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• 1. [Article] Alpine glacier and pluvial lake records of late pleistocene climate variability in the western United States

  Citation × Citation Citation Abstract Copy Title: Alpine glacier and pluvial lake records of late pleistocene climate variability in the western United States Author: Licciardi, Joseph M. Title: Alpine glacier and pluvial lake records of late pleistocene climate variability in the western United States Author: Licciardi, Joseph M. Close

• 2. [Article] Reconstruction of late Pleistocene paleoclimatic characteristics in the Great Basin and adjacent areas

  A sequence of glaciation based on relative dating parameters was established in each of nine mountain ranges located along a northwest to southeast transect through the northern Great Basin. Each sequence ...

  Citation × Citation Citation Abstract Copy Title: Reconstruction of late Pleistocene paleoclimatic characteristics in the Great Basin and adjacent areas Author: Bevis, Kenneth A. A sequence of glaciation based on relative dating parameters was established in each of nine mountain ranges located along a northwest to southeast transect through the northern Great Basin. Each sequence consists of two or three drift units. Degree of weathering suggests that the younger drift unit in a two-fold sequence and the intermediate drift unit in a three-fold sequence represents deposition during the late Pleistocene. The late Pleistocene equilibrium-line altitude (ELA) in each range was determined by reconstructing the maximum ice extent associated with these drift units and using the accumulation area ratio technique. Paleo-ELAs increase from about 2100 m in northeastern Oregon to approximately 3200 m in central Utah. Paleoclimatic conditions along the study transect were estimated by comparing modern climatic conditions at the reconstructed late Pleistocene ELAs with climatic conditions occurring at the ELAs of modem mid-latitude glaciers. Assuming no change in winter accumulation or in the seasonal distribution of precipitation from the present, a mean summer temperature depression ranging from about 9.0 °C at the northern end of the transect to about 4.0 °C at the southern end would have been necessary to sustain glaciers in these ranges during the late Pleistocene. To simulate possible changes in late Pleistocene precipitation patterns, a change in winter accumulation between 0.5 and 2.0 times the modem value resulted in a respective increase or decrease in temperature depression by approximately 2.0 °C. These results suggest that increases in precipitation during the late Pleistocene alone could not have sustained glaciers in the mountain ranges of the study transect, except possibly at its southern end, in the central Great Basin. An increase in precipitation in this area during the late Pleistocene agrees with the interpretation of other paleoclimatic records and paleoclimatic model simulations for the Great Basin. Title: Reconstruction of late Pleistocene paleoclimatic characteristics in the Great Basin and adjacent areas Author: Bevis, Kenneth A. A sequence of glaciation based on relative dating parameters was established in each of nine mountain ranges located along a northwest to southeast transect through the northern Great Basin. Each sequence consists of two or three drift units. Degree of weathering suggests that the younger drift unit in a two-fold sequence and the intermediate drift unit in a three-fold sequence represents deposition during the late Pleistocene. The late Pleistocene equilibrium-line altitude (ELA) in each range was determined by reconstructing the maximum ice extent associated with these drift units and using the accumulation area ratio technique. Paleo-ELAs increase from about 2100 m in northeastern Oregon to approximately 3200 m in central Utah. Paleoclimatic conditions along the study transect were estimated by comparing modern climatic conditions at the reconstructed late Pleistocene ELAs with climatic conditions occurring at the ELAs of modem mid-latitude glaciers. Assuming no change in winter accumulation or in the seasonal distribution of precipitation from the present, a mean summer temperature depression ranging from about 9.0 °C at the northern end of the transect to about 4.0 °C at the southern end would have been necessary to sustain glaciers in these ranges during the late Pleistocene. To simulate possible changes in late Pleistocene precipitation patterns, a change in winter accumulation between 0.5 and 2.0 times the modem value resulted in a respective increase or decrease in temperature depression by approximately 2.0 °C. These results suggest that increases in precipitation during the late Pleistocene alone could not have sustained glaciers in the mountain ranges of the study transect, except possibly at its southern end, in the central Great Basin. An increase in precipitation in this area during the late Pleistocene agrees with the interpretation of other paleoclimatic records and paleoclimatic model simulations for the Great Basin. Close

• 3. [Article] Late Pleistocene and postglacial sedimentation and stratigraphy of deep-sea environments off Oregon

  Citation × Citation Citation Abstract Copy Title: Late Pleistocene and postglacial sedimentation and stratigraphy of deep-sea environments off Oregon Author: Duncan, John Russell Jr Title: Late Pleistocene and postglacial sedimentation and stratigraphy of deep-sea environments off Oregon Author: Duncan, John Russell Jr Close

• 4. [Article] Linking top-down forces to the pleistocene megafaunal extinctions

  Humans, in conjunction with natural top-down processes and through a sequence of cascading trophic interactions, may have contributed to the Pleistocene megafaunal extinctions. The arrival of the first ...

  Citation × Citation Citation Abstract Copy Title: Linking top-down forces to the pleistocene megafaunal extinctions Author: Van Valkenburgh, Blaire, Ripple, William J. Humans, in conjunction with natural top-down processes and through a sequence of cascading trophic interactions, may have contributed to the Pleistocene megafaunal extinctions. The arrival of the first humans, as hunters and scavengers, through top-down forcing, could have triggered a population collapse of large herbivores and their predators. We present evidence that the large mammalian herbivores of the North American Pleistocene were primarily predator limited and at low densities, and therefore highly susceptible to extinction when humans were added to the predator guild. Our empirical evidence comes from data on carnivore dental attrition, proboscidean age structure, life history, tusk growth rates, and stable isotopes from the fossil record. We suggest a research agenda for further testing of this hypothesis that will provide a more detailed comprehension of late Pleistocene megafaunal ecology, and thereby allow us to better understand and manage remaining megafauna Title: Linking top-down forces to the pleistocene megafaunal extinctions Author: Van Valkenburgh, Blaire, Ripple, William J. Humans, in conjunction with natural top-down processes and through a sequence of cascading trophic interactions, may have contributed to the Pleistocene megafaunal extinctions. The arrival of the first humans, as hunters and scavengers, through top-down forcing, could have triggered a population collapse of large herbivores and their predators. We present evidence that the large mammalian herbivores of the North American Pleistocene were primarily predator limited and at low densities, and therefore highly susceptible to extinction when humans were added to the predator guild. Our empirical evidence comes from data on carnivore dental attrition, proboscidean age structure, life history, tusk growth rates, and stable isotopes from the fossil record. We suggest a research agenda for further testing of this hypothesis that will provide a more detailed comprehension of late Pleistocene megafaunal ecology, and thereby allow us to better understand and manage remaining megafauna Close

• 5. [Article] Paleoenvironmental reconstruction of late pleistocene and holocene human ecologies : a case study of phytoliths from the Lower Salmon River Canyon, Idaho

  Archaeological excavations of the Cooper's Ferry site in the Lower Salmon River Canyon, Idaho, have revealed a stratified record of cultural occupation, spanning the late Pleistocene and early Holocene ...

  Citation × Citation Citation Abstract Copy Title: Paleoenvironmental reconstruction of late pleistocene and holocene human ecologies : a case study of phytoliths from the Lower Salmon River Canyon, Idaho Author: Knapp, Dante L. Archaeological excavations of the Cooper's Ferry site in the Lower Salmon River Canyon, Idaho, have revealed a stratified record of cultural occupation, spanning the late Pleistocene and early Holocene periods. The purpose of this study was to contribute to the understanding of cultural adaptive strategies represented in the archaeological record at this site, as part of the larger ongoing research agenda for the Cooper's Ferry locale. In order to develop a human ecological perspective of the late Pleistocene and Holocene environments associated with the archaeological record, datasets examining past environmental conditions are required. This study advances these datasets through the analysis of late Pleistocene and Holocene phytolith assemblages derived from both the Cooper's Ferry site and within the Lower Salmon River Canyon. In total, 129 samples were processed for phytolith analysis from four stratigraphic sections--SR 23, SR 27, SR 34, and the north wall of Unit A--at Cooper's Ferry. Through comparisons of the phytolith assemblages obtained for this study with other locally available paleoenvironmental proxy records, this study facilitates the reconstruction of the biophysical environment of the Lower Salmon River Canyon during the late Pleistocene and Holocene periods, thus contributing to a contextualized human ecological model. Results show that the Lower Salmon River Canyon provided a variety of economic opportunities and constraints associated with grass-and shrub-step vegetative communities during these periods. Findings also indicate the ways in which phytolith analyses may be applied in the development of locally derived paleoecological models that can be used to address questions regarding human behavior in the archaeological record. Title: Paleoenvironmental reconstruction of late pleistocene and holocene human ecologies : a case study of phytoliths from the Lower Salmon River Canyon, Idaho Author: Knapp, Dante L. Archaeological excavations of the Cooper's Ferry site in the Lower Salmon River Canyon, Idaho, have revealed a stratified record of cultural occupation, spanning the late Pleistocene and early Holocene periods. The purpose of this study was to contribute to the understanding of cultural adaptive strategies represented in the archaeological record at this site, as part of the larger ongoing research agenda for the Cooper's Ferry locale. In order to develop a human ecological perspective of the late Pleistocene and Holocene environments associated with the archaeological record, datasets examining past environmental conditions are required. This study advances these datasets through the analysis of late Pleistocene and Holocene phytolith assemblages derived from both the Cooper's Ferry site and within the Lower Salmon River Canyon. In total, 129 samples were processed for phytolith analysis from four stratigraphic sections--SR 23, SR 27, SR 34, and the north wall of Unit A--at Cooper's Ferry. Through comparisons of the phytolith assemblages obtained for this study with other locally available paleoenvironmental proxy records, this study facilitates the reconstruction of the biophysical environment of the Lower Salmon River Canyon during the late Pleistocene and Holocene periods, thus contributing to a contextualized human ecological model. Results show that the Lower Salmon River Canyon provided a variety of economic opportunities and constraints associated with grass-and shrub-step vegetative communities during these periods. Findings also indicate the ways in which phytolith analyses may be applied in the development of locally derived paleoecological models that can be used to address questions regarding human behavior in the archaeological record. Close

• 6. [Article] Structural evolution of the Carpinteria Basin, Western Transverse Ranges, California

  The Pleistocene Carpinteria basin is an east-trending northward-verging, faulted syncline containing up to 1220m of partially intertonguing Santa Barbara and Casitas Formations deposited on previously ...

  Citation × Citation Citation Abstract Copy Title: Structural evolution of the Carpinteria Basin, Western Transverse Ranges, California Author: Jackson, Patrick A. The Pleistocene Carpinteria basin is an east-trending northward-verging, faulted syncline containing up to 1220m of partially intertonguing Santa Barbara and Casitas Formations deposited on previously folded pre- Pleistocene strata with up to 80° discordance. Structures subcropping against the unconformity indicate most of the deformation in the Santa Ynez Range prior to deposition of the Santa Barbara Formation approximately one Ma ago was by folding. During that time, the Carpinteria area was the northern margin of the offshore Ventura basin; subsequent uplift north of the Red Mountain fault (RMF) isolated the Carpinteria basin during middle to late Pleistocene time. Quaternary faults in the area are either south-dipping reverse faults related to bedding-slip in pre- Pleistocene strata or north-dipping reverse faults that truncate bedding and are seismically active. The Rincon Creek fault (RCF) dips 35°-60° south steepening to near-vertical at depth, where it apparently passes into bedding within the upper Sespe Formation. It offsets late Pleistocene marine terraces and is itself deformed by the RMF. The RMF dips 55°-63° north at the surface and steepens to 75° north with depth; and also steepens westward south of the Summerland Offshore oil field to 85° north. Vertical separation decreases westward from 4500m north of the Rincon field to 350m at Rincon Point. The main branch of the RMF offsets a 45,000yr marine terrace, but not a 4,500yr terrace. The Summerland Offshore oil field occurs within a disharmonically folded anticline in which incompetent, severely deformed Miocene mudstone overlies competent, broadly folded Oligocene sandstone. Because the anticline formed after deposition of the Santa Barbara Formation, the age of oil migration into the field was post-Santa Barbara during middle to late Pleistocene time. Title: Structural evolution of the Carpinteria Basin, Western Transverse Ranges, California Author: Jackson, Patrick A. The Pleistocene Carpinteria basin is an east-trending northward-verging, faulted syncline containing up to 1220m of partially intertonguing Santa Barbara and Casitas Formations deposited on previously folded pre- Pleistocene strata with up to 80° discordance. Structures subcropping against the unconformity indicate most of the deformation in the Santa Ynez Range prior to deposition of the Santa Barbara Formation approximately one Ma ago was by folding. During that time, the Carpinteria area was the northern margin of the offshore Ventura basin; subsequent uplift north of the Red Mountain fault (RMF) isolated the Carpinteria basin during middle to late Pleistocene time. Quaternary faults in the area are either south-dipping reverse faults related to bedding-slip in pre- Pleistocene strata or north-dipping reverse faults that truncate bedding and are seismically active. The Rincon Creek fault (RCF) dips 35°-60° south steepening to near-vertical at depth, where it apparently passes into bedding within the upper Sespe Formation. It offsets late Pleistocene marine terraces and is itself deformed by the RMF. The RMF dips 55°-63° north at the surface and steepens to 75° north with depth; and also steepens westward south of the Summerland Offshore oil field to 85° north. Vertical separation decreases westward from 4500m north of the Rincon field to 350m at Rincon Point. The main branch of the RMF offsets a 45,000yr marine terrace, but not a 4,500yr terrace. The Summerland Offshore oil field occurs within a disharmonically folded anticline in which incompetent, severely deformed Miocene mudstone overlies competent, broadly folded Oligocene sandstone. Because the anticline formed after deposition of the Santa Barbara Formation, the age of oil migration into the field was post-Santa Barbara during middle to late Pleistocene time. Close

• 7. [Article] Reconnaissance botany of alpine ecosystems on Prince of Wales Island, southeast Alaska

  A study of the Prince of Wales Island alpine areas was undertaken to determine what species occur in the region and to describe plant communities making up the alpine vegetation. For one month in 1972, ...

  Citation × Citation Citation Abstract Copy Title: Reconnaissance botany of alpine ecosystems on Prince of Wales Island, southeast Alaska Author: Jaques, Dennis Randall A study of the Prince of Wales Island alpine areas was undertaken to determine what species occur in the region and to describe plant communities making up the alpine vegetation. For one month in 1972, specimens were collected and 78 micro-plots were analyzed for cover, frequency and constancy data. Three basic habitat types were discovered, with different associations being recognized on calcareous and noncalcareous substrates. Alpine vegetation patterns are formed in a physiographically unstable area. However, where conditions remain favorable for a long enough period of time, a climatic climax of Empetrum-heath vegetation develops. Elsewhere topographic climax vegetation exists. The region is thought to have maintained a flora of significant proportions at least since early post-Pleistocene time. The presence of many disjunct species indicates that floral elements may have survived Pleistocene ice advances in various refugial sites. The west coast of Prince of Wales Island appears to have served as a small migration center following Pleistocene ice recession. Title: Reconnaissance botany of alpine ecosystems on Prince of Wales Island, southeast Alaska Author: Jaques, Dennis Randall A study of the Prince of Wales Island alpine areas was undertaken to determine what species occur in the region and to describe plant communities making up the alpine vegetation. For one month in 1972, specimens were collected and 78 micro-plots were analyzed for cover, frequency and constancy data. Three basic habitat types were discovered, with different associations being recognized on calcareous and noncalcareous substrates. Alpine vegetation patterns are formed in a physiographically unstable area. However, where conditions remain favorable for a long enough period of time, a climatic climax of Empetrum-heath vegetation develops. Elsewhere topographic climax vegetation exists. The region is thought to have maintained a flora of significant proportions at least since early post-Pleistocene time. The presence of many disjunct species indicates that floral elements may have survived Pleistocene ice advances in various refugial sites. The west coast of Prince of Wales Island appears to have served as a small migration center following Pleistocene ice recession. Close

• 8. [Article] The structure and stratigraphy of the Virgin Valley-McGee Mountain area, Humboldt County, Nevada

  The Virgin Valley-McGee Mountain area is located in the northwest corner of Nevada in the northwestern part of the Basin and Range structural province. Rocks within the area consist predominantly of Miocene ...

  Citation × Citation Citation Abstract Copy Title: The structure and stratigraphy of the Virgin Valley-McGee Mountain area, Humboldt County, Nevada Author: Wendell, William Glen The Virgin Valley-McGee Mountain area is located in the northwest corner of Nevada in the northwestern part of the Basin and Range structural province. Rocks within the area consist predominantly of Miocene to Pleistocene volcanic rocks and volcanic derived sedimentary rocks. The volcanic rocks include rhyolite, rhyolite welded tuffs, and basalt. Sedimentary rocks are volcanic conglomerates, sandstones, siltstones, and mudstones with subordinate amounts of diatomite, lignite, opaline chert, and volcanic tuff. Unconsolidated deposits include Quaternary alluvium, landslide debris, and playa sediments. The entire sequence is 2200± feet thick. Rock units within the thesis area can be correlated with units of the same age throughout northeastern California, northwestern Nevada, central and southern Oregon, and western Idaho. The principal structural features within the area are the Virgin Valley syncline, Big Mountain-McGee Mountain anticline, and the tilted fault-block mountain that gives rise to the Big Mountain- McGee Mountain complex. The deformation that produced the broad, gentle folds and fault-block mountain were part of the Basin and Range orogeny. The episode of greatest faulting occurred during Pleistocene time, producing the present features of the Basin and Range structure within the thesis area and the surrounding region. Title: The structure and stratigraphy of the Virgin Valley-McGee Mountain area, Humboldt County, Nevada Author: Wendell, William Glen The Virgin Valley-McGee Mountain area is located in the northwest corner of Nevada in the northwestern part of the Basin and Range structural province. Rocks within the area consist predominantly of Miocene to Pleistocene volcanic rocks and volcanic derived sedimentary rocks. The volcanic rocks include rhyolite, rhyolite welded tuffs, and basalt. Sedimentary rocks are volcanic conglomerates, sandstones, siltstones, and mudstones with subordinate amounts of diatomite, lignite, opaline chert, and volcanic tuff. Unconsolidated deposits include Quaternary alluvium, landslide debris, and playa sediments. The entire sequence is 2200± feet thick. Rock units within the thesis area can be correlated with units of the same age throughout northeastern California, northwestern Nevada, central and southern Oregon, and western Idaho. The principal structural features within the area are the Virgin Valley syncline, Big Mountain-McGee Mountain anticline, and the tilted fault-block mountain that gives rise to the Big Mountain- McGee Mountain complex. The deformation that produced the broad, gentle folds and fault-block mountain were part of the Basin and Range orogeny. The episode of greatest faulting occurred during Pleistocene time, producing the present features of the Basin and Range structure within the thesis area and the surrounding region. Close

• 9. [Article] Progress in the search for early sites in the lower Salmon River canyon, Idaho : a case study in geoarchaeological prospection

  The search for and discovery of early archaeological sites is an inherently geoarchaeological problem. Archaeological sites of late Pleistocene-age are known to be located in the Intermountain West, however, ...

  Citation × Citation Citation Abstract Copy Title: Progress in the search for early sites in the lower Salmon River canyon, Idaho : a case study in geoarchaeological prospection Author: Lancaster, JD L. The search for and discovery of early archaeological sites is an inherently geoarchaeological problem. Archaeological sites of late Pleistocene-age are known to be located in the Intermountain West, however, the record of these early sites remains limited to only a few examples. In the lower Salmon River canyon (LSRC), the Cooper’s Ferry site has been shown to be of late Pleistocene age, however this early archaeological record remains limited to this site. In order to accelerate the process of discovery of these early sites in the LSRC, the present study mapped landforms, and investigated several natural exposures of sediments and soils in the Horseshoe Bend area of the Salmon River, Idaho. AMS radiocarbon ages were obtained on bulk soil organic matter from the truncated B horizons and A horizons of several buried soils. Soil morphology, radiocarbon ages, and sedimentary sequences suggest that a stable paleolandscape, signaled by soil formation across several landforms, was buried sometime after 12,700 yr BP in the study area, and has the potential of holding late Pleistocene to early Holocene-age archaeological sites. Title: Progress in the search for early sites in the lower Salmon River canyon, Idaho : a case study in geoarchaeological prospection Author: Lancaster, JD L. The search for and discovery of early archaeological sites is an inherently geoarchaeological problem. Archaeological sites of late Pleistocene-age are known to be located in the Intermountain West, however, the record of these early sites remains limited to only a few examples. In the lower Salmon River canyon (LSRC), the Cooper’s Ferry site has been shown to be of late Pleistocene age, however this early archaeological record remains limited to this site. In order to accelerate the process of discovery of these early sites in the LSRC, the present study mapped landforms, and investigated several natural exposures of sediments and soils in the Horseshoe Bend area of the Salmon River, Idaho. AMS radiocarbon ages were obtained on bulk soil organic matter from the truncated B horizons and A horizons of several buried soils. Soil morphology, radiocarbon ages, and sedimentary sequences suggest that a stable paleolandscape, signaled by soil formation across several landforms, was buried sometime after 12,700 yr BP in the study area, and has the potential of holding late Pleistocene to early Holocene-age archaeological sites. Close

• 10. [Article] Pleistocene drainage reorganization driven by the isostatic response to deep incision into the northeastern Tibetan Plateau

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Geological Society of America and can be found at: http://geology.gsapubs.o...

  Citation × Citation Citation Abstract Copy Title: Pleistocene drainage reorganization driven by the isostatic response to deep incision into the northeastern Tibetan Plateau Author: Champagnac, Jean-Daniel, Kirby, Eric, Zhang, Huiping, et al., Zhang, Peizhen This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Geological Society of America and can be found at: http://geology.gsapubs.org/. Title: Pleistocene drainage reorganization driven by the isostatic response to deep incision into the northeastern Tibetan Plateau Author: Champagnac, Jean-Daniel, Kirby, Eric, Zhang, Huiping, et al., Zhang, Peizhen This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Geological Society of America and can be found at: http://geology.gsapubs.org/. Close

• 11. [Article] The fruits and seeds of the Rancho La Brea Pleistocene deposits

  More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, ...

  Citation × Citation Citation Abstract Copy Title: The fruits and seeds of the Rancho La Brea Pleistocene deposits Author: Templeton, Bonnie Carolyn More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, spproximately 1,445 specimens are involved in this study. Many comparisons with modern fruits and seeds made it possible to make identification of this material. There are 15 families comprising 20 genera and 30 species recorded in this report of the Rancho La Brea Pleistocene flora. Of this number, four species and four varieties are new to the Pleistocene floras. Eleven of the 30 species occur in the flora of the area today, eleven now occur in areas so remote from the Rancho La Brea site that they could not have been carried by flood waters into the areas of deposition, and therefore, must have been living near to the asphalt beds in order that entrapment could occur. Eight of the species are now extinct. Based on the requirements of their modern counterparts, ecologically, many of the species live in riparian situations or more moist locations than prevail today in the area of deposition. The average rainfall for the range of a number of the modern representatives of the fossils was correlated. From these data it appears that the climate may have been cooler and more moist during the period of deposition, and the species occurring in southern California at that time would have required 2- to 25 inches for their continued existence. It may be assumed that when this average dropped below 20 inches for long periods of time, the species either receded to areas with suitable rainfall or became extinct. Title: The fruits and seeds of the Rancho La Brea Pleistocene deposits Author: Templeton, Bonnie Carolyn More than 4,000 specimens of fruits and seeds were extracted from the matrix removed from inside the skulls of sabre-tooth cats excavated from various pits in the Rancho La Brea deposits. Of this number, spproximately 1,445 specimens are involved in this study. Many comparisons with modern fruits and seeds made it possible to make identification of this material. There are 15 families comprising 20 genera and 30 species recorded in this report of the Rancho La Brea Pleistocene flora. Of this number, four species and four varieties are new to the Pleistocene floras. Eleven of the 30 species occur in the flora of the area today, eleven now occur in areas so remote from the Rancho La Brea site that they could not have been carried by flood waters into the areas of deposition, and therefore, must have been living near to the asphalt beds in order that entrapment could occur. Eight of the species are now extinct. Based on the requirements of their modern counterparts, ecologically, many of the species live in riparian situations or more moist locations than prevail today in the area of deposition. The average rainfall for the range of a number of the modern representatives of the fossils was correlated. From these data it appears that the climate may have been cooler and more moist during the period of deposition, and the species occurring in southern California at that time would have required 2- to 25 inches for their continued existence. It may be assumed that when this average dropped below 20 inches for long periods of time, the species either receded to areas with suitable rainfall or became extinct. Close

• 12. [Article] Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon

  A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological ...

  Citation × Citation Citation Abstract Copy Title: Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon Author: Gudjonsson, Sigurdur A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological formations of Iceland are very different in character depending on their age and formation history. Three major types of formations occur: Tertiary, Plio-Pleistocene, and Pleistocene. These formations have different hydrological characters and different landscapes. There are also large differences in the climate within Iceland. Four major river types are found in Iceland: spring-fed rivers in Pleistocene areas, direct runoff rivers in Plio-Pleistocene areas, direct runoff rivers in Tertiary areas and wetland heath rivers in Tertiary areas. Eleven biogeoclimatic regions occur in Iceland, each having a different watershed type. The classification together with life history theory can explain the distributions, abundances, and life history strategies of Icelandic salmonids. Oceanic conditions must also be considered to explain the life history patterns of anadromous populations. When the freshwater and marine habitat is stable, the life history patterns of individuals in a population tend to be uniform, one life history form being most common. In an unstable environment many life history forms occur and the life span of one generation is long. The properties of the habitat can further explain which life history types are present. In the most stable and favorable rivers of Iceland resident life history forms are more common. Such a classification of a river habitat greatly aids the understanding of the habitat and how it enables and constrains the salmonid populations within it. Consequently adaptations in life histories are better understood and conservation, utilization, and management of these valuable natural resources are made more coherent and efficient. Title: Classification of Icelandic watersheds and rivers to explain life history strategies of Atlantic salmon Author: Gudjonsson, Sigurdur A hierarchical classification system of Iceland's watersheds and rivers is presented. The classification is based on Iceland's substrate, climate, water, biota, and human cultural influences. The geological formations of Iceland are very different in character depending on their age and formation history. Three major types of formations occur: Tertiary, Plio-Pleistocene, and Pleistocene. These formations have different hydrological characters and different landscapes. There are also large differences in the climate within Iceland. Four major river types are found in Iceland: spring-fed rivers in Pleistocene areas, direct runoff rivers in Plio-Pleistocene areas, direct runoff rivers in Tertiary areas and wetland heath rivers in Tertiary areas. Eleven biogeoclimatic regions occur in Iceland, each having a different watershed type. The classification together with life history theory can explain the distributions, abundances, and life history strategies of Icelandic salmonids. Oceanic conditions must also be considered to explain the life history patterns of anadromous populations. When the freshwater and marine habitat is stable, the life history patterns of individuals in a population tend to be uniform, one life history form being most common. In an unstable environment many life history forms occur and the life span of one generation is long. The properties of the habitat can further explain which life history types are present. In the most stable and favorable rivers of Iceland resident life history forms are more common. Such a classification of a river habitat greatly aids the understanding of the habitat and how it enables and constrains the salmonid populations within it. Consequently adaptations in life histories are better understood and conservation, utilization, and management of these valuable natural resources are made more coherent and efficient. Close

• 13. [Article] Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene

  Citation × Citation Citation Abstract Copy Title: Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene Author: Phillips, Fred, Marrero, Shasta, Kirby, Eric, Shi, Xuhua, Gosse, John, Furlong, Kevin P., Wang, Erchie, Meng, Kai Title: Evaluating the size and extent of paleolakes in central Tibet during the late Pleistocene Author: Phillips, Fred, Marrero, Shasta, Kirby, Eric, Shi, Xuhua, Gosse, John, Furlong, Kevin P., Wang, Erchie, Meng, Kai Close

• 14. [Article] Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon

  This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination ...

