tectonism in the Cuyama basin was limited to folding and reverse-faulting in response to regional north-south compression. The Central Cuyama dome and associated north-dipping reverse faults formed during an early episode of this deformation. Subsequent deformation occurred on the Morales fault, the South Cuyama fault, and the rejuvenated Ozena fault. This Quaternary thrusting obscured the structures of the older wrench-tectonic regime and resulted in the formation of the Caliente and Sierra Madre Ranges and the present-day Cuyama Valley. Title: Subsurface geology of the southeastern Cuyama Valley, southern Coast Ranges, California Author: Spitz, Herbert M. The southeastern Cuyama Valley is located in the southern Coast Ranges, west of Bakersfield, California. Subsurface geologic mapping using data from 62 prospect wells was integrated with surface mapping to determine the depositional and deformational history of this part of the Neogene Cuyama basin. The northwest-trending Russell fault system was active from late Oligocene to Pliocene time. Deformation along this major wrench system began during deposition of the late Oligocene to early Miocene Soda Lake Shale Member of the Vaqueros Formation and ended prior to deposition of the Plio-Pleistocene Morales Formation. The southern extension of this fault system remains uncertain, but it probably joins the Ozena fault southeast of the South Cuyama oil field. Removal of 16 to 18 miles of right-lateral offset on the Russell fault system restores the Ozena fault to a position directly east of the La Panza fault. These two faults were probably a single fault, designated the La Panza-Ozena fault, which was active, north-side down, during the Oligocene. Nonmarine conglomerates of the Simmler and lower Caliente formations were deposited north of this fault during the Oligocene, prior to the initiation of notion on the Russell fault system. Three major faults of the Cox fault zone on the west and the Lundstrom-Becker and Becker-Heller faults on the east define the margins of the Cox trough, a complex north- to northeast-trending graben north of the Russell fault which was active from Saucesian through Relizian time (early Miocene). The Saltos Shale Member of the Monterey Formation increases in thickness by 3 to 7 times across the margins of the trough. Growth faulting associated with the Cox trough ended prior to deposition of the middle Johnston sand on all faults except the Cox 46-5 fault, which was active through deposition of the Branch Canyon Sandstone. Post-Pliocene tectonism in the Cuyama basin was limited to folding and reverse-faulting in response to regional north-south compression. The Central Cuyama dome and associated north-dipping reverse faults formed during an early episode of this deformation. Subsequent deformation occurred on the Morales fault, the South Cuyama fault, and the rejuvenated Ozena fault. This Quaternary thrusting obscured the structures of the older wrench-tectonic regime and resulted in the formation of the Caliente and Sierra Madre Ranges and the present-day Cuyama Valley. Close

• 197. [Article] Geology of part of the northeast quarter of the Mitchell quadrangle, Oregon

  The thesis area covers 165 square miles including the greater part of the northeastern quarter of the Mitchell quadrangle in north-central Oregon. The three stratigraphic units exposed in the area consist ...

  Citation × Citation Citation Abstract Copy Title: Geology of part of the northeast quarter of the Mitchell quadrangle, Oregon Author: Patterson, Robert Lynn The thesis area covers 165 square miles including the greater part of the northeastern quarter of the Mitchell quadrangle in north-central Oregon. The three stratigraphic units exposed in the area consist of a variety of Tertiary volcanic rocks including the Clarno Formation, the John Day Formation, and the Columbia River Basalt. The Clarno Formation of Eocene to Early Oligocene age is the oldest rock unit in the thesis area. From oldest to youngest, the mapped units include volcanic boulder conglomerates, andesite and basalt flows and flow breccias, tuffaceous sandstones intercalated with lava flows, and twelve plugs and dikes of andesite and basalt. The composition, lack of sorting, stratigraphic and structural features, and the included flora indicate that the volcanic boulder conglomerates were deposited as mudflows on a terrain of high relief in a humid, subtropical climate. Andesite lavas were extruded intermittently during deposition of the mudflows resulting in complex intertonguing of the two rock types. Later, Clarno lavas poured from numerous isolated fissures and covered the volcanic boulder conglomerates. Near Middle Oligocene time the formation was folded into a broad NE-trending anticline which swings sharply eastward in the north-central half of the area. Following uplift, the Clarno rocks were eroded into a surface of moderate relief and thick fossil soils developed on scoriaceous portions of the lava flows. The John Day Formation of Late Oligocene to Early Miocene age consists of ash flows and ash falls of acid to intermediate pyroclastic material which were deposited unconformably on the deformed and eroded Clarno rocks. These pyroclastics were erupted from unknown local sources, and probably from distant volcanoes to the west. Much of the material deposited on the pre-Miocene anticlinal crest was reworked by streams and formed thick tuff beds on the flanks of the fold. In Middle Miocene time the consolidated John Day Formation was slightly folded parallel to pre-Miocene anticlinal trends and underwent erosion. The Columbia River Basalt was extruded from fissures onto the tuffs during Middle Miocene time. Following deposition the thick layers of basalt were gently folded as the pre-Miocene anticlinal trend again served as the pattern for mild uplift and deformation in latest Miocene time. Rocks younger than Middle Miocene were either never deposited on the basalt plateaus of the area, or have been completely removed by erosion. In Pleistocene and Recent time the plateaus were dissected and the flows were eroded from the anticlinal crest. Landslide, fluvial, and terrace deposits were laid down in the valleys. White volcanic ash was transported by wind from an unknown source and intercalated with Recent fluvial and slope wash deposits. Title: Geology of part of the northeast quarter of the Mitchell quadrangle, Oregon Author: Patterson, Robert Lynn The thesis area covers 165 square miles including the greater part of the northeastern quarter of the Mitchell quadrangle in north-central Oregon. The three stratigraphic units exposed in the area consist of a variety of Tertiary volcanic rocks including the Clarno Formation, the John Day Formation, and the Columbia River Basalt. The Clarno Formation of Eocene to Early Oligocene age is the oldest rock unit in the thesis area. From oldest to youngest, the mapped units include volcanic boulder conglomerates, andesite and basalt flows and flow breccias, tuffaceous sandstones intercalated with lava flows, and twelve plugs and dikes of andesite and basalt. The composition, lack of sorting, stratigraphic and structural features, and the included flora indicate that the volcanic boulder conglomerates were deposited as mudflows on a terrain of high relief in a humid, subtropical climate. Andesite lavas were extruded intermittently during deposition of the mudflows resulting in complex intertonguing of the two rock types. Later, Clarno lavas poured from numerous isolated fissures and covered the volcanic boulder conglomerates. Near Middle Oligocene time the formation was folded into a broad NE-trending anticline which swings sharply eastward in the north-central half of the area. Following uplift, the Clarno rocks were eroded into a surface of moderate relief and thick fossil soils developed on scoriaceous portions of the lava flows. The John Day Formation of Late Oligocene to Early Miocene age consists of ash flows and ash falls of acid to intermediate pyroclastic material which were deposited unconformably on the deformed and eroded Clarno rocks. These pyroclastics were erupted from unknown local sources, and probably from distant volcanoes to the west. Much of the material deposited on the pre-Miocene anticlinal crest was reworked by streams and formed thick tuff beds on the flanks of the fold. In Middle Miocene time the consolidated John Day Formation was slightly folded parallel to pre-Miocene anticlinal trends and underwent erosion. The Columbia River Basalt was extruded from fissures onto the tuffs during Middle Miocene time. Following deposition the thick layers of basalt were gently folded as the pre-Miocene anticlinal trend again served as the pattern for mild uplift and deformation in latest Miocene time. Rocks younger than Middle Miocene were either never deposited on the basalt plateaus of the area, or have been completely removed by erosion. In Pleistocene and Recent time the plateaus were dissected and the flows were eroded from the anticlinal crest. Landslide, fluvial, and terrace deposits were laid down in the valleys. White volcanic ash was transported by wind from an unknown source and intercalated with Recent fluvial and slope wash deposits. Close

• 198. [Article] Phylogeography, evolution, and conservation in forest-associated Pacific Northwest salamanders

  Phylogeographic studies of six Pacific Northwest forest-associated salamanders provide insight into historical and contemporary processes on population genetic structure. Among Larch Mountain Salamanders ...

  Citation × Citation Citation Abstract Copy Title: Phylogeography, evolution, and conservation in forest-associated Pacific Northwest salamanders Author: Wagner, R. Steven Phylogeographic studies of six Pacific Northwest forest-associated salamanders provide insight into historical and contemporary processes on population genetic structure. Among Larch Mountain Salamanders (Plethodon larselli), cytochrome b mitochondrial (mtDNA) sequences (381 bp) and random amplified polymorphic DNA (RAPDs; 34 loci) supported separate Management Units for northern and southern populations (12 populations, N 184 individuals) as delineated by the Columbia River. Southern populations exhibited significantly reduced expected heterozygosity at RAPD loci, which may be a consequence of a founder event or bottleneck. Similarly, significant population structure was found in Oregon Slender Salamanders (Batrachoseps wrighti). Cytochrome b sequences (744 bp) revealed two historical lineages among 22 populations (N = 339 individuals). RAPD markers further differentiated mid-range populations. Therefore, overlapping Management Units are warranted for northern-most, mid-range, and southern-most populations. Phylogenetic relationships, taxonomic identity, and population differentiation was examined among four morphologically conserved Torrent Salamanders species (Family Rhyacotritonidae). Analysis of three mitochondrial genes (cytochrome b, 16S, and 12S ribosomal RNA) indicated each species represented a well-supported monophyletic group. Results agreed with allozyme data (Good et. al. 1987, Good and Wake 1992) suggesting three groups of Torrent Salamanders (Rhyacotriton variegatus, R. cascadae, and the ancestor of R. olympicus and R. kezeri) diverged during the Miocene. A more recent divergence appears to have occurred between R. olympicus and R. kezeri during the late Pliocene/early Pleistocene. Populations within R. variegatus appear to be as diverged as R. olympicus and R. kezeri, supporting conservation unit designation within R. variegatus. MtDNA 16S ribosomal RNA sequences and allozymes (5 loci) identified Cascade and Southern Torrent Salamanders recently discovered in the Central Oregon Cascades. Results indicate a range extension for both species and suggest the Middle Fork of the Willamette River may provide a geographic barrier to dispersal. Phylogenetic analyses of Southern Torrent Salamanders (72 localities) based upon cytochrome b sequences revealed three divergent clades (north coast, Oregon, and California) that coincide with possible geographic barriers to dispersal. Merging mtDNA results with previous allozyme studies provides support for an Evolutionary Significant Unit for the California dade and separate Management Units for the north coast and Oregon clades. Title: Phylogeography, evolution, and conservation in forest-associated Pacific Northwest salamanders Author: Wagner, R. Steven Phylogeographic studies of six Pacific Northwest forest-associated salamanders provide insight into historical and contemporary processes on population genetic structure. Among Larch Mountain Salamanders (Plethodon larselli), cytochrome b mitochondrial (mtDNA) sequences (381 bp) and random amplified polymorphic DNA (RAPDs; 34 loci) supported separate Management Units for northern and southern populations (12 populations, N 184 individuals) as delineated by the Columbia River. Southern populations exhibited significantly reduced expected heterozygosity at RAPD loci, which may be a consequence of a founder event or bottleneck. Similarly, significant population structure was found in Oregon Slender Salamanders (Batrachoseps wrighti). Cytochrome b sequences (744 bp) revealed two historical lineages among 22 populations (N = 339 individuals). RAPD markers further differentiated mid-range populations. Therefore, overlapping Management Units are warranted for northern-most, mid-range, and southern-most populations. Phylogenetic relationships, taxonomic identity, and population differentiation was examined among four morphologically conserved Torrent Salamanders species (Family Rhyacotritonidae). Analysis of three mitochondrial genes (cytochrome b, 16S, and 12S ribosomal RNA) indicated each species represented a well-supported monophyletic group. Results agreed with allozyme data (Good et. al. 1987, Good and Wake 1992) suggesting three groups of Torrent Salamanders (Rhyacotriton variegatus, R. cascadae, and the ancestor of R. olympicus and R. kezeri) diverged during the Miocene. A more recent divergence appears to have occurred between R. olympicus and R. kezeri during the late Pliocene/early Pleistocene. Populations within R. variegatus appear to be as diverged as R. olympicus and R. kezeri, supporting conservation unit designation within R. variegatus. MtDNA 16S ribosomal RNA sequences and allozymes (5 loci) identified Cascade and Southern Torrent Salamanders recently discovered in the Central Oregon Cascades. Results indicate a range extension for both species and suggest the Middle Fork of the Willamette River may provide a geographic barrier to dispersal. Phylogenetic analyses of Southern Torrent Salamanders (72 localities) based upon cytochrome b sequences revealed three divergent clades (north coast, Oregon, and California) that coincide with possible geographic barriers to dispersal. Merging mtDNA results with previous allozyme studies provides support for an Evolutionary Significant Unit for the California dade and separate Management Units for the north coast and Oregon clades. Close

• 199. [Article] Functional Morphology of the Postcranium of Theropithecus brumpti (Primates: Cercopithecidae)

  xvi, 169 p. ： ill. (some col.)

  Citation × Citation Citation Abstract Copy Title: Functional Morphology of the Postcranium of Theropithecus brumpti (Primates: Cercopithecidae) Author: Guthrie, Emily Henderson Year: 2012, 2011 xvi, 169 p. ： ill. (some col.) Title: Functional Morphology of the Postcranium of Theropithecus brumpti (Primates: Cercopithecidae) Author: Guthrie, Emily Henderson Year: 2012, 2011 xvi, 169 p. ： ill. (some col.) Close

• 200. [Article] The contribution of large, slow-moving landslides to landscape evolution

  xvi, 136 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.

  Citation × Citation Citation Abstract Copy Title: The contribution of large, slow-moving landslides to landscape evolution Author: Mackey, Benjamin Hunter Year: 2010, 2009 xvi, 136 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Title: The contribution of large, slow-moving landslides to landscape evolution Author: Mackey, Benjamin Hunter Year: 2010, 2009 xvi, 136 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Close