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• 51. [Article] Clay mineral origin and distribution on Astoria Fan

  Clay minerals from sediment samples obtained on Astoria Fan were analyzed by X-ray diffraction. Clay minerals are defined for the purpose of this study as crystalline phyllosilicates less than two microns ...

  Citation × Citation Citation Abstract Copy Title: Clay mineral origin and distribution on Astoria Fan Author: Russell, Kenneth Lloyd Clay minerals from sediment samples obtained on Astoria Fan were analyzed by X-ray diffraction. Clay minerals are defined for the purpose of this study as crystalline phyllosilicates less than two microns in equivalent settling diameter. The clay minerals are subdivided into the five common families: montmorillonite, chlorite, vermiculite, illite, and kaolinite. One X-ray scan of a magnesium ion saturated, ethylene glycol treated sample was sufficient for the identification of all the clay minerals. A typical Recent hemipelagic sediment contains about 40 percent montmorillonite, 30 percent illite, and 30 percent chlorite. Neither kaolinite nor vermiculite is detectable in these samples. These concentrations are similar to those reported for Columbia River sediments. The surface sediments have an identical clay mineral assemblage from the head of Astoria Canyon to the outer edge of the fan approximately 250 kilometers offshore. All of the Recent sediments in piston cores from Astoria Fan are the same as the surface sediments on the fan. This similarity indicates an unchanging source during Recent time and a lack of any visible marine diagenesis after burial. X-ray traces of Pleistocene clay minerals are distinctly different from those of the Recent. One can use this change in clay mineralogy as a time marker across the fan. Presumably the Pleistocene clays were formed under different weathering conditions caused by different climatic conditions. Title: Clay mineral origin and distribution on Astoria Fan Author: Russell, Kenneth Lloyd Clay minerals from sediment samples obtained on Astoria Fan were analyzed by X-ray diffraction. Clay minerals are defined for the purpose of this study as crystalline phyllosilicates less than two microns in equivalent settling diameter. The clay minerals are subdivided into the five common families: montmorillonite, chlorite, vermiculite, illite, and kaolinite. One X-ray scan of a magnesium ion saturated, ethylene glycol treated sample was sufficient for the identification of all the clay minerals. A typical Recent hemipelagic sediment contains about 40 percent montmorillonite, 30 percent illite, and 30 percent chlorite. Neither kaolinite nor vermiculite is detectable in these samples. These concentrations are similar to those reported for Columbia River sediments. The surface sediments have an identical clay mineral assemblage from the head of Astoria Canyon to the outer edge of the fan approximately 250 kilometers offshore. All of the Recent sediments in piston cores from Astoria Fan are the same as the surface sediments on the fan. This similarity indicates an unchanging source during Recent time and a lack of any visible marine diagenesis after burial. X-ray traces of Pleistocene clay minerals are distinctly different from those of the Recent. One can use this change in clay mineralogy as a time marker across the fan. Presumably the Pleistocene clays were formed under different weathering conditions caused by different climatic conditions. Close

• 52. [Article] Structure and tectonics of the southern Willamette Valley, Oregon

  Surface geology, seismic data, petroleum exploratory well data, and water well data have been used to analyze the structural and tectonic history of the southern Willamette Valley. Tertiary strata beneath ...