  Citation × Citation Citation Abstract Copy Title: Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon Author: Punke, Michele Leigh This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination of the stratigraphic record can reveal depositional signatures that provide insights into the geomorphic and tectonic forces active within coastal river basins. Three case studies from the southern Oregon coast illustrate the complex relationship between tectonics and geomorphic processes along an active margin coast such as Oregon's Cascadia subduction zone. This work illustrates that the differential preservation of late Pleistocene-age terrestrial deposits in Oregon's coastal landscape, and the early cultural sites they may contain, is not random but can be closely related to larger tectonogeomorphic processes operating at local and regional scales. Detailed subsurface investigation of one case study site, the lower Sixes River valley, reveals a complex history of depositional environment evolution in relation to geomorphic and tectonic forces. Litho- and biostratigraphic data sets are used to develop a depositional environment reconstruction for the lower Sixes River site through time. This reconstruction of the depositional environment from the late Pleistocene to the present indicates a transgressive evolution that differs from models of transgressive coastal facies and from other studied Northwest coast estuarine life histories. Factors such as eustatic sea level rise, regional and local tectonic alteration of the landscape, sediment supply, or valley morphology may have played roles in the creation and preservation of this atypical depositional sequence. Litho- and biostratigraphic evidence of six Cascadia subduction zone earthquakes younger than 6200 cal yr BP is recorded in a long sediment core from the Sixes River valley. All six of these events correlate with events previously reported for the area by Kelsey et al. (2002). At least five additional plate boundary earthquakes lowered tidal marshes and freshwater wetlands prior to 6200 cal yr BP. The presence within the lower Sixes River valley of an intertidal environment capable of recording Cascadia subduction zone earthquakes dating to the late Pleistocene and early Holocene has not been found at any other location on the Northwest coast. Title: Paleoenvironmental reconstruction of an active margin coast from the Pleistocene to the present : examples from southwestern Oregon Author: Punke, Michele Leigh This study illustrates geoarchaeological and paleoenvironmental approaches to the investigation of an active margin coastal setting and provides examples of how information gleaned through examination of the stratigraphic record can reveal depositional signatures that provide insights into the geomorphic and tectonic forces active within coastal river basins. Three case studies from the southern Oregon coast illustrate the complex relationship between tectonics and geomorphic processes along an active margin coast such as Oregon's Cascadia subduction zone. This work illustrates that the differential preservation of late Pleistocene-age terrestrial deposits in Oregon's coastal landscape, and the early cultural sites they may contain, is not random but can be closely related to larger tectonogeomorphic processes operating at local and regional scales. Detailed subsurface investigation of one case study site, the lower Sixes River valley, reveals a complex history of depositional environment evolution in relation to geomorphic and tectonic forces. Litho- and biostratigraphic data sets are used to develop a depositional environment reconstruction for the lower Sixes River site through time. This reconstruction of the depositional environment from the late Pleistocene to the present indicates a transgressive evolution that differs from models of transgressive coastal facies and from other studied Northwest coast estuarine life histories. Factors such as eustatic sea level rise, regional and local tectonic alteration of the landscape, sediment supply, or valley morphology may have played roles in the creation and preservation of this atypical depositional sequence. Litho- and biostratigraphic evidence of six Cascadia subduction zone earthquakes younger than 6200 cal yr BP is recorded in a long sediment core from the Sixes River valley. All six of these events correlate with events previously reported for the area by Kelsey et al. (2002). At least five additional plate boundary earthquakes lowered tidal marshes and freshwater wetlands prior to 6200 cal yr BP. The presence within the lower Sixes River valley of an intertidal environment capable of recording Cascadia subduction zone earthquakes dating to the late Pleistocene and early Holocene has not been found at any other location on the Northwest coast. Close

• 15. [Article] Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes

  The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake ...

  Citation × Citation Citation Abstract Copy Title: Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes Author: Steinkamp, Matthew J. The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake Tanganyika is the second deepest and one of the oldest lakes in the world. The horst and graben geometry of the lake has created subaqueous structural platforms that accumulate pelagic sediments that contain and archive changes in micro-fossil assemblages controlled by changes in climate and lake levels. One such structural platform is the Moba-Kalya Horst. Micro-fossil analysis of lacustrine sediments from a single Kullenberg piston core from the Moba-Kalya Horst indicate dramatic Late Pleistocene and Early Holocene climate and lake level changes that appear to be synchronized with regional, as well as hemispherical climate shifts. During the Late Pleistocene at the Last Glacial Maximum which ended approximately 15 ky B.P., Lake Tanganyika experienced low-lake stands of 250-350 meters or more below the present lake level. From 17,537 to 15,000 calendar years BP, periphytic diatoms such as Rhopalodia gibberula and Surirella fuellebornii were abundant, as were grass phytoliths and sponge spicules, indicative of a dry climate regime. The dominant planktonic diatom was Stephanodiscus astraea, which thrived in low Si:P supply ratio, stratified lake environments in Na-HCO3 rich waters, indicative of a cool, arid climate regime. Periphytic diatoms were also abundant in Lake Malawi to the south and significantly negative δ180 values were recorded in Greenland ice cores for this period. Following the low-lake stands of the Late Glacial Maximum, lake levels generally rose as East Africa experienced the AHP (African Humid Period) (14.4-5.5 cal ky BP). An increase in planktonic diatoms and decrease in periphytic diatoms were recorded in the lacustrine sediments at this time which indicate a positive water balance and rising lake levels. The accumulation of dark-bundled, laminated sediments indicate that the climate was wet and the coring site was below the annual thermocline. A decrease in S. astraea and increase in Cyclostephanos damasii signal conditions of increased moisture to the lake, and decreased evaporation. Around 13 ky B.P. conditions at Lake Tanganyika reverted to Late Glacial Maximum conditions which lasted until approximately 11.5 ky B.P.. Periphytic diatoms once again became abundant, and sponge spicule and grass phytolith counts rose. S.astraea dominance again rose as lake conditions were calm and stratified and the climate was cool and arid. Periphytic diatoms became abundant in Lake Malawi during this period, and increased negative δ180 values were recorded in the Greenland ice cores correlating with increased periphytic diatoms in both Lake Tanganyika and Lake Malawi. Following the Late Pleistocene cold period, lake levels once again began rising as the climate became wetter and windier. Fluctuations from wet and windy to wet and calm occurred at the terminus of the Late Pleistocene as diatom dominance alternated from Aulacoseira granulata, which indicates wet and windy with increase upwelling, to C.damasii, which indicate wet and stratified. Around 9800 B.P. lake conditions stabilized and remained wet and windy with increase turbulence and upwelling which optimized conditions for the dominance of A.granulata. These conditions prevailed through the Early Holocene to at least 6500 B.P. From the Middle Holocene to the present, the general climate of East Africa was and is more arid than the early Holocene, with dry windy conditions and continued upwelling. Title: Lacustrine micro-fossil assemblage in core NP04-KH3, a Kullenberg piston core from the Moba-Kalya Horst region of Lake Tanganyika, East Africa, as a biogeochemical proxy for Late Pleistocene and Early Holocene climate and lake level changes Author: Steinkamp, Matthew J. The objective of this research is to determine the correlation of lacustrine micro-fossils in Lake Tanganyika to changes in climate and lake levels during the Late Pleistocene and Early Holocene. Lake Tanganyika is the second deepest and one of the oldest lakes in the world. The horst and graben geometry of the lake has created subaqueous structural platforms that accumulate pelagic sediments that contain and archive changes in micro-fossil assemblages controlled by changes in climate and lake levels. One such structural platform is the Moba-Kalya Horst. Micro-fossil analysis of lacustrine sediments from a single Kullenberg piston core from the Moba-Kalya Horst indicate dramatic Late Pleistocene and Early Holocene climate and lake level changes that appear to be synchronized with regional, as well as hemispherical climate shifts. During the Late Pleistocene at the Last Glacial Maximum which ended approximately 15 ky B.P., Lake Tanganyika experienced low-lake stands of 250-350 meters or more below the present lake level. From 17,537 to 15,000 calendar years BP, periphytic diatoms such as Rhopalodia gibberula and Surirella fuellebornii were abundant, as were grass phytoliths and sponge spicules, indicative of a dry climate regime. The dominant planktonic diatom was Stephanodiscus astraea, which thrived in low Si:P supply ratio, stratified lake environments in Na-HCO3 rich waters, indicative of a cool, arid climate regime. Periphytic diatoms were also abundant in Lake Malawi to the south and significantly negative δ180 values were recorded in Greenland ice cores for this period. Following the low-lake stands of the Late Glacial Maximum, lake levels generally rose as East Africa experienced the AHP (African Humid Period) (14.4-5.5 cal ky BP). An increase in planktonic diatoms and decrease in periphytic diatoms were recorded in the lacustrine sediments at this time which indicate a positive water balance and rising lake levels. The accumulation of dark-bundled, laminated sediments indicate that the climate was wet and the coring site was below the annual thermocline. A decrease in S. astraea and increase in Cyclostephanos damasii signal conditions of increased moisture to the lake, and decreased evaporation. Around 13 ky B.P. conditions at Lake Tanganyika reverted to Late Glacial Maximum conditions which lasted until approximately 11.5 ky B.P.. Periphytic diatoms once again became abundant, and sponge spicule and grass phytolith counts rose. S.astraea dominance again rose as lake conditions were calm and stratified and the climate was cool and arid. Periphytic diatoms became abundant in Lake Malawi during this period, and increased negative δ180 values were recorded in the Greenland ice cores correlating with increased periphytic diatoms in both Lake Tanganyika and Lake Malawi. Following the Late Pleistocene cold period, lake levels once again began rising as the climate became wetter and windier. Fluctuations from wet and windy to wet and calm occurred at the terminus of the Late Pleistocene as diatom dominance alternated from Aulacoseira granulata, which indicates wet and windy with increase upwelling, to C.damasii, which indicate wet and stratified. Around 9800 B.P. lake conditions stabilized and remained wet and windy with increase turbulence and upwelling which optimized conditions for the dominance of A.granulata. These conditions prevailed through the Early Holocene to at least 6500 B.P. From the Middle Holocene to the present, the general climate of East Africa was and is more arid than the early Holocene, with dry windy conditions and continued upwelling. Close

• 16. [Article] Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon

  The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that ...

  Citation × Citation Citation Abstract Copy Title: Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon Author: Wozniak, Karl C. The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that were extruded from a number of composite cones, shield volcanoes, and cinder cones. The principal eruptive centers include Sphinx Butte, The Wife, The Husband, and South Sister volcanoes. Sphinx Butte, The Wife, and The Husband are typical High Cascade shield and composite volcanoes whose compositions are limited to basalt and basaltic andesite. South Sister is a complex composite volcano composed of a diverse assemblage of rocks. In contrast with earlier studies, the present investigation finds that South Sister is not a simple accumulation of andesite and dacite lavas; nor does the eruptive sequence display obvious evolutionary trends or late stage divergence to basalt and rhyolite. Rather, the field relations indicate that magmas of diverse composition have been extruded from South Sister vents throughout the lifespan of this volcano. The compositional variation at South Sister is atypical of the Oregon High Cascade platform. This variation, however, represents part of a continued pattern of late Pliocene and Pleistocene magmatic diversity in a local region that includes Middle Sister, South Sister, and Broken Top volcanoes. Regional and local geologic constraints combined with chemical and petrographic criteria indicate that a local subcrustal process probably produced the magmas extruded from South Sister, whereas a regional subcrustal process probably produced the magmas extruded from Sphinx Butte, The Wife, and The Husband. All of the volcanoes in the field area are probably less than 720,000 years old. Sphinx Butte, The Wife, and The Husband are older than South Sister and have been subjected to at least two glaciations. Late Pleistocene glaciers covered all but the upper ridges and summit of South Sister; however, evidence for multiple glaciation is obscure and it is possible that the bulk of South Sister is younger than the second-to-last Pleistocene glaciation. Glaciated andesite lavas at the summit of South Sister are capped by a veneer of basaltic andesite lavas. The basaltic andesite lavas were extruded prior to 6840 yrs. B.P., but are probably of late Pleistocene rather than Holocene age. At some time between 12,000 and 2300 yrs. B.P., basaltic andesite lavas and cinders were extruded from the Le Conte vent at the southwest base of South Sister. The Le Conte lavas may bear only a spatial relation to South Sister. Between 2300 and 1900 yrs. B.P., a series of rhyodacite domes and block flows were extruded from flank vents on South Sister. Future eruptive activity is likely at this volcano. Title: Geology of the northern part of the Southeast Three Sisters quadrangle, Oregon Author: Wozniak, Karl C. The northern part of the Southeast Three Sisters quadrangle straddles the crest of the central High Cascades of Oregon. The area is covered by Pleistocene and Holocene volcanic and volcaniclastic rocks that were extruded from a number of composite cones, shield volcanoes, and cinder cones. The principal eruptive centers include Sphinx Butte, The Wife, The Husband, and South Sister volcanoes. Sphinx Butte, The Wife, and The Husband are typical High Cascade shield and composite volcanoes whose compositions are limited to basalt and basaltic andesite. South Sister is a complex composite volcano composed of a diverse assemblage of rocks. In contrast with earlier studies, the present investigation finds that South Sister is not a simple accumulation of andesite and dacite lavas; nor does the eruptive sequence display obvious evolutionary trends or late stage divergence to basalt and rhyolite. Rather, the field relations indicate that magmas of diverse composition have been extruded from South Sister vents throughout the lifespan of this volcano. The compositional variation at South Sister is atypical of the Oregon High Cascade platform. This variation, however, represents part of a continued pattern of late Pliocene and Pleistocene magmatic diversity in a local region that includes Middle Sister, South Sister, and Broken Top volcanoes. Regional and local geologic constraints combined with chemical and petrographic criteria indicate that a local subcrustal process probably produced the magmas extruded from South Sister, whereas a regional subcrustal process probably produced the magmas extruded from Sphinx Butte, The Wife, and The Husband. All of the volcanoes in the field area are probably less than 720,000 years old. Sphinx Butte, The Wife, and The Husband are older than South Sister and have been subjected to at least two glaciations. Late Pleistocene glaciers covered all but the upper ridges and summit of South Sister; however, evidence for multiple glaciation is obscure and it is possible that the bulk of South Sister is younger than the second-to-last Pleistocene glaciation. Glaciated andesite lavas at the summit of South Sister are capped by a veneer of basaltic andesite lavas. The basaltic andesite lavas were extruded prior to 6840 yrs. B.P., but are probably of late Pleistocene rather than Holocene age. At some time between 12,000 and 2300 yrs. B.P., basaltic andesite lavas and cinders were extruded from the Le Conte vent at the southwest base of South Sister. The Le Conte lavas may bear only a spatial relation to South Sister. Between 2300 and 1900 yrs. B.P., a series of rhyodacite domes and block flows were extruded from flank vents on South Sister. Future eruptive activity is likely at this volcano. Close

• 17. [Article] Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae)

  Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.o...

  Citation × Citation Citation Abstract Copy Title: Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Author: Liston, Aaron, Kadereit, Joachim W., Coleman, Max, Abbott, Richard J. Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.org/content/vol90/issue10/ Title: Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Author: Liston, Aaron, Kadereit, Joachim W., Coleman, Max, Abbott, Richard J. Repeat intercontinental dispersal and Pleistocene speciation in disjunct Mediterranean and desert Senecio (Asteraceae) Published version can be found at American Journal of Botany: http://www.amjbot.org/content/vol90/issue10/ Close

• 18. [Article] Preliminary report on the geology of the Molalla quadrangle, Oregon

  The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as ...

  Citation × Citation Citation Abstract Copy Title: Preliminary report on the geology of the Molalla quadrangle, Oregon Author: Harper, Herbert Ewing The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as a portion of the Willamette Valley lowland. The rocks in the Cascade foothills are marine and terrestrial sediments interlayered with volcanic flows and pyroclastics which range from Eocene (?) to Pliocene or early Pleistocene in age. The oldest rocks consist of approximately 1500 feet of basaltic and andesitic lavas, present in the southeastern portion of the area, and described here as the Pre-Butte Creek lavas. The base or lower part of the series contains interbedded marine pebble conglomerates presumably of Eocene age. To the southwest the laves are unconformably ever-lain with about 1200 feet of marine and terrestrial sediments which have been termed the Butte Creek beds. Field relations indicate a correlation of these sediments with the Oligocene Illahe sandstone, while the faunal study made by Durham suggests a lower Miocene age. In the southwestern part of the quadrangle the Butte Creek beds are unconformably overlain by the middle Miocene Stayton lavas. Several hundred feet of pyroclastics and terrestrial sediments considered early Pliocene in age and described as the Molalla formation are exposed along Molalla River in the eastern and northeastern part of the quadrangle. They rest unconformably on the Pre-Butte Creek lavas and are overlain by Pliocene or early Pleistocene Boring lavas. Where exposed along the western edge of the Cascade foothills these older formations are covered by middle Pleistocene alluvial deposits which blanket the Willamette valley lowland. All of the Tertiary rocks have been tilted or gently folded. Dips observed in the Butte Creek beds in the southern half of the area average about 6 degrees and indicate an elongate domal fold trending northeasterly. A regional dip of 5 to 8 degrees to the northwest is present in the Molallla formation in the northern part of the area. Minor normal faulting in present locally in the Butte Creek beds. Residual and transported high-alumina clays are present in the Molalla formation. Exploration by the United States Bureau of Mines and Unites States Geological Survey revealed an estimated 53,460,000 wet tons of ore in the Molalla area. Title: Preliminary report on the geology of the Molalla quadrangle, Oregon Author: Harper, Herbert Ewing The Molalla quadrangle is located in northwestern Oregon along the eastern edge of Willamette Valley about 30 miles south of Portland. The area includes part of the Western Cascade foothills as well as a portion of the Willamette Valley lowland. The rocks in the Cascade foothills are marine and terrestrial sediments interlayered with volcanic flows and pyroclastics which range from Eocene (?) to Pliocene or early Pleistocene in age. The oldest rocks consist of approximately 1500 feet of basaltic and andesitic lavas, present in the southeastern portion of the area, and described here as the Pre-Butte Creek lavas. The base or lower part of the series contains interbedded marine pebble conglomerates presumably of Eocene age. To the southwest the laves are unconformably ever-lain with about 1200 feet of marine and terrestrial sediments which have been termed the Butte Creek beds. Field relations indicate a correlation of these sediments with the Oligocene Illahe sandstone, while the faunal study made by Durham suggests a lower Miocene age. In the southwestern part of the quadrangle the Butte Creek beds are unconformably overlain by the middle Miocene Stayton lavas. Several hundred feet of pyroclastics and terrestrial sediments considered early Pliocene in age and described as the Molalla formation are exposed along Molalla River in the eastern and northeastern part of the quadrangle. They rest unconformably on the Pre-Butte Creek lavas and are overlain by Pliocene or early Pleistocene Boring lavas. Where exposed along the western edge of the Cascade foothills these older formations are covered by middle Pleistocene alluvial deposits which blanket the Willamette valley lowland. All of the Tertiary rocks have been tilted or gently folded. Dips observed in the Butte Creek beds in the southern half of the area average about 6 degrees and indicate an elongate domal fold trending northeasterly. A regional dip of 5 to 8 degrees to the northwest is present in the Molallla formation in the northern part of the area. Minor normal faulting in present locally in the Butte Creek beds. Residual and transported high-alumina clays are present in the Molalla formation. Exploration by the United States Bureau of Mines and Unites States Geological Survey revealed an estimated 53,460,000 wet tons of ore in the Molalla area. Close

• 19. [Article] Origin and configuration of the present-day land surface, Goodhue County, Minnesota

  This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface ...

  Citation × Citation Citation Abstract Copy Title: Origin and configuration of the present-day land surface, Goodhue County, Minnesota Author: Sansome, Constance J. (Constance Jefferson) This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface configuration and the composition and distribution of rock material underlying that surface, and a theoretical portion--a speculative examination of the factors controlling the land surface configuration and discussion of the probable origin of that configuration. I found that the configuration of any land surface is described in terms of drainage and topography and that the origin and age of any land surface is determined by an examination of the materials making up that surface, the present and past processes acting on that surface, and the amount of time available for the processes to act. I also found that the age of land surface configuration is distinct from the age of the underlying materials and that the degree to which configuration of any land surface is dependent on structure, process, and time is dependent on the scale of the investigation and the surface itself. The surface of Goodhue County ranges in elevation from approximately 670 feet to 1275 feet. The southern two-thirds of the county is a broad upland; the northern third of the county is slightly lower and more dissected. The county has a dendritic and well-integrated drainage system and is underlain by virtually flat-lying sedimentary rocks and thick deposits of glacial drift. The surface configuration of Goodhue County is the result of: (1) geographic location near the center of North America and alongside its major river; (2) marine deposition during the early Paleozoic; (3) minor folding and faulting during the later Paleozoic; (4) extensive solution and erosion during the late Paleozoic and/or parts of the Mesozoic; (5) fluvial deposition during the Cretaceous; (6) glacial and glaciofluvial deposition during the early and middle Pleistocene; (7) aeolian deposition and mass movement late in the Pleistocene; and (8) fluvial erosion and deposition during the late Pleistocene and Recent. Title: Origin and configuration of the present-day land surface, Goodhue County, Minnesota Author: Sansome, Constance J. (Constance Jefferson) This study describes the surface configuration of Goodhue County and attempts to determine the origin of that configuration. The research has a descriptive portion--an objective examination of land surface configuration and the composition and distribution of rock material underlying that surface, and a theoretical portion--a speculative examination of the factors controlling the land surface configuration and discussion of the probable origin of that configuration. I found that the configuration of any land surface is described in terms of drainage and topography and that the origin and age of any land surface is determined by an examination of the materials making up that surface, the present and past processes acting on that surface, and the amount of time available for the processes to act. I also found that the age of land surface configuration is distinct from the age of the underlying materials and that the degree to which configuration of any land surface is dependent on structure, process, and time is dependent on the scale of the investigation and the surface itself. The surface of Goodhue County ranges in elevation from approximately 670 feet to 1275 feet. The southern two-thirds of the county is a broad upland; the northern third of the county is slightly lower and more dissected. The county has a dendritic and well-integrated drainage system and is underlain by virtually flat-lying sedimentary rocks and thick deposits of glacial drift. The surface configuration of Goodhue County is the result of: (1) geographic location near the center of North America and alongside its major river; (2) marine deposition during the early Paleozoic; (3) minor folding and faulting during the later Paleozoic; (4) extensive solution and erosion during the late Paleozoic and/or parts of the Mesozoic; (5) fluvial deposition during the Cretaceous; (6) glacial and glaciofluvial deposition during the early and middle Pleistocene; (7) aeolian deposition and mass movement late in the Pleistocene; and (8) fluvial erosion and deposition during the late Pleistocene and Recent. Close

• 20. [Article] Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California

  The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene ...

  Citation × Citation Citation Abstract Copy Title: Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California Author: Grigsby, F. Bryan The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene clastic strata. The north-dipping Red Mountain reverse fault system, which forms the northern boundary of the basin, has been active since the early Pliocene and has maximum reverse separation of 7300 m (23,900 ft). In the basin, the Grubb and Oak Grove faults were active in the early Pleistocene and were reactivated during late Pleistocene folding. Both are tear faults that dip steeply northeast and strike northwest, in contrast to the west-trending structural grain of the region. The Rincon anticline is the western extension of the Ventura Avenue anticline. Both anticlines formed approximately 200,000 years ago as rootless folds which die out in subjacent fine-grained Miocene strata. Above the Rincon anticline synchronous shortening occurred on the Javon Canyon/Padre Juan fault and San Miguelito anticline. The Padre Juan fault is a south-dipping reverse fault that flattens over the axis of the Rincon anticline and dies out to the north. Where it flattens, the Javon Canyon fault rises upwards and offsets 3500 year old marine terrace deposits at the surface. Maximum reverse separation across the Javon Canyon/Padre Juan fault is 2800 m (9200 ft). The steeply north-dipping to overfolded region between the Javon Canyon and Padre Juan faults constitutes a large portion of the north limb of the San Miguelito anticline. This anticline, constrained above the Padre Juan fault, is a complex example of a fault-propagation fold. Total shortening in the Ventura basin along a cross-section through the study area is approximately 7825 m (25,700 ft). For the last 200,000 years this north-south directed shortening has occurred at a rate of 12.5 to 22.3 mm/yr (0.49 to 0.87 in/yr). These values compare favorably with shortening values obtained at other locations in the basin, and support the concept of decreasing horizontal contraction from east to west across the basin for the last 200,000 years. Title: Quaternary tectonics of the Rincon and San Miguelito oil fields area, western Ventura basin, California Author: Grigsby, F. Bryan The Ventura basin is an elongate sedimentary trough extending from the San Gabriel fault west into the Santa Barbara Channel. West of Ventura it contains over 4 km of severely deformed Pliocene and Pleistocene clastic strata. The north-dipping Red Mountain reverse fault system, which forms the northern boundary of the basin, has been active since the early Pliocene and has maximum reverse separation of 7300 m (23,900 ft). In the basin, the Grubb and Oak Grove faults were active in the early Pleistocene and were reactivated during late Pleistocene folding. Both are tear faults that dip steeply northeast and strike northwest, in contrast to the west-trending structural grain of the region. The Rincon anticline is the western extension of the Ventura Avenue anticline. Both anticlines formed approximately 200,000 years ago as rootless folds which die out in subjacent fine-grained Miocene strata. Above the Rincon anticline synchronous shortening occurred on the Javon Canyon/Padre Juan fault and San Miguelito anticline. The Padre Juan fault is a south-dipping reverse fault that flattens over the axis of the Rincon anticline and dies out to the north. Where it flattens, the Javon Canyon fault rises upwards and offsets 3500 year old marine terrace deposits at the surface. Maximum reverse separation across the Javon Canyon/Padre Juan fault is 2800 m (9200 ft). The steeply north-dipping to overfolded region between the Javon Canyon and Padre Juan faults constitutes a large portion of the north limb of the San Miguelito anticline. This anticline, constrained above the Padre Juan fault, is a complex example of a fault-propagation fold. Total shortening in the Ventura basin along a cross-section through the study area is approximately 7825 m (25,700 ft). For the last 200,000 years this north-south directed shortening has occurred at a rate of 12.5 to 22.3 mm/yr (0.49 to 0.87 in/yr). These values compare favorably with shortening values obtained at other locations in the basin, and support the concept of decreasing horizontal contraction from east to west across the basin for the last 200,000 years. Close

• 21. [Article] The Ore bin ; Vol. 36 No. 3 (March 1974)

  Wright's Point, a 250-foot-high, sinuous, flat-topped ridge, projects eastward into Harney Basin, Harney County, Oregon. This 6-mile-long feature ranges from 200 to 600 yards wide and merges with a broad ...

  Citation × Citation Citation Abstract Copy Title: The Ore bin ; Vol. 36 No. 3 (March 1974) Author: Niem, Alan R., Oregon. Dept. of Geology and Mineral Industries Wright's Point, a 250-foot-high, sinuous, flat-topped ridge, projects eastward into Harney Basin, Harney County, Oregon. This 6-mile-long feature ranges from 200 to 600 yards wide and merges with a broad mesa at its western end. The nearest topographic highs are Dog Mountain, 2 miles southwest, and foothills of the Blue Mountains near Burns, 12 miles northwest. The point is composed of a fluvial sequence of tuffaceous channel sandstones, mudstones, and conglomerates (Pliocene-Pleistocene Harney Formation) capped by two thin, early Pleistocene diktytaxitic olivine basalt flows. The configuration of the ridge and the paleocurrent pattern, sedimentary structures, fossils, and stratigraphic relations of the rocks to nearby topographic highs suggest that the fluvial sequence and capping basalts were deposited in a narrow valley of an eastward flowing meandering stream(s). The basalts acted as a protective cap while the less-resistant valley walls were eroded away to produce an inverted topography. Remnants of the valley walls consist of a Plio-Pleistocene palagonite tuff ring at Dog Mountain and ignimbrites and tuffaceous sediments of the middle Pliocene Danforth Formation in the Blue Mountain foothills. Reworked palagonite tuff, pumice sands, and Danforth ignimbrite pebbles compose the sandstone and conglomerates of Wright's Point. Measured elevation differences at the base of the lower flow, orientations of filled and open lava tubes, and increasing number of flows to the west suggest that the basalt flowed from west to east down the stream valley. Probable sources of the basalts are several vents 6 miles west of Wright's Point near the Palomino Buttes. Title: The Ore bin ; Vol. 36 No. 3 (March 1974) Author: Niem, Alan R., Oregon. Dept. of Geology and Mineral Industries Wright's Point, a 250-foot-high, sinuous, flat-topped ridge, projects eastward into Harney Basin, Harney County, Oregon. This 6-mile-long feature ranges from 200 to 600 yards wide and merges with a broad mesa at its western end. The nearest topographic highs are Dog Mountain, 2 miles southwest, and foothills of the Blue Mountains near Burns, 12 miles northwest. The point is composed of a fluvial sequence of tuffaceous channel sandstones, mudstones, and conglomerates (Pliocene-Pleistocene Harney Formation) capped by two thin, early Pleistocene diktytaxitic olivine basalt flows. The configuration of the ridge and the paleocurrent pattern, sedimentary structures, fossils, and stratigraphic relations of the rocks to nearby topographic highs suggest that the fluvial sequence and capping basalts were deposited in a narrow valley of an eastward flowing meandering stream(s). The basalts acted as a protective cap while the less-resistant valley walls were eroded away to produce an inverted topography. Remnants of the valley walls consist of a Plio-Pleistocene palagonite tuff ring at Dog Mountain and ignimbrites and tuffaceous sediments of the middle Pliocene Danforth Formation in the Blue Mountain foothills. Reworked palagonite tuff, pumice sands, and Danforth ignimbrite pebbles compose the sandstone and conglomerates of Wright's Point. Measured elevation differences at the base of the lower flow, orientations of filled and open lava tubes, and increasing number of flows to the west suggest that the basalt flowed from west to east down the stream valley. Probable sources of the basalts are several vents 6 miles west of Wright's Point near the Palomino Buttes. Close

• 22. [Article] Seismic stratigraphy of the central South China Sea basin and implications for neotectonics

  This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292...

