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• 1. [Article] A stratigraphic and geochemical investigation of ferruginous bauxite deposits in the Salem Hills, Marion County, Oregon

  Pacific Northwest ferruginous bauxite deposits have formed in four main areas of northwestern Oregon and southwestern Washington by laterization of flows of the Columbia River Basalt Group (CRBG). The ...

  Citation × Citation Citation Abstract Copy Title: A stratigraphic and geochemical investigation of ferruginous bauxite deposits in the Salem Hills, Marion County, Oregon Author: Hoffman, Charles William Year: 1981 Pacific Northwest ferruginous bauxite deposits have formed in four main areas of northwestern Oregon and southwestern Washington by laterization of flows of the Columbia River Basalt Group (CRBG). The deposits, averaging 36.3% Al2O3 , 31.8% Fe2O3 , and 5.9% Sio2, generally occur near the surface of hilltops in gently rolling areas. Two very different views have been advanced regarding the setting in which the deposits have formed. The first hypothesis calls for a blanket-type laterization by erosion of much of the original deposit upon uplift and dissection of the area. Title: A stratigraphic and geochemical investigation of ferruginous bauxite deposits in the Salem Hills, Marion County, Oregon Author: Hoffman, Charles William Year: 1981 Pacific Northwest ferruginous bauxite deposits have formed in four main areas of northwestern Oregon and southwestern Washington by laterization of flows of the Columbia River Basalt Group (CRBG). The deposits, averaging 36.3% Al2O3 , 31.8% Fe2O3 , and 5.9% Sio2, generally occur near the surface of hilltops in gently rolling areas. Two very different views have been advanced regarding the setting in which the deposits have formed. The first hypothesis calls for a blanket-type laterization by erosion of much of the original deposit upon uplift and dissection of the area. Close

• 2. [Article] Geophysical and geochemical analyses of selected Miocene coastal basalt features, Clatsop County, Oregon

  The proximity of Miocene Columbia River basalts to the "locally-erupted" coastal Miocene basalts in northwestern Oregon, and the compelling similarities between the two groups, suggest that the coastal ...

  Citation × Citation Citation Abstract Copy Title: Geophysical and geochemical analyses of selected Miocene coastal basalt features, Clatsop County, Oregon Author: Pfaff, Virginia Josette Year: 1980 The proximity of Miocene Columbia River basalts to the "locally-erupted" coastal Miocene basalts in northwestern Oregon, and the compelling similarities between the two groups, suggest that the coastal basalts, rather than being locally erupted, may be the westward extension of plateau basalts derived from eastern Oregon and Washington. The local-origin hypothesis is based largely on the interpretation of coastal dikes and sills as representing vent areas; however, a complex mechanism, as yet unsatisfactorily defined, would be required to cause the eruption of virtually identical magmas simultaneously from source areas 500 km apart. This study, therefore, has investigated the coastal basalt intrusions both laterally and vertically. Geochemical and paleomagnetic analysis was used to determine the occurrence and distribution of basalt units; gravity surveys enabled an examination of the subsurface extensions of basalt intrusions in sedimentary rocks. Title: Geophysical and geochemical analyses of selected Miocene coastal basalt features, Clatsop County, Oregon Author: Pfaff, Virginia Josette Year: 1980 The proximity of Miocene Columbia River basalts to the "locally-erupted" coastal Miocene basalts in northwestern Oregon, and the compelling similarities between the two groups, suggest that the coastal basalts, rather than being locally erupted, may be the westward extension of plateau basalts derived from eastern Oregon and Washington. The local-origin hypothesis is based largely on the interpretation of coastal dikes and sills as representing vent areas; however, a complex mechanism, as yet unsatisfactorily defined, would be required to cause the eruption of virtually identical magmas simultaneously from source areas 500 km apart. This study, therefore, has investigated the coastal basalt intrusions both laterally and vertically. Geochemical and paleomagnetic analysis was used to determine the occurrence and distribution of basalt units; gravity surveys enabled an examination of the subsurface extensions of basalt intrusions in sedimentary rocks. Close

• 3. [Article] CHANCE: a probabilistic model for electrical energy planning

  The energy resource planning process for electric utilities in the Northwestern United States is unique because the region relies upon a mix of hydro and thermal resources. Consequently, methods used to ...