  Citation × Citation Citation Abstract Copy Title: Structure and tectonics of the southern Willamette Valley, Oregon Author: Graven, Erik P. Surface geology, seismic data, petroleum exploratory well data, and water well data have been used to analyze the structural and tectonic history of the southern Willamette Valley. Tertiary strata beneath the southern Willamette Valley appear to have had an early Cascade or Clarno volcanic source to the east by the middle Eocene. The Tertiary strata have been deformed into a series of broad north-northeast trending folds and northeast and northwest trending faults which initially developed under east-northeast compression during the middle Eocene and have since been rotated clockwise to their present positions. The cross-cutting pattern of subsurface faults has been complicated by reactivation during the clockwise rotation of Si to its present orientation of north-south. Uplift of the Coast Range prior to emplacement of the Miocene Columbia River Basalt Group (CRBG) produced the gentle east dip of strata beneath the western edge of the Valley and beneath the CRBG in the Salem and Eola Hills. The southern Willamette Valley is controlled by erosion of the relatively incompetent Eugene Formation following emplacement of the CRBG. Neogene sediments deposited after this degradational event suggest that during the late Miocene to Pliocene, the proto-Willamette River flowed east of the Salem Hills before uplift along the Waldo Hills forced its course to the west. This aggradation appears to have been caused by increased uplift of the Coast Range and/or subsidence of the Willamette Valley over the slab bend in the subducting Juan de Fuca plate. Degradational and aggradational periods during the Pleistocene appear to have been caused by readjustment of the Willamette River system to new base levels and changes in sediment supply to the valley. Neotectonic features in the valley include: 1) the Owl Creek fault which is at least Pleistocene in age and possibly younger, 2) the Harrisburg anticline, 3) the Turner fault, and 4) deformation in the North Santiam River basin including the Mill Creek fault. With the exception of the Owl Creek fault, the minimum age of these structures is poorly constrained but is at least post-Miocene and possibly younger. Title: Structure and tectonics of the southern Willamette Valley, Oregon Author: Graven, Erik P. Surface geology, seismic data, petroleum exploratory well data, and water well data have been used to analyze the structural and tectonic history of the southern Willamette Valley. Tertiary strata beneath the southern Willamette Valley appear to have had an early Cascade or Clarno volcanic source to the east by the middle Eocene. The Tertiary strata have been deformed into a series of broad north-northeast trending folds and northeast and northwest trending faults which initially developed under east-northeast compression during the middle Eocene and have since been rotated clockwise to their present positions. The cross-cutting pattern of subsurface faults has been complicated by reactivation during the clockwise rotation of Si to its present orientation of north-south. Uplift of the Coast Range prior to emplacement of the Miocene Columbia River Basalt Group (CRBG) produced the gentle east dip of strata beneath the western edge of the Valley and beneath the CRBG in the Salem and Eola Hills. The southern Willamette Valley is controlled by erosion of the relatively incompetent Eugene Formation following emplacement of the CRBG. Neogene sediments deposited after this degradational event suggest that during the late Miocene to Pliocene, the proto-Willamette River flowed east of the Salem Hills before uplift along the Waldo Hills forced its course to the west. This aggradation appears to have been caused by increased uplift of the Coast Range and/or subsidence of the Willamette Valley over the slab bend in the subducting Juan de Fuca plate. Degradational and aggradational periods during the Pleistocene appear to have been caused by readjustment of the Willamette River system to new base levels and changes in sediment supply to the valley. Neotectonic features in the valley include: 1) the Owl Creek fault which is at least Pleistocene in age and possibly younger, 2) the Harrisburg anticline, 3) the Turner fault, and 4) deformation in the North Santiam River basin including the Mill Creek fault. With the exception of the Owl Creek fault, the minimum age of these structures is poorly constrained but is at least post-Miocene and possibly younger. Close

• 53. [Article] Seismic sequence stratigraphy and tectonic evolution of southern hydrate ridge

  A 3D seismic volume was acquired summer 2000 over the southern end of Hydrate Ridge (FIR), an anomalously shallow ridge 100 km offshore Newport, Oregon. The survey followed a succession of scientific expeditions ...