  Citation × Citation Citation Abstract Copy Title: Seismic stratigraphy of the central South China Sea basin and implications for neotectonics Author: Li, Jiabiao, Colwell, Frederick S., Koppers, Anthony A. P., Li, Chun-Feng, Ding, Weiwei, et al. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292169-9356/. Title: Seismic stratigraphy of the central South China Sea basin and implications for neotectonics Author: Li, Jiabiao, Colwell, Frederick S., Koppers, Anthony A. P., Li, Chun-Feng, Ding, Weiwei, et al. This is the publisher’s final pdf. The published article is copyrighted by the American Geophysical Union and can be found at: http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.1002/%28ISSN%292169-9356/. Close

• 23. [Article] Ocean Temperature Variability during the Late Pleistocene

  This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution ...

  Citation × Citation Citation Abstract Copy Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Title: Ocean Temperature Variability during the Late Pleistocene Author: Hoffman, Jeremy Scott This dissertation explores one overarching question relevant to the paleoclimate of the latest Pleistocene glacial cycle (approximately the last 130,000 years): “How did spatial and temporal evolution of ocean temperature, both at the surface and interior, relate to other parts of the climate system in the late Pleistocene?” Results from three studies are presented that seek to address longstanding questions in paleoceanography and paleoclimatology for the late Pleistocene using a combination of novel and accepted statistical and geochemical analysis techniques and leveraging comparisons with available global climate model data. The last interglaciation (LIG; ~129-116 ka) was the most recent period in Earth’s history with higher-than-present global sea level (≥6-9 m) under similar-to-preindustrial concentrations of atmospheric CO₂. This suggests that additional feedbacks related to albedo, insolation, and ocean overturning circulation may have resulted in the apparent warming required to cause the higher sea level. Our understanding of how much warmer the LIG was relative to the present interglaciation remains uncertain, however, with current estimates suggesting that sea-surface temperatures (SSTs) were 0-2°C warmer than late-20th century average global temperatures. We present a global compilation of proxy-based annual SST spanning the LIG. Using Monte Carlo and Bayesian techniques to propagate uncertainties in age-model and proxy-based SST reconstructions, our results quantify the spatial timing, amplitude, and uncertainty in global and regional SST change during the LIG. Our conclusions suggest that the LIG surface ocean was indistinguishable from the average surface ocean temperatures observed for the last two decades (1995-2014). This may ultimately imply that the Earth is currently committed to ≥6-9m of equilibrium sea-level rise. Although the LIG is not an analogue for present and future climate change due to the large differences in seasonal orbital insolation and absence of anthropogenic greenhouse gas radiative forcing, it provides an opportunity to test the ability of global climate models to simulate the mechanisms and climate feedbacks responsible for the warmer climate and higher global mean sea level during the LIG. However, when forced only by LIG greenhouse gas concentrations and insolation changes, climate models suggest that the annual mean temperature response was not significantly different from preindustrial control simulations. We present the first multi-model and multiscenario ensemble of transient and equilibrium global climate modeling results spanning the LIG. We show, using a novel model-data comparison framework, that these scenario-specific model results exhibit regionally independent agreement with ocean basin-specific proxy-based SST stacks. This result ultimately implies structural uncertainties and/or misrepresentations of climate feedbacks in the existing suite of climate model simulations, or underestimations of additional proxy-based SST uncertainties. Our conclusions suggest a new target LIG time period for future model-data comparisons and highlight the need for higher resolution transient climate modeling of the LIG and its dependence on meltwater input to the high latitude oceans during the preceding deglaciation. Few discoveries have stimulated the paleoclimate community more so than Heinrich events. Nevertheless, the cause of Heinrich events, characterized by a large flux of icebergs sourced from the Hudson Strait Ice Stream into the North Atlantic, remains debated. Commonly attributed to internal ice-sheet instability, the occurrence of Heinrich events during the coldest intervals of the last glacial cycle instead suggests an external climate control. We expand on recent studies that have shown that incursions of warm subsurface waters into the intermediate depth North Atlantic Ocean destabilized an ice shelf fronting the Hudson Strait Ice Stream, causing a Heinrich event. We present new surface- and bottom-water stable isotope, trace metal, and sedimentary records from two cores taken along the Labrador margin that further support subsurface warming as a trigger of Hudson Strait Heinrich events. We further relate these changes to other sediment core records from the North Atlantic and transient deglacial climate modeling results to show that subsurface warming was ubiquitous across the intermediate North Atlantic during the early part of the last deglaciation and was most likely caused by a preceding reduction in the Atlantic Meridional Overturning Circulation. Close

• 24. [Article] Data report : composition of clay minerals from hemiplegic sediments at Hydrate Ridge, Cascadia subduction zone

  This report describes the results of semiquantitative analysis of clay mineral composition by X-ray diffraction. The samples consist of hemipelagic mud and mudstone cored from Hydrate Ridge during Leg ...

  Citation × Citation Citation Abstract Copy Title: Data report : composition of clay minerals from hemiplegic sediments at Hydrate Ridge, Cascadia subduction zone Author: Torres, Marta E., Underwood, Michael This report describes the results of semiquantitative analysis of clay mineral composition by X-ray diffraction. The samples consist of hemipelagic mud and mudstone cored from Hydrate Ridge during Leg 204 of the Ocean Drilling Program. We analyzed oriented aggregates of the clay-sized fractions (<2 μm) to estimate relative percentages of smectite, illite, and chlorite (+ kaolinite). For the most part, stratigraphic variations in clay mineral composition are modest and there are no significant differences among the seven sites that were included in the study. On average, early Pleistocene to Holocene trench slope and slope basin deposits contain 29% smectite, 31% illite, and 40% chlorite (+ kaolinite). Late Pliocene to early Pleistocene strata from the underlying accretionary prism contain moderately larger proportions of smectite with average values of 38% smectite, 27% illite, and 35% chlorite (+ kaolinite). There is no evidence of clay mineral diagenesis at the depths sampled. The expandability of smectite is, on average, equal to 64%, and there are no systematic variations in expandability as a function of burial depth or depositional age. The absence of clay mineral diagenesis is consistent with the relatively shallow sample depths and corresponding maximum temperatures of only 24°–33°C. Title: Data report : composition of clay minerals from hemiplegic sediments at Hydrate Ridge, Cascadia subduction zone Author: Torres, Marta E., Underwood, Michael This report describes the results of semiquantitative analysis of clay mineral composition by X-ray diffraction. The samples consist of hemipelagic mud and mudstone cored from Hydrate Ridge during Leg 204 of the Ocean Drilling Program. We analyzed oriented aggregates of the clay-sized fractions (<2 μm) to estimate relative percentages of smectite, illite, and chlorite (+ kaolinite). For the most part, stratigraphic variations in clay mineral composition are modest and there are no significant differences among the seven sites that were included in the study. On average, early Pleistocene to Holocene trench slope and slope basin deposits contain 29% smectite, 31% illite, and 40% chlorite (+ kaolinite). Late Pliocene to early Pleistocene strata from the underlying accretionary prism contain moderately larger proportions of smectite with average values of 38% smectite, 27% illite, and 35% chlorite (+ kaolinite). There is no evidence of clay mineral diagenesis at the depths sampled. The expandability of smectite is, on average, equal to 64%, and there are no systematic variations in expandability as a function of burial depth or depositional age. The absence of clay mineral diagenesis is consistent with the relatively shallow sample depths and corresponding maximum temperatures of only 24°–33°C. Close

• 25. [Article] Geology of Babyshoe Ridge Area, Southern Cascades, Washington

  The thesis area consists of approximately thirty square miles in the Southern Cascades of Washington near Mount Adams. The oldest exposed rocks are sedimentary volcanic clastics and pyroclastic flows of ...

  Citation × Citation Citation Abstract Copy Title: Geology of Babyshoe Ridge Area, Southern Cascades, Washington Author: Harle, David Sig The thesis area consists of approximately thirty square miles in the Southern Cascades of Washington near Mount Adams. The oldest exposed rocks are sedimentary volcanic clastics and pyroclastic flows of late-Oligocene age that form a homocline in the northwest corner of the area. A thick pile of younger Tertiary lavas, mudflows, and volcanic clastics unconformably overlie the Oligocene rocks, and contain two hydrothermally altered zones. Andesitic lavas from Mount Adams lap onto older rocks and are of Recent to Pleistocene age. Two glacial till deposits and two airfall pyroclastic layers are present throughout the area. One major fault and two broad folds are present in the area. The geothermal potential is not believed to be great, because genetic relationships indicate the hydrothermal systems that produced the two alteration zones were active only in pre- Pleistocene time. There are no external manifestations of a presently active hydrothermal system with geothermal potential. Title: Geology of Babyshoe Ridge Area, Southern Cascades, Washington Author: Harle, David Sig The thesis area consists of approximately thirty square miles in the Southern Cascades of Washington near Mount Adams. The oldest exposed rocks are sedimentary volcanic clastics and pyroclastic flows of late-Oligocene age that form a homocline in the northwest corner of the area. A thick pile of younger Tertiary lavas, mudflows, and volcanic clastics unconformably overlie the Oligocene rocks, and contain two hydrothermally altered zones. Andesitic lavas from Mount Adams lap onto older rocks and are of Recent to Pleistocene age. Two glacial till deposits and two airfall pyroclastic layers are present throughout the area. One major fault and two broad folds are present in the area. The geothermal potential is not believed to be great, because genetic relationships indicate the hydrothermal systems that produced the two alteration zones were active only in pre- Pleistocene time. There are no external manifestations of a presently active hydrothermal system with geothermal potential. Close

• 26. [Article] Late Pleistocene lithic technological organization on the southern Oregon coast : investigations at Indian Sands (35-CU-67C)

  Excavations conducted at Indian Sands (35-CU-67C), located along Oregon's southern coast, during 2002 and 2003 identified two discreet, artifact-bearing stratigraphic units. The uppermost unit is a deflated ...

  Citation × Citation Citation Abstract Copy Title: Late Pleistocene lithic technological organization on the southern Oregon coast : investigations at Indian Sands (35-CU-67C) Author: Willis, Samuel C. Excavations conducted at Indian Sands (35-CU-67C), located along Oregon's southern coast, during 2002 and 2003 identified two discreet, artifact-bearing stratigraphic units. The uppermost unit is a deflated surface containing burnt shell and lithic artifacts associated with early Holocene ¹⁴C dates, while the underlying unit contained only lithic tools and debitage, some of which were associated with a ¹⁴C date of 10,430 ± 150 RCYBP. The late Pleistocene lithic assemblage at 35-CU-67C provides the earliest evidence for human presence on the Oregon coast to date. Analysis performed on the late Pleistocene assemblage addresses the validity of existing hypotheses regarding the nature of early Oregon coastal hunter-gatherer technological and subsistence strategies. These hypotheses are focused on whether early populations on the Oregon coast practiced a generalist-forager or collector subsistence strategy. Using theoretical approaches that deal with the organization of hunter-gatherer technology, analyses were conducted on the lithic tool and debitage assemblages at 35-CU- 67C in order to infer past hunter-gatherer behavior. Through the implementation of multiple tool and debitage analysis methodologies, issues of hunter-gatherer mobility, raw material procurement, stages of lithic reduction, tool production, and site function are presented. The data generated by the late Pleistocene lithic assemblage at 35-CU-67C are compared with the overlying surficial assemblage, additional early sites along the North American Pacific coast, and to contemporaneous sites located further inland within the Pacific Northwest region. Results of the lithic analyses at 35-CU-67C show distinct similarities in debitage trends between the assemblages of each stratigraphic unit. However, when tool assemblages from these units are compared, discrepancies in the types and amount of tools are found. Reasons for intra-site variability and similarity are explained through raw material studies and site function at 35-CU-67C. Additionally, similarities between the early tool assemblage at 35-CU-67C and those found in early tool assemblages on the extended Pacific coast and interior Pacific Northwest regions are discussed. This thesis demonstrates that early southern Oregon coastal populations had a tendency towards high mobility and used a generalized toolkit organization. Early lithic technology used at 35-CU-67C emphasized multidirectional core technology and biface manufacture in the form of preforms and leaf-shaped projectile-points. This type of technological organization is to be expected from hunter-gatherers practicing a generalist-forager subsistence strategy. Based on the 10,430 ± 150 RCYBP date and technological organization at 35-CU-67C, early Oregon coastal occupation is seen as encompassing a generalist-forager subsistence strategy most likely adapted to both coastal and terrestrial environments. Title: Late Pleistocene lithic technological organization on the southern Oregon coast : investigations at Indian Sands (35-CU-67C) Author: Willis, Samuel C. Excavations conducted at Indian Sands (35-CU-67C), located along Oregon's southern coast, during 2002 and 2003 identified two discreet, artifact-bearing stratigraphic units. The uppermost unit is a deflated surface containing burnt shell and lithic artifacts associated with early Holocene ¹⁴C dates, while the underlying unit contained only lithic tools and debitage, some of which were associated with a ¹⁴C date of 10,430 ± 150 RCYBP. The late Pleistocene lithic assemblage at 35-CU-67C provides the earliest evidence for human presence on the Oregon coast to date. Analysis performed on the late Pleistocene assemblage addresses the validity of existing hypotheses regarding the nature of early Oregon coastal hunter-gatherer technological and subsistence strategies. These hypotheses are focused on whether early populations on the Oregon coast practiced a generalist-forager or collector subsistence strategy. Using theoretical approaches that deal with the organization of hunter-gatherer technology, analyses were conducted on the lithic tool and debitage assemblages at 35-CU- 67C in order to infer past hunter-gatherer behavior. Through the implementation of multiple tool and debitage analysis methodologies, issues of hunter-gatherer mobility, raw material procurement, stages of lithic reduction, tool production, and site function are presented. The data generated by the late Pleistocene lithic assemblage at 35-CU-67C are compared with the overlying surficial assemblage, additional early sites along the North American Pacific coast, and to contemporaneous sites located further inland within the Pacific Northwest region. Results of the lithic analyses at 35-CU-67C show distinct similarities in debitage trends between the assemblages of each stratigraphic unit. However, when tool assemblages from these units are compared, discrepancies in the types and amount of tools are found. Reasons for intra-site variability and similarity are explained through raw material studies and site function at 35-CU-67C. Additionally, similarities between the early tool assemblage at 35-CU-67C and those found in early tool assemblages on the extended Pacific coast and interior Pacific Northwest regions are discussed. This thesis demonstrates that early southern Oregon coastal populations had a tendency towards high mobility and used a generalized toolkit organization. Early lithic technology used at 35-CU-67C emphasized multidirectional core technology and biface manufacture in the form of preforms and leaf-shaped projectile-points. This type of technological organization is to be expected from hunter-gatherers practicing a generalist-forager subsistence strategy. Based on the 10,430 ± 150 RCYBP date and technological organization at 35-CU-67C, early Oregon coastal occupation is seen as encompassing a generalist-forager subsistence strategy most likely adapted to both coastal and terrestrial environments. Close

• 27. [Article] Millennial-scale surface and deep water oscillations in the N.E. Pacific : implications for late pleistocene climate change

  Citation × Citation Citation Abstract Copy Title: Millennial-scale surface and deep water oscillations in the N.E. Pacific : implications for late pleistocene climate change Author: Lund, David Charles Title: Millennial-scale surface and deep water oscillations in the N.E. Pacific : implications for late pleistocene climate change Author: Lund, David Charles Close

• 28. [Article] Constraints of the origin of the middle Pleistocene transition from the glacial sedimentary record of the north-central United States

  This dissertation focuses on the role of ice sheets in the transition during the middle Pleistocene (-1.2 Ma) from 41-kyr glacial cycles to 100-kyr glacial cycles. This research evaluates the hypothesis ...

  Citation × Citation Citation Abstract Copy Title: Constraints of the origin of the middle Pleistocene transition from the glacial sedimentary record of the north-central United States Author: Roy, Martin This dissertation focuses on the role of ice sheets in the transition during the middle Pleistocene (-1.2 Ma) from 41-kyr glacial cycles to 100-kyr glacial cycles. This research evaluates the hypothesis that the middle Pleistocene transition (MPT) was related to the glacial erosion of a regolith mantle and the subsequent exposure of fresh crystalline bedrock. This issue is addressed through the study of glacial sedimentary sequences in Iowa, Nebraska, Kansas, and Missouri. Testing the hypothesis first required the establishment of a stratigraphic framework for pre-Illinoian glacial sequences. A chronology developed around till compositional data and chronological constraints provided by paleomagnetic measurements on glacigenic sediments, and three volcanic ashes, indicate that the midcontinent tills can be grouped under three categories representing at least seven ice advances: two older groups of reverse-polarity tills containing a low and intermediate proportion of clasts and minerals derived from crystalline bedrock, respectively, and one younger group of normal-polarity tills enriched in crystalline materials. The bulk geochemistry of the silicate fraction of the midcontinent tills was then used to evaluate the character of the rock source eroded by ice sheets. The results show a general trend in which geochemical indices, from oldest to youngest tills, fall parallel to a mixing line defined by the composition of a weathered and fresh crystalline rock sources, respectively. The content in meteoric 10Be of tills also supports the existence of a regolith and its glacial erosion by -1.3 Ma, thus concordant with the onset of the MPT. Marine records of strontium, hafnium, and osmium isotopes provide additional support for the hypothesis. The nature of the till compositional changes was further addressed through a provenance study based on 504 40Ar/39Ar ages measured on individual K-feldspar grains retrieved from tills that span the last 2 Myr. Most samples yielded ages identical to those of numerical ages of the Churchill Province, thereby constraining deposition by ice from the western (Keewatin) sector of the Laurentide ice sheet. These results rule out a change in provenance, and thus show support for a change in the composition of the Churchill bedrock source during the late Cenozoic. Title: Constraints of the origin of the middle Pleistocene transition from the glacial sedimentary record of the north-central United States Author: Roy, Martin This dissertation focuses on the role of ice sheets in the transition during the middle Pleistocene (-1.2 Ma) from 41-kyr glacial cycles to 100-kyr glacial cycles. This research evaluates the hypothesis that the middle Pleistocene transition (MPT) was related to the glacial erosion of a regolith mantle and the subsequent exposure of fresh crystalline bedrock. This issue is addressed through the study of glacial sedimentary sequences in Iowa, Nebraska, Kansas, and Missouri. Testing the hypothesis first required the establishment of a stratigraphic framework for pre-Illinoian glacial sequences. A chronology developed around till compositional data and chronological constraints provided by paleomagnetic measurements on glacigenic sediments, and three volcanic ashes, indicate that the midcontinent tills can be grouped under three categories representing at least seven ice advances: two older groups of reverse-polarity tills containing a low and intermediate proportion of clasts and minerals derived from crystalline bedrock, respectively, and one younger group of normal-polarity tills enriched in crystalline materials. The bulk geochemistry of the silicate fraction of the midcontinent tills was then used to evaluate the character of the rock source eroded by ice sheets. The results show a general trend in which geochemical indices, from oldest to youngest tills, fall parallel to a mixing line defined by the composition of a weathered and fresh crystalline rock sources, respectively. The content in meteoric 10Be of tills also supports the existence of a regolith and its glacial erosion by -1.3 Ma, thus concordant with the onset of the MPT. Marine records of strontium, hafnium, and osmium isotopes provide additional support for the hypothesis. The nature of the till compositional changes was further addressed through a provenance study based on 504 40Ar/39Ar ages measured on individual K-feldspar grains retrieved from tills that span the last 2 Myr. Most samples yielded ages identical to those of numerical ages of the Churchill Province, thereby constraining deposition by ice from the western (Keewatin) sector of the Laurentide ice sheet. These results rule out a change in provenance, and thus show support for a change in the composition of the Churchill bedrock source during the late Cenozoic. Close

• 29. [Article] The case for NE-SW extension in northeast Oregon

  A zone of diffuse deformation -600 km-wide extending from northern California to Washington has developed resulting from the oblique subduction of the Juan de Fuca plate beneath North America, and the ...

  Citation × Citation Citation Abstract Copy Title: The case for NE-SW extension in northeast Oregon Author: Essman, Jim E. A zone of diffuse deformation -600 km-wide extending from northern California to Washington has developed resulting from the oblique subduction of the Juan de Fuca plate beneath North America, and the northwestward migration of the Pacific plate. This zone is marked by a change in structural style from transtension in the southern Oregon and western Nevada to transpression in southern and western Washington. The transition occurs across a relatively inactive zone in northeastern Oregon. New geologic mapping near the northern edge of this transitional zone suggests that extensional deformation persists into northeastern Oregon. The study area on the Oregon-Idaho border, is a complex zone characterized by NNWtrending primarily sinistral-oblique normal faults linking the NW-trending Halfway and Sturgill Peak (both down to the NE) normal faults to the NW and SE, respectively. The Halfway fault, -20 km-long - 730 m dip-slip separation, marks the southern boundary of a half-graben; whereas the Sturgill Peak fault, - 10 to 15 km long and not associated with a half-graben, has a minimum dip-slip separation of - 660 m. In contrast, the transfer zone informally named the Powder River Peninsula Fault Zone, or PRPFZ, houses numerous -NNW-striking, 2 to 3 km-long normal and sinistral-oblique normal faults with dip-slip separations of < 130 m. Evidence of late Pleistocene-Holocene deformation within the transfer zone is found in at least four places, and at two of those involves sinistral-oblique normal faults (-10-15 m vertical separation on a bedrock scarp) cutting late Pleistocene Bonneville flood gravels, -14 ka, with flood gravels both entrained in the fault plane and interbedded with Holocene colluvium implying significant activity in the late Pleistocene and possibly the early Holocene. Additionally, one fault in the PRPFZ cuts Holocene (?) soils/clays and deforms Pleistocene ash beds. Slip rates calculated from slickenlines and separations in the PRPFZ range from 0.01 mm/yr to possibly as high as 2.8 mm/yr to. This detailed slip data for the PRPFZ can be used as a proxy for the more regional deformational styles. Although the Halfway and Sturgill Peak faults have been interpreted to represent the southeastern extension of the Olympic-Wallowa Lineament (OWL), the tectonic and structural significance of the OWL remains poorly understood. It is suggested here that these structures reflect the continuation of Basinand-Range style deformation into northeastern Oregon, and western Idaho, and any connection to the OWL to be circumstantial. Furthermore, the presence of these structures poses a potential seismic hazard to local hydroelectric facilities. Title: The case for NE-SW extension in northeast Oregon Author: Essman, Jim E. A zone of diffuse deformation -600 km-wide extending from northern California to Washington has developed resulting from the oblique subduction of the Juan de Fuca plate beneath North America, and the northwestward migration of the Pacific plate. This zone is marked by a change in structural style from transtension in the southern Oregon and western Nevada to transpression in southern and western Washington. The transition occurs across a relatively inactive zone in northeastern Oregon. New geologic mapping near the northern edge of this transitional zone suggests that extensional deformation persists into northeastern Oregon. The study area on the Oregon-Idaho border, is a complex zone characterized by NNWtrending primarily sinistral-oblique normal faults linking the NW-trending Halfway and Sturgill Peak (both down to the NE) normal faults to the NW and SE, respectively. The Halfway fault, -20 km-long - 730 m dip-slip separation, marks the southern boundary of a half-graben; whereas the Sturgill Peak fault, - 10 to 15 km long and not associated with a half-graben, has a minimum dip-slip separation of - 660 m. In contrast, the transfer zone informally named the Powder River Peninsula Fault Zone, or PRPFZ, houses numerous -NNW-striking, 2 to 3 km-long normal and sinistral-oblique normal faults with dip-slip separations of < 130 m. Evidence of late Pleistocene-Holocene deformation within the transfer zone is found in at least four places, and at two of those involves sinistral-oblique normal faults (-10-15 m vertical separation on a bedrock scarp) cutting late Pleistocene Bonneville flood gravels, -14 ka, with flood gravels both entrained in the fault plane and interbedded with Holocene colluvium implying significant activity in the late Pleistocene and possibly the early Holocene. Additionally, one fault in the PRPFZ cuts Holocene (?) soils/clays and deforms Pleistocene ash beds. Slip rates calculated from slickenlines and separations in the PRPFZ range from 0.01 mm/yr to possibly as high as 2.8 mm/yr to. This detailed slip data for the PRPFZ can be used as a proxy for the more regional deformational styles. Although the Halfway and Sturgill Peak faults have been interpreted to represent the southeastern extension of the Olympic-Wallowa Lineament (OWL), the tectonic and structural significance of the OWL remains poorly understood. It is suggested here that these structures reflect the continuation of Basinand-Range style deformation into northeastern Oregon, and western Idaho, and any connection to the OWL to be circumstantial. Furthermore, the presence of these structures poses a potential seismic hazard to local hydroelectric facilities. Close

• 30. [Article] Soil solution chemistry, profile development, and mineral authigenesis in several western Oregon soils

  Clay mineral genesis was studied in soils representative of several different geomorphic surfaces in western Oregon, ranging in age from Pliocene-early Pleistocene to late Pleistocene. Soil solution studies, clay ...

  Citation × Citation Citation Abstract Copy Title: Soil solution chemistry, profile development, and mineral authigenesis in several western Oregon soils Author: Glasmann, Joseph Reed Clay mineral genesis was studied in soils representative of several different geomorphic surfaces in western Oregon, ranging in age from Pliocene-early Pleistocene to late Pleistocene. Soil solution studies, clay mineralogy, and soil raicromorphology were employed to provide evidence of clay mineral synthesis and interpret soil genesis. Soils at each study area were characterized by distinct differences in soil solution chemistry, clay mineralogy, plasmic fabric, and genetic history, although parent material compositions between sites were often similar. Soil solution studies suggested that clay mineral synthesis from solution does not occur in soils representing the oldest geomorphic surface. The cxic soil properties at this location were developed during a prior weathering cycle and the soils are at a genetic endpoint in the present environment. Soil solutions from Ultisols on remnants of Pleistocene surfaces in the Oregon Coast Range were in equilibrium with respect to kaolinite in the solum, but stable with respect to Mg-montmorillonite in the zone characterizing active bedrock weathering. Microraorphological, clay mineralogical, and chemical evidence suggested that alteration of Mgchlorite in sedimentary rocks leads to smectite genesis in the Cr horizon of the Ultisols, followed by conversion of smectite to halloysite and chloritic intergrade in the solum. Alteration of basalt in these soils also leads to the formation of smectite, which is unstable with respect to halloysite in well-drained microenvironments within soil profiles. Soil solutions from soils characteristic of silt-mantled late Pleistocene surfaces on the western margins of the Willamette Valley showed compositional variation from pedon to pedon and horizon to horizon within individual pedons, reflecting the influence of soil parent material compositional variation. Soil solutions were generally in equilibrium with respect to kaolinite, although solutions from horizons developed in tuffaceous sediments were in equilibrium with Mg-montmorillonite. Both kaolinite and smectite were observed as products of mineral authigenesis in these soils. Authigenic clay showed delicate honeycomb or hexagonal morphology in contrast to the parallel oriented appearance of illuvial clays. Andesite alteration in wet, unstable soils of Oregon's western Cascades also resulted in the formation of smectite. The sequence of mineral alteration in andesites is similar to that described for basalts; however, the final products of mineral authigenesis are distinctly microenvironment dependent. Morphologic evidence suggests that chemical properties of bulk soil solutions can not always be considered to represent the solution conditions at the site of mineral authigenesis. In the absence of reliable in situ micro-chemical analytical techniques, detailed micromorphological studies can aid'in interpreting soil microchemical properties at weathering surfaces by revealing the identity of neoformed secondary phases. Title: Soil solution chemistry, profile development, and mineral authigenesis in several western Oregon soils Author: Glasmann, Joseph Reed Clay mineral genesis was studied in soils representative of several different geomorphic surfaces in western Oregon, ranging in age from Pliocene-early Pleistocene to late Pleistocene. Soil solution studies, clay mineralogy, and soil raicromorphology were employed to provide evidence of clay mineral synthesis and interpret soil genesis. Soils at each study area were characterized by distinct differences in soil solution chemistry, clay mineralogy, plasmic fabric, and genetic history, although parent material compositions between sites were often similar. Soil solution studies suggested that clay mineral synthesis from solution does not occur in soils representing the oldest geomorphic surface. The cxic soil properties at this location were developed during a prior weathering cycle and the soils are at a genetic endpoint in the present environment. Soil solutions from Ultisols on remnants of Pleistocene surfaces in the Oregon Coast Range were in equilibrium with respect to kaolinite in the solum, but stable with respect to Mg-montmorillonite in the zone characterizing active bedrock weathering. Microraorphological, clay mineralogical, and chemical evidence suggested that alteration of Mgchlorite in sedimentary rocks leads to smectite genesis in the Cr horizon of the Ultisols, followed by conversion of smectite to halloysite and chloritic intergrade in the solum. Alteration of basalt in these soils also leads to the formation of smectite, which is unstable with respect to halloysite in well-drained microenvironments within soil profiles. Soil solutions from soils characteristic of silt-mantled late Pleistocene surfaces on the western margins of the Willamette Valley showed compositional variation from pedon to pedon and horizon to horizon within individual pedons, reflecting the influence of soil parent material compositional variation. Soil solutions were generally in equilibrium with respect to kaolinite, although solutions from horizons developed in tuffaceous sediments were in equilibrium with Mg-montmorillonite. Both kaolinite and smectite were observed as products of mineral authigenesis in these soils. Authigenic clay showed delicate honeycomb or hexagonal morphology in contrast to the parallel oriented appearance of illuvial clays. Andesite alteration in wet, unstable soils of Oregon's western Cascades also resulted in the formation of smectite. The sequence of mineral alteration in andesites is similar to that described for basalts; however, the final products of mineral authigenesis are distinctly microenvironment dependent. Morphologic evidence suggests that chemical properties of bulk soil solutions can not always be considered to represent the solution conditions at the site of mineral authigenesis. In the absence of reliable in situ micro-chemical analytical techniques, detailed micromorphological studies can aid'in interpreting soil microchemical properties at weathering surfaces by revealing the identity of neoformed secondary phases. Close

• 31. [Article] Late Cenozoic Climate, Ice-sheet and Earth-surface Evolution Derived from Terrestrial and Marine Sedimentary Archives

  The goals of this dissertation are centered on understanding changes in Earth surface and climate systems through the use of geologic proxies as records of past changes in these systems. Specifically, ...