  Citation × Citation Citation Abstract Copy Title: CHANCE: a probabilistic model for electrical energy planning Author: Wakeland, Wayne William Year: 1977 The energy resource planning process for electric utilities in the Northwestern United States is unique because the region relies upon a mix of hydro and thermal resources. Consequently, methods used to study predominantly thermal or predominantly hydro systems are not applicable. Methods are needed to determine if a particular configuration of resources will be adequate to meet future energy load, taking into account various sources of uncertainty. A literature survey of presently available methods is described, and one method is studied in some detail. A new method for analyzing systems that rely upon a mix of hydro and thermal resources is then described. The primary contributors to uncertainty in a hydro/thermal electricity supply system are: (1) uncertain rainfall and snowfall, which results in uncertain availability of hydro energy; (2) the uncertain arrival times of planned nuclear and coal plants; (3) uncertain capacity factors for thermal plants; and (4) the uncertain amount of energy that customers will require in future years. The new model, called CHANCE, characterizes each of these uncertain phenomena with a probability density function. Mathematical convolution and an algorithm developed by the author are then used to determine the probability density function for the energy margin--the difference between supply and demand. Measures of the "energy adequacy" of the supply system are then computed from the energy margin probability density function. A computer program was designed so that the conceptual model can be easily applied to any desired electrical supply system. Once an appropriate set of input assumptions h2ve been determined, they are easily entered into the computer via a question and answer sequence and stored for future use. The computer program then computes the energy adequacy of the system. The user can then change assumptions and/or resource schedules via a question and answer sequence, and recompute the energy adequacy. The computer then prepares a report showing how the alternative assumptions and/or schedules compare. CHANCE has been applied to Pacific Power and Light Company, Portland, Oregon. At the present time, about half of their energy is generated by hydro plants and the other half is generated by coal plants. Only a small fraction is generated by nuclear plants. All planned additional generation is either coal-fired or nuclear-fired. The results of applying CHANCE indicate that planned resources are not likely to be adequate to meet the needs in the early 1980's. Several evaluation exercises have also been carried out. First, CHANCE was calibrated against other electrical energy planning models used by Pacific Power and Light. Next, the sensitivity of the CHANCE model to changes in input assumptions was measured. As was anticipated, the model is highly sensitive to the assumed energy load forecast, to the assumed potential delays in the arrival of resources, and to the assumed thermal plant capacity factors. Thus, more research in these areas is warranted. Research that might lead to improvements in the CHANCE model is then outlined, and final conclusions are drawn. The final conclusions are that the CHANCE model: (1) is valid relative to the outlined scope, (2) is quite versatile and flexible, and (3) fulfills an important need in electrical energy planning. Title: CHANCE: a probabilistic model for electrical energy planning Author: Wakeland, Wayne William Year: 1977 The energy resource planning process for electric utilities in the Northwestern United States is unique because the region relies upon a mix of hydro and thermal resources. Consequently, methods used to study predominantly thermal or predominantly hydro systems are not applicable. Methods are needed to determine if a particular configuration of resources will be adequate to meet future energy load, taking into account various sources of uncertainty. A literature survey of presently available methods is described, and one method is studied in some detail. A new method for analyzing systems that rely upon a mix of hydro and thermal resources is then described. The primary contributors to uncertainty in a hydro/thermal electricity supply system are: (1) uncertain rainfall and snowfall, which results in uncertain availability of hydro energy; (2) the uncertain arrival times of planned nuclear and coal plants; (3) uncertain capacity factors for thermal plants; and (4) the uncertain amount of energy that customers will require in future years. The new model, called CHANCE, characterizes each of these uncertain phenomena with a probability density function. Mathematical convolution and an algorithm developed by the author are then used to determine the probability density function for the energy margin--the difference between supply and demand. Measures of the "energy adequacy" of the supply system are then computed from the energy margin probability density function. A computer program was designed so that the conceptual model can be easily applied to any desired electrical supply system. Once an appropriate set of input assumptions h2ve been determined, they are easily entered into the computer via a question and answer sequence and stored for future use. The computer program then computes the energy adequacy of the system. The user can then change assumptions and/or resource schedules via a question and answer sequence, and recompute the energy adequacy. The computer then prepares a report showing how the alternative assumptions and/or schedules compare. CHANCE has been applied to Pacific Power and Light Company, Portland, Oregon. At the present time, about half of their energy is generated by hydro plants and the other half is generated by coal plants. Only a small fraction is generated by nuclear plants. All planned additional generation is either coal-fired or nuclear-fired. The results of applying CHANCE indicate that planned resources are not likely to be adequate to meet the needs in the early 1980's. Several evaluation exercises have also been carried out. First, CHANCE was calibrated against other electrical energy planning models used by Pacific Power and Light. Next, the sensitivity of the CHANCE model to changes in input assumptions was measured. As was anticipated, the model is highly sensitive to the assumed energy load forecast, to the assumed potential delays in the arrival of resources, and to the assumed thermal plant capacity factors. Thus, more research in these areas is warranted. Research that might lead to improvements in the CHANCE model is then outlined, and final conclusions are drawn. The final conclusions are that the CHANCE model: (1) is valid relative to the outlined scope, (2) is quite versatile and flexible, and (3) fulfills an important need in electrical energy planning. Close

• 4. [Article] Biostratigraphy of the type Weberg Member, Snowshoe Formation, Grant County, Oregon

  Thirty three species of ammonites are recorded from the composite type section of the Weberg Member of the Snowshoe Formation in the Suplee area, Grant County, Oregon. Holcophylloceras burkei, Euhoploceras ...