  Citation × Citation Citation Abstract Copy Title: Seismic sequence stratigraphy and tectonic evolution of southern hydrate ridge Author: Chevallier, Johanna A 3D seismic volume was acquired summer 2000 over the southern end of Hydrate Ridge (FIR), an anomalously shallow ridge 100 km offshore Newport, Oregon. The survey followed a succession of scientific expeditions aimed at studying the gas hydrates present in the shallow subsurface that gave the name to the ridge. This thesis consists of a seismic sequence analysis of the high-resolution (125 Hz) 3D survey. Identification of seismic units and interpretation of depositional sequences observed on the seismic sections is presented. The sequence analysis is compared with the results from nine sites cored during ODP Leg 204 during summer 2002. The first objective is to document in detail the stratigraphy of the ridge so that we can compare it with the gas hydrate distribution. The second is to reconstruct the structural evolution through time of this complex anticline as inferred from the depositional history. The result is a time series of structural evolutionary cross-sections as well as a series of paleo-bathymetric maps revealing the development of and interplay between the structures now buried in the subsurface of southern HR. The structural evolutionary diagrams show the existence of three anticlines, interpreted as thrust-related folds. They formed at the deformation front and controlled the distribution and deformation of the sediments during the Pleistocene. The current southern HR started its uplift less than 0.5 Ma. A seismic relict in the form of a double BSR is a witness to the evolution of the gas hydrate system of HR. It confirms the recent uplift of the ridge and consequent shallowing of the base of the gas hydrate stability zone (GHSZ). Further detailed studies of the stratigraphy reveal stratigraphic controls on the fluid flow, which in turn control the distribution of gas hydrates. Analysis of the amplitude map of the bottom-simulating reflector (BSR), which is a proxy for the free gas distribution, shows a relationship between anticlinal features within the older strata (older than 1.6 Ma) and strong amplitude anomalies of the BSR, which confirm previous observations suggesting a very low permeability for the young slope-basin sediments and an accumulation of gas within the older sediments underneath. Title: Seismic sequence stratigraphy and tectonic evolution of southern hydrate ridge Author: Chevallier, Johanna A 3D seismic volume was acquired summer 2000 over the southern end of Hydrate Ridge (FIR), an anomalously shallow ridge 100 km offshore Newport, Oregon. The survey followed a succession of scientific expeditions aimed at studying the gas hydrates present in the shallow subsurface that gave the name to the ridge. This thesis consists of a seismic sequence analysis of the high-resolution (125 Hz) 3D survey. Identification of seismic units and interpretation of depositional sequences observed on the seismic sections is presented. The sequence analysis is compared with the results from nine sites cored during ODP Leg 204 during summer 2002. The first objective is to document in detail the stratigraphy of the ridge so that we can compare it with the gas hydrate distribution. The second is to reconstruct the structural evolution through time of this complex anticline as inferred from the depositional history. The result is a time series of structural evolutionary cross-sections as well as a series of paleo-bathymetric maps revealing the development of and interplay between the structures now buried in the subsurface of southern HR. The structural evolutionary diagrams show the existence of three anticlines, interpreted as thrust-related folds. They formed at the deformation front and controlled the distribution and deformation of the sediments during the Pleistocene. The current southern HR started its uplift less than 0.5 Ma. A seismic relict in the form of a double BSR is a witness to the evolution of the gas hydrate system of HR. It confirms the recent uplift of the ridge and consequent shallowing of the base of the gas hydrate stability zone (GHSZ). Further detailed studies of the stratigraphy reveal stratigraphic controls on the fluid flow, which in turn control the distribution of gas hydrates. Analysis of the amplitude map of the bottom-simulating reflector (BSR), which is a proxy for the free gas distribution, shows a relationship between anticlinal features within the older strata (older than 1.6 Ma) and strong amplitude anomalies of the BSR, which confirm previous observations suggesting a very low permeability for the young slope-basin sediments and an accumulation of gas within the older sediments underneath. Close

• 54. [Article] Geology of the Whetstone anticline area, Teton County Wyoming

  Over 10,000 feet of marine and nonmarine Late Cretaceous sedimentary rocks are exposed within a 110 square mile area in northeastern Teton County, Wyoming. An additional 1400 feet of nonmarine Paleocene ...