  Citation × Citation Citation Abstract Copy Title: Late Cenozoic Climate, Ice-sheet and Earth-surface Evolution Derived from Terrestrial and Marine Sedimentary Archives Author: Bill, Nicholas S. The goals of this dissertation are centered on understanding changes in Earth surface and climate systems through the use of geologic proxies as records of past changes in these systems. Specifically, this dissertation (1) establishes a new chronology for retreat of the Ross Sea sector of the West Antarctic Ice during the last deglaciation, (2) investigates the changes in the global climate system during the mid- Pleistocene transition, and (3) constrains the timing of surface uplift in Alaska, and the control that topography has on regional climate and the hydrologic cycle over the tectonic timescale. This dissertation establishes the timing of the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet (WAIS), addressing the question of whether grounded ice in the Ross Embayment deglaciated entirely in the Holocene or earlier. ¹⁰Be surface exposure dating of granitic glacial erratic boulders indicates that the onset of sustained retreat from the local Last Glacial Maximum started at 18.6 ± 1.1 ka, and that sustained retreat occurred into the middle Holocene. We attribute most of this retreat to temperature and radiative forcing of the ablation zone in McMurdo Sound with only the final stages of retreat possibly influenced by Holocene grounding line retreat. The mid-Pleistocene transition (MPT) represents a transition from predominantly 40-kyr climate cycles to predominantly 100-kyr cycles in the absence of any change in orbital forcing. Here I combine all existing records of SST (n=7) and δ¹³C (n=17) that span the entirety of the last 2 Ma and use principal component analysis to detect the shared global signal of these records across the MPT. I also develop stacks of ice volume, ocean basin-scale δ¹³C gradients and CO₂ reconstructions in an attempt to characterize the interaction between deep ocean circulation and climate change across the MPT. I find that the characteristic change in cyclicity of the MPT appears in SST, δ¹³C and ice-volume reconstructions. I interpret marine isotope stage (MIS) 23 (~900 ka) as a skipped interglacial that led to MIS 25- 21 as being the first 100-kyr period, potentially initiating the 100-kyr cycle during the rest of the Pleistocene. I also find that the largest global negative δ¹³C excursion in the Pleistocene occurred during the glacial periods MIS 24 and MIS 22. This excursion is likely related to a mean shift to a reduced glacial-period AMOC across the MPT that is observed in multiple AMOC strength reconstructions, and that I interpret as a key component of the MPT. The topography of southern Alaska has been shown to have likely experienced rapid exhumation during the early Pliocene stating ~5-6 Ma. Using δD measurements on OH- groups of clay minerals, I constrain the change in isotopic composition of paleo-meteoric water from the Miocene-Holocene in the interior of Alaska as a proxy for the surface uplift history of Alaskan topography via its control on the δD signal of surface water. My results suggest that there was rapid surface uplift of the several mountain ranges encompassing southern Alaska during the period from ~6.5-3 Ma. Title: Late Cenozoic Climate, Ice-sheet and Earth-surface Evolution Derived from Terrestrial and Marine Sedimentary Archives Author: Bill, Nicholas S. The goals of this dissertation are centered on understanding changes in Earth surface and climate systems through the use of geologic proxies as records of past changes in these systems. Specifically, this dissertation (1) establishes a new chronology for retreat of the Ross Sea sector of the West Antarctic Ice during the last deglaciation, (2) investigates the changes in the global climate system during the mid- Pleistocene transition, and (3) constrains the timing of surface uplift in Alaska, and the control that topography has on regional climate and the hydrologic cycle over the tectonic timescale. This dissertation establishes the timing of the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet (WAIS), addressing the question of whether grounded ice in the Ross Embayment deglaciated entirely in the Holocene or earlier. ¹⁰Be surface exposure dating of granitic glacial erratic boulders indicates that the onset of sustained retreat from the local Last Glacial Maximum started at 18.6 ± 1.1 ka, and that sustained retreat occurred into the middle Holocene. We attribute most of this retreat to temperature and radiative forcing of the ablation zone in McMurdo Sound with only the final stages of retreat possibly influenced by Holocene grounding line retreat. The mid-Pleistocene transition (MPT) represents a transition from predominantly 40-kyr climate cycles to predominantly 100-kyr cycles in the absence of any change in orbital forcing. Here I combine all existing records of SST (n=7) and δ¹³C (n=17) that span the entirety of the last 2 Ma and use principal component analysis to detect the shared global signal of these records across the MPT. I also develop stacks of ice volume, ocean basin-scale δ¹³C gradients and CO₂ reconstructions in an attempt to characterize the interaction between deep ocean circulation and climate change across the MPT. I find that the characteristic change in cyclicity of the MPT appears in SST, δ¹³C and ice-volume reconstructions. I interpret marine isotope stage (MIS) 23 (~900 ka) as a skipped interglacial that led to MIS 25- 21 as being the first 100-kyr period, potentially initiating the 100-kyr cycle during the rest of the Pleistocene. I also find that the largest global negative δ¹³C excursion in the Pleistocene occurred during the glacial periods MIS 24 and MIS 22. This excursion is likely related to a mean shift to a reduced glacial-period AMOC across the MPT that is observed in multiple AMOC strength reconstructions, and that I interpret as a key component of the MPT. The topography of southern Alaska has been shown to have likely experienced rapid exhumation during the early Pliocene stating ~5-6 Ma. Using δD measurements on OH- groups of clay minerals, I constrain the change in isotopic composition of paleo-meteoric water from the Miocene-Holocene in the interior of Alaska as a proxy for the surface uplift history of Alaskan topography via its control on the δD signal of surface water. My results suggest that there was rapid surface uplift of the several mountain ranges encompassing southern Alaska during the period from ~6.5-3 Ma. Close

• 32. [Article] Late Pleistocene and Holocene glacier and climate change

  This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical ...

  Citation × Citation Citation Abstract Copy Title: Late Pleistocene and Holocene glacier and climate change Author: Marcott, Shaun Andrew This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that have not been applied to the problem thus far. A longstanding question in glaciology is the nature and mechanism of the so- called "Heinrich events" of the last ~60 ka. These massive iceberg discharge events into the North Atlantic from the partial breakup of the Laurentide Ice Sheet are identified from distinct ice rafted debris and detrital carbonate layers in marine sediment cores. The mechanism associated with the initiation of these events is commonly thought to be related to internal ice sheet instabilities. However, Heinrich events consistently occur following a long cooling trend that culminates in an extreme cold event, thus suggesting a possible triggering mechanism by climate. Recent modeling work has proposed an oceanic mechanism associated with ocean warming, but no physical evidence has been made available to date. To test this ocean-warming hypothesis, we measured temperature sensitive trace metals and stable isotopes in benthic foraminifera from a sediment core collected in the western North Atlantic that spans the last six Heinrich events and compared our results to climate model simulations using CCSM3. Our results show subsurface warming occurred prior to or coeval with nearly all of the Heinrich events of the last ~60 ka, thus implicating subsurface ocean warming as the main trigger of these rapid breakups of the Laurentide Ice Sheet. In the field of glacial geology a longstanding question has been the timing of alpine glacial advances during the Holocene. A number of studies have interpreted several Holocene glacial advances in western North America, but age control is based largely on relative dating techniques, which have been shown to be in error by up to 10,000 yrs in some cases. Based on 124 ¹⁰Be surface exposure ages from twenty cirque moraines in ten mountain ranges across western North America, glacier were retreating from moraine positions during the latest Pleistocene or earliest Holocene and not throughout the Holocene epoch as previously assumed, thus requiring a refined interpretation of Holocene glacial activity in western North America and the associated climate forcing. In the field of paleoclimatology a question regarding how global temperature varied over the entirety of the Holocene epoch has remained to be answered for some time. While many temperature reconstructions exist for the last 2000 years, a full Holocene temperature stack does not exist, despite its potential utility of putting modern climate change into a full interglacial perspective. Based on a global composite of 73 proxy based temperature record, a Holocene temperature stack was constructed and used to demonstrate that a general cooling of ~1°C has occurred from the early to mid Holocene and that centennial and millennial scale variability is modest. We account for both temperature calibration and chronologic uncertainties using a Monte Carlo based approach. Our results are consistent with prior reconstructions of the last 2000 years and now allow for a full Holocene temperature perspective for evaluation with present and future climate change. Title: Late Pleistocene and Holocene glacier and climate change Author: Marcott, Shaun Andrew This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that have not been applied to the problem thus far. A longstanding question in glaciology is the nature and mechanism of the so- called "Heinrich events" of the last ~60 ka. These massive iceberg discharge events into the North Atlantic from the partial breakup of the Laurentide Ice Sheet are identified from distinct ice rafted debris and detrital carbonate layers in marine sediment cores. The mechanism associated with the initiation of these events is commonly thought to be related to internal ice sheet instabilities. However, Heinrich events consistently occur following a long cooling trend that culminates in an extreme cold event, thus suggesting a possible triggering mechanism by climate. Recent modeling work has proposed an oceanic mechanism associated with ocean warming, but no physical evidence has been made available to date. To test this ocean-warming hypothesis, we measured temperature sensitive trace metals and stable isotopes in benthic foraminifera from a sediment core collected in the western North Atlantic that spans the last six Heinrich events and compared our results to climate model simulations using CCSM3. Our results show subsurface warming occurred prior to or coeval with nearly all of the Heinrich events of the last ~60 ka, thus implicating subsurface ocean warming as the main trigger of these rapid breakups of the Laurentide Ice Sheet. In the field of glacial geology a longstanding question has been the timing of alpine glacial advances during the Holocene. A number of studies have interpreted several Holocene glacial advances in western North America, but age control is based largely on relative dating techniques, which have been shown to be in error by up to 10,000 yrs in some cases. Based on 124 ¹⁰Be surface exposure ages from twenty cirque moraines in ten mountain ranges across western North America, glacier were retreating from moraine positions during the latest Pleistocene or earliest Holocene and not throughout the Holocene epoch as previously assumed, thus requiring a refined interpretation of Holocene glacial activity in western North America and the associated climate forcing. In the field of paleoclimatology a question regarding how global temperature varied over the entirety of the Holocene epoch has remained to be answered for some time. While many temperature reconstructions exist for the last 2000 years, a full Holocene temperature stack does not exist, despite its potential utility of putting modern climate change into a full interglacial perspective. Based on a global composite of 73 proxy based temperature record, a Holocene temperature stack was constructed and used to demonstrate that a general cooling of ~1°C has occurred from the early to mid Holocene and that centennial and millennial scale variability is modest. We account for both temperature calibration and chronologic uncertainties using a Monte Carlo based approach. Our results are consistent with prior reconstructions of the last 2000 years and now allow for a full Holocene temperature perspective for evaluation with present and future climate change. Close

• 33. [Article] The Ore bin ; Vol. 28 No. 11 (November 1966)

  Introduction -- Stratigraphy -- Pre-Tertiary rocks -- Umpqua Formation -- Tyee Formation -- Pre-Coaledo - Post-Tyee beds -- Coaledo Formation -- Bastendorff Formation -- Tunnel Point Formation -- Miocene ...

  Citation × Citation Citation Abstract Copy Title: The Ore bin ; Vol. 28 No. 11 (November 1966) Author: Oregon. Dept. of Geology and Mineral Industries, Baldwin, Ewart Merlin, 1915- Introduction -- Stratigraphy -- Pre-Tertiary rocks -- Umpqua Formation -- Tyee Formation -- Pre-Coaledo - Post-Tyee beds -- Coaledo Formation -- Bastendorff Formation -- Tunnel Point Formation -- Miocene beds -- Empire Formation -- Coquille Formation -- Pleistocene terraces -- Structural geology -- Faulting -- Folding and warping -- Bibliography. Title: The Ore bin ; Vol. 28 No. 11 (November 1966) Author: Oregon. Dept. of Geology and Mineral Industries, Baldwin, Ewart Merlin, 1915- Introduction -- Stratigraphy -- Pre-Tertiary rocks -- Umpqua Formation -- Tyee Formation -- Pre-Coaledo - Post-Tyee beds -- Coaledo Formation -- Bastendorff Formation -- Tunnel Point Formation -- Miocene beds -- Empire Formation -- Coquille Formation -- Pleistocene terraces -- Structural geology -- Faulting -- Folding and warping -- Bibliography. Close

• 34. [Article] Surface and subsurface geology of the Santa Barbara-Goleta metropolitan area, Santa Barbara County, California

  The Santa Barbara-Montecito and Goleta basins are structurally continuous fault-controlled Pleistocene basins containing up to 3000 feet (925 m) of marine Pleistocene Santa Barbara Formation which were ...

  Citation × Citation Citation Abstract Copy Title: Surface and subsurface geology of the Santa Barbara-Goleta metropolitan area, Santa Barbara County, California Author: Olson, Daniel J. The Santa Barbara-Montecito and Goleta basins are structurally continuous fault-controlled Pleistocene basins containing up to 3000 feet (925 m) of marine Pleistocene Santa Barbara Formation which were deposited on previously deformed Sisquoc and older strata. Structures subcropping against the unconformity at the base of the Santa Barbara Formation show that pre-basin deformation was mainly by folding. In addition, high-angle reverse faulting occurred along the Cameros, Goleta, and Modoc faults prior to Santa Barbara deposition in the Goleta basin. These are the oldest faults in the study area. Deposition of the Santa Barbara Formation began less than 1.2 Ma ago. Post-Santa Barbara (post-basin) deformation includes disharmonic folding of incompetent Miocene strata above broad folds in competent Oligocene strata, as displayed in the Elwood oil field and La Goleta gas field, and reverse faulting along several south-dipping faults of large displacement. The More Ranch fault, which juxtaposes Sisquoc and older strata against the Santa Barbara and Pico(?) Formations, displaces a 40,000 year old marine terrace, forms a north-facing eroded fault scarp, and marks the southern edge of the Goleta basin. The fault dips more than 80° south and displays up to a maximum of 2000 feet (610 m) vertical separation. The fault in the area with the largest amount of vertical separation, is the Coal Oil Point fault of post-Sisquoc age. This fault fails to reach the surface even though vertical separation of the Oligocene Vaqueros Formation is as great as 5400 feet (1650 m). Comparison with other faults in the area suggests that this fault belongs to the set of south-dipping, east-trending, Quaternary reverse faults that are characteristic of the coastal basins adjacent to the central Santa Ynez Mountains. All post-basin faults disrupt late Pleistocene strata and are potentially active. Other post-basin faults include the Mesa fault, which may link the More Ranch and Rincon Creek faults, the Lavigia fault which cuts older alluvium, and the San Jose fault which forms a north-facing scarp in late-Pleistocene fanglomerate. Distribution of aftershocks and focal mechanism solutions of the 1978 Santa Barbara earthquake suggest a gently north-dipping fault plane which would be unrelated to any of the faults exposed at the surface in the study area. However, the linear pattern of aftershock epicenters is parallel to the Mesa and Mission Ridge- Arroyo Parida faults; if the alternate south-dipping nodal plane is the correct solution then the earthquake could have originated on a member of the south-dipping fault set. Title: Surface and subsurface geology of the Santa Barbara-Goleta metropolitan area, Santa Barbara County, California Author: Olson, Daniel J. The Santa Barbara-Montecito and Goleta basins are structurally continuous fault-controlled Pleistocene basins containing up to 3000 feet (925 m) of marine Pleistocene Santa Barbara Formation which were deposited on previously deformed Sisquoc and older strata. Structures subcropping against the unconformity at the base of the Santa Barbara Formation show that pre-basin deformation was mainly by folding. In addition, high-angle reverse faulting occurred along the Cameros, Goleta, and Modoc faults prior to Santa Barbara deposition in the Goleta basin. These are the oldest faults in the study area. Deposition of the Santa Barbara Formation began less than 1.2 Ma ago. Post-Santa Barbara (post-basin) deformation includes disharmonic folding of incompetent Miocene strata above broad folds in competent Oligocene strata, as displayed in the Elwood oil field and La Goleta gas field, and reverse faulting along several south-dipping faults of large displacement. The More Ranch fault, which juxtaposes Sisquoc and older strata against the Santa Barbara and Pico(?) Formations, displaces a 40,000 year old marine terrace, forms a north-facing eroded fault scarp, and marks the southern edge of the Goleta basin. The fault dips more than 80° south and displays up to a maximum of 2000 feet (610 m) vertical separation. The fault in the area with the largest amount of vertical separation, is the Coal Oil Point fault of post-Sisquoc age. This fault fails to reach the surface even though vertical separation of the Oligocene Vaqueros Formation is as great as 5400 feet (1650 m). Comparison with other faults in the area suggests that this fault belongs to the set of south-dipping, east-trending, Quaternary reverse faults that are characteristic of the coastal basins adjacent to the central Santa Ynez Mountains. All post-basin faults disrupt late Pleistocene strata and are potentially active. Other post-basin faults include the Mesa fault, which may link the More Ranch and Rincon Creek faults, the Lavigia fault which cuts older alluvium, and the San Jose fault which forms a north-facing scarp in late-Pleistocene fanglomerate. Distribution of aftershocks and focal mechanism solutions of the 1978 Santa Barbara earthquake suggest a gently north-dipping fault plane which would be unrelated to any of the faults exposed at the surface in the study area. However, the linear pattern of aftershock epicenters is parallel to the Mesa and Mission Ridge- Arroyo Parida faults; if the alternate south-dipping nodal plane is the correct solution then the earthquake could have originated on a member of the south-dipping fault set. Close

• 35. [Article] Tectonic controls for transverse drainage and timing of the Xin-Ding paleolake breach in the upper reach of the Hutuo River, North China

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geomorphology/.

  Citation × Citation Citation Abstract Copy Title: Tectonic controls for transverse drainage and timing of the Xin-Ding paleolake breach in the upper reach of the Hutuo River, North China Author: Zhang, Shimin, Yeats, Robert S., Ren, Junjie, Meigs, Andrew J., Shen, Xiaoming, Ding, Rui This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geomorphology/. Title: Tectonic controls for transverse drainage and timing of the Xin-Ding paleolake breach in the upper reach of the Hutuo River, North China Author: Zhang, Shimin, Yeats, Robert S., Ren, Junjie, Meigs, Andrew J., Shen, Xiaoming, Ding, Rui This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geomorphology/. Close

• 36. [Article] Biogenic and terrigenous sedimetations at Ceara rise, western tropical Altantic, supports Pliocene - Pleistocene deep - water linkage between hemispheres

  Calcium carbonate percentages at five Ceara Rise sites were estimated at 1- to 2-k.y. intervals over the past 5 m.y., using reflectance spectroscopy and magnetic susceptibility proxies. From these estimates ...

  Citation × Citation Citation Abstract Copy Title: Biogenic and terrigenous sedimetations at Ceara rise, western tropical Altantic, supports Pliocene - Pleistocene deep - water linkage between hemispheres Author: Harris, Sara E., King, Terri, Mix, Alan C. Calcium carbonate percentages at five Ceara Rise sites were estimated at 1- to 2-k.y. intervals over the past 5 m.y., using reflectance spectroscopy and magnetic susceptibility proxies. From these estimates and detailed correlations between sites, gradients of calcite and terrigenous sediment accumulation rates in a depth transect of sites reveal variations in local climate and calcite dissolution related to deep-water masses. Relative to shallow sites on the southern Ceara Rise, accumulation rates of terrigenous sediments at deeper sites near the Amazon Fan were higher during glacial periods. Analogous variations in terrigenous sedimentation before the expansion of Northern Hemisphere ice sheets ~3 m.y. ago suggests that tropical climate cycles occurred independently of polar glaciation. Decreasing accumulation rates of calcite with increasing water depth reveal patterns of carbonate dissolution, which varied on orbital time-scales (10- 100 k.y. periods) throughout the Pliocene-Pleistocene. Maximum dissolution at deep relative to shallow sites occurred in the transition from interglacial to glacial conditions, and maximum preservation occurred during global warming, at all orbital periods. If the local dissolution gradient is linked to relative contributions of North Atlantic Deep Water and Antarctic Bottom Water, this phasing of events confirms a key prediction of SPECMAP that deep-water adjustments may translate climate changes between hemispheres. Dissolution and preservation events, however, may also reflect a transient response to a net flux of organic matter between the continents and the oceans during ice-age climate transitions. Title: Biogenic and terrigenous sedimetations at Ceara rise, western tropical Altantic, supports Pliocene - Pleistocene deep - water linkage between hemispheres Author: Harris, Sara E., King, Terri, Mix, Alan C. Calcium carbonate percentages at five Ceara Rise sites were estimated at 1- to 2-k.y. intervals over the past 5 m.y., using reflectance spectroscopy and magnetic susceptibility proxies. From these estimates and detailed correlations between sites, gradients of calcite and terrigenous sediment accumulation rates in a depth transect of sites reveal variations in local climate and calcite dissolution related to deep-water masses. Relative to shallow sites on the southern Ceara Rise, accumulation rates of terrigenous sediments at deeper sites near the Amazon Fan were higher during glacial periods. Analogous variations in terrigenous sedimentation before the expansion of Northern Hemisphere ice sheets ~3 m.y. ago suggests that tropical climate cycles occurred independently of polar glaciation. Decreasing accumulation rates of calcite with increasing water depth reveal patterns of carbonate dissolution, which varied on orbital time-scales (10- 100 k.y. periods) throughout the Pliocene-Pleistocene. Maximum dissolution at deep relative to shallow sites occurred in the transition from interglacial to glacial conditions, and maximum preservation occurred during global warming, at all orbital periods. If the local dissolution gradient is linked to relative contributions of North Atlantic Deep Water and Antarctic Bottom Water, this phasing of events confirms a key prediction of SPECMAP that deep-water adjustments may translate climate changes between hemispheres. Dissolution and preservation events, however, may also reflect a transient response to a net flux of organic matter between the continents and the oceans during ice-age climate transitions. Close

• 37. [Article] Oblique strike-slip faulting of the central Cascadia submarine forearc

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Oblique strike-slip faulting of the central Cascadia submarine forearc Author: Yeats, Robert S., Goldfinger, Chris, Hummon, Cheryl, McNeill, Lisa, Kulm, LaVerne D. Copyrighted by American Geophysical Union. Title: Oblique strike-slip faulting of the central Cascadia submarine forearc Author: Yeats, Robert S., Goldfinger, Chris, Hummon, Cheryl, McNeill, Lisa, Kulm, LaVerne D. Copyrighted by American Geophysical Union. Close

• 38. [Article] Garwood Valley, Antarctica: A new record of Last Glacial Maximum to Holocene glaciofluvial processes in the McMurdo Dry Valleys

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Geological ...

  Citation × Citation Citation Abstract Copy Title: Garwood Valley, Antarctica: A new record of Last Glacial Maximum to Holocene glaciofluvial processes in the McMurdo Dry Valleys Author: Fountain, Andrew G., Welch, Kathy A., Lyons, W. Berry, O'Connor, Jim E., Levy, Joseph S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Geological Society of America and can be found at: http://gsabulletin.gsapubs.org/. Title: Garwood Valley, Antarctica: A new record of Last Glacial Maximum to Holocene glaciofluvial processes in the McMurdo Dry Valleys Author: Fountain, Andrew G., Welch, Kathy A., Lyons, W. Berry, O'Connor, Jim E., Levy, Joseph S. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Geological Society of America and can be found at: http://gsabulletin.gsapubs.org/. Close

• 39. [Article] Paleomagnetic inclination shallowing in deep-sea sediments

  In this thesis anomalous downcore shallowing of paleomagnetic inclinations is interpreted to be caused by sediment compaction. Thus, compaction-induced inclination shallowing may influence tectonic reconstructions ...

  Citation × Citation Citation Abstract Copy Title: Paleomagnetic inclination shallowing in deep-sea sediments Author: Arason, Pórdur In this thesis anomalous downcore shallowing of paleomagnetic inclinations is interpreted to be caused by sediment compaction. Thus, compaction-induced inclination shallowing may influence tectonic reconstructions that are based on inclinations from deep-sea sediment cores. Progressive downcore shallowing of the remanent inclination was observed in a 120-m section of Plio- Pleistocene sediments at Deep Sea Drilling Project (DSDP) site 578 in the northwest Pacific. Near the top of the section the average inclination corresponds to the expected geocentric axial dipole value of 53° but shallows downcore by about 6° to 8°. In sediments spanning the same time interval of neighboring site 576, no inclination shallowing was observed. This second site has considerably lower sedimentation rates, and the Plio- Pleistocene is represented by a 26-m sedimentary section. The inclination shallowing at site 578 was correlated to a downhole decrease in porosity, and these results are interpreted to suggest that both the downhole inclination shallowing and decrease of porosity in site 578 were caused by sediment compaction. Microscopic models demonstrate that sediment compaction may lead to inclination shallowing of the magnetic remanence. Furthermore, it is shown that inherent initial within-sample dispersion of the magnetic moments will transform any form of microscopic mechanism to an equation of a standardized form: tan (I-ΔI) = (1-a ΔV) tan I, where I is the inclination of the ambient field, ΔI is the inclination shallowing, a is a constant and ΔV the compaction. Paleomagnetic inclinations of Cretaceous DSDP sediments from the Pacific plate are known to be systematically shallower than predicted from paleolatitudes of hot spot reconstructions. Published paleomagnetic data were reexamined and the shallow Cretaceous inclinations explained as a result of sediment compaction. The Cretaceous data are used to estimate the parameter a. The resulting a values are comparable to those of previous studies of compaction-induced inclination shallowing, both from laboratory experiments and the considerably younger deep-sea sediments at site 578. Values of the parameter a suggest that it might be controlled by sediment lithology with greater shallowing for clayey than calcareous sediments. Title: Paleomagnetic inclination shallowing in deep-sea sediments Author: Arason, Pórdur In this thesis anomalous downcore shallowing of paleomagnetic inclinations is interpreted to be caused by sediment compaction. Thus, compaction-induced inclination shallowing may influence tectonic reconstructions that are based on inclinations from deep-sea sediment cores. Progressive downcore shallowing of the remanent inclination was observed in a 120-m section of Plio- Pleistocene sediments at Deep Sea Drilling Project (DSDP) site 578 in the northwest Pacific. Near the top of the section the average inclination corresponds to the expected geocentric axial dipole value of 53° but shallows downcore by about 6° to 8°. In sediments spanning the same time interval of neighboring site 576, no inclination shallowing was observed. This second site has considerably lower sedimentation rates, and the Plio- Pleistocene is represented by a 26-m sedimentary section. The inclination shallowing at site 578 was correlated to a downhole decrease in porosity, and these results are interpreted to suggest that both the downhole inclination shallowing and decrease of porosity in site 578 were caused by sediment compaction. Microscopic models demonstrate that sediment compaction may lead to inclination shallowing of the magnetic remanence. Furthermore, it is shown that inherent initial within-sample dispersion of the magnetic moments will transform any form of microscopic mechanism to an equation of a standardized form: tan (I-ΔI) = (1-a ΔV) tan I, where I is the inclination of the ambient field, ΔI is the inclination shallowing, a is a constant and ΔV the compaction. Paleomagnetic inclinations of Cretaceous DSDP sediments from the Pacific plate are known to be systematically shallower than predicted from paleolatitudes of hot spot reconstructions. Published paleomagnetic data were reexamined and the shallow Cretaceous inclinations explained as a result of sediment compaction. The Cretaceous data are used to estimate the parameter a. The resulting a values are comparable to those of previous studies of compaction-induced inclination shallowing, both from laboratory experiments and the considerably younger deep-sea sediments at site 578. Values of the parameter a suggest that it might be controlled by sediment lithology with greater shallowing for clayey than calcareous sediments. Close

• 40. [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

• 41. [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

• 42. [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

• 43. [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

• 44. [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

• 45. [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

• 46. [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

• 47. [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

• 48. [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

• 49. [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

• 50. [Article] Palynological Perspectives on Younger Dryas to Early Holocene Human Ecology at Paisley Caves, Oregon

  The Younger Dryas climatic event is a global phenomenon associated with a 1,000 year return to glacial conditions during the late Pleistocene period between 12,800 and 11,500 cal BP. Because of its significant ...