  Citation × Citation Citation Abstract Copy Title: Biostratigraphy of the type Weberg Member, Snowshoe Formation, Grant County, Oregon Author: Taylor, David G. Year: 1977 Thirty three species of ammonites are recorded from the composite type section of the Weberg Member of the Snowshoe Formation in the Suplee area, Grant County, Oregon. Holcophylloceras burkei, Euhoploceras westi, E. tubereulosum and Strigoceras taylori are described as new, while four new species belonging to the genera Sonninia [?], Bradfordia, Pseudotoites and Witchellia are not formally named. Three ammonite zonules characterize the ammonite sequence of the type Weberg composite section. The sequence correlates with parts of the standard lower and middle Bajocian (Jurassic) of northwestern Europe. In addition, four associations (paleo-communities) of benthic mega invertebrates, the Gervillia, Protocardia, Isocyprina and Bositra buahii associations are delineated. The type Weberg composite section is a record of a local marine transgression westward onto an island system. The section also represents sedimentation over an irregular pre-Snowshoe topographic high, and indicates a progressive change from proximal to distal source of pre-Snowshoe sediments, from high to low energy conditions, and perhaps a slight deepening of the ocean bottom. Ammonites are rare in the lower division of the Weberg Member, locally present in fine sandy limestones of the lower part of the upper division, abundant and most diverse in silt-rich, clay-poor limestones of the upper part of the upper division, and locally abundant in mudstones of the Warm Springs Member. Recurrent associations of certain ammonite species, strong correlation of the associations with lithofacies and biofacies, and pervasive faunal differences of ammonites between facies indicate in general that the distributional patterns of the ammonites reflect spatial life-habitats. The spotty yet widespread geographic occurrence of several ammonite species suggest they had undergone extensive planktic dispersal, thus ocean currents probably played an important role in their distributional patterns. Title: Biostratigraphy of the type Weberg Member, Snowshoe Formation, Grant County, Oregon Author: Taylor, David G. Year: 1977 Thirty three species of ammonites are recorded from the composite type section of the Weberg Member of the Snowshoe Formation in the Suplee area, Grant County, Oregon. Holcophylloceras burkei, Euhoploceras westi, E. tubereulosum and Strigoceras taylori are described as new, while four new species belonging to the genera Sonninia [?], Bradfordia, Pseudotoites and Witchellia are not formally named. Three ammonite zonules characterize the ammonite sequence of the type Weberg composite section. The sequence correlates with parts of the standard lower and middle Bajocian (Jurassic) of northwestern Europe. In addition, four associations (paleo-communities) of benthic mega invertebrates, the Gervillia, Protocardia, Isocyprina and Bositra buahii associations are delineated. The type Weberg composite section is a record of a local marine transgression westward onto an island system. The section also represents sedimentation over an irregular pre-Snowshoe topographic high, and indicates a progressive change from proximal to distal source of pre-Snowshoe sediments, from high to low energy conditions, and perhaps a slight deepening of the ocean bottom. Ammonites are rare in the lower division of the Weberg Member, locally present in fine sandy limestones of the lower part of the upper division, abundant and most diverse in silt-rich, clay-poor limestones of the upper part of the upper division, and locally abundant in mudstones of the Warm Springs Member. Recurrent associations of certain ammonite species, strong correlation of the associations with lithofacies and biofacies, and pervasive faunal differences of ammonites between facies indicate in general that the distributional patterns of the ammonites reflect spatial life-habitats. The spotty yet widespread geographic occurrence of several ammonite species suggest they had undergone extensive planktic dispersal, thus ocean currents probably played an important role in their distributional patterns. Close

• 5. [Article] Geochemical Evolution of Ferruginous Bauxite Deposits in Northwestern Oregon and Southwestern Washington

  Ferruginous bauxite deposits developed from flows of the Columbia River Basalt Group in northwestern Oregon and southwestern Washington. Samples of the iron pisolite and the gibbsite nodular zones from ...