  Citation × Citation Citation Abstract Copy Title: Geology of the Whetstone anticline area, Teton County Wyoming Author: Hill, David Ray Over 10,000 feet of marine and nonmarine Late Cretaceous sedimentary rocks are exposed within a 110 square mile area in northeastern Teton County, Wyoming. An additional 1400 feet of nonmarine Paleocene and Miocene rocks overlie these. Landslide deposits and Pleistocene glacial moraine cover over one-half of the area. The Late Cretaceous Cody Shale and Bacon Ridge Sandstone, which are the oldest rocks exposed, represent the last marine invasion of the region. The overlying Late Cretaceous nonmarine rocks consist of the Coaly Sequence, Lenticular Sandstone and Shale Sequence, Mesaverde Formation, and Harebell Formation. These formations are composed largely of poorly sorted quartz arenites with intercalated mudstones, claystones, shales, and coals. A few quartzite conglomerate lenses are present near the top of the sequence. These rocks, which contain numerous quartz, chert, and metaquartzite grains, were derived from Precambrian metamorphic and Paleozoic sedimentary rocks exposed to the west and northwest. The sediments were carried into the area by streams and were deposited on a broad coastal plain similar to the modern Texas Gulf Coast. Many of the fine-grained sediments were deposited in swamps and small freshwater lakes. Near the end of Cretaceous time, a large area of Precambrian Beltian quartzite was exposed in central Montana. Powerful streams carried large volumes of coarse sediments into the area mapped forming the Paleocene Pinyon Conglomerate. Basalt and andesite were extruded locally during the Miocene. Morainal deposits from two Pleistocene glacial stages are recognized. Two periods of Laramide deformation are represented by broad asymmetric folds. The Spread Creek anticline, a large doubly plunging fold, was formed near the end of Cretaceous time. Three adjacent folds to the northeast are post-Paleocene in age. Several high-angle faults are present. Structural and stratigraphic conditions appear to be favorable for the formation and accumulation of oil and gas. However, five dry oil and gas test holes have been drilled. The possibilities of finding commercial production are not encouraging. The area has also been prospected for coal and alluvial gold. Title: Geology of the Whetstone anticline area, Teton County Wyoming Author: Hill, David Ray Over 10,000 feet of marine and nonmarine Late Cretaceous sedimentary rocks are exposed within a 110 square mile area in northeastern Teton County, Wyoming. An additional 1400 feet of nonmarine Paleocene and Miocene rocks overlie these. Landslide deposits and Pleistocene glacial moraine cover over one-half of the area. The Late Cretaceous Cody Shale and Bacon Ridge Sandstone, which are the oldest rocks exposed, represent the last marine invasion of the region. The overlying Late Cretaceous nonmarine rocks consist of the Coaly Sequence, Lenticular Sandstone and Shale Sequence, Mesaverde Formation, and Harebell Formation. These formations are composed largely of poorly sorted quartz arenites with intercalated mudstones, claystones, shales, and coals. A few quartzite conglomerate lenses are present near the top of the sequence. These rocks, which contain numerous quartz, chert, and metaquartzite grains, were derived from Precambrian metamorphic and Paleozoic sedimentary rocks exposed to the west and northwest. The sediments were carried into the area by streams and were deposited on a broad coastal plain similar to the modern Texas Gulf Coast. Many of the fine-grained sediments were deposited in swamps and small freshwater lakes. Near the end of Cretaceous time, a large area of Precambrian Beltian quartzite was exposed in central Montana. Powerful streams carried large volumes of coarse sediments into the area mapped forming the Paleocene Pinyon Conglomerate. Basalt and andesite were extruded locally during the Miocene. Morainal deposits from two Pleistocene glacial stages are recognized. Two periods of Laramide deformation are represented by broad asymmetric folds. The Spread Creek anticline, a large doubly plunging fold, was formed near the end of Cretaceous time. Three adjacent folds to the northeast are post-Paleocene in age. Several high-angle faults are present. Structural and stratigraphic conditions appear to be favorable for the formation and accumulation of oil and gas. However, five dry oil and gas test holes have been drilled. The possibilities of finding commercial production are not encouraging. The area has also been prospected for coal and alluvial gold. Close

• 55. [Article] Geologic structure of the Upper Ojai Valley and Chaffee Canyon areas, Ventura County, California

  The Upper Ojai Valley is a tectonic depression between opposing reverse faults, Its northern border is formed by the active, north-dipping San Cayetano fault with 6.0 km of dip-slip displacement in the ...