  Citation × Citation Citation Abstract Copy Title: Palynological Perspectives on Younger Dryas to Early Holocene Human Ecology at Paisley Caves, Oregon Author: Saban, Chantel V. The Younger Dryas climatic event is a global phenomenon associated with a 1,000 year return to glacial conditions during the late Pleistocene period between 12,800 and 11,500 cal BP. Because of its significant effects on paleoenvironmental conditions in some parts of the world, archaeologists commonly seek to assess whether the Younger Dryas climatic event had any measureable influence on prehistoric human societies. The early, well preserved archaeological and paleoenvironmental records held in the Paisley Caves site of Oregon's Northern Great Basin provide an opportunity to examine questions human-environmental interaction at the end of the Pleistocene Epoch. Based on a study of pollen records and artifact frequency in the site's Cave 2 deposits, this thesis reports a positive relationship between artifact deposition and marsh expansion in the Summer Lake sub-basin during the Younger Dryas chronozone. While not indicative of a major change in early forager cultural patterns in the Northern Great Basin, these results provide an important perspective on early settlement patterns and human ecology in the far western region of North America. Title: Palynological Perspectives on Younger Dryas to Early Holocene Human Ecology at Paisley Caves, Oregon Author: Saban, Chantel V. The Younger Dryas climatic event is a global phenomenon associated with a 1,000 year return to glacial conditions during the late Pleistocene period between 12,800 and 11,500 cal BP. Because of its significant effects on paleoenvironmental conditions in some parts of the world, archaeologists commonly seek to assess whether the Younger Dryas climatic event had any measureable influence on prehistoric human societies. The early, well preserved archaeological and paleoenvironmental records held in the Paisley Caves site of Oregon's Northern Great Basin provide an opportunity to examine questions human-environmental interaction at the end of the Pleistocene Epoch. Based on a study of pollen records and artifact frequency in the site's Cave 2 deposits, this thesis reports a positive relationship between artifact deposition and marsh expansion in the Summer Lake sub-basin during the Younger Dryas chronozone. While not indicative of a major change in early forager cultural patterns in the Northern Great Basin, these results provide an important perspective on early settlement patterns and human ecology in the far western region of North America. Close

• 51. [Article] A 37,000-year record of paleomagnetic and environmental magnetic variability from Burial Lake, Arctic Alaska

  Burial Lake sediments from the Noatak Basin in the northwest Brooks Range of Arctic Alaska (68.43°N, 159.17°W, 21.5 m water depth) provide the oldest continuous lacustrine record of paleo-environmental ...

  Citation × Citation Citation Abstract Copy Title: A 37,000-year record of paleomagnetic and environmental magnetic variability from Burial Lake, Arctic Alaska Author: Dorfman, Jason Michael Burial Lake sediments from the Noatak Basin in the northwest Brooks Range of Arctic Alaska (68.43°N, 159.17°W, 21.5 m water depth) provide the oldest continuous lacustrine record of paleo-environmental change and paleomagnetic secular variation (PSV) in eastern Beringia. A precise radiocarbon chronology, determined through accelerator mass spectrometry (AMS) allows us to independently constrain the region's climatic and geomagnetic evolution over the last ~37,000 years. Progressive alternating field (AF) demagnetization of u-channel samples and additionally acquired physical, geochemical, and rock-magnetic datasets, reveal three distinct lithologic subunits associated with the last glacial period (37.2 - 19.4 ka), the deglacial transition (19.4 - 9.8 ka), and the Holocene (9.8 ka - present). Rock magnetic variability suggests changes in sediment provenance associated with the transition from glacial to interglacial conditions. This is interpreted to result from a variable flux of aeolian derived sediment, and is supported by complimentary internal proxy data from Burial Lake. Other regional paleoclimate data, various glacial chronologies for the Brooks Range, and a relative sea level reconstruction facilitate a discussion of possible local, widespread, and far-field sources of dust, and the time-dependency of potential forcing mechanisms governing its production, availability, transport, and deposition. Results indicate an overall reduction in dust input from the glacial period to the Holocene that is largely attributed to increases in terrestrial and aquatic productivity, warming, and moisture availability, which limited widespread landscape deflation and production of dust. Subaerial continental shelves may have provided significant far-field sources of dust to interior Alaska during the glacial period, that were shut off by sea level inundation following the Last Glacial Maximum (LGM; 19 - 26.5 ka), further contributing to diminishing dust emissions. While glacial activity in the Brooks Range may provide local revenue of dust, activation of those deposits and timing of deposition in Burial Lake often appears to be more directly linked with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. Despite this lithologic complexity, we isolate a stable, single-component characteristic remanent magnetization, carried predominately by low-coercivity (titano)magnetite in the pseudo single-domain (PSD) to multi-domain (MD) magnetic grain size range. We reconstruct directional paleomagnetic secular variation (PSV) over the full length of the record, and relative paleointensity (RPI) for the last ~14,700 years, which are consistent with available regional PSV records and continuous spherical harmonic model outputs. We observe only small deviations from geocentric axial dipole (GAD) predictions during the Holocene, while larger amplitude directional features are prevalent before 10 ka, and inclinations lay significantly shallower than GAD. While this may be related to lithology and the sediment magnetic acquisition process, regional records (including those derived from lava flows) indicate similar Holocene-Pleistocene discrepancies. Following on the "eccentric dipole" hypothesis, subdued secular variation and GAD-like behavior in the Pacific appears confined to the Holocene high-intensity state, showing greater variability as Pleistocene field strength diminishes, and/or the dipole axis is shifted away from the Pacific hemisphere. Long period trends in PSV from in the Alaskan Arctic are also similar in character to far-field sites (e.g., Hawaii and Siberia), suggesting large-scale coherent core-fluid flow regimes, expressed over surface geographical extents >5,000 km, and spanning Holocene-Pleistocene time intervals. The well-dated Burial Lake record fills a significant data gap in the growing Holocene paleomagnetic database, while allowing us to extend our understanding of PSV beyond the Holocene and into the Pleistocene, and continue the development of regional stratigraphic dating curves. Title: A 37,000-year record of paleomagnetic and environmental magnetic variability from Burial Lake, Arctic Alaska Author: Dorfman, Jason Michael Burial Lake sediments from the Noatak Basin in the northwest Brooks Range of Arctic Alaska (68.43°N, 159.17°W, 21.5 m water depth) provide the oldest continuous lacustrine record of paleo-environmental change and paleomagnetic secular variation (PSV) in eastern Beringia. A precise radiocarbon chronology, determined through accelerator mass spectrometry (AMS) allows us to independently constrain the region's climatic and geomagnetic evolution over the last ~37,000 years. Progressive alternating field (AF) demagnetization of u-channel samples and additionally acquired physical, geochemical, and rock-magnetic datasets, reveal three distinct lithologic subunits associated with the last glacial period (37.2 - 19.4 ka), the deglacial transition (19.4 - 9.8 ka), and the Holocene (9.8 ka - present). Rock magnetic variability suggests changes in sediment provenance associated with the transition from glacial to interglacial conditions. This is interpreted to result from a variable flux of aeolian derived sediment, and is supported by complimentary internal proxy data from Burial Lake. Other regional paleoclimate data, various glacial chronologies for the Brooks Range, and a relative sea level reconstruction facilitate a discussion of possible local, widespread, and far-field sources of dust, and the time-dependency of potential forcing mechanisms governing its production, availability, transport, and deposition. Results indicate an overall reduction in dust input from the glacial period to the Holocene that is largely attributed to increases in terrestrial and aquatic productivity, warming, and moisture availability, which limited widespread landscape deflation and production of dust. Subaerial continental shelves may have provided significant far-field sources of dust to interior Alaska during the glacial period, that were shut off by sea level inundation following the Last Glacial Maximum (LGM; 19 - 26.5 ka), further contributing to diminishing dust emissions. While glacial activity in the Brooks Range may provide local revenue of dust, activation of those deposits and timing of deposition in Burial Lake often appears to be more directly linked with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. Despite this lithologic complexity, we isolate a stable, single-component characteristic remanent magnetization, carried predominately by low-coercivity (titano)magnetite in the pseudo single-domain (PSD) to multi-domain (MD) magnetic grain size range. We reconstruct directional paleomagnetic secular variation (PSV) over the full length of the record, and relative paleointensity (RPI) for the last ~14,700 years, which are consistent with available regional PSV records and continuous spherical harmonic model outputs. We observe only small deviations from geocentric axial dipole (GAD) predictions during the Holocene, while larger amplitude directional features are prevalent before 10 ka, and inclinations lay significantly shallower than GAD. While this may be related to lithology and the sediment magnetic acquisition process, regional records (including those derived from lava flows) indicate similar Holocene-Pleistocene discrepancies. Following on the "eccentric dipole" hypothesis, subdued secular variation and GAD-like behavior in the Pacific appears confined to the Holocene high-intensity state, showing greater variability as Pleistocene field strength diminishes, and/or the dipole axis is shifted away from the Pacific hemisphere. Long period trends in PSV from in the Alaskan Arctic are also similar in character to far-field sites (e.g., Hawaii and Siberia), suggesting large-scale coherent core-fluid flow regimes, expressed over surface geographical extents >5,000 km, and spanning Holocene-Pleistocene time intervals. The well-dated Burial Lake record fills a significant data gap in the growing Holocene paleomagnetic database, while allowing us to extend our understanding of PSV beyond the Holocene and into the Pleistocene, and continue the development of regional stratigraphic dating curves. Close

• 52. [Article] The Ore bin ; Vol. 25 No. 4 (April 1963)

  Introduction -- Seismology -- Recording stations -- Travel-time curve -- Main earthquake -- Epicenter and origin time -- Magnitude and intensity -- Depth of focus -- Source motion -- Aftershocks -- Geology ...

  Citation × Citation Citation Abstract Copy Title: The Ore bin ; Vol. 25 No. 4 (April 1963) Author: Dehlinger, Peter, Chiburis, E. F., Bowen, Richard G., Oregon. Dept. of Geology and Mineral Industries, Westphal, Warren H. Introduction -- Seismology -- Recording stations -- Travel-time curve -- Main earthquake -- Epicenter and origin time -- Magnitude and intensity -- Depth of focus -- Source motion -- Aftershocks -- Geology -- Stratigraphy -- Gable Volcanics -- Oligocene marine sedimentary rocks -- Columbia River basalt -- Plio-Pleistocene rocks -- Recent alluvium -- Structure -- Recommendations -- Acknowledgements -- References Title: The Ore bin ; Vol. 25 No. 4 (April 1963) Author: Dehlinger, Peter, Chiburis, E. F., Bowen, Richard G., Oregon. Dept. of Geology and Mineral Industries, Westphal, Warren H. Introduction -- Seismology -- Recording stations -- Travel-time curve -- Main earthquake -- Epicenter and origin time -- Magnitude and intensity -- Depth of focus -- Source motion -- Aftershocks -- Geology -- Stratigraphy -- Gable Volcanics -- Oligocene marine sedimentary rocks -- Columbia River basalt -- Plio-Pleistocene rocks -- Recent alluvium -- Structure -- Recommendations -- Acknowledgements -- References Close

• 53. [Article] Bathymetry and structure of San Clemente Island, California, and tectonic implications for the southern California continental borderland

  Five lithologic units, ranging in age from Middle Miocene to Recent, are defined on the basis of continuous seismic reflection profile records. Two of the units are Miocene sedimentary and volcanic rocks ...

  Citation × Citation Citation Abstract Copy Title: Bathymetry and structure of San Clemente Island, California, and tectonic implications for the southern California continental borderland Author: Ridlon, James Barr Five lithologic units, ranging in age from Middle Miocene to Recent, are defined on the basis of continuous seismic reflection profile records. Two of the units are Miocene sedimentary and volcanic rocks that have been truncated to form a major unconformity (post-orogenic surface) related to the most recent major tectonism of the region. The remaining units are post-orogenic unconsolidated sediments. The fault pattern offshore is generally related to that exhibited on the island. The pattern conforms to a wrench-fault system hypothesized by Moody and Hill (1956) modified by a general north-south tensional fracturing. The San Clemente Fault is assumed to be the primary wrench fault of the system. Anomalies in the thicknesses and the structure of the unconsolidated sediment and rock units tend to confirm the structural model. A canyon (Eel Ridge Canyon) off the west side of San Clemente Island appears to have been caused by pivotal faulting and erosion, and represents a boundary between different structural trends north and south. A prominent terrace around the island is postulated to have been wave-cut during and since the Late Pleistocene. The island has been tilted slightly to the west by Recent tectonism. A steep magnetic gradient off the east side of the island is considered the consequence of faulted volcanic flows comprising the island itself and a deep basic rock mass responsible for a large positive magnetic anomaly off the northwest side. Other magnetic anomalies reflect major structural trends. Earthquake epicenter data suggest a recent and possibly cyclical occurrence of fault activity in the northern Continental Borderland region and the study area. Fault offsets at the sea floor and earthquake epicenters along the San Clemente fault zone imply recent adjustments along the fault. Wrench-fault movement resulting from a simple shear or shear couple is considered to have caused the zone of brecciation along the San Clemente Fault and produced the fault-trace curvature so evident in a series of en echelon, northwest-striking major faults of the Borderland. Tensile release during periods of wrench-fault development has been a fundamental factor in the structural development of the Borderland basins. The entire structure of the Continental Borderland is believed to have developed by right-lateral movement along the series of wrench faults. These faults are believed to have resulted from a translation of force by sea-floor spreading originating on the East Pacific Rise in the Gulf of California region. This force is considered to have moved a northern Continental Borderland crustal plate westward by east to west release along major wrench faults bordering the north and south ends of this plate. Sediments, transported along channels developed along faults in the island block, were deposited in basins developed by faulting and folding of the pre-orogenic rocks. Transportation appears to have been by means of turbidity-current flows, sand flows, and slides. A maximum average depositional rate of 35 to 47 centimeters per 1,000 years is estimated for post-orogenic sediments. The following findings are suggested for inclusion in the Neogene history of the island: (1) the top 365 meters of Miocene andesitic lavas were deposited above sea level and tend to become slightly more basic in composition with depth; (2) subsidence of the island region and temporary sea-level stand(s) occurred after the deposition of the volcanic rocks, with possible periods of foundering to about the Late Pliocene; (3) emergence, lengthy subaerial exposure, and a period of partial submergence took place from about Late Pliocene through Early Pleistocene; (4) a north-south compressive force developed or recurred across the Borderland during Late Pliocene, developing the present northwest-southeast and east-west wrench-fault systems that have been intermittently active to the present time; (5) much of the present Borderland topography formed during the Pleistocene to Recent. Title: Bathymetry and structure of San Clemente Island, California, and tectonic implications for the southern California continental borderland Author: Ridlon, James Barr Five lithologic units, ranging in age from Middle Miocene to Recent, are defined on the basis of continuous seismic reflection profile records. Two of the units are Miocene sedimentary and volcanic rocks that have been truncated to form a major unconformity (post-orogenic surface) related to the most recent major tectonism of the region. The remaining units are post-orogenic unconsolidated sediments. The fault pattern offshore is generally related to that exhibited on the island. The pattern conforms to a wrench-fault system hypothesized by Moody and Hill (1956) modified by a general north-south tensional fracturing. The San Clemente Fault is assumed to be the primary wrench fault of the system. Anomalies in the thicknesses and the structure of the unconsolidated sediment and rock units tend to confirm the structural model. A canyon (Eel Ridge Canyon) off the west side of San Clemente Island appears to have been caused by pivotal faulting and erosion, and represents a boundary between different structural trends north and south. A prominent terrace around the island is postulated to have been wave-cut during and since the Late Pleistocene. The island has been tilted slightly to the west by Recent tectonism. A steep magnetic gradient off the east side of the island is considered the consequence of faulted volcanic flows comprising the island itself and a deep basic rock mass responsible for a large positive magnetic anomaly off the northwest side. Other magnetic anomalies reflect major structural trends. Earthquake epicenter data suggest a recent and possibly cyclical occurrence of fault activity in the northern Continental Borderland region and the study area. Fault offsets at the sea floor and earthquake epicenters along the San Clemente fault zone imply recent adjustments along the fault. Wrench-fault movement resulting from a simple shear or shear couple is considered to have caused the zone of brecciation along the San Clemente Fault and produced the fault-trace curvature so evident in a series of en echelon, northwest-striking major faults of the Borderland. Tensile release during periods of wrench-fault development has been a fundamental factor in the structural development of the Borderland basins. The entire structure of the Continental Borderland is believed to have developed by right-lateral movement along the series of wrench faults. These faults are believed to have resulted from a translation of force by sea-floor spreading originating on the East Pacific Rise in the Gulf of California region. This force is considered to have moved a northern Continental Borderland crustal plate westward by east to west release along major wrench faults bordering the north and south ends of this plate. Sediments, transported along channels developed along faults in the island block, were deposited in basins developed by faulting and folding of the pre-orogenic rocks. Transportation appears to have been by means of turbidity-current flows, sand flows, and slides. A maximum average depositional rate of 35 to 47 centimeters per 1,000 years is estimated for post-orogenic sediments. The following findings are suggested for inclusion in the Neogene history of the island: (1) the top 365 meters of Miocene andesitic lavas were deposited above sea level and tend to become slightly more basic in composition with depth; (2) subsidence of the island region and temporary sea-level stand(s) occurred after the deposition of the volcanic rocks, with possible periods of foundering to about the Late Pliocene; (3) emergence, lengthy subaerial exposure, and a period of partial submergence took place from about Late Pliocene through Early Pleistocene; (4) a north-south compressive force developed or recurred across the Borderland during Late Pliocene, developing the present northwest-southeast and east-west wrench-fault systems that have been intermittently active to the present time; (5) much of the present Borderland topography formed during the Pleistocene to Recent. Close

• 54. [Article] Geology of the southernmost Deschutes basin, Tumalo quadrangle, Deschutes County, Oregon

  The Tumalo quadrangle lies approximately 30 kilometers behind the Cascade volcanic arc and marks the southernmost extent of continuously exposed Deschutes Formation rocks. Deschutes Formation rocks in ...

  Citation × Citation Citation Abstract Copy Title: Geology of the southernmost Deschutes basin, Tumalo quadrangle, Deschutes County, Oregon Author: McDannel, Angela K. The Tumalo quadrangle lies approximately 30 kilometers behind the Cascade volcanic arc and marks the southernmost extent of continuously exposed Deschutes Formation rocks. Deschutes Formation rocks in the Tumalo quadrangle include late Miocene volcaniclastic sedimentary rocks, ignimbrites and lapillistones, and late Miocene to early Pliocene basalts and basaltic andesites. Volcaniclastic sediment and pyroclastic flows originated from sources west to southwest of the Tumalo area and were the products of Early High Cascade arc volcanism. Most pyroclastic flows and falls had silicic compositions and silicic volcanic material dominated the sedimentary deposits. Intermittent and apparently widespread, high discharge events onto a back-arc alluvial plain deposited tuffaceous sediments, much of which became incipient soils during long periods of subaerial exposure. The close of sedimentation was coincident with the initiation of local volcanism at approximately 5.4 Ma. Several small monogenetic shield volcanoes and cinder cones in the Tumalo area erupted the basalt and basaltic andesite lavas which cap the sedimentary section. The basalts are typically porphyritic and high in A1203. Basaltic andesites are aphyric to sparsely porphyritic, are commonly high in FeO and Ti02, appear younger than the basalts, and are not related to the basalts by simple fractionation. Both lava types have relatively evolved compositions based on their Fe' values. An inlier of older Tertiary rhyodacite lavas known as Cline Buttes lies near the northern boundary of the study and is the only locally exposed pre-Deschutes Formation unit. The southern part of the Tumalo quadrangle marks the boundary between continuously exposed Deschutes Formation rocks to the north and Late High Cascade volcanic units to the south. After a hiatus of approximately 4 million years, deposition in the Tumalo area resumed at approximately 0.6 Ma when pyroclastic flows from the High Cascade Range flowed east and northeast into the Tumalo area to rest disconformably above the Deschutes Formation. A diktytaxitic basalt from Newberry volcano locally overlies the pyroclastic units. Widespread, thick alluvium obscures some 16 km2 of bedrock in the study area and appears to be the result of deposition during high discharge events associated with late Pleistocene to Holocene age glaciation of the High Cascade Range. Some thirty en echelon normal faults of the Tumalo fault zone trend between N15°-35°W and cut Pleistocene and older units in the Tumalo quadrangle. Deschutes Formation basalt and basaltic andesite vents are localized in the fault zone. This suggests volcanism was structurally controlled and that an tensional stress regime with a northeast-southwest least compressive stress orientation prevailed in the Tumalo area between the late Miocene to late Pleistocene. Title: Geology of the southernmost Deschutes basin, Tumalo quadrangle, Deschutes County, Oregon Author: McDannel, Angela K. The Tumalo quadrangle lies approximately 30 kilometers behind the Cascade volcanic arc and marks the southernmost extent of continuously exposed Deschutes Formation rocks. Deschutes Formation rocks in the Tumalo quadrangle include late Miocene volcaniclastic sedimentary rocks, ignimbrites and lapillistones, and late Miocene to early Pliocene basalts and basaltic andesites. Volcaniclastic sediment and pyroclastic flows originated from sources west to southwest of the Tumalo area and were the products of Early High Cascade arc volcanism. Most pyroclastic flows and falls had silicic compositions and silicic volcanic material dominated the sedimentary deposits. Intermittent and apparently widespread, high discharge events onto a back-arc alluvial plain deposited tuffaceous sediments, much of which became incipient soils during long periods of subaerial exposure. The close of sedimentation was coincident with the initiation of local volcanism at approximately 5.4 Ma. Several small monogenetic shield volcanoes and cinder cones in the Tumalo area erupted the basalt and basaltic andesite lavas which cap the sedimentary section. The basalts are typically porphyritic and high in A1203. Basaltic andesites are aphyric to sparsely porphyritic, are commonly high in FeO and Ti02, appear younger than the basalts, and are not related to the basalts by simple fractionation. Both lava types have relatively evolved compositions based on their Fe' values. An inlier of older Tertiary rhyodacite lavas known as Cline Buttes lies near the northern boundary of the study and is the only locally exposed pre-Deschutes Formation unit. The southern part of the Tumalo quadrangle marks the boundary between continuously exposed Deschutes Formation rocks to the north and Late High Cascade volcanic units to the south. After a hiatus of approximately 4 million years, deposition in the Tumalo area resumed at approximately 0.6 Ma when pyroclastic flows from the High Cascade Range flowed east and northeast into the Tumalo area to rest disconformably above the Deschutes Formation. A diktytaxitic basalt from Newberry volcano locally overlies the pyroclastic units. Widespread, thick alluvium obscures some 16 km2 of bedrock in the study area and appears to be the result of deposition during high discharge events associated with late Pleistocene to Holocene age glaciation of the High Cascade Range. Some thirty en echelon normal faults of the Tumalo fault zone trend between N15°-35°W and cut Pleistocene and older units in the Tumalo quadrangle. Deschutes Formation basalt and basaltic andesite vents are localized in the fault zone. This suggests volcanism was structurally controlled and that an tensional stress regime with a northeast-southwest least compressive stress orientation prevailed in the Tumalo area between the late Miocene to late Pleistocene. Close

• 55. [Article] Morphological variation in the clouded salamander, Aneides ferreus (Cope) (Amphibia: Caudata: Plethodontidae)

  Multivariate morphometric analyses performed on ten populations of Aneides ferreus indicate that phenotypic expression in this species is exceedingly similar, but that on a fine scale there is considerable significant ...

  Citation × Citation Citation Abstract Copy Title: Morphological variation in the clouded salamander, Aneides ferreus (Cope) (Amphibia: Caudata: Plethodontidae) Author: Beatty, Joseph J. Multivariate morphometric analyses performed on ten populations of Aneides ferreus indicate that phenotypic expression in this species is exceedingly similar, but that on a fine scale there is considerable significant heterogeneity between most populations as well as between regional groups of populations. in terms of variation between California, Oregon, and Vancouver Island specimens. California is differentiated from Vancouver Island at of 2.13; Oregon-California D² of 2.13; Oregon-California D² = 1.35, and Oregon-Vancouver Island exhibited D² of 1.38. These values represent significant F-ratio comparisons at p <<.01. These slight but significant differences in phenotypic expression are not unexpected for a species which ranges over such a wide and varied geographic area, and can be correlated with major topographic features of the Pacific Northwest. Prior to Pleistocene glaciation, populations of A. ferreus were probably continuous throughout northwestern California, western Oregon and Washington, as well as Vancouver Island and British Columbia. As Cordilleran ice advanced and inundated most of British Columbia, and Vancouver Island, populations became isolated in refugia on Vancouver Island, and were probably extirpated from British Columbia proper. The slight, but significant levels of heterogeneity produced from comparisons of Vancouver Island specimens with California and Oregon specimens indicate that the observed disjunction between Vancouver Island populations and those inhabiting coterminous U.S. is probably a relatively recent occurrence, correlating well with events produced by the Fraser Glaciation approximately 15,000 yr BP. Since other plethodontids inhabit Vancouver Island and Washington it is impossible to utilize Pleistocene glaciation as a direct causal mechanism which produced the disjunction, accounting for the absence of A. ferreus in Washington. On a finer scale, significant phenotypic dissimilarity was found to exist between a majority of the pairwise comparisons between populations within each of the three regions. Patterns of heterogeneity within California populations are consistent with predictions derived by utilizing a model based upon a gradual latitudinal environmental dine. No apparent pattern can be seen when pairwise comparisons are made between Oregon populations, although all populations exhibit slight but significant levels of heterogeneity. The effects of Pleistocene climatic events upon California and Oregon populations were probably slight since the maximum southern incursion of Cordilleran ice reached latitudes just south of Olympia, Washington. Montaine glaciers in the Klamath-Siskiyou Mountains provided potential barriers to gene flow between California and Oregon populations until about 10,000 yr BP. The equable redwood forest ecosystem in northwestern California must be considered to be the ancestral habitat for Aneides in general and A. ferreus in particular. Specimens from this region exhibit high tooth counts, a character that has been considered to be primitive by Wake (1963; 1966). Also, all three western Aneides occur in sympatry in northwestern California redwood associations, and the earliest known fossil Aneides were associated with redwood forests during Eocene times in Montana. Comparison of morphological relationships with electrophoretic and chromosomal data for each region and population indicates that there is little agreement between morphological and electrophoretic relationships, but that karyotypic variation is present which allows classification of a collection of individuals to one of the three regions with a high degree of certainty. Title: Morphological variation in the clouded salamander, Aneides ferreus (Cope) (Amphibia: Caudata: Plethodontidae) Author: Beatty, Joseph J. Multivariate morphometric analyses performed on ten populations of Aneides ferreus indicate that phenotypic expression in this species is exceedingly similar, but that on a fine scale there is considerable significant heterogeneity between most populations as well as between regional groups of populations. in terms of variation between California, Oregon, and Vancouver Island specimens. California is differentiated from Vancouver Island at of 2.13; Oregon-California D² of 2.13; Oregon-California D² = 1.35, and Oregon-Vancouver Island exhibited D² of 1.38. These values represent significant F-ratio comparisons at p <<.01. These slight but significant differences in phenotypic expression are not unexpected for a species which ranges over such a wide and varied geographic area, and can be correlated with major topographic features of the Pacific Northwest. Prior to Pleistocene glaciation, populations of A. ferreus were probably continuous throughout northwestern California, western Oregon and Washington, as well as Vancouver Island and British Columbia. As Cordilleran ice advanced and inundated most of British Columbia, and Vancouver Island, populations became isolated in refugia on Vancouver Island, and were probably extirpated from British Columbia proper. The slight, but significant levels of heterogeneity produced from comparisons of Vancouver Island specimens with California and Oregon specimens indicate that the observed disjunction between Vancouver Island populations and those inhabiting coterminous U.S. is probably a relatively recent occurrence, correlating well with events produced by the Fraser Glaciation approximately 15,000 yr BP. Since other plethodontids inhabit Vancouver Island and Washington it is impossible to utilize Pleistocene glaciation as a direct causal mechanism which produced the disjunction, accounting for the absence of A. ferreus in Washington. On a finer scale, significant phenotypic dissimilarity was found to exist between a majority of the pairwise comparisons between populations within each of the three regions. Patterns of heterogeneity within California populations are consistent with predictions derived by utilizing a model based upon a gradual latitudinal environmental dine. No apparent pattern can be seen when pairwise comparisons are made between Oregon populations, although all populations exhibit slight but significant levels of heterogeneity. The effects of Pleistocene climatic events upon California and Oregon populations were probably slight since the maximum southern incursion of Cordilleran ice reached latitudes just south of Olympia, Washington. Montaine glaciers in the Klamath-Siskiyou Mountains provided potential barriers to gene flow between California and Oregon populations until about 10,000 yr BP. The equable redwood forest ecosystem in northwestern California must be considered to be the ancestral habitat for Aneides in general and A. ferreus in particular. Specimens from this region exhibit high tooth counts, a character that has been considered to be primitive by Wake (1963; 1966). Also, all three western Aneides occur in sympatry in northwestern California redwood associations, and the earliest known fossil Aneides were associated with redwood forests during Eocene times in Montana. Comparison of morphological relationships with electrophoretic and chromosomal data for each region and population indicates that there is little agreement between morphological and electrophoretic relationships, but that karyotypic variation is present which allows classification of a collection of individuals to one of the three regions with a high degree of certainty. Close

• 56. [Article] Searching for early archaeological sites along the central Oregon coast : a case study from Neptune State Park (35LA3), Lane County, Oregon

  Locating archaeological sites that predate the arrival of modern sea level has been difficult along the Oregon coast. This is in part believed to be the result of geologic processes that have influenced ...