  Citation × Citation Citation Abstract Copy Title: Geochemical Evolution of Ferruginous Bauxite Deposits in Northwestern Oregon and Southwestern Washington Author: Fassio, Joseph Michael Year: 1990 Ferruginous bauxite deposits developed from flows of the Columbia River Basalt Group in northwestern Oregon and southwestern Washington. Samples of the iron pisolite and the gibbsite nodular zones from the upper portion of the weathering profile of drill core from Columbia County, Oregon and Cowlitz County, Washington, were analyzed by instrumental neutron activation. The mineralogy was determined using Xray diffraction and Mossbauer spectroscopy. The gibbsite nodular zone is above the clay-rich saprolite or relic basalt zone. The nodules contain relic vesicles and well preserved relic plagioclase microlites. Gibbsite occurs with poorly crystalline goethite and hematite in the gibbsite nodular zone. Clays are absent in this part of the profile . The iron pisolite zone is at the top of the profile above the gibbsite nodular zone. Both maghemite and goethite pisolites occur in the lower part of the zone while maghemite pisolites are dominant in the upper part of the pisolite zone. The parent flow is the Frenchman Springs Member of the Wanapum Basalt for the Columbia County profile and the Pomona Member of the Saddle Mountains Basalt for the Cowlitz County profile. Distribution of the major, minor and trace elements through the profile shows three distinct sympathetic patterns consisting of lanthanide elements and Na; As, Sbi Th, Hf, and Ta; and transition metals Fe, Ti, V, and Cr. Ratios between the high-field strength elements Ta and Hf are nearly constant through the profile, and Hf appears to be the least mobile elements of the elements analyzed in the profile. Ratios of other elements were calculated against Hf, based on the assumption that it has remained largely immobile during weathering, to show element enrichment and depletion in the profile independent of mass-volume changes. Transition metals and Al show a progressive depletion through the upper gibbsite nodular and iron pisolite zone due to leaching in the profile. Lanthanide elements (except Ce), As, and Sb show an obvious enrichment in the iron pisolite zone relative to the gibbsite nodular zone. Volume reduction during weathering was calculated based on the immobility of Hf. In the gibbsite nodular zone, the volume reduction calculated for bulk samples is greater than for gibbsite nodule separates suggesting that a greater volume reduction occurred the matrix material surrounding the nodules. Ratios between gibbsite nodules and parent basalt of the immobile elements Hf, Ta, Fe, Ti, Th and Cr suggest that the nodules, where the relic textures are preserved, have undergone volume reduction. Based on the immobility of Hf, the gibbsite nodules lost approximately 40% of the original volume. The volume factors based on the immobility of Hf show that the pisolite zone experienced a greater volume reduction than the gibbsite nodular zone. Absolute gains and losses relative to the parent basalt show the following relative order of depletion: Na > La > Eu > Sm > Co > Mn > Ce > Sc > Ta > V > Cr > Lu > Th > Fe > Ga > Al. The lesser mobility of Ce and Lu relative to other lanthanide elements suggests fractionation of lanthanide elements in the bauxite profile. Aluminum is both enriched and depleted at different depths in the gibbsite nodular zone suggesting that Al is mobilized from the matrix and possibly the pisolite zone into Al enriched gibbsite nodules. Volume reduction and destruction of relic textures in the pisolite zone is accompanied by small-scale mobilization of Th, Cr, Fe, Hf, Ga, Sc, and Ta during the formation of iron pisolites. Formation of the iron pisolite zone above the gibbsite nodular zone may indicate a change in climate from a heavy year round to a seasonal rainfall pattern. Title: Geochemical Evolution of Ferruginous Bauxite Deposits in Northwestern Oregon and Southwestern Washington Author: Fassio, Joseph Michael Year: 1990 Ferruginous bauxite deposits developed from flows of the Columbia River Basalt Group in northwestern Oregon and southwestern Washington. Samples of the iron pisolite and the gibbsite nodular zones from the upper portion of the weathering profile of drill core from Columbia County, Oregon and Cowlitz County, Washington, were analyzed by instrumental neutron activation. The mineralogy was determined using Xray diffraction and Mossbauer spectroscopy. The gibbsite nodular zone is above the clay-rich saprolite or relic basalt zone. The nodules contain relic vesicles and well preserved relic plagioclase microlites. Gibbsite occurs with poorly crystalline goethite and hematite in the gibbsite nodular zone. Clays are absent in this part of the profile . The iron pisolite zone is at the top of the profile above the gibbsite nodular zone. Both maghemite and goethite pisolites occur in the lower part of the zone while maghemite pisolites are dominant in the upper part of the pisolite zone. The parent flow is the Frenchman Springs Member of the Wanapum Basalt for the Columbia County profile and the Pomona Member of the Saddle Mountains Basalt for the Cowlitz County profile. Distribution of the major, minor and trace elements through the profile shows three distinct sympathetic patterns consisting of lanthanide elements and Na; As, Sbi Th, Hf, and Ta; and transition metals Fe, Ti, V, and Cr. Ratios between the high-field strength elements Ta and Hf are nearly constant through the profile, and Hf appears to be the least mobile elements of the elements analyzed in the profile. Ratios of other elements were calculated against Hf, based on the assumption that it has remained largely immobile during weathering, to show element enrichment and depletion in the profile independent of mass-volume changes. Transition metals and Al show a progressive depletion through the upper gibbsite nodular and iron pisolite zone due to leaching in the profile. Lanthanide elements (except Ce), As, and Sb show an obvious enrichment in the iron pisolite zone relative to the gibbsite nodular zone. Volume reduction during weathering was calculated based on the immobility of Hf. In the gibbsite nodular zone, the volume reduction calculated for bulk samples is greater than for gibbsite nodule separates suggesting that a greater volume reduction occurred the matrix material surrounding the nodules. Ratios between gibbsite nodules and parent basalt of the immobile elements Hf, Ta, Fe, Ti, Th and Cr suggest that the nodules, where the relic textures are preserved, have undergone volume reduction. Based on the immobility of Hf, the gibbsite nodules lost approximately 40% of the original volume. The volume factors based on the immobility of Hf show that the pisolite zone experienced a greater volume reduction than the gibbsite nodular zone. Absolute gains and losses relative to the parent basalt show the following relative order of depletion: Na > La > Eu > Sm > Co > Mn > Ce > Sc > Ta > V > Cr > Lu > Th > Fe > Ga > Al. The lesser mobility of Ce and Lu relative to other lanthanide elements suggests fractionation of lanthanide elements in the bauxite profile. Aluminum is both enriched and depleted at different depths in the gibbsite nodular zone suggesting that Al is mobilized from the matrix and possibly the pisolite zone into Al enriched gibbsite nodules. Volume reduction and destruction of relic textures in the pisolite zone is accompanied by small-scale mobilization of Th, Cr, Fe, Hf, Ga, Sc, and Ta during the formation of iron pisolites. Formation of the iron pisolite zone above the gibbsite nodular zone may indicate a change in climate from a heavy year round to a seasonal rainfall pattern. Close