  Citation × Citation Citation Abstract Copy Title: Geologic structure of the Upper Ojai Valley and Chaffee Canyon areas, Ventura County, California Author: Huftile, Gary J. The Upper Ojai Valley is a tectonic depression between opposing reverse faults, Its northern border is formed by the active, north-dipping San Cayetano fault with 6.0 km of dip-slip displacement in the Silverthread oil field and 2.6 km displacement west of Sisar Creek; the fault dies out farther west in Ojai Valley. The southern border is formed by the late Quaternary Sisar-Big Canyon-Lion fault set which dips south and merges into the Sisar decollement within the south-dipping, ductile Rincon Formation. Folds with north-dipping axial planes, including the Lion Mountain anticline and Reeves syncline, are middle Pleistocene or older and are related to movement on a frontal strand of the San Cayetano fault. In late Quaternary time, the Sulphur Mountain anticlinorium and the Big Canyon syncline began forming as fault-propagation folds, followed closely by the ramping of the south-dipping faults to the surface over the Saugus Formation. To the east, the San Cayetano fault locally overrides and folds the south-dipping faults. Cross-section balancing shows that the Miocene and younger rocks above the Sisar decollement are shortened 6.7km more than the more, competent rocks below. A solution to this bed-length problem is that the decollement becomes a ramp and merges at depth with the steeply south-dipping Oak Ridge fault. This implies that the Sisar, Big Canyon, and Lion faults are frontal thrusts to the Oak Ridge fault. The total horizontal shortening since Pliocene time is 14.5km. Recently-drilled wells in the Chaffee Canyon oil field, Ventura County, California, reveal that the Wiley Canyon producing anticline formed in the Pleistocene prior to much of the displacement on the Oak Ridge fault. The east and west plunge in part predates deposition of the Vaqueros Formation of early Miocene age. The dip on the south strand of the Oak Ridge fault increases eastward across the field from 70-75° to 83-85°; farther east, the fault plane is overturned and dips north. The Torrey fault can be traced northwest under a landslide east of Wiley Canyon anticline but not farther northwest. Title: Geologic structure of the Upper Ojai Valley and Chaffee Canyon areas, Ventura County, California Author: Huftile, Gary J. The Upper Ojai Valley is a tectonic depression between opposing reverse faults, Its northern border is formed by the active, north-dipping San Cayetano fault with 6.0 km of dip-slip displacement in the Silverthread oil field and 2.6 km displacement west of Sisar Creek; the fault dies out farther west in Ojai Valley. The southern border is formed by the late Quaternary Sisar-Big Canyon-Lion fault set which dips south and merges into the Sisar decollement within the south-dipping, ductile Rincon Formation. Folds with north-dipping axial planes, including the Lion Mountain anticline and Reeves syncline, are middle Pleistocene or older and are related to movement on a frontal strand of the San Cayetano fault. In late Quaternary time, the Sulphur Mountain anticlinorium and the Big Canyon syncline began forming as fault-propagation folds, followed closely by the ramping of the south-dipping faults to the surface over the Saugus Formation. To the east, the San Cayetano fault locally overrides and folds the south-dipping faults. Cross-section balancing shows that the Miocene and younger rocks above the Sisar decollement are shortened 6.7km more than the more, competent rocks below. A solution to this bed-length problem is that the decollement becomes a ramp and merges at depth with the steeply south-dipping Oak Ridge fault. This implies that the Sisar, Big Canyon, and Lion faults are frontal thrusts to the Oak Ridge fault. The total horizontal shortening since Pliocene time is 14.5km. Recently-drilled wells in the Chaffee Canyon oil field, Ventura County, California, reveal that the Wiley Canyon producing anticline formed in the Pleistocene prior to much of the displacement on the Oak Ridge fault. The east and west plunge in part predates deposition of the Vaqueros Formation of early Miocene age. The dip on the south strand of the Oak Ridge fault increases eastward across the field from 70-75° to 83-85°; farther east, the fault plane is overturned and dips north. The Torrey fault can be traced northwest under a landslide east of Wiley Canyon anticline but not farther northwest. Close

• 56. [Article] Geology of part of the southeastern Wallowa Mountains, northeastern Oregon

  Within 40 square miles of the southeastern Wallowa Mountains, Oregon, eugeosynclinal Permian and Triassic formations comprising a section about 25,000 feet thick have been exposed by uplift and erosion ...

  Citation × Citation Citation Abstract Copy Title: Geology of part of the southeastern Wallowa Mountains, northeastern Oregon Author: Wetherell, Clyde Elbert Within 40 square miles of the southeastern Wallowa Mountains, Oregon, eugeosynclinal Permian and Triassic formations comprising a section about 25,000 feet thick have been exposed by uplift and erosion of overlying Miocene Columbia River basalt. Deposition appears to have been continuous from Permian into Upper Triassic, but an apparent angular nonconformity exists between Triassic formations. Neritic clastics of the Permian Trinity Creek formation are overlain by mixed volcanics and elastics of the Triassic Imnaha formation, which is terrestrial and littoral in its lower Russel member and neritic in Its upper Norway member. Sandstone and conglomerate of the Upper Triassic Lower Sedimentary Series apparently rest unconformably on deformed pillow lavas and breccias of the Norway member. A varied suite of small stocks Intrudes the area. Gabbroic units of the Fish Lake complex are most widespread; other stocks are composed of metadiorite, keratophyre, bostonite, and trondjemlte. Varied dikes are extremely abundant In older formations. Marble and skarn of uncertain age, but believed unrelated to the Imnaha or Trinity Creek formations, are intimately associated with gabbroic stocks. Deformation increases from east to west, and culminates with an overturned anticline in the Upper Triassic Lower sedimentary Series at the western margin of the area. Faulting is minor except for the Pine Creek reverse fault which has a minimum vertical displacement of 2500 feet. Alpine topography resulted from Pleistocene stream erosion and glaciation; post-Pleistocene erosion has not been extensive. Title: Geology of part of the southeastern Wallowa Mountains, northeastern Oregon Author: Wetherell, Clyde Elbert Within 40 square miles of the southeastern Wallowa Mountains, Oregon, eugeosynclinal Permian and Triassic formations comprising a section about 25,000 feet thick have been exposed by uplift and erosion of overlying Miocene Columbia River basalt. Deposition appears to have been continuous from Permian into Upper Triassic, but an apparent angular nonconformity exists between Triassic formations. Neritic clastics of the Permian Trinity Creek formation are overlain by mixed volcanics and elastics of the Triassic Imnaha formation, which is terrestrial and littoral in its lower Russel member and neritic in Its upper Norway member. Sandstone and conglomerate of the Upper Triassic Lower Sedimentary Series apparently rest unconformably on deformed pillow lavas and breccias of the Norway member. A varied suite of small stocks Intrudes the area. Gabbroic units of the Fish Lake complex are most widespread; other stocks are composed of metadiorite, keratophyre, bostonite, and trondjemlte. Varied dikes are extremely abundant In older formations. Marble and skarn of uncertain age, but believed unrelated to the Imnaha or Trinity Creek formations, are intimately associated with gabbroic stocks. Deformation increases from east to west, and culminates with an overturned anticline in the Upper Triassic Lower sedimentary Series at the western margin of the area. Faulting is minor except for the Pine Creek reverse fault which has a minimum vertical displacement of 2500 feet. Alpine topography resulted from Pleistocene stream erosion and glaciation; post-Pleistocene erosion has not been extensive. Close