  Citation × Citation Citation Abstract Copy Title: Searching for early archaeological sites along the central Oregon coast : a case study from Neptune State Park (35LA3), Lane County, Oregon Author: Jenevein, Steve Locating archaeological sites that predate the arrival of modern sea level has been difficult along the Oregon coast. This is in part believed to be the result of geologic processes that have influenced the preservation, distribution, and visibility of sites within the Oregon coastal landscape. Because of these changes, researchers have a poor understanding of where sites that predate modern sea level are located within the modern landscape. Geoarchaeological techniques and concepts are well suited to address these types of questions and can help place the fragments of a once much larger paleocoastal landscape into a modern context. In this thesis I use a Geographic Information System (GIS) and geoarchaeological field and laboratory techniques and concepts to conceptualize, locate, and evaluate landforms located within both the paleo and modern central Oregon coastal landscapes. Geoarchaeological investigations conducted as part of this project at the Neptune Site (35LA3) identified mid to late Holocene aged archaeological materials in addition to an erosional contact located between late Pleistocene and Holocene-aged deposits representing the loss of up to 11,400 years of stratigraphic time. To account for this loss of time, a model of landscape change that is occurring at 35LA3 is presented. Depositional sequences such as truncated late Pleistocene aged deposits that underlie mid to late Holocene sediment that are observed at the Neptune Site are similar to, and have been associated with other early sites along the Oregon coast. The identification of these types of deposits and their associated erosional features may serve as key target horizons for future coastal researchers looking for landforms and archaeological deposits and date to the late Pleistocene to mid Holocene. Title: Searching for early archaeological sites along the central Oregon coast : a case study from Neptune State Park (35LA3), Lane County, Oregon Author: Jenevein, Steve Locating archaeological sites that predate the arrival of modern sea level has been difficult along the Oregon coast. This is in part believed to be the result of geologic processes that have influenced the preservation, distribution, and visibility of sites within the Oregon coastal landscape. Because of these changes, researchers have a poor understanding of where sites that predate modern sea level are located within the modern landscape. Geoarchaeological techniques and concepts are well suited to address these types of questions and can help place the fragments of a once much larger paleocoastal landscape into a modern context. In this thesis I use a Geographic Information System (GIS) and geoarchaeological field and laboratory techniques and concepts to conceptualize, locate, and evaluate landforms located within both the paleo and modern central Oregon coastal landscapes. Geoarchaeological investigations conducted as part of this project at the Neptune Site (35LA3) identified mid to late Holocene aged archaeological materials in addition to an erosional contact located between late Pleistocene and Holocene-aged deposits representing the loss of up to 11,400 years of stratigraphic time. To account for this loss of time, a model of landscape change that is occurring at 35LA3 is presented. Depositional sequences such as truncated late Pleistocene aged deposits that underlie mid to late Holocene sediment that are observed at the Neptune Site are similar to, and have been associated with other early sites along the Oregon coast. The identification of these types of deposits and their associated erosional features may serve as key target horizons for future coastal researchers looking for landforms and archaeological deposits and date to the late Pleistocene to mid Holocene. Close

• 57. [Article] Timescales of large silicic magma systems : implications from accessory minerals in Pleistocene lavas of the Altiplano-Puna Volcanic Complex, central Andes

  Constraining the development, evolution, and timescales of large silicic magma systems is important to understanding the development of granite batholiths, the relationships between volcanoes and their ...

  Citation × Citation Citation Abstract Copy Title: Timescales of large silicic magma systems : implications from accessory minerals in Pleistocene lavas of the Altiplano-Puna Volcanic Complex, central Andes Author: Tierney, Casey R. Constraining the development, evolution, and timescales of large silicic magma systems is important to understanding the development of granite batholiths, the relationships between volcanoes and their plutonic underpinnings, and the development of the continental crust. The ignimbrite flare up that produced the Altiplano-Puna Volcanic Complex of the Central Andes is characterized by episodic volcanism over a ~11 Ma time-span that climaxed about 4 Ma. Since peak activity, the temporal and spatial record of volcanism suggests a waning of the system with only one other supervolcanic eruption at 2.6 Ma. The most recent phase of volcanism from the APVC comprises a series of late Pleistocene domes that share a general petrochemical resemblance to the ignimbrites. New U-Th/U-Pb data on zircons and high precision 40Ar/39Ar age determinations reveal that these effusive eruptions represent a temporally coherent magmatic episode. The five largest domes (Chao, Chillahuita, Chanka, Chascon-Runtu Jarita, and Tocopuri) have a combined volume >40 km³, and are distributed over a roughly elliptical area of almost 2000km² centered at 22°S 68°W. They are crystal rich (>50%) dacites to rhyolites. ⁴⁰Ar/³⁹Ar ages from biotite reveals eruption ages from 108±6 to 120±5 ka while more accurate sanidine for some of the domes reveal eruption ages from 87±4 to 97±2 ka. SIMS U-series crystallization ages from the rims of 215 zircon crystals from the domes show a similar age spectra from dome to dome, with common peaks in zircon ages at ~100ka and ~220ka. Furthermore, the ages reveal a fairly continuous spread of ages from near eruption to >300ka indicating that the residence time of this magma body was likely over a similar time interval. Ubiquitous andesitic inclusions evidence a vital role for recharge in sustaining and maybe eventual eruption of these magmas. Lastly, the interiors of crystals with rim U-Th secular equilibrium ages were re-analyzed and have yielded U-Pb ages of up to 3.5 Ma. The presence of these older interiors suggests that the source region of these magmas retained a record of an earlier history dating back to the last supervolcanic eruption in the region from the nearby Pastos Grandes caldera. This suggests that the thermal history of the system precluded complete resorption of antecrysts. The volcanological, petrological, temporal and spatial coherence of this series of eruptions combined with the similar ⁴⁰Ar/³⁹Ar and zircon age spectra argue for a long-lived and unitary magma chamber revealing perhaps the waning of this major continental magma system. Title: Timescales of large silicic magma systems : implications from accessory minerals in Pleistocene lavas of the Altiplano-Puna Volcanic Complex, central Andes Author: Tierney, Casey R. Constraining the development, evolution, and timescales of large silicic magma systems is important to understanding the development of granite batholiths, the relationships between volcanoes and their plutonic underpinnings, and the development of the continental crust. The ignimbrite flare up that produced the Altiplano-Puna Volcanic Complex of the Central Andes is characterized by episodic volcanism over a ~11 Ma time-span that climaxed about 4 Ma. Since peak activity, the temporal and spatial record of volcanism suggests a waning of the system with only one other supervolcanic eruption at 2.6 Ma. The most recent phase of volcanism from the APVC comprises a series of late Pleistocene domes that share a general petrochemical resemblance to the ignimbrites. New U-Th/U-Pb data on zircons and high precision 40Ar/39Ar age determinations reveal that these effusive eruptions represent a temporally coherent magmatic episode. The five largest domes (Chao, Chillahuita, Chanka, Chascon-Runtu Jarita, and Tocopuri) have a combined volume >40 km³, and are distributed over a roughly elliptical area of almost 2000km² centered at 22°S 68°W. They are crystal rich (>50%) dacites to rhyolites. ⁴⁰Ar/³⁹Ar ages from biotite reveals eruption ages from 108±6 to 120±5 ka while more accurate sanidine for some of the domes reveal eruption ages from 87±4 to 97±2 ka. SIMS U-series crystallization ages from the rims of 215 zircon crystals from the domes show a similar age spectra from dome to dome, with common peaks in zircon ages at ~100ka and ~220ka. Furthermore, the ages reveal a fairly continuous spread of ages from near eruption to >300ka indicating that the residence time of this magma body was likely over a similar time interval. Ubiquitous andesitic inclusions evidence a vital role for recharge in sustaining and maybe eventual eruption of these magmas. Lastly, the interiors of crystals with rim U-Th secular equilibrium ages were re-analyzed and have yielded U-Pb ages of up to 3.5 Ma. The presence of these older interiors suggests that the source region of these magmas retained a record of an earlier history dating back to the last supervolcanic eruption in the region from the nearby Pastos Grandes caldera. This suggests that the thermal history of the system precluded complete resorption of antecrysts. The volcanological, petrological, temporal and spatial coherence of this series of eruptions combined with the similar ⁴⁰Ar/³⁹Ar and zircon age spectra argue for a long-lived and unitary magma chamber revealing perhaps the waning of this major continental magma system. Close

• 58. [Article] Leg 202 synthesis: Southeast Pacific paleoceangraphy

  Ocean Drilling Program (ODP) Leg 202 has opened a new window into understanding late Paleogene and Neogene global environmental change by providing high-quality sediment sequences from a previously unsampled ...

  Citation × Citation Citation Abstract Copy Title: Leg 202 synthesis: Southeast Pacific paleoceangraphy Author: Tiedemann, Ralf, Mix, Alan C. Ocean Drilling Program (ODP) Leg 202 has opened a new window into understanding late Paleogene and Neogene global environmental change by providing high-quality sediment sequences from a previously unsampled region, the eastern South Pacific. Eleven sites (1232– 1242) that record variations on timescales ranging from decades to tens of millions of years were drilled and investigated on transects of both depth (489–4072 m) and latitude (41°S–8°N). Building on the shipboard results presented in the Leg 202 Initial Reports volume, postcruise research has significantly improved the stratigraphic framework and provided new insights into climate-related processes, which operate on different timescales and are relevant to hypotheses concerning the bipolar “see-saw” climate mechanism, orbitally driven changes in the continent-ocean-ice-atmosphere system and tectonic processes associated with the uplift of the Andes, closure of the Central American Seaway, and major expansions of polar ice sheets. Stable isotope records and refinements in bio- and magnetostratigraphy in combination with orbitally tuned cyclostratigraphy significantly improved the Pleistocene stratigraphy at Sites 1233 and 1234, the Miocene– Pliocene stratigraphy at Sites 1236, 1237, 1239, and 1241, and the Oligocene stratigraphy around the late Oligocene climate optimum at Site 1237. Site 1233 filled a crucial gap in the stratigraphic and paleoceanographic archive of the South Pacific sector of the Southern Ocean by providing an outstanding reproducible accelerator mass spectrometry (AMS) ¹⁴C-dated paleomagnetic record of centennial- and millennial- scale variability, representing regional variations in environmental/climatic conditions for the past 70,000 yr. With regard to the Cenozoic timetable, the continuous and complete sedimentary sequence of Site 1237, spanning the last ~31 m.y., has the potential of becoming a stratigraphic reference section for the South Pacific. Postcruise work demonstrated the excellence of this record for producing a stratigraphic framework that combines the biostratigraphy and terrific magnetostratigraphy with orbitally tuned stable isotope records. With respect to the bipolar see-saw hypotheses, Leg 202 studies on high-resolution records changed the view of the global distribution of millennial-scale climate change. These studies clearly demonstrate that millennial-scale climate and biogeochemical systems of the southeast Pacific and Chile closely align with those recorded in Antarctica and the southern oceans and that these climate patterns extend to the equatorial Pacific, either transmitted directly by the eastern boundary current or indirectly by “the oceanic tunnel” (subsurface transport via Antarctic Mode or Intermediate Water, Equatorial Undercurrent) injecting Southern Hemisphere extratropical water masses into the equatorial upwelling system. On orbital timescales, most spectacular was the finding that Earth’s final transition into an “icehouse” climate ~13.9 m.y. ago, the middle Miocene intensification of Antarctic glaciation, coincided with a striking transition from obliquity to eccentricity as the drivers of climate change. Thus, the late Pleistocene 100-k.y. climate cycles are not unique in Earth’s history, and although the examples from the Miocene and Pleistocene are both associated with climate cooling, they occur under significantly different global boundary conditions. This important contribution from Leg 202 issues a challenge to climatologists to understand multiple origins of 100-k.y. climate cycles that are now well documented in the geologic record. On timescales of millions of years, late Neogene upper ocean temperature reconstructions in combination with salinity assessments at selected sites from Leg 202 provide further insights into the reorganization of ocean-atmosphere couplings that are linked to the shoaling of the Central American Seaway (CAS), uplift of the Andes, and Pliocene amplification of polar ice sheet expansion. Regional shoaling of the thermocline in the low-latitude eastern Pacific from 5.3 to 4.0 Ma most likely resulted from shoaling of the CAS, as suggested by model experiments. Mixed-layer cooling and freshening in the tropical northeast Pacific warm pool as well as declining sea-surface temperature (SST) and increasing biological productivity off Chile parallel intensification of Northern Hemisphere glaciation from 3.6 to 2.4 Ma. The similarity of temporal changes in SST, upwelling, and dust flux between the Benguela and Chile upwelling systems suggests that uplift of the Andes was probably of secondary importance for generating the observed changes in the southeast Pacific within the last 6 m.y., as the Benguela upwelling system was not affected by mountain uplift. The expected atmosphere- oceanic response of the southeast Pacific to uplift of the Andes probably played a larger role during the late Miocene, prior to 6 Ma. A particular scientific challenge of future Leg 202 paleoclimate research is to better understand the transitions between these different timescales with respect to couplings between global, regional, and local processes. Title: Leg 202 synthesis: Southeast Pacific paleoceangraphy Author: Tiedemann, Ralf, Mix, Alan C. Ocean Drilling Program (ODP) Leg 202 has opened a new window into understanding late Paleogene and Neogene global environmental change by providing high-quality sediment sequences from a previously unsampled region, the eastern South Pacific. Eleven sites (1232– 1242) that record variations on timescales ranging from decades to tens of millions of years were drilled and investigated on transects of both depth (489–4072 m) and latitude (41°S–8°N). Building on the shipboard results presented in the Leg 202 Initial Reports volume, postcruise research has significantly improved the stratigraphic framework and provided new insights into climate-related processes, which operate on different timescales and are relevant to hypotheses concerning the bipolar “see-saw” climate mechanism, orbitally driven changes in the continent-ocean-ice-atmosphere system and tectonic processes associated with the uplift of the Andes, closure of the Central American Seaway, and major expansions of polar ice sheets. Stable isotope records and refinements in bio- and magnetostratigraphy in combination with orbitally tuned cyclostratigraphy significantly improved the Pleistocene stratigraphy at Sites 1233 and 1234, the Miocene– Pliocene stratigraphy at Sites 1236, 1237, 1239, and 1241, and the Oligocene stratigraphy around the late Oligocene climate optimum at Site 1237. Site 1233 filled a crucial gap in the stratigraphic and paleoceanographic archive of the South Pacific sector of the Southern Ocean by providing an outstanding reproducible accelerator mass spectrometry (AMS) ¹⁴C-dated paleomagnetic record of centennial- and millennial- scale variability, representing regional variations in environmental/climatic conditions for the past 70,000 yr. With regard to the Cenozoic timetable, the continuous and complete sedimentary sequence of Site 1237, spanning the last ~31 m.y., has the potential of becoming a stratigraphic reference section for the South Pacific. Postcruise work demonstrated the excellence of this record for producing a stratigraphic framework that combines the biostratigraphy and terrific magnetostratigraphy with orbitally tuned stable isotope records. With respect to the bipolar see-saw hypotheses, Leg 202 studies on high-resolution records changed the view of the global distribution of millennial-scale climate change. These studies clearly demonstrate that millennial-scale climate and biogeochemical systems of the southeast Pacific and Chile closely align with those recorded in Antarctica and the southern oceans and that these climate patterns extend to the equatorial Pacific, either transmitted directly by the eastern boundary current or indirectly by “the oceanic tunnel” (subsurface transport via Antarctic Mode or Intermediate Water, Equatorial Undercurrent) injecting Southern Hemisphere extratropical water masses into the equatorial upwelling system. On orbital timescales, most spectacular was the finding that Earth’s final transition into an “icehouse” climate ~13.9 m.y. ago, the middle Miocene intensification of Antarctic glaciation, coincided with a striking transition from obliquity to eccentricity as the drivers of climate change. Thus, the late Pleistocene 100-k.y. climate cycles are not unique in Earth’s history, and although the examples from the Miocene and Pleistocene are both associated with climate cooling, they occur under significantly different global boundary conditions. This important contribution from Leg 202 issues a challenge to climatologists to understand multiple origins of 100-k.y. climate cycles that are now well documented in the geologic record. On timescales of millions of years, late Neogene upper ocean temperature reconstructions in combination with salinity assessments at selected sites from Leg 202 provide further insights into the reorganization of ocean-atmosphere couplings that are linked to the shoaling of the Central American Seaway (CAS), uplift of the Andes, and Pliocene amplification of polar ice sheet expansion. Regional shoaling of the thermocline in the low-latitude eastern Pacific from 5.3 to 4.0 Ma most likely resulted from shoaling of the CAS, as suggested by model experiments. Mixed-layer cooling and freshening in the tropical northeast Pacific warm pool as well as declining sea-surface temperature (SST) and increasing biological productivity off Chile parallel intensification of Northern Hemisphere glaciation from 3.6 to 2.4 Ma. The similarity of temporal changes in SST, upwelling, and dust flux between the Benguela and Chile upwelling systems suggests that uplift of the Andes was probably of secondary importance for generating the observed changes in the southeast Pacific within the last 6 m.y., as the Benguela upwelling system was not affected by mountain uplift. The expected atmosphere- oceanic response of the southeast Pacific to uplift of the Andes probably played a larger role during the late Miocene, prior to 6 Ma. A particular scientific challenge of future Leg 202 paleoclimate research is to better understand the transitions between these different timescales with respect to couplings between global, regional, and local processes. Close

• 59. [Article] Sedimentation, economic enrichment and evaluation of heavy mineral concentrations on the southern Oregon continental margin

  Heavy minerals can contain potentially economic amounts of metals as both matrix and trace constituents. Such minerals appear as unconsolidated black sands on the continental shelf off southwest Oregon ...

  Citation × Citation Citation Abstract Copy Title: Sedimentation, economic enrichment and evaluation of heavy mineral concentrations on the southern Oregon continental margin Author: Bowman, Kenneth Charles Jr Heavy minerals can contain potentially economic amounts of metals as both matrix and trace constituents. Such minerals appear as unconsolidated black sands on the continental shelf off southwest Oregon and along the Oregon coast. Two diverse energies are considered in this investigation. Environmental energy of the depositional regimen, Part I; energy involved in crystallization of transition metals from a magma, Part III. In Part II, an analytical scheme for the evaluation of opaque oxides is proposed, and an examination of the results as applied to two samples is presented. Part I The unconsolidated black sands on the Oregon continental margin have been profoundly affected by tectonic uplift aid by cyclic erosive transgression and regression. Progressive enrichment in heavy minerals from the Klamath Mountains has apparently occurred during each glacio-eustatic regression of the Pleistocene seas, each regression a period of intensified erosion and sediment transport. Subsequent erosive transgressions selectively sort and redistribute these heavy minerals into paralic beach and nearshore deposits. Uplift of the coast and shelf implies that the heavy minerals were reworked during the Holocene transgression into concentrations of greater extent and higher ore tenor than relict deposits of earlier transgressions in upraised Pleistocene terraces. Extrapolation of ore reserve values from the terraces by "Mirror Image" concepts might seriously underestimate the potential of offshore deposits. Offshore heavy mineral concentrations should be coincident with observed submarine terraces. Part II An analytic scheme was developed to investigate opaque oxides in two samples; one from the Pleistocene terraces; the other from near the present shelf edge. Analyses involving X-ray diffraction techniques, atomic absorption and neutron activation established the mineralogy and elemental distribution in magnetically separated diagnostic splits. Chrome spinel, ilmenite and magnetite comprise the opaque oxide fraction in both samples. Correlation studies of these analyses suggest: (1) Chromium is a matrix metal of chrome spinel and is diadochic into magnetite. (2) Iron appears in all opaque oxides and in increasing amounts with increasing magnetic susceptibility. (3) Titanium is a matrix metal in ilmenite, and diadochic into chrome spinel and magnetite. (4) Nickel and ruthenium are diadochic into and correlated to the spinel structure; i.e. to chrome spinel and magnetite. (5) Osmium appears to be correlated to chromium. (6) Zinc is limited to spinel in these samples. Part III Goldschmidt's and Ringwood's criteria for diadochy often fail to explain the distribution of the transition metals because crystal field effects are not considered. Favored d[superscript n] configurations, e.g. octahedrally coordinated, low spin d⁶ cations in the spinel minerals, result in shortened interatomic distance and significantly strengthened cation-ligand bonds, possibly affecting the distribution of such metal cations. The octahedral site preference energy parameter (OSPE) has been used to explain distributional behavior of the first (3d) transition series metals. OSPE calculations for four low spin d⁶ cations - Co(III), Ru(II), Rh(III), and Pt(IV) - give significantly high values for this parameter. High OSPE valued transition metal cations possibly form stable proto-mineral oxide complexes in the magma which persist through crystallization. These associations predetermine the enrichment of transition metals in oxide minerals and act as nuclei during cooling and solidification. Subduction of oxidized and hydrolyzed near-surface rocks down a Benioff zone provides progressively higher Eh in the magma, a variety of cation oxidation states, and water for sepentinization of ultramafic rocks. The distribution of the platinum metals in a strongly reducing magma environment should be different than in the oxidizing magma proposed for the Klamath ultramafics. The OSPE parameter offers an explanation for the observed distribution of platinum group metals in spinel minerals from this investigation, in chromites from Uralian dunitic massifs and the Stillwater complex; and of iridium from the Great Lake Doleritic Sheet, Tasmania. Chrome spinel from Oregon had twice the concentration of ruthenium, and one-third the amount of osmium as similar Uralian chromite deposits. The first significant concentration of ruthenium in magnetite is herein reported recommending continued research into the platinum metal distribution in southwest Oregon. Title: Sedimentation, economic enrichment and evaluation of heavy mineral concentrations on the southern Oregon continental margin Author: Bowman, Kenneth Charles Jr Heavy minerals can contain potentially economic amounts of metals as both matrix and trace constituents. Such minerals appear as unconsolidated black sands on the continental shelf off southwest Oregon and along the Oregon coast. Two diverse energies are considered in this investigation. Environmental energy of the depositional regimen, Part I; energy involved in crystallization of transition metals from a magma, Part III. In Part II, an analytical scheme for the evaluation of opaque oxides is proposed, and an examination of the results as applied to two samples is presented. Part I The unconsolidated black sands on the Oregon continental margin have been profoundly affected by tectonic uplift aid by cyclic erosive transgression and regression. Progressive enrichment in heavy minerals from the Klamath Mountains has apparently occurred during each glacio-eustatic regression of the Pleistocene seas, each regression a period of intensified erosion and sediment transport. Subsequent erosive transgressions selectively sort and redistribute these heavy minerals into paralic beach and nearshore deposits. Uplift of the coast and shelf implies that the heavy minerals were reworked during the Holocene transgression into concentrations of greater extent and higher ore tenor than relict deposits of earlier transgressions in upraised Pleistocene terraces. Extrapolation of ore reserve values from the terraces by "Mirror Image" concepts might seriously underestimate the potential of offshore deposits. Offshore heavy mineral concentrations should be coincident with observed submarine terraces. Part II An analytic scheme was developed to investigate opaque oxides in two samples; one from the Pleistocene terraces; the other from near the present shelf edge. Analyses involving X-ray diffraction techniques, atomic absorption and neutron activation established the mineralogy and elemental distribution in magnetically separated diagnostic splits. Chrome spinel, ilmenite and magnetite comprise the opaque oxide fraction in both samples. Correlation studies of these analyses suggest: (1) Chromium is a matrix metal of chrome spinel and is diadochic into magnetite. (2) Iron appears in all opaque oxides and in increasing amounts with increasing magnetic susceptibility. (3) Titanium is a matrix metal in ilmenite, and diadochic into chrome spinel and magnetite. (4) Nickel and ruthenium are diadochic into and correlated to the spinel structure; i.e. to chrome spinel and magnetite. (5) Osmium appears to be correlated to chromium. (6) Zinc is limited to spinel in these samples. Part III Goldschmidt's and Ringwood's criteria for diadochy often fail to explain the distribution of the transition metals because crystal field effects are not considered. Favored d[superscript n] configurations, e.g. octahedrally coordinated, low spin d⁶ cations in the spinel minerals, result in shortened interatomic distance and significantly strengthened cation-ligand bonds, possibly affecting the distribution of such metal cations. The octahedral site preference energy parameter (OSPE) has been used to explain distributional behavior of the first (3d) transition series metals. OSPE calculations for four low spin d⁶ cations - Co(III), Ru(II), Rh(III), and Pt(IV) - give significantly high values for this parameter. High OSPE valued transition metal cations possibly form stable proto-mineral oxide complexes in the magma which persist through crystallization. These associations predetermine the enrichment of transition metals in oxide minerals and act as nuclei during cooling and solidification. Subduction of oxidized and hydrolyzed near-surface rocks down a Benioff zone provides progressively higher Eh in the magma, a variety of cation oxidation states, and water for sepentinization of ultramafic rocks. The distribution of the platinum metals in a strongly reducing magma environment should be different than in the oxidizing magma proposed for the Klamath ultramafics. The OSPE parameter offers an explanation for the observed distribution of platinum group metals in spinel minerals from this investigation, in chromites from Uralian dunitic massifs and the Stillwater complex; and of iridium from the Great Lake Doleritic Sheet, Tasmania. Chrome spinel from Oregon had twice the concentration of ruthenium, and one-third the amount of osmium as similar Uralian chromite deposits. The first significant concentration of ruthenium in magnetite is herein reported recommending continued research into the platinum metal distribution in southwest Oregon. Close

• 60. [Article] Late Pleistocene Slip Rate along the Panamint Valley Fault System, Eastern California

  The Eastern California Shear Zone (ECSZ) is a broad zone of dextral shear inboard of the North American - Pacific plate boundary. Despite decades of study, the significance of a mismatch between geodetic ...