• 6. [Article] Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon

  The Dinner Creek Tuff is a mid-Miocene rhyolitic to dacitic ignimbrite, consisting of four cooling units with 40Ar/39Ar ages 16--15 Ma. Previous geologists have suspected that the source of the tuff is ...

  Citation × Citation Citation Abstract Copy Title: Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon Author: Cruz, Matthew Year: 2017 The Dinner Creek Tuff is a mid-Miocene rhyolitic to dacitic ignimbrite, consisting of four cooling units with 40Ar/39Ar ages 16--15 Ma. Previous geologists have suspected that the source of the tuff is located in northwestern Malheur County, eastern Oregon. This broad area is called the Dinner Creek Tuff Eruptive Center. This thesis summarizes field work, XRF/ICP-MS geochemistry, thin section petrography, and SEM feldspar analysis from the summers of 2015 and 2016. The main purpose of this study is to identify sources for the Dinner Creek Tuff units within the Dinner Creek Tuff Eruptive Center. The secondary purpose is to map lave flows that pre-date and post-date the Dinner Creek Tuff, and correlate them with regionally extensive volcanic units. Two volcanic centers related to the Dinner Creek Tuff were identified. The southern volcanic center, centered at Castle Rock, is a caldera and source of the Dinner Creek Tuff unit 1 (DIT1). Rheomorphic, densely welded DIT1 is over 300 m thick along the east side of Castle Rock. The northwestern margin of the caldera has been uplifted along faults, showing vertically foliated tuff dikes and associated mega-breccia deposits. Up to 200 m of incipiently welded tuffs, and fluvial volcanoclastic sediments were deposited on the caldera floor, which has been uplifted due to resurgence and regional extension, creating the complex structural relationships between the volcanic units. The northern volcanic center is located at Ironside Mountain, where densely welded rheomorphic Dinner Creek Tuff unit 2 (DIT2) is exposed in outcrops over 600 m thick. The top of the DIT2 consists of glassy, moderately welded tuff. Sources for the DIT2 are tuff dikes along the south and western flanks of Ironside Mountain. The thick deposits of DIT2 at Ironside Mountain indicate that the mountain is an uplifted caldera, herein named the Ironside Mountain caldera. Uplift may have been due to resurgence, but it is most likely due to normal faulting along the Border Fault, a major regional normal fault that strikes across the northern margin of the caldera. Pre-Dinner Creek Tuff lava flows occur throughout the study area, and can be correlated with the Strawberry Volcanics and the Basalt of Malheur Gorge. A distinct lava flow, herein called the Ring Butte trachy-basalt occurs within the center of the study area, and is distinct from regional lava flows. Following the eruptions of the Dinner Creek Tuff units 1 & 2, aphyric basaltic-andesite and icelandite intrude into, and overlie the intra-caldera tuffs and caldera floor sediments at both calderas. These aphyric lavas are similar in appearance and stratigraphic position with the regionally extensive Hunter Creek basalt. Porphyritic olivine basalt overlies the aphyric Hunter Creek basalt at the Castle Rock caldera. This porphyritic lava is similar in appearance and major/trace element geochemistry to the regional Tim's Peak basalt. Title: Field Mapping Investigation and Geochemical Analysis of Volcanic Units within the Dinner Creek Tuff Eruptive Center, Malheur County, Eastern Oregon Author: Cruz, Matthew Year: 2017 The Dinner Creek Tuff is a mid-Miocene rhyolitic to dacitic ignimbrite, consisting of four cooling units with 40Ar/39Ar ages 16--15 Ma. Previous geologists have suspected that the source of the tuff is located in northwestern Malheur County, eastern Oregon. This broad area is called the Dinner Creek Tuff Eruptive Center. This thesis summarizes field work, XRF/ICP-MS geochemistry, thin section petrography, and SEM feldspar analysis from the summers of 2015 and 2016. The main purpose of this study is to identify sources for the Dinner Creek Tuff units within the Dinner Creek Tuff Eruptive Center. The secondary purpose is to map lave flows that pre-date and post-date the Dinner Creek Tuff, and correlate them with regionally extensive volcanic units. Two volcanic centers related to the Dinner Creek Tuff were identified. The southern volcanic center, centered at Castle Rock, is a caldera and source of the Dinner Creek Tuff unit 1 (DIT1). Rheomorphic, densely welded DIT1 is over 300 m thick along the east side of Castle Rock. The northwestern margin of the caldera has been uplifted along faults, showing vertically foliated tuff dikes and associated mega-breccia deposits. Up to 200 m of incipiently welded tuffs, and fluvial volcanoclastic sediments were deposited on the caldera floor, which has been uplifted due to resurgence and regional extension, creating the complex structural relationships between the volcanic units. The northern volcanic center is located at Ironside Mountain, where densely welded rheomorphic Dinner Creek Tuff unit 2 (DIT2) is exposed in outcrops over 600 m thick. The top of the DIT2 consists of glassy, moderately welded tuff. Sources for the DIT2 are tuff dikes along the south and western flanks of Ironside Mountain. The thick deposits of DIT2 at Ironside Mountain indicate that the mountain is an uplifted caldera, herein named the Ironside Mountain caldera. Uplift may have been due to resurgence, but it is most likely due to normal faulting along the Border Fault, a major regional normal fault that strikes across the northern margin of the caldera. Pre-Dinner Creek Tuff lava flows occur throughout the study area, and can be correlated with the Strawberry Volcanics and the Basalt of Malheur Gorge. A distinct lava flow, herein called the Ring Butte trachy-basalt occurs within the center of the study area, and is distinct from regional lava flows. Following the eruptions of the Dinner Creek Tuff units 1 & 2, aphyric basaltic-andesite and icelandite intrude into, and overlie the intra-caldera tuffs and caldera floor sediments at both calderas. These aphyric lavas are similar in appearance and stratigraphic position with the regionally extensive Hunter Creek basalt. Porphyritic olivine basalt overlies the aphyric Hunter Creek basalt at the Castle Rock caldera. This porphyritic lava is similar in appearance and major/trace element geochemistry to the regional Tim's Peak basalt. Close

• 7. [Article] Reservoir Evolution Following the Removal of Marmot Dam on the Sandy River, Oregon

  The October 2007 removal of Marmot Dam, a 14.3-m-tall dam on the Sandy River in northwestern Oregon storing approximately 730,000 m3 of impounded sediment, provided an opportunity to study short- and long-term ...

  Citation × Citation Citation Abstract Copy Title: Reservoir Evolution Following the Removal of Marmot Dam on the Sandy River, Oregon Author: Keith, Mackenzie Karli Year: 2012 The October 2007 removal of Marmot Dam, a 14.3-m-tall dam on the Sandy River in northwestern Oregon storing approximately 730,000 m3 of impounded sediment, provided an opportunity to study short- and long-term geomorphic effects of dam removal. Monitoring reservoir morphology during the two years following dam decommissioning yields a timeline of reservoir channel change. Comparison of a pre-dam survey in 1911 with post-removal surveys provides a basis from which to gage the Reservoir Reach evolution in the context of pre-dam conditions. Analyses of time-lapse photography, topographic surveys, and repeat LiDAR data sets provide detailed spatial and temporal documentation of a release of sediment from the reservoir following dam removal. The majority of morphologic changes to the reservoir largely took place during the first few days and weeks following removal. Channel incision and widening, along with gradient changes through the Reservoir Reach, exhibit diminishing changes with time. Channel incision rates of up to 13 m/hr and widening rates of up to 26 m/hr occurred within the first 24 hours following breaching of the coffer dam. Although channel position through the Reservoir Reach has remained relatively stable due to valley confinement, its width increased substantially. The channel reached an average width of 45 m within two weeks of breaching, but then erosion rates slowed and the channel width reached about 70 to 80 m after one and two years, respectively. Diminishing volumes of evacuated sediment were measured over time through quantitative analysis of survey datasets. About 15 percent of the initial impounded sediment was eroded from the Reservoir Reach within 60 hours of breaching; after one and two years, 50 and 58 percent was eroded, respectively. Grain-size analysis of terraces cut into reservoir fill following dam removal show that bed material coarsened over time at fixed elevations and vertically downward as the channel incised. Overall, these findings indicate valley morphology and local in-channel bedrock topography controlled the spatial distribution of sediment within the reservoir reach while variability in river discharge determined the timing of episodic sediment release. Changes within the Reservoir Reach shortly after dam removal and subsequent evolution over the two years following removal are likely attributable to 1) the timing and intensity of flow events, 2) the longitudinal and stratigraphic spatial variations in deposit grain-size distributions initially and over time, and 3) the pre-dam topography and existing valley morphology. Title: Reservoir Evolution Following the Removal of Marmot Dam on the Sandy River, Oregon Author: Keith, Mackenzie Karli Year: 2012 The October 2007 removal of Marmot Dam, a 14.3-m-tall dam on the Sandy River in northwestern Oregon storing approximately 730,000 m3 of impounded sediment, provided an opportunity to study short- and long-term geomorphic effects of dam removal. Monitoring reservoir morphology during the two years following dam decommissioning yields a timeline of reservoir channel change. Comparison of a pre-dam survey in 1911 with post-removal surveys provides a basis from which to gage the Reservoir Reach evolution in the context of pre-dam conditions. Analyses of time-lapse photography, topographic surveys, and repeat LiDAR data sets provide detailed spatial and temporal documentation of a release of sediment from the reservoir following dam removal. The majority of morphologic changes to the reservoir largely took place during the first few days and weeks following removal. Channel incision and widening, along with gradient changes through the Reservoir Reach, exhibit diminishing changes with time. Channel incision rates of up to 13 m/hr and widening rates of up to 26 m/hr occurred within the first 24 hours following breaching of the coffer dam. Although channel position through the Reservoir Reach has remained relatively stable due to valley confinement, its width increased substantially. The channel reached an average width of 45 m within two weeks of breaching, but then erosion rates slowed and the channel width reached about 70 to 80 m after one and two years, respectively. Diminishing volumes of evacuated sediment were measured over time through quantitative analysis of survey datasets. About 15 percent of the initial impounded sediment was eroded from the Reservoir Reach within 60 hours of breaching; after one and two years, 50 and 58 percent was eroded, respectively. Grain-size analysis of terraces cut into reservoir fill following dam removal show that bed material coarsened over time at fixed elevations and vertically downward as the channel incised. Overall, these findings indicate valley morphology and local in-channel bedrock topography controlled the spatial distribution of sediment within the reservoir reach while variability in river discharge determined the timing of episodic sediment release. Changes within the Reservoir Reach shortly after dam removal and subsequent evolution over the two years following removal are likely attributable to 1) the timing and intensity of flow events, 2) the longitudinal and stratigraphic spatial variations in deposit grain-size distributions initially and over time, and 3) the pre-dam topography and existing valley morphology. Close

• 8. [Article] Phylogeography of Two Species of the Genus Apochthonius Chamberlin, 1929, in the Pacific Northwest (Arachnida, Pseudoscorpiones)

  I used mitochondrial COI sequence data from forty one individuals to investigate phylogenetic relationships among populations of two morphologically similar species of the pseudoscorpion genus Apochthonius, ...

  Citation × Citation Citation Abstract Copy Title: Phylogeography of Two Species of the Genus Apochthonius Chamberlin, 1929, in the Pacific Northwest (Arachnida, Pseudoscorpiones) Author: Welch, Brandi Lynn Year: 2016 I used mitochondrial COI sequence data from forty one individuals to investigate phylogenetic relationships among populations of two morphologically similar species of the pseudoscorpion genus Apochthonius, A. minimus and A. occidentalis, in western Washington, Oregon, and northern California. My goal was to assess whether genetic structure in the two species was congruent with geography. Many plant and animal species in the Pacific Northwestern United States have shown patterns of genetic differentiation that follow both north-south and east-west trends, indicating that geologic and climatic events in the past separated populations to the extent that they became genetically differentiated. A distinct geographic pattern emerged within A. occidentalis, with at least one northern and two southern populations. A clade containing all A. minimus sequences was recovered. However, this clade falls within the larger clade of A. occidentalis, rendering A. occidentalis paraphyletic. Furthermore, the A. minimus sequences showed north-south geographic structuring within the clade. Population genetic analyses were performed based on geographic location within the Pacific Northwest. I found high genetic differentiation coupled with low gene flow between most populations, with the exception of the Portland and North Coast Range populations. These data suggest the presence of more than two species of Apochthonius in the Pacific Northwest. Title: Phylogeography of Two Species of the Genus Apochthonius Chamberlin, 1929, in the Pacific Northwest (Arachnida, Pseudoscorpiones) Author: Welch, Brandi Lynn Year: 2016 I used mitochondrial COI sequence data from forty one individuals to investigate phylogenetic relationships among populations of two morphologically similar species of the pseudoscorpion genus Apochthonius, A. minimus and A. occidentalis, in western Washington, Oregon, and northern California. My goal was to assess whether genetic structure in the two species was congruent with geography. Many plant and animal species in the Pacific Northwestern United States have shown patterns of genetic differentiation that follow both north-south and east-west trends, indicating that geologic and climatic events in the past separated populations to the extent that they became genetically differentiated. A distinct geographic pattern emerged within A. occidentalis, with at least one northern and two southern populations. A clade containing all A. minimus sequences was recovered. However, this clade falls within the larger clade of A. occidentalis, rendering A. occidentalis paraphyletic. Furthermore, the A. minimus sequences showed north-south geographic structuring within the clade. Population genetic analyses were performed based on geographic location within the Pacific Northwest. I found high genetic differentiation coupled with low gene flow between most populations, with the exception of the Portland and North Coast Range populations. These data suggest the presence of more than two species of Apochthonius in the Pacific Northwest. Close

• 9. [Article] Scenario Development and Analysis of Freshwater Ecosystem Services under Land Cover and Climate Change in the Tualatin and Yamhill River Basins, Oregon

  Humans make decisions within ecosystems to enhance their well-being, but choices can lead to unintended consequences. The ecosystem services (ES) approach supports decision-making that considers all environmental ...