• 57. [Article] Predictive locational modeling of late Pleistocene archaeological sites on the southern Oregon Coast using a Geographic Information System (GIS)

  The search for archaeological materials dating to 15,000 yr BP along the southern Oregon coast is a formidable task. Using ethnographic, theoretical, and archaeological data, landscape resources which ...

  Citation × Citation Citation Abstract Copy Title: Predictive locational modeling of late Pleistocene archaeological sites on the southern Oregon Coast using a Geographic Information System (GIS) Author: Punke, Michele Leigh The search for archaeological materials dating to 15,000 yr BP along the southern Oregon coast is a formidable task. Using ethnographic, theoretical, and archaeological data, landscape resources which would have influenced land-use and occupation location decisions in the past are highlighted. Additionally, environmental data pertaining to the late Pleistocene is examined to determine what landscape features may have been used by human groups 15,000 years ago and to determine how these landscape features may have changed since that time. These landscape resource features are included in the modeling project as independent variables. The dependent variable in this modeling project is relative probability that an area will contain archaeological materials dating to the time period of interest. Two predictive locational models are created to facilitate the search process. These models mathematically combine the independent variables using two separate approaches. The hierarchical decision rule model approach assumes that decision makers in the past would have viewed landscape features sequentially rather than simultaneously. The additive, or weighted-value, approach assumes that a number of conditional preference aspects were evaluated simultaneously and that different environmental variables had varying amounts of influence on the locational choices of prehistoric peoples. Integration of the data and mathematical model structures into a Geographic Information System (GIS) allows for spatial analysis of the landscape and the prediction of locations most likely to contain evidence of human activity dating to 15,000 years ago. The process involved with variable integration into the GIS is delineated and results of the modeling procedures are presented in spatial, map-based formats. Title: Predictive locational modeling of late Pleistocene archaeological sites on the southern Oregon Coast using a Geographic Information System (GIS) Author: Punke, Michele Leigh The search for archaeological materials dating to 15,000 yr BP along the southern Oregon coast is a formidable task. Using ethnographic, theoretical, and archaeological data, landscape resources which would have influenced land-use and occupation location decisions in the past are highlighted. Additionally, environmental data pertaining to the late Pleistocene is examined to determine what landscape features may have been used by human groups 15,000 years ago and to determine how these landscape features may have changed since that time. These landscape resource features are included in the modeling project as independent variables. The dependent variable in this modeling project is relative probability that an area will contain archaeological materials dating to the time period of interest. Two predictive locational models are created to facilitate the search process. These models mathematically combine the independent variables using two separate approaches. The hierarchical decision rule model approach assumes that decision makers in the past would have viewed landscape features sequentially rather than simultaneously. The additive, or weighted-value, approach assumes that a number of conditional preference aspects were evaluated simultaneously and that different environmental variables had varying amounts of influence on the locational choices of prehistoric peoples. Integration of the data and mathematical model structures into a Geographic Information System (GIS) allows for spatial analysis of the landscape and the prediction of locations most likely to contain evidence of human activity dating to 15,000 years ago. The process involved with variable integration into the GIS is delineated and results of the modeling procedures are presented in spatial, map-based formats. Close

• 58. [Article] Holocene and latest Pleistocene paleoceanography of the northeast Pacific and its relationship to climate change in the Pacific Northwest

  Northeast Pacific Ocean sediments were analyzed to determine the past relationship between northeast Pacific sea surface conditions and the climate on the adjacent continent, the Pacific Northwest of North ...