  Citation × Citation Citation Abstract Copy Title: Late Pleistocene Slip Rate along the Panamint Valley Fault System, Eastern California Author: Choi, Na Hyung The Eastern California Shear Zone (ECSZ) is a broad zone of dextral shear inboard of the North American - Pacific plate boundary. Despite decades of study, the significance of a mismatch between geodetic velocities and geologic fault slip rates across the ECSZ remains incompletely understood. Geodetically determined interseismic strain across the ECSZ has been determined to be 9-11 mm/yr, but across much of the ECSZ, the geologic rates sum to only about 50% that rate. At the latitude of 36°-37°N, geologic slip rates have been constrained along the length of Owens Valley and Death Valley fault systems; however, the neighboring Panamint Valley fault system (PVFS) has limited geologic slip data. Existing estimates of Late Pleistocene - Holocene slip rates along the PVFS are relatively slow (~2-3 mm/yr) and come from a single site along the southernmost fault segment. In contrast, geodetic measurements through GPS and InSAR suggest that the northernmost segment of the PVFS, the Hunter Mountain fault, may experience slip rates as high as 6 mm/yr. Offset Holocene geomorphic markers along the Hunter Mountain fault have been proposed to record 3-4 mm/yr of slip, albeit with a qualitative age constraint; however, slip rates along the central PVFS are completely lacking. In this thesis, I present results from an investigation of displaced alluvial fan surfaces along the central PVFS, at the mouth of Jail Canyon. This site is characterized by a relict channel system associated with a large alluvial fan complex: The channel is displaced dextrally across a ~500 m wide zone of distributed deformation. Restoration of the channel with the aid of LiDAR digital topography suggests 118 m of net slip, oriented 303°, across the PVFS. The degree of soil development and the degraded morphology of channel walls place bounds on the abandonment ages of displaced surfaces. Soil ages are based on a set of soils in twelve alluvial deposits of known age in Panamint Valley and the Mojave Desert (Hoffman, 2009). Profile development indices (PDI) of these soils suggest a strong correlation of soil development with age; interpolation of this empirical relationship to soils at Jail Canyon suggests that soils in the displaced surfaces are likely 11-22 ka (and up to 29 ka within 95% confidence). To model the age of the offset channel walls at Jail Canyon, a range of diffusivity constants, which controls the rate of change in elevation, was locally calibrated for Panamint Valley. Calibration with fault scarps and wave-cut scarps of known age suggests a best-estimate diffusivity range of 1.2 - 2.5 m²/ka. Applying this range to the degradation of channel risers at Jail Canyon results in a best-estimate age of 9 - 19 ka, consistent with soil ages. Using an age range of 20-30 ka, bounded by the conservative end of age estimate from each method, the minimum slip rate along this segment of the PVFS is 4-6 mm/yr. This rate is faster than any existing geologic slip rate along the PVFS and confirms previous suggestions that (1) the PVFS carries a large fraction of dextral shear in the ECSZ north of the Garlock Fault, (2) slip along the PVFS has been accelerating in the past 3-4 Ma, and (3) all three major fault systems north of the Garlock decrease in slip southward despite the steady geodetic velocities. Title: Late Pleistocene Slip Rate along the Panamint Valley Fault System, Eastern California Author: Choi, Na Hyung The Eastern California Shear Zone (ECSZ) is a broad zone of dextral shear inboard of the North American - Pacific plate boundary. Despite decades of study, the significance of a mismatch between geodetic velocities and geologic fault slip rates across the ECSZ remains incompletely understood. Geodetically determined interseismic strain across the ECSZ has been determined to be 9-11 mm/yr, but across much of the ECSZ, the geologic rates sum to only about 50% that rate. At the latitude of 36°-37°N, geologic slip rates have been constrained along the length of Owens Valley and Death Valley fault systems; however, the neighboring Panamint Valley fault system (PVFS) has limited geologic slip data. Existing estimates of Late Pleistocene - Holocene slip rates along the PVFS are relatively slow (~2-3 mm/yr) and come from a single site along the southernmost fault segment. In contrast, geodetic measurements through GPS and InSAR suggest that the northernmost segment of the PVFS, the Hunter Mountain fault, may experience slip rates as high as 6 mm/yr. Offset Holocene geomorphic markers along the Hunter Mountain fault have been proposed to record 3-4 mm/yr of slip, albeit with a qualitative age constraint; however, slip rates along the central PVFS are completely lacking. In this thesis, I present results from an investigation of displaced alluvial fan surfaces along the central PVFS, at the mouth of Jail Canyon. This site is characterized by a relict channel system associated with a large alluvial fan complex: The channel is displaced dextrally across a ~500 m wide zone of distributed deformation. Restoration of the channel with the aid of LiDAR digital topography suggests 118 m of net slip, oriented 303°, across the PVFS. The degree of soil development and the degraded morphology of channel walls place bounds on the abandonment ages of displaced surfaces. Soil ages are based on a set of soils in twelve alluvial deposits of known age in Panamint Valley and the Mojave Desert (Hoffman, 2009). Profile development indices (PDI) of these soils suggest a strong correlation of soil development with age; interpolation of this empirical relationship to soils at Jail Canyon suggests that soils in the displaced surfaces are likely 11-22 ka (and up to 29 ka within 95% confidence). To model the age of the offset channel walls at Jail Canyon, a range of diffusivity constants, which controls the rate of change in elevation, was locally calibrated for Panamint Valley. Calibration with fault scarps and wave-cut scarps of known age suggests a best-estimate diffusivity range of 1.2 - 2.5 m²/ka. Applying this range to the degradation of channel risers at Jail Canyon results in a best-estimate age of 9 - 19 ka, consistent with soil ages. Using an age range of 20-30 ka, bounded by the conservative end of age estimate from each method, the minimum slip rate along this segment of the PVFS is 4-6 mm/yr. This rate is faster than any existing geologic slip rate along the PVFS and confirms previous suggestions that (1) the PVFS carries a large fraction of dextral shear in the ECSZ north of the Garlock Fault, (2) slip along the PVFS has been accelerating in the past 3-4 Ma, and (3) all three major fault systems north of the Garlock decrease in slip southward despite the steady geodetic velocities. Close

• 61. [Article] An Interdisciplinary approach towards understanding late Pleistocene ice sheet change

  The results presented in this dissertation address a number of questions regarding late Pleistocene and Holocene ice-sheet and climate interactions, spanning disciplines involving paleoclimatology and ...

  Citation × Citation Citation Abstract Copy Title: An Interdisciplinary approach towards understanding late Pleistocene ice sheet change Author: Cuzzone, Joshua The results presented in this dissertation address a number of questions regarding late Pleistocene and Holocene ice-sheet and climate interactions, spanning disciplines involving paleoclimatology and atmospheric science. These studies use various techniques in geochemistry, climate modeling, and ice-sheet modeling to address ice- sheet response to climate and the attendant interactions between the atmosphere and ice- sheets. An important question in paleoclimatology involves the response of past ice sheets to a warming climate, with the end goal of providing context for understanding the response of future ice sheets to anthropogenic warming. A longstanding question regards the timing and rate of retreat for the Scandinavian Ice Sheet (SIS) during the Holocene. Much work has been done to constrain the retreat of the SIS from the last glacial maximum to the well-defined Younger Dryas moraines, however, little is known regarding the SIS Holocene retreat. Presented is a compilation of 87 ¹⁰Be surface exposure ages from Sweden and Norway. These ages provide a high-resolution reconstruction of the SIS deglaciation during the Holocene, and allow for close comparison with proxies of temperature and insolation. The results suggest an asymmetric deglaciation of the SIS, with retreat forced by both a warming climate and and ice-sheet dynamics depending on time and location. The record also provides a means for evaluating the SIS contribution to Holocene sea-level rise. Combining this with estimates from the Laurentide Ice Sheet and the Greenland Ice Sheet, our results suggest that ~23 m of residual sea-level rise exists at the start of the Holocene. We suggest an Antarctic source, which has implications for understanding the sensitivity of the Antarctic Ice Sheet to Holocene climate change. Ice-sheets exert a large presence on the overlying atmosphere, with these interactions influencing the general circulation and ultimately the surface mass balance of the ice sheet. Prior work has indicated striking differences in the atmospheric circulation between the LGM and present day. Using a fully coupled climate simulation of the last deglaciation, the atmospheric circulation is studied, with respect to the stationary waves and storm tracks. For this study, we focus on the LIS. Our results show an enhanced stationary wave, forced mechanically by the topography of the LIS along western North America, which provides moisture, driven by enhanced ridging. This mechanism provides a positive feedback, whereby a larger ice sheet drives a more positive wintertime mass balance. Eventually, as the ice sheet melts, this stationary wave weakens, and the moisture flux decreases. Over the eastern LIS, coupled atmosphere and ice-sheet dynamics conspire to weaken the storm track at the LGM. As the ice melts, however, the storm track becomes broader and strengthens. The storm track becomes an efficient means for moisture delivery to the eastern LIS, with this relationship strengthening through the deglaciation. We suggest that enhanced wintertime accumulation from the strengthening storm track may have played a strong role in offsetting summertime ablation along the eastern LIS, and thus may be a reason why the LIS terminated over eastern North America. Another longstanding question in paleoclimatology involves the role of CO₂ and insolation on driving the deglaciation of the great Northern hemisphere ice sheets. To investigate this question we one way coupled the 3-dimensional thermomechanical ice- sheet model, Glimmer to climate simulations of the last deglaciation using GENMOM. We first built up a realistic LIS, constrained by the best available reconstructions of the area and volume, by perturbing parameters to obtain the best fit. Once a suitable spun-up LGM LIS was created, we forced the deglaciation of the LIS using climate simulations of the last deglaciation using either varying insolation only, and varying CO₂ only. Our results show similar trends in the deglaciation of the LIS relative to simulations of the deglaciation forced with all forcings (CO₂ and insolation). Upon further inspection, our results prove that the one way coupling scheme is unable to capture the influence of the separate forcings. Instead, the topography boundary condition used to drive the climate simulations dictates the distribution of heat and moisture, and thus the deglaciation. Our results show that in order to properly simulate the response of the LIS to CO₂ and insolation only forcings, an asynchronous coupling scheme or coupled climate-ice-sheet models should be used. Title: An Interdisciplinary approach towards understanding late Pleistocene ice sheet change Author: Cuzzone, Joshua The results presented in this dissertation address a number of questions regarding late Pleistocene and Holocene ice-sheet and climate interactions, spanning disciplines involving paleoclimatology and atmospheric science. These studies use various techniques in geochemistry, climate modeling, and ice-sheet modeling to address ice- sheet response to climate and the attendant interactions between the atmosphere and ice- sheets. An important question in paleoclimatology involves the response of past ice sheets to a warming climate, with the end goal of providing context for understanding the response of future ice sheets to anthropogenic warming. A longstanding question regards the timing and rate of retreat for the Scandinavian Ice Sheet (SIS) during the Holocene. Much work has been done to constrain the retreat of the SIS from the last glacial maximum to the well-defined Younger Dryas moraines, however, little is known regarding the SIS Holocene retreat. Presented is a compilation of 87 ¹⁰Be surface exposure ages from Sweden and Norway. These ages provide a high-resolution reconstruction of the SIS deglaciation during the Holocene, and allow for close comparison with proxies of temperature and insolation. The results suggest an asymmetric deglaciation of the SIS, with retreat forced by both a warming climate and and ice-sheet dynamics depending on time and location. The record also provides a means for evaluating the SIS contribution to Holocene sea-level rise. Combining this with estimates from the Laurentide Ice Sheet and the Greenland Ice Sheet, our results suggest that ~23 m of residual sea-level rise exists at the start of the Holocene. We suggest an Antarctic source, which has implications for understanding the sensitivity of the Antarctic Ice Sheet to Holocene climate change. Ice-sheets exert a large presence on the overlying atmosphere, with these interactions influencing the general circulation and ultimately the surface mass balance of the ice sheet. Prior work has indicated striking differences in the atmospheric circulation between the LGM and present day. Using a fully coupled climate simulation of the last deglaciation, the atmospheric circulation is studied, with respect to the stationary waves and storm tracks. For this study, we focus on the LIS. Our results show an enhanced stationary wave, forced mechanically by the topography of the LIS along western North America, which provides moisture, driven by enhanced ridging. This mechanism provides a positive feedback, whereby a larger ice sheet drives a more positive wintertime mass balance. Eventually, as the ice sheet melts, this stationary wave weakens, and the moisture flux decreases. Over the eastern LIS, coupled atmosphere and ice-sheet dynamics conspire to weaken the storm track at the LGM. As the ice melts, however, the storm track becomes broader and strengthens. The storm track becomes an efficient means for moisture delivery to the eastern LIS, with this relationship strengthening through the deglaciation. We suggest that enhanced wintertime accumulation from the strengthening storm track may have played a strong role in offsetting summertime ablation along the eastern LIS, and thus may be a reason why the LIS terminated over eastern North America. Another longstanding question in paleoclimatology involves the role of CO₂ and insolation on driving the deglaciation of the great Northern hemisphere ice sheets. To investigate this question we one way coupled the 3-dimensional thermomechanical ice- sheet model, Glimmer to climate simulations of the last deglaciation using GENMOM. We first built up a realistic LIS, constrained by the best available reconstructions of the area and volume, by perturbing parameters to obtain the best fit. Once a suitable spun-up LGM LIS was created, we forced the deglaciation of the LIS using climate simulations of the last deglaciation using either varying insolation only, and varying CO₂ only. Our results show similar trends in the deglaciation of the LIS relative to simulations of the deglaciation forced with all forcings (CO₂ and insolation). Upon further inspection, our results prove that the one way coupling scheme is unable to capture the influence of the separate forcings. Instead, the topography boundary condition used to drive the climate simulations dictates the distribution of heat and moisture, and thus the deglaciation. Our results show that in order to properly simulate the response of the LIS to CO₂ and insolation only forcings, an asynchronous coupling scheme or coupled climate-ice-sheet models should be used. Close

• 62. [Article] Ecological Change on California’s Channel Islands from the Pleistocene to the Anthropocene

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by Oxford University ...

  Citation × Citation Citation Abstract Copy Title: Ecological Change on California’s Channel Islands from the Pleistocene to the Anthropocene Author: Ghalambor, Cameron K., Still, Christopher, Rick, Torben C., et al., Sillett, T. Scott To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by Oxford University Press on behalf of the American Institute of Biological Sciences and is in the public domain. The published article can be found at: http://bioscience.oxfordjournals.org/. Title: Ecological Change on California’s Channel Islands from the Pleistocene to the Anthropocene Author: Ghalambor, Cameron K., Still, Christopher, Rick, Torben C., et al., Sillett, T. Scott To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by Oxford University Press on behalf of the American Institute of Biological Sciences and is in the public domain. The published article can be found at: http://bioscience.oxfordjournals.org/. Close

• 63. [Article] Paleointensity of the Earth's magnetic field and K-Ar dating of the Louchadiere volcanic flow (Central France) : new evidence for the Laschamp excursion

  copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: Paleointensity of the Earth's magnetic field and K-Ar dating of the Louchadiere volcanic flow (Central France) : new evidence for the Laschamp excursion Author: Chauvin, Annick, Duncan, Robert A., Bonhommet, Norbert, Levi, Saul copyrighted by American Geophysical Union. Title: Paleointensity of the Earth's magnetic field and K-Ar dating of the Louchadiere volcanic flow (Central France) : new evidence for the Laschamp excursion Author: Chauvin, Annick, Duncan, Robert A., Bonhommet, Norbert, Levi, Saul copyrighted by American Geophysical Union. Close

• 64. [Article] Seismoturbidite record as preserved at core sites at the Cascadia and Sumatra–Andaman subduction zones

  This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/home.html.

  Citation × Citation Citation Abstract Copy Title: Seismoturbidite record as preserved at core sites at the Cascadia and Sumatra–Andaman subduction zones Author: Patton, J. R., Udrekh, Goldfinger, C., Djadjadihardja, Y., Morey, A. E., Romsos, C., Black, B. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/home.html. Title: Seismoturbidite record as preserved at core sites at the Cascadia and Sumatra–Andaman subduction zones Author: Patton, J. R., Udrekh, Goldfinger, C., Djadjadihardja, Y., Morey, A. E., Romsos, C., Black, B. This is the publisher’s final pdf. The published article is copyrighted by Copernicus Publications and can be found at: http://publications.copernicus.org/home.html. Close

• 65. [Article] Export production and carbonate dissolution in the central equatorial Pacific Ocean over the past 1 Myr

  Copyright 2000 by the American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Export production and carbonate dissolution in the central equatorial Pacific Ocean over the past 1 Myr Author: Polsky, C. H., Leinen, M., Murray, R. W., Knowlton, C. W., Mix, Alan C. Copyright 2000 by the American Geophysical Union Title: Export production and carbonate dissolution in the central equatorial Pacific Ocean over the past 1 Myr Author: Polsky, C. H., Leinen, M., Murray, R. W., Knowlton, C. W., Mix, Alan C. Copyright 2000 by the American Geophysical Union Close

• 66. [Article] Volcanoes of the Three Sisters region, Oregon Cascades

  Gerald W. Williams Collection

  Citation × Citation Citation Abstract Copy Title: Volcanoes of the Three Sisters region, Oregon Cascades Author: Williams, Howel, 1898-1980 Gerald W. Williams Collection Title: Volcanoes of the Three Sisters region, Oregon Cascades Author: Williams, Howel, 1898-1980 Gerald W. Williams Collection Close

• 67. [Article] Virola dominicana sp. nov., (Myristicaceae) from Dominican amber

  This is an author's manuscript version. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/doi/full/10.1139/cjb-2013-0019.

  Citation × Citation Citation Abstract Copy Title: Virola dominicana sp. nov., (Myristicaceae) from Dominican amber Author: Poinar, George, Jr., Steeves, Royce This is an author's manuscript version. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/doi/full/10.1139/cjb-2013-0019. Title: Virola dominicana sp. nov., (Myristicaceae) from Dominican amber Author: Poinar, George, Jr., Steeves, Royce This is an author's manuscript version. The published article is copyrighted by NRC Research Press and can be found at: http://www.nrcresearchpress.com/doi/full/10.1139/cjb-2013-0019. Close

• 68. [Article] Origin and distribution of the fish fauna of the Harney Basin, Oregon

  A theory of the origin and distribution of fishes in the Harney Basin is presented. Blitzen River, the hydrographically and ecologically isolated creeks, and the upland tributaries of Silvies River all ...

  Citation × Citation Citation Abstract Copy Title: Origin and distribution of the fish fauna of the Harney Basin, Oregon Author: Bisson, Peter Andre A theory of the origin and distribution of fishes in the Harney Basin is presented. Blitzen River, the hydrographically and ecologically isolated creeks, and the upland tributaries of Silvies River all contain populations derived from the basin's Pleistocene connection with Malheur River of the Snake system. Colonization of many streams took Place during periods of high precipitation; isolation has resulted froth dessicating trends since the last glaciation. Stream capture has apparently facilitated a secondary invasion of fishes into Silvies River from John Day River, a tributary of the lower Columbia. This conclusion is further supported by the presence of several species only in central Silvies River within the basin. Certain populations similar to those occurring in isolated regions of the Harney Basin also exist above the barrier falls of the south fork of John Day River, but this drainage is believed to be another disrupted fragment containing descendants of a more ancient Columbia fauna. Speculation regarding the sequence of radiation of different species throughout the Columbia watershed is aided by distributional patterns and knowledge of hydrographic history. Title: Origin and distribution of the fish fauna of the Harney Basin, Oregon Author: Bisson, Peter Andre A theory of the origin and distribution of fishes in the Harney Basin is presented. Blitzen River, the hydrographically and ecologically isolated creeks, and the upland tributaries of Silvies River all contain populations derived from the basin's Pleistocene connection with Malheur River of the Snake system. Colonization of many streams took Place during periods of high precipitation; isolation has resulted froth dessicating trends since the last glaciation. Stream capture has apparently facilitated a secondary invasion of fishes into Silvies River from John Day River, a tributary of the lower Columbia. This conclusion is further supported by the presence of several species only in central Silvies River within the basin. Certain populations similar to those occurring in isolated regions of the Harney Basin also exist above the barrier falls of the south fork of John Day River, but this drainage is believed to be another disrupted fragment containing descendants of a more ancient Columbia fauna. Speculation regarding the sequence of radiation of different species throughout the Columbia watershed is aided by distributional patterns and knowledge of hydrographic history. Close

• 69. [Article] Structure and stratigraphy of the Sheep Mountain area, Centennial Range, Montana-Idaho

  The thesis area includes 44 square miles of the Centennial Range in Beaverhead County, Montana, and Clark County, Idaho. The rocks exposed in the area range in age from Precambrian to Recent and have been ...

  Citation × Citation Citation Abstract Copy Title: Structure and stratigraphy of the Sheep Mountain area, Centennial Range, Montana-Idaho Author: Moran, John Lee The thesis area includes 44 square miles of the Centennial Range in Beaverhead County, Montana, and Clark County, Idaho. The rocks exposed in the area range in age from Precambrian to Recent and have been divided into 23 mapped units. Pre-Belt metamorphic basement rocks are overlain unconformably by 3,433 feet of Paleozoic strata included in eleven formations. These formations represent all of the periods of the Paleozoic except the Ordovician and Silurian. Nine formations represent all the periods of the Mesozoic and total approximately 3,127 feet in thickness. Cenozoic units present in the area are basalts and rhyolites, landslide debris, glacial deposits, and alluvium. The major structure of the thesis area is a fault block that is the result of uplifting and tilting of the east-west trending Centennial Range during the downwarp of the Snake River Plain in late Pliocene and Pleistocene time. No stratigraphic or structural conditions in the thesis area are favorable for the accumulation and entrapment of oil and gas. Phosphorite has been mined from the Phosphoria Formation in the area. Title: Structure and stratigraphy of the Sheep Mountain area, Centennial Range, Montana-Idaho Author: Moran, John Lee The thesis area includes 44 square miles of the Centennial Range in Beaverhead County, Montana, and Clark County, Idaho. The rocks exposed in the area range in age from Precambrian to Recent and have been divided into 23 mapped units. Pre-Belt metamorphic basement rocks are overlain unconformably by 3,433 feet of Paleozoic strata included in eleven formations. These formations represent all of the periods of the Paleozoic except the Ordovician and Silurian. Nine formations represent all the periods of the Mesozoic and total approximately 3,127 feet in thickness. Cenozoic units present in the area are basalts and rhyolites, landslide debris, glacial deposits, and alluvium. The major structure of the thesis area is a fault block that is the result of uplifting and tilting of the east-west trending Centennial Range during the downwarp of the Snake River Plain in late Pliocene and Pleistocene time. No stratigraphic or structural conditions in the thesis area are favorable for the accumulation and entrapment of oil and gas. Phosphorite has been mined from the Phosphoria Formation in the area. Close

• 70. [Article] Calcium carbonate, organic carbon, and quartz in hemipelagic sediments off Oregon : a preliminary investigation

  An analysis of the amounts of calcium carbonate, organic carbon, quartz, and the rates of sediment accumulation in hemipelagic sediments off Oregon has revealed that the accumulation rates of the total sediment, ...

  Citation × Citation Citation Abstract Copy Title: Calcium carbonate, organic carbon, and quartz in hemipelagic sediments off Oregon : a preliminary investigation Author: Peterson, Robert E. An analysis of the amounts of calcium carbonate, organic carbon, quartz, and the rates of sediment accumulation in hemipelagic sediments off Oregon has revealed that the accumulation rates of the total sediment, organic carbon, and quartz were at least twice as high in the late Pleistocene as they were during the Holocene. The accumulation rate of calcium carbonate was at least 8 times as high. There may have been a short transition period at the end of the last glacial stage from about 14,000 to 12,500 years B.P. when the sedimentation rate was very high up to 75 cm/l000 years. There is evidence that the amount of organic carbon in deep-sea sediments is a function of terrigenous influx, of preservation, and possibly of depth of burial in the sediment. Turbidite sequences in the deep-sea environment off Oregon contain much higher amounts of organic carbon in the upper fine-grained portion of the sequence than in the coarser basal sediment of the sequence, indicating that organic carbon is concentrated in the finer and slower settling parts of the flow. In lower continental slope sediments, the greatest amounts of organic carbon are found in the <4 micron size fraction. Title: Calcium carbonate, organic carbon, and quartz in hemipelagic sediments off Oregon : a preliminary investigation Author: Peterson, Robert E. An analysis of the amounts of calcium carbonate, organic carbon, quartz, and the rates of sediment accumulation in hemipelagic sediments off Oregon has revealed that the accumulation rates of the total sediment, organic carbon, and quartz were at least twice as high in the late Pleistocene as they were during the Holocene. The accumulation rate of calcium carbonate was at least 8 times as high. There may have been a short transition period at the end of the last glacial stage from about 14,000 to 12,500 years B.P. when the sedimentation rate was very high up to 75 cm/l000 years. There is evidence that the amount of organic carbon in deep-sea sediments is a function of terrigenous influx, of preservation, and possibly of depth of burial in the sediment. Turbidite sequences in the deep-sea environment off Oregon contain much higher amounts of organic carbon in the upper fine-grained portion of the sequence than in the coarser basal sediment of the sequence, indicating that organic carbon is concentrated in the finer and slower settling parts of the flow. In lower continental slope sediments, the greatest amounts of organic carbon are found in the <4 micron size fraction. Close

• 71. [Article] Interrelationships of spodosols, andepts, and ultisols on coastal terraces in Curry County, Oregon

  Distribution and characteristics of soils were determined across a series of six coastal terraces in Curry Co., Oregon. Classification of soils and interrelationships of properties were determined. Soil-landscape ...

  Citation × Citation Citation Abstract Copy Title: Interrelationships of spodosols, andepts, and ultisols on coastal terraces in Curry County, Oregon Author: Hoppe, Diane A. S. Distribution and characteristics of soils were determined across a series of six coastal terraces in Curry Co., Oregon. Classification of soils and interrelationships of properties were determined. Soil-landscape relationships were examined and soil profile development related to relative ages of terraces. Ten pedons were sampled from five terraces of Pleistocene age. All profiles were analyzed for particle size distribution; bulk density; water retention, -1.5 MPa; aluminum and iron extracted with oxalate, citrate-dithionite and sodium pyrophosphate; pH; phosphate retention; exchangeable aluminum; organic carbon; and cation exchange capacity. Andeptic Humitropepts occur on intermediate terraces, in close proximity to the coast. Andeptic Haplohumults occur on the better drained areas of the intermediate terrace, but further inland. Soils in less well drained areas of the intermediate and higher terraces classify as Spodosols, based on morphological features. Ultisols occur on the highest terraces. Profile morphology, particle size and iron extracts are compared between terraces to derive age relationships. Title: Interrelationships of spodosols, andepts, and ultisols on coastal terraces in Curry County, Oregon Author: Hoppe, Diane A. S. Distribution and characteristics of soils were determined across a series of six coastal terraces in Curry Co., Oregon. Classification of soils and interrelationships of properties were determined. Soil-landscape relationships were examined and soil profile development related to relative ages of terraces. Ten pedons were sampled from five terraces of Pleistocene age. All profiles were analyzed for particle size distribution; bulk density; water retention, -1.5 MPa; aluminum and iron extracted with oxalate, citrate-dithionite and sodium pyrophosphate; pH; phosphate retention; exchangeable aluminum; organic carbon; and cation exchange capacity. Andeptic Humitropepts occur on intermediate terraces, in close proximity to the coast. Andeptic Haplohumults occur on the better drained areas of the intermediate terrace, but further inland. Soils in less well drained areas of the intermediate and higher terraces classify as Spodosols, based on morphological features. Ultisols occur on the highest terraces. Profile morphology, particle size and iron extracts are compared between terraces to derive age relationships. Close

• 72. [Article] Geology and structure of the Brothers Fault Zone in the central part of the Millican SE quadrangle, Deschutes County, Oregon

  The thesis is a structural and petrographic study of approximately 23 square miles in the Millican SE quadrangle, Deschutes County, Oregon. The area lies along the Brothers fault zone. Bedrock in the area ...

  Citation × Citation Citation Abstract Copy Title: Geology and structure of the Brothers Fault Zone in the central part of the Millican SE quadrangle, Deschutes County, Oregon Author: Tucker, Elizabeth Ruth The thesis is a structural and petrographic study of approximately 23 square miles in the Millican SE quadrangle, Deschutes County, Oregon. The area lies along the Brothers fault zone. Bedrock in the area is of Pliocene to Recent age and consists of an older basaltic unit with an associated dacite, a younger dacite, and a younger basaltic unit. The older basaltic unit and both dacites have been severely faulted. The younger basaltic unit has filled in topographic lows and is relatively undeformed. The dominant faults in the area are en echelon high-angle normal faults trending N. 40°W. with vertical displacements up to 600 feet. Cross faults with smaller displacements trend N. 45°E. The normal faults are Reidel and conjugate Reidel shears and are interpreted as the surface expression of a deep-seated right lateral displacement. The fault zone displaces units of Miocene to Pleistocene age and is considered to have been active during that time. Title: Geology and structure of the Brothers Fault Zone in the central part of the Millican SE quadrangle, Deschutes County, Oregon Author: Tucker, Elizabeth Ruth The thesis is a structural and petrographic study of approximately 23 square miles in the Millican SE quadrangle, Deschutes County, Oregon. The area lies along the Brothers fault zone. Bedrock in the area is of Pliocene to Recent age and consists of an older basaltic unit with an associated dacite, a younger dacite, and a younger basaltic unit. The older basaltic unit and both dacites have been severely faulted. The younger basaltic unit has filled in topographic lows and is relatively undeformed. The dominant faults in the area are en echelon high-angle normal faults trending N. 40°W. with vertical displacements up to 600 feet. Cross faults with smaller displacements trend N. 45°E. The normal faults are Reidel and conjugate Reidel shears and are interpreted as the surface expression of a deep-seated right lateral displacement. The fault zone displaces units of Miocene to Pleistocene age and is considered to have been active during that time. Close

• 73. [Article] Morphometric properties of nivation hollows on Hart Mountain, Lake County, Oregon

  Hart Mountain is a basaltic fault block mountain in the semi-desert region of the northern Basin and Range province in south-central Oregon. Geomorphic processes associated with lingering snowpatches have ...