  Citation × Citation Citation Abstract Copy Title: Scenario Development and Analysis of Freshwater Ecosystem Services under Land Cover and Climate Change in the Tualatin and Yamhill River Basins, Oregon Author: Hoyer, Robert Wesley Year: 2013 Humans make decisions within ecosystems to enhance their well-being, but choices can lead to unintended consequences. The ecosystem services (ES) approach supports decision-making that considers all environmental goods and services. Many challenges remain in the implementation of the ES approach like how specific ES vary through space and time. We address this research problem using the Tualatin and Yamhill river basins in northwestern Oregon as a study area. Freshwater ES are quantified and mapped with the spatially-explicit ES modeling tool, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). In chapter II, we develop a simple urban land cover change modeling approach with selected stakeholder input. The products of this analysis are used in part to answer the question of how the freshwater ES of water yield, nutrient retention, and sediment retention will change in the future, and how their distribution potentially will change? In chapter III, these ES are modeled in InVEST using the land cover scenarios and three downscaled global climate models. The base period is 1981 to 2010 and the future period is 2036 to 2065. The models are calibrated to empirical estimates, and display different sensitivities to inputs. Water yield increases with higher rainfall but decreases with the highest temperature scenario. Nutrient export and retention estimates are positively correlated. In the Tualatin basin, more urban lands generally lead to increases in nutrient exports and retention. The effect is reversed in the Yamhill basin from much larger agricultural exports. Sediment exports and retention increase with higher winter rainfall but are negatively spatially correlated due to topographic effects. Simulation of a landscape scale installation of riparian buffers leads to decreases in exports and increases in retention. The distribution of the provision of freshwater ES remains unchanged throughout the scenarios. With few parameters in each InVEST model, all display a high degree of sensitivity. Parameterization is subject to high uncertainty even with calibrated values. We discuss the assumptions and limitations of InVEST's freshwater models. The spatially explicit nature of InVEST is its main advantage. This work coupled with other analyses in the study area can facilitate the identification of tradeoffs amongst ES leading to better ecosystem management. Title: Scenario Development and Analysis of Freshwater Ecosystem Services under Land Cover and Climate Change in the Tualatin and Yamhill River Basins, Oregon Author: Hoyer, Robert Wesley Year: 2013 Humans make decisions within ecosystems to enhance their well-being, but choices can lead to unintended consequences. The ecosystem services (ES) approach supports decision-making that considers all environmental goods and services. Many challenges remain in the implementation of the ES approach like how specific ES vary through space and time. We address this research problem using the Tualatin and Yamhill river basins in northwestern Oregon as a study area. Freshwater ES are quantified and mapped with the spatially-explicit ES modeling tool, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). In chapter II, we develop a simple urban land cover change modeling approach with selected stakeholder input. The products of this analysis are used in part to answer the question of how the freshwater ES of water yield, nutrient retention, and sediment retention will change in the future, and how their distribution potentially will change? In chapter III, these ES are modeled in InVEST using the land cover scenarios and three downscaled global climate models. The base period is 1981 to 2010 and the future period is 2036 to 2065. The models are calibrated to empirical estimates, and display different sensitivities to inputs. Water yield increases with higher rainfall but decreases with the highest temperature scenario. Nutrient export and retention estimates are positively correlated. In the Tualatin basin, more urban lands generally lead to increases in nutrient exports and retention. The effect is reversed in the Yamhill basin from much larger agricultural exports. Sediment exports and retention increase with higher winter rainfall but are negatively spatially correlated due to topographic effects. Simulation of a landscape scale installation of riparian buffers leads to decreases in exports and increases in retention. The distribution of the provision of freshwater ES remains unchanged throughout the scenarios. With few parameters in each InVEST model, all display a high degree of sensitivity. Parameterization is subject to high uncertainty even with calibrated values. We discuss the assumptions and limitations of InVEST's freshwater models. The spatially explicit nature of InVEST is its main advantage. This work coupled with other analyses in the study area can facilitate the identification of tradeoffs amongst ES leading to better ecosystem management. Close

• 10. [Article] Stratigraphic relationships of the Tillamook Volcanics and the Cowlitz Formation in the upper Nehalem River-Wolf Creek area, northwestern Oregon

  The upper Nehalem River-Wolf Creek area is located on the northeastern flank of the Tillamook Highlands in the northern Oregon Coast Range. Three rock stratigraphic units underlie the thesis area, and ...

  Citation × Citation Citation Abstract Copy Title: Stratigraphic relationships of the Tillamook Volcanics and the Cowlitz Formation in the upper Nehalem River-Wolf Creek area, northwestern Oregon Author: Jackson, Michael Keith Year: 1983 The upper Nehalem River-Wolf Creek area is located on the northeastern flank of the Tillamook Highlands in the northern Oregon Coast Range. Three rock stratigraphic units underlie the thesis area, and these units range from late Eocene to Oligocene in age. Title: Stratigraphic relationships of the Tillamook Volcanics and the Cowlitz Formation in the upper Nehalem River-Wolf Creek area, northwestern Oregon Author: Jackson, Michael Keith Year: 1983 The upper Nehalem River-Wolf Creek area is located on the northeastern flank of the Tillamook Highlands in the northern Oregon Coast Range. Three rock stratigraphic units underlie the thesis area, and these units range from late Eocene to Oligocene in age. Close