  Citation × Citation Citation Abstract Copy Title: Holocene and latest Pleistocene paleoceanography of the northeast Pacific and its relationship to climate change in the Pacific Northwest Author: Sabin, Ann Louise Northeast Pacific Ocean sediments were analyzed to determine the past relationship between northeast Pacific sea surface conditions and the climate on the adjacent continent, the Pacific Northwest of North America. Studies of modern ocean-atmosphere interactions demonstrate the significant effect sea surface conditions and atmospheric circulation in the Northeast Pacific Ocean has on the climate of the west coast of North America. Thus, it is likely that past continental climate change can be correlated to changes in sea surface temperature in the northeast Pacific Ocean. We analyzed radiolaria from twelve sediment cores, ranging from 33.62°N to 54.42°N latitude along the west coast of North America to reconstruct past sea surface conditions. Relationships between modern radiolaria and mean annual sea surface temperature calibrate equations used to estimate sea surface conditions for the past 20,000 years. Chronology is controlled by radiocarbon ages from planktonic foraminifera and bulk organic carbon. The reconstructions of sea surface conditions from changes in radiolaria assemblages indicate that the upwelling center off the west coast of North America was further south 15,000 years ago than it is today, and reached its present location 13,000 years ago. We infer that the West Wind Drift and Transition Zone were further south in the latest Pleistocene as a result of a more southerly North Pacific High pressure cell prior to 13,000 years ago. Two Pacific Northwest continental records of paleotemperature are well correlated to the sea surface temperature record the northeast Pacific around 48N latitude, with temperatures increasing over the past 20,000 years. Significant temperature minima and glacial expansions occurred at 13,000 and 4,000 years ago in the records examined, as did a minor minimum at 16,000 years ago. We conclude that changes in the past latitudinal position of the West Wind Drift played a significant role in controlling continental climate immediately to its east, as it does in the present day environment. Title: Holocene and latest Pleistocene paleoceanography of the northeast Pacific and its relationship to climate change in the Pacific Northwest Author: Sabin, Ann Louise Northeast Pacific Ocean sediments were analyzed to determine the past relationship between northeast Pacific sea surface conditions and the climate on the adjacent continent, the Pacific Northwest of North America. Studies of modern ocean-atmosphere interactions demonstrate the significant effect sea surface conditions and atmospheric circulation in the Northeast Pacific Ocean has on the climate of the west coast of North America. Thus, it is likely that past continental climate change can be correlated to changes in sea surface temperature in the northeast Pacific Ocean. We analyzed radiolaria from twelve sediment cores, ranging from 33.62°N to 54.42°N latitude along the west coast of North America to reconstruct past sea surface conditions. Relationships between modern radiolaria and mean annual sea surface temperature calibrate equations used to estimate sea surface conditions for the past 20,000 years. Chronology is controlled by radiocarbon ages from planktonic foraminifera and bulk organic carbon. The reconstructions of sea surface conditions from changes in radiolaria assemblages indicate that the upwelling center off the west coast of North America was further south 15,000 years ago than it is today, and reached its present location 13,000 years ago. We infer that the West Wind Drift and Transition Zone were further south in the latest Pleistocene as a result of a more southerly North Pacific High pressure cell prior to 13,000 years ago. Two Pacific Northwest continental records of paleotemperature are well correlated to the sea surface temperature record the northeast Pacific around 48N latitude, with temperatures increasing over the past 20,000 years. Significant temperature minima and glacial expansions occurred at 13,000 and 4,000 years ago in the records examined, as did a minor minimum at 16,000 years ago. We conclude that changes in the past latitudinal position of the West Wind Drift played a significant role in controlling continental climate immediately to its east, as it does in the present day environment. Close

• 59. [Article] δ¹³C record of Upper North Atlantic Deep Water during the past 2.6 million years

  Copyright 1995 by the American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: δ¹³C record of Upper North Atlantic Deep Water during the past 2.6 million years Author: Wright, J. D., Oppo, D. W., Prell, W. L., Raymo, M. E., Mix, Alan C., Lohmann, G. P. Copyright 1995 by the American Geophysical Union Title: δ¹³C record of Upper North Atlantic Deep Water during the past 2.6 million years Author: Wright, J. D., Oppo, D. W., Prell, W. L., Raymo, M. E., Mix, Alan C., Lohmann, G. P. Copyright 1995 by the American Geophysical Union Close

• 60. [Article] Stratigraphy and structure of the Greenstone Mountain area, Beaverhead County, Montana

  The Greenstone Mountain area, which includes the Utopia mining district, is located in the foothills of the Pioneer Range, Beaverhead County, Montana. Approximately 12, 600 feet of Paleozoic and Mesozoic ...

  Citation × Citation Citation Abstract Copy Title: Stratigraphy and structure of the Greenstone Mountain area, Beaverhead County, Montana Author: Sharp, George Carter, Jr The Greenstone Mountain area, which includes the Utopia mining district, is located in the foothills of the Pioneer Range, Beaverhead County, Montana. Approximately 12, 600 feet of Paleozoic and Mesozoic sedimentary rocks and an undetermined thickness of Precambrian sediments and Late Cretaceous igneous rocks are exposed within the area of investigation. Most of the sedimentary rocks were deposited along the margin of the Cordilleran miogeosyncline. Precambrian Beltian sediments are the oldest exposed rocks in the map area. Pre-Mississippian Paleozoic rocks have not been differentiated in this study but probably represent the Cambrian and Devonian Systems. Other Paleozoic rock units include the Lodgepole and Mission Canyon Formations of Mississippian age, the Amsden Formation of Mississippian to Pennsylvanian age, the Quadrant Formation of Pennsylvanian age, and the Phosphoria Formation of Permian age. Mesozoic sediments include the Dinwoody and Woodside Formations of Triassic age and the Kootenai Formation and Colorado Group of Cretaceous age. The Jurassic System is not represented. During the Late Cretaceous Laramide orogeny the sedimentary rocks of the area were folded and faulted. The dominant structures produced during this period of deformation are northeast- to north-trending anticlines and synclines that are locally overturned to the east. Steep faults of small to moderate displacement disrupt the folds. Quartz monzonite intrusive rocks were emplaced following the Laramide orogeny and are probably genetically related to the Boulder Batholith. The intrusion gave rise to mineralization and thermal metamorphism of the surrounding country rocks. Quaternary glacial and fluvial deposits mantle parts of the area. At least three valley glaciers advanced into the northwestern corner of the area in Late Pleistocene time and left lateral and terminal moraines. Pleistocene terrace gravels are situated along Birch Creek and on lowlands in the west, and Recent alluvium is being deposited along existing streams. Title: Stratigraphy and structure of the Greenstone Mountain area, Beaverhead County, Montana Author: Sharp, George Carter, Jr The Greenstone Mountain area, which includes the Utopia mining district, is located in the foothills of the Pioneer Range, Beaverhead County, Montana. Approximately 12, 600 feet of Paleozoic and Mesozoic sedimentary rocks and an undetermined thickness of Precambrian sediments and Late Cretaceous igneous rocks are exposed within the area of investigation. Most of the sedimentary rocks were deposited along the margin of the Cordilleran miogeosyncline. Precambrian Beltian sediments are the oldest exposed rocks in the map area. Pre-Mississippian Paleozoic rocks have not been differentiated in this study but probably represent the Cambrian and Devonian Systems. Other Paleozoic rock units include the Lodgepole and Mission Canyon Formations of Mississippian age, the Amsden Formation of Mississippian to Pennsylvanian age, the Quadrant Formation of Pennsylvanian age, and the Phosphoria Formation of Permian age. Mesozoic sediments include the Dinwoody and Woodside Formations of Triassic age and the Kootenai Formation and Colorado Group of Cretaceous age. The Jurassic System is not represented. During the Late Cretaceous Laramide orogeny the sedimentary rocks of the area were folded and faulted. The dominant structures produced during this period of deformation are northeast- to north-trending anticlines and synclines that are locally overturned to the east. Steep faults of small to moderate displacement disrupt the folds. Quartz monzonite intrusive rocks were emplaced following the Laramide orogeny and are probably genetically related to the Boulder Batholith. The intrusion gave rise to mineralization and thermal metamorphism of the surrounding country rocks. Quaternary glacial and fluvial deposits mantle parts of the area. At least three valley glaciers advanced into the northwestern corner of the area in Late Pleistocene time and left lateral and terminal moraines. Pleistocene terrace gravels are situated along Birch Creek and on lowlands in the west, and Recent alluvium is being deposited along existing streams. Close