  Citation × Citation Citation Abstract Copy Title: Morphometric properties of nivation hollows on Hart Mountain, Lake County, Oregon Author: Rademacher, Christopher L. Hart Mountain is a basaltic fault block mountain in the semi-desert region of the northern Basin and Range province in south-central Oregon. Geomorphic processes associated with lingering snowpatches have formed nivation hollows, which are small scale depressions in the hillsides. The lingering snow in the hollows prohibits shrub growth. Bedrock scarps, present in some of the hollows, show indications of chemical alteration. Bills are present below most of the hollows, indicating that surface runoff from these sites occurs. Average hillslope, which controls the shear stress placed on soil particles, is statistically related to morphometric attributes defining the size and angles of the hollows. Simple linear regressions and the nonparametric Kendall's rank correlation coefficient (p-) and Theil's C test for the regression line slope suggest that average hillslope is directly related to the morphometric attributes of the hollows. Heat transfer controls the areal distribution and duration of snowpatcnes. A relative insolation factor and elevation are taken as surrogates for heat transfer. These surrogates are likewise correlated with the morphometric attributes of the hollows. Both the elevation and the relative insolation factor suggest an inverse relationship between heat transfer and the size of nivation hollows. The hollows on Hart Mountain appear to have been formed by accelerated nivation processes during the Pleistocene and are currently being modified by less intense nivation. Title: Morphometric properties of nivation hollows on Hart Mountain, Lake County, Oregon Author: Rademacher, Christopher L. Hart Mountain is a basaltic fault block mountain in the semi-desert region of the northern Basin and Range province in south-central Oregon. Geomorphic processes associated with lingering snowpatches have formed nivation hollows, which are small scale depressions in the hillsides. The lingering snow in the hollows prohibits shrub growth. Bedrock scarps, present in some of the hollows, show indications of chemical alteration. Bills are present below most of the hollows, indicating that surface runoff from these sites occurs. Average hillslope, which controls the shear stress placed on soil particles, is statistically related to morphometric attributes defining the size and angles of the hollows. Simple linear regressions and the nonparametric Kendall's rank correlation coefficient (p-) and Theil's C test for the regression line slope suggest that average hillslope is directly related to the morphometric attributes of the hollows. Heat transfer controls the areal distribution and duration of snowpatcnes. A relative insolation factor and elevation are taken as surrogates for heat transfer. These surrogates are likewise correlated with the morphometric attributes of the hollows. Both the elevation and the relative insolation factor suggest an inverse relationship between heat transfer and the size of nivation hollows. The hollows on Hart Mountain appear to have been formed by accelerated nivation processes during the Pleistocene and are currently being modified by less intense nivation. Close

• 74. [Article] The Ore Bin ; Vol. 34 No. 5 (May 1972)

  The Oregon Coast between Yachats and Newport is a narrow, slightly elevated coastal plain. With the exceptions of basalt rock at Yachats and Seal Rock, the bedrock along this segment of the coast is sedimentary. ...

  Citation × Citation Citation Abstract Copy Title: The Ore Bin ; Vol. 34 No. 5 (May 1972) Author: Lund, Ernest H., Oregon. Dept. of Geology and Mineral Industries The Oregon Coast between Yachats and Newport is a narrow, slightly elevated coastal plain. With the exceptions of basalt rock at Yachats and Seal Rock, the bedrock along this segment of the coast is sedimentary. Several Pleistocene marine terrace levels are discernible at places along the plain, and sand dunes, both active and stabilized, impart a rolling topography to most of it. Numerous streams have incised small valleys and ravines into its surface; at Waldport the plain is interrupted by the estuary of the Alsea River and at Ona Beach State Park by the alluvial plain of Beaver Creek. Except in the two localities where basalt is exposed, the shore is marked by long stretches of sandy beaches bounded by low sea cliffs. Where the basalt is exposed, the shore has the rugged features that are characteristic of Oregon shores bounded by this type of rock. Title: The Ore Bin ; Vol. 34 No. 5 (May 1972) Author: Lund, Ernest H., Oregon. Dept. of Geology and Mineral Industries The Oregon Coast between Yachats and Newport is a narrow, slightly elevated coastal plain. With the exceptions of basalt rock at Yachats and Seal Rock, the bedrock along this segment of the coast is sedimentary. Several Pleistocene marine terrace levels are discernible at places along the plain, and sand dunes, both active and stabilized, impart a rolling topography to most of it. Numerous streams have incised small valleys and ravines into its surface; at Waldport the plain is interrupted by the estuary of the Alsea River and at Ona Beach State Park by the alluvial plain of Beaver Creek. Except in the two localities where basalt is exposed, the shore is marked by long stretches of sandy beaches bounded by low sea cliffs. Where the basalt is exposed, the shore has the rugged features that are characteristic of Oregon shores bounded by this type of rock. Close

• 75. [Article] The Ore bin ; Vol. 33 No. 2 (February 1971)

  The 26-mile stretch of shore extending from Florence to Yachats is one of the most rugged and scenic parts of the Oregon Coast. Along most of this part of the coast the shore is bounded by basalt bedrock ...

  Citation × Citation Citation Abstract Copy Title: The Ore bin ; Vol. 33 No. 2 (February 1971) Author: Lund, Ernest H., Oregon. Dept. of Geology and Mineral Industries The 26-mile stretch of shore extending from Florence to Yachats is one of the most rugged and scenic parts of the Oregon Coast. Along most of this part of the coast the shore is bounded by basalt bedrock of varied types. Through differential erosion of the basalt, the many landforms, such as headlands, rocky shores, reefs, and sea stacks, that impart the rugged character to the coast have been and are still in the process of being developed. In places where the basalt bedrock is least resistant to erosion, small embayments with bay-head beaches have been formed, and areas where the bedrock is sedimentary are characterized by coastal plains as much as 4 miles wide. The larger areas of coastal plain are also areas of sand dunes; here the surface configuration is attributed to dune development that has gone on from late Pleistocene to the present. Title: The Ore bin ; Vol. 33 No. 2 (February 1971) Author: Lund, Ernest H., Oregon. Dept. of Geology and Mineral Industries The 26-mile stretch of shore extending from Florence to Yachats is one of the most rugged and scenic parts of the Oregon Coast. Along most of this part of the coast the shore is bounded by basalt bedrock of varied types. Through differential erosion of the basalt, the many landforms, such as headlands, rocky shores, reefs, and sea stacks, that impart the rugged character to the coast have been and are still in the process of being developed. In places where the basalt bedrock is least resistant to erosion, small embayments with bay-head beaches have been formed, and areas where the bedrock is sedimentary are characterized by coastal plains as much as 4 miles wide. The larger areas of coastal plain are also areas of sand dunes; here the surface configuration is attributed to dune development that has gone on from late Pleistocene to the present. Close

• 76. [Article] Organic matter compositions and loadings in soils and sediments along the Fly River, Papua New Guinea

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geochimica-et-co...

  Citation × Citation Citation Abstract Copy Title: Organic matter compositions and loadings in soils and sediments along the Fly River, Papua New Guinea Author: Merrell, David, Goni, Miguel A., Kurtz, Andrew, Alleau, Yvan, Moore, Eric, Portier, Evan This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geochimica-et-cosmochimica-acta/ Title: Organic matter compositions and loadings in soils and sediments along the Fly River, Papua New Guinea Author: Merrell, David, Goni, Miguel A., Kurtz, Andrew, Alleau, Yvan, Moore, Eric, Portier, Evan This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by Elsevier and can be found at: http://www.journals.elsevier.com/geochimica-et-cosmochimica-acta/ Close

• 77. [Article] Continuous seismic profiling investigation of the southern Oregon continental shelf between Cape Blanco and Coos Bay

  A structure map was constructed of the continental shelf between Cape Blanco and Coos Bay, Oregon, exclusively from an interpretation of approximately 700 km of continuous seismic profiles. At least ten ...

  Citation × Citation Citation Abstract Copy Title: Continuous seismic profiling investigation of the southern Oregon continental shelf between Cape Blanco and Coos Bay Author: Mackay, Angus James A structure map was constructed of the continental shelf between Cape Blanco and Coos Bay, Oregon, exclusively from an interpretation of approximately 700 km of continuous seismic profiles. At least ten discernible seismic units were mapped on the bases of acoustic appearance, lateral continuity, angular unconformities, and faults. The offshore units tentatively were correlated with onshore geology and are believed to range in age from the latest Jurassic to late Pleistocene. The sparker profiles reveal that the continental shelf off southern Oregon has experienced significant late Tertiary and Quaternary accretion due to deposition and tectonic uplift. The oldest rock exposures, believed to be the latest Jurassic in age, crop out on the inner continental shelf on the topographic highs off Cape Blanco and Coquille Point. Erosional remnants of probable Late Cretaceous turbidites and the middle Eocene sandstone beds also are exposed on the bathymetric high on the inner shelf southwest of Cape Arago. The initial emplacement of these three uplifted structural blocks is probably a result of late Eocene wrench faulting of the Port Orford shear zone and of the postulated shear zone at Coquille Point. No other early Tertiary sediments apparently are exposed on this portion of the Oregon continental shelf, but they probably extend seaward at depth on the continental margin. Middle Tertiary strata are believed to be exposed on the outer shelf topographic high southwest of Cape Arago. Sediments of Miocene to Pliocene age were deposited throughout much of the continental shelf that was surveyed. The greatest amount of deposition occurred in a north-south trending basin between Cape Blanco and Coquille Bank. Late to post-Pliocene tectonism uplifted and exposed the older underlying rocks on the inner shelf, which are probably of uppermost Jurassic to middle Tertiary age. These same stresses also deformed the Mio-Pliocene sediments into gently undulating structures on the inner shelf. The greatest deformation occurred on the outer shelf and formed Coquille Bank, a north-south trending, doubly plunging, asymmetrical anticline. The terraces or benches on the upper continental slope to the north and south of the Bank are structural features resulting from the doubly plunging anticline. Eustatic sea level lowerings during the Pleistocene truncated the shelf structures as deep as 130 m below present sea level. The detritus was deposited as a wedge of sediments, which forms an unconformable contact with the underlying strata on the outer shelf and upper slope between Coos Bay and Coquille Bank. In areas of deposition there is no distinct break between the shelf and the upper slope; the former merely merges into the latter in a continuous convex curve. In areas of nondeposition, the edge of the shelf is an erosional and structural feature. A possible buried channel was detected northwest of the mouth of the Coquille River. This sediment filled channel is believed to be an erosional remnant of a former course of the Coquille River during a lower stand of sea level. Title: Continuous seismic profiling investigation of the southern Oregon continental shelf between Cape Blanco and Coos Bay Author: Mackay, Angus James A structure map was constructed of the continental shelf between Cape Blanco and Coos Bay, Oregon, exclusively from an interpretation of approximately 700 km of continuous seismic profiles. At least ten discernible seismic units were mapped on the bases of acoustic appearance, lateral continuity, angular unconformities, and faults. The offshore units tentatively were correlated with onshore geology and are believed to range in age from the latest Jurassic to late Pleistocene. The sparker profiles reveal that the continental shelf off southern Oregon has experienced significant late Tertiary and Quaternary accretion due to deposition and tectonic uplift. The oldest rock exposures, believed to be the latest Jurassic in age, crop out on the inner continental shelf on the topographic highs off Cape Blanco and Coquille Point. Erosional remnants of probable Late Cretaceous turbidites and the middle Eocene sandstone beds also are exposed on the bathymetric high on the inner shelf southwest of Cape Arago. The initial emplacement of these three uplifted structural blocks is probably a result of late Eocene wrench faulting of the Port Orford shear zone and of the postulated shear zone at Coquille Point. No other early Tertiary sediments apparently are exposed on this portion of the Oregon continental shelf, but they probably extend seaward at depth on the continental margin. Middle Tertiary strata are believed to be exposed on the outer shelf topographic high southwest of Cape Arago. Sediments of Miocene to Pliocene age were deposited throughout much of the continental shelf that was surveyed. The greatest amount of deposition occurred in a north-south trending basin between Cape Blanco and Coquille Bank. Late to post-Pliocene tectonism uplifted and exposed the older underlying rocks on the inner shelf, which are probably of uppermost Jurassic to middle Tertiary age. These same stresses also deformed the Mio-Pliocene sediments into gently undulating structures on the inner shelf. The greatest deformation occurred on the outer shelf and formed Coquille Bank, a north-south trending, doubly plunging, asymmetrical anticline. The terraces or benches on the upper continental slope to the north and south of the Bank are structural features resulting from the doubly plunging anticline. Eustatic sea level lowerings during the Pleistocene truncated the shelf structures as deep as 130 m below present sea level. The detritus was deposited as a wedge of sediments, which forms an unconformable contact with the underlying strata on the outer shelf and upper slope between Coos Bay and Coquille Bank. In areas of deposition there is no distinct break between the shelf and the upper slope; the former merely merges into the latter in a continuous convex curve. In areas of nondeposition, the edge of the shelf is an erosional and structural feature. A possible buried channel was detected northwest of the mouth of the Coquille River. This sediment filled channel is believed to be an erosional remnant of a former course of the Coquille River during a lower stand of sea level. Close

• 78. [Article] Geology of the Picture Gorge quadrangle, Oregon

  There are seven stratigraphic units exposed in the Picture Gorge quadrangle, a 204-square mile area in east-central Oregon. isolated exposures of pre-Cretaceous serpentinites, metalimestones, and other ...

  Citation × Citation Citation Abstract Copy Title: Geology of the Picture Gorge quadrangle, Oregon Author: White, Willis Harkness There are seven stratigraphic units exposed in the Picture Gorge quadrangle, a 204-square mile area in east-central Oregon. isolated exposures of pre-Cretaceous serpentinites, metalimestones, and other metamorphic rocks record marine deposition of sands silts, and limy sediments followed by burial, lithification, peridotite intrusion, and several periods of deformation. Intrusion and deformation were accompanied by serpentinization, silcification. and calcite veination. Cretaceous conglomerates and intercalated sandstones, which unconformably overlie the metamorphic rocks, are a result of fluvial deposition in a nearshore or continental environment, burial, lithification, uplift, and erosion. Pebbles were derived from plutonicmetamorphic highlands. The Eocene Clamo Formation unconformably overlies the Cretaceous rocks and is made up of basalt conglomerate, silicified conglomerate, andesite breccias, and andesite flows. The fossiliferous John Day Formation, Oligo-Miocene in age, lies unconformably on the Clamo Formation and is pyroclastic in character. Ash was wind-transported from trachytic-andesitic sources to the west and deposited on land, in lakes, and in swamps. The 2, 400-foot section of volcanic siltstones and waterlaid volcaniclastic rocks includes some basalt near the base and an ash-flow tuff near the middle. The John Day Formation was folded slightly after consolidation. The fissure-fed Middle Mjocene Columbia River Basalt flows, at least 2, 300 feet thick, blanket 124 square miles of the quadrangle. Modal analyses of thin sections from 22 basalt flows suggest that flows cannot be correlated on the basis of mineralogy. Correlation must involve a combination of criteria, such as color, texture, and nature of outcrop, together with mineralogy and chemical analyses. Interfiow breccias, tuffs, volcanic siltstones and sandstones, dikes, and an irregular intrusion are also present. The Columbia River Basalt unconformably overlies the John Day Formation. After emplacement, the basalt flow rocks were folded into the west-trending Sunflower anticline and John Day syncline. Normal faulting occurred on the shared flank of the two folds. The Upper Miocene Mascall Formation lies unconformably upon the Columbia River Basalt. About 400 feet of well-bedded, rhy-. olitic volcanic siltstones and intercalated sand and gravel lenses suggest eoliari and fluvial deposition of ash in lakes and swamps. Folding and faulting occurred along the same trends which were active during Columbia River Basalt time. 'lhe Plio-Pleistocene Rattlesnake Formation rests with pronounced angular unconformity on the Mascall Formation. About 10 feet of poorly consolidated fluvial gravels enclose a 38-foot-thick ash-flow tuff. Pleistocene and recent events include capture of the middle fork of the John Day River, slumping, development of pediments, formation of stone garlands, stone stripes, and talus-free mounds, and deposition of stream gravels. An andesitic, hornblende-bearing white volcanic ash was deposited by wind. Title: Geology of the Picture Gorge quadrangle, Oregon Author: White, Willis Harkness There are seven stratigraphic units exposed in the Picture Gorge quadrangle, a 204-square mile area in east-central Oregon. isolated exposures of pre-Cretaceous serpentinites, metalimestones, and other metamorphic rocks record marine deposition of sands silts, and limy sediments followed by burial, lithification, peridotite intrusion, and several periods of deformation. Intrusion and deformation were accompanied by serpentinization, silcification. and calcite veination. Cretaceous conglomerates and intercalated sandstones, which unconformably overlie the metamorphic rocks, are a result of fluvial deposition in a nearshore or continental environment, burial, lithification, uplift, and erosion. Pebbles were derived from plutonicmetamorphic highlands. The Eocene Clamo Formation unconformably overlies the Cretaceous rocks and is made up of basalt conglomerate, silicified conglomerate, andesite breccias, and andesite flows. The fossiliferous John Day Formation, Oligo-Miocene in age, lies unconformably on the Clamo Formation and is pyroclastic in character. Ash was wind-transported from trachytic-andesitic sources to the west and deposited on land, in lakes, and in swamps. The 2, 400-foot section of volcanic siltstones and waterlaid volcaniclastic rocks includes some basalt near the base and an ash-flow tuff near the middle. The John Day Formation was folded slightly after consolidation. The fissure-fed Middle Mjocene Columbia River Basalt flows, at least 2, 300 feet thick, blanket 124 square miles of the quadrangle. Modal analyses of thin sections from 22 basalt flows suggest that flows cannot be correlated on the basis of mineralogy. Correlation must involve a combination of criteria, such as color, texture, and nature of outcrop, together with mineralogy and chemical analyses. Interfiow breccias, tuffs, volcanic siltstones and sandstones, dikes, and an irregular intrusion are also present. The Columbia River Basalt unconformably overlies the John Day Formation. After emplacement, the basalt flow rocks were folded into the west-trending Sunflower anticline and John Day syncline. Normal faulting occurred on the shared flank of the two folds. The Upper Miocene Mascall Formation lies unconformably upon the Columbia River Basalt. About 400 feet of well-bedded, rhy-. olitic volcanic siltstones and intercalated sand and gravel lenses suggest eoliari and fluvial deposition of ash in lakes and swamps. Folding and faulting occurred along the same trends which were active during Columbia River Basalt time. 'lhe Plio-Pleistocene Rattlesnake Formation rests with pronounced angular unconformity on the Mascall Formation. About 10 feet of poorly consolidated fluvial gravels enclose a 38-foot-thick ash-flow tuff. Pleistocene and recent events include capture of the middle fork of the John Day River, slumping, development of pediments, formation of stone garlands, stone stripes, and talus-free mounds, and deposition of stream gravels. An andesitic, hornblende-bearing white volcanic ash was deposited by wind. Close

• 79. [Article] Quaternary marine terraces on Cyprus : constraints on uplift and pedogenesis, and the geoarchaeology of Palaipafos

  Numerous flights of Quaternary marine terraces are present around the island of Cyprus, in the Eastern Mediterranean. These terraces are a result of the global eustatic sea-level curve and local tectonism. ...

  Citation × Citation Citation Abstract Copy Title: Quaternary marine terraces on Cyprus : constraints on uplift and pedogenesis, and the geoarchaeology of Palaipafos Author: Zomeni, Zomenia Numerous flights of Quaternary marine terraces are present around the island of Cyprus, in the Eastern Mediterranean. These terraces are a result of the global eustatic sea-level curve and local tectonism. Marine Isotope Stage (MIS) 5 through MIS 13 terraces are identified, mapped and dated. Palaeoshoreline elevation, an excellent indicator for a past sea–level, and new numerical geochronology are used to calculate an Upper Pleistocene uplift rate for various coastal sectors. Southwestern Cyprus presents the highest uplift rates of 0.35-0.65 mm/year with other sections suggesting uplift of 0.07-0.15 mm/year. This Upper Pleistocene tectonic signal is attributed to an active offshore subduction/collision system to the southwest of Cyprus, evidenced from the seismic activity offshore and the surface expression of a blind thrust fault in the Pafos region. Soil chronosequences and geology in southwestern Cyprus are studied in order to understand the Quaternary development on this uplifting landscape. Soil profile properties are used to calculate a profile development index (PDI), a method often applied to geomorphic surfaces as a relative dating method. Well-developed red and clayey soils occur in the coastal sector, on broad and low-angle surfaces, specifically on marine terraces and alluvial fans. Higher elevations of steep slopes consisting of carbonate and ophiolite lithologies host poorly developed soils. Results show variable PDI's on uplifted terraces, obscured by transported materials, active alluvial fan buildup and hillslope erosion. Calcium carbonate build-up in soil profiles in the form of nodular and laminar accumulations are used as another relative dating method. Geochronology of marine terraces is used as an age range approximation for carbonate stages. Geomorphologic mapping focuses on the southeastern part of the Pafos thrust fault, the only point on the landscape where this otherwise blind fault is exposed on the surface. This is the location of Palaipafos, an important Ancient polity, today the site of the village of Kouklia. Geoarchaeological study suggests little landscape change over the last 4000 years in the vicinity of the urban core of Palaipafos, this being attributed to bedrock and landscape resistance of its location, a plateau at 80 m amsl. Copper deposits in the Palaipafos hinterland had provided a valuable resource at one time. Soil and water resources continue to sustain agriculture.Tectonic uplift in this part of the Pafos thrust fault is estimated to be 2.1mm/year, considered, together with Late Holocene sea-level change responsible for the shifting locations and eventual abandonment of the Palaipafos harbor in the coastal lowlands. Title: Quaternary marine terraces on Cyprus : constraints on uplift and pedogenesis, and the geoarchaeology of Palaipafos Author: Zomeni, Zomenia Numerous flights of Quaternary marine terraces are present around the island of Cyprus, in the Eastern Mediterranean. These terraces are a result of the global eustatic sea-level curve and local tectonism. Marine Isotope Stage (MIS) 5 through MIS 13 terraces are identified, mapped and dated. Palaeoshoreline elevation, an excellent indicator for a past sea–level, and new numerical geochronology are used to calculate an Upper Pleistocene uplift rate for various coastal sectors. Southwestern Cyprus presents the highest uplift rates of 0.35-0.65 mm/year with other sections suggesting uplift of 0.07-0.15 mm/year. This Upper Pleistocene tectonic signal is attributed to an active offshore subduction/collision system to the southwest of Cyprus, evidenced from the seismic activity offshore and the surface expression of a blind thrust fault in the Pafos region. Soil chronosequences and geology in southwestern Cyprus are studied in order to understand the Quaternary development on this uplifting landscape. Soil profile properties are used to calculate a profile development index (PDI), a method often applied to geomorphic surfaces as a relative dating method. Well-developed red and clayey soils occur in the coastal sector, on broad and low-angle surfaces, specifically on marine terraces and alluvial fans. Higher elevations of steep slopes consisting of carbonate and ophiolite lithologies host poorly developed soils. Results show variable PDI's on uplifted terraces, obscured by transported materials, active alluvial fan buildup and hillslope erosion. Calcium carbonate build-up in soil profiles in the form of nodular and laminar accumulations are used as another relative dating method. Geochronology of marine terraces is used as an age range approximation for carbonate stages. Geomorphologic mapping focuses on the southeastern part of the Pafos thrust fault, the only point on the landscape where this otherwise blind fault is exposed on the surface. This is the location of Palaipafos, an important Ancient polity, today the site of the village of Kouklia. Geoarchaeological study suggests little landscape change over the last 4000 years in the vicinity of the urban core of Palaipafos, this being attributed to bedrock and landscape resistance of its location, a plateau at 80 m amsl. Copper deposits in the Palaipafos hinterland had provided a valuable resource at one time. Soil and water resources continue to sustain agriculture.Tectonic uplift in this part of the Pafos thrust fault is estimated to be 2.1mm/year, considered, together with Late Holocene sea-level change responsible for the shifting locations and eventual abandonment of the Palaipafos harbor in the coastal lowlands. Close

• 80. [Article] Ice surface reconstruction and energy balance modeling of alpine glaciers

  Glacial deposits on San Francisco Mountain, Arizona, were mapped in order to provide constraints on ice extents in separate valleys for late Pleistocene glacial events. Qualitative and semi-quantitative ...

  Citation × Citation Citation Abstract Copy Title: Ice surface reconstruction and energy balance modeling of alpine glaciers Author: Poellot, Colin Daniel Glacial deposits on San Francisco Mountain, Arizona, were mapped in order to provide constraints on ice extents in separate valleys for late Pleistocene glacial events. Qualitative and semi-quantitative relative dating methods were employed in order to correlate moraines between drainages and to provide a basis for distinguishing between separate glacial events within drainages. Morphologic and surficial weathering characteristics that were measured include degree of moraine dissection, moraine crestal width, moraine inner and outer slope angle, surface boulder frequency, percentage of weathered surface boulders, percentage of pitted surface boulders, maximum pit depth, and percentage of split boulders. Results of the relative dating study support past studies that differentiate 3 separate drift sequences on the mountain. Five separate glacier surfaces were reconstructed from the mapped moraine crests, four for the most recent glaciation, and one for the intermediate glacial event. ELAs from the reconstructed glaciers range from 3140 to 3400 meters. In addition, a numerical model was developed that uses an energy balance approach to calculate annual ablation over a glacier surface. The energy balance approach used in the model was designed to allow the model to test sensitivity of former glaciers to changes in temperature or precipitation. Required model inputs include a two-dimensional elevation map of the glacier surface and surrounding topography, as well as climate records that include daily values of air temperature, wind speed, precipitation, atmospheric vapor pressure, incoming shortwave radiation, and incoming longwave radiation. Model outputs include the net specific balance and equilibrium line altitude of the glacier. Model simulations of mass balance are compared with observed data from the 1990 ablation season at Haut Glacier d'Arolla, Valais, Switzerland. Calculated ablation values closely match observed values, thereby supporting the validity of the model. A preliminary model run was also accomplished for the 5 Pleistocene glaciers reconstructed on San Francisco Mountain, Arizona, using output from a regional climate model as input. The model delivers a glacier that is nearly in mass balance for one of the reconstructions. Title: Ice surface reconstruction and energy balance modeling of alpine glaciers Author: Poellot, Colin Daniel Glacial deposits on San Francisco Mountain, Arizona, were mapped in order to provide constraints on ice extents in separate valleys for late Pleistocene glacial events. Qualitative and semi-quantitative relative dating methods were employed in order to correlate moraines between drainages and to provide a basis for distinguishing between separate glacial events within drainages. Morphologic and surficial weathering characteristics that were measured include degree of moraine dissection, moraine crestal width, moraine inner and outer slope angle, surface boulder frequency, percentage of weathered surface boulders, percentage of pitted surface boulders, maximum pit depth, and percentage of split boulders. Results of the relative dating study support past studies that differentiate 3 separate drift sequences on the mountain. Five separate glacier surfaces were reconstructed from the mapped moraine crests, four for the most recent glaciation, and one for the intermediate glacial event. ELAs from the reconstructed glaciers range from 3140 to 3400 meters. In addition, a numerical model was developed that uses an energy balance approach to calculate annual ablation over a glacier surface. The energy balance approach used in the model was designed to allow the model to test sensitivity of former glaciers to changes in temperature or precipitation. Required model inputs include a two-dimensional elevation map of the glacier surface and surrounding topography, as well as climate records that include daily values of air temperature, wind speed, precipitation, atmospheric vapor pressure, incoming shortwave radiation, and incoming longwave radiation. Model outputs include the net specific balance and equilibrium line altitude of the glacier. Model simulations of mass balance are compared with observed data from the 1990 ablation season at Haut Glacier d'Arolla, Valais, Switzerland. Calculated ablation values closely match observed values, thereby supporting the validity of the model. A preliminary model run was also accomplished for the 5 Pleistocene glaciers reconstructed on San Francisco Mountain, Arizona, using output from a regional climate model as input. The model delivers a glacier that is nearly in mass balance for one of the reconstructions. Close

• 81. [Article] Man and the land : an ecological history of fire and grazing on eastern Oregon rangelands

  Ecological and historical information are combined in examining the environmental influence of fire and grazing on rangelands in eastern Oregon through time. Competitive relationships between herbaceous ...

  Citation × Citation Citation Abstract Copy Title: Man and the land : an ecological history of fire and grazing on eastern Oregon rangelands Author: Shinn, Dean Allison Ecological and historical information are combined in examining the environmental influence of fire and grazing on rangelands in eastern Oregon through time. Competitive relationships between herbaceous and woody flora in the northern Great Basin are discussed, focusing broadly on the shrubsteppe regions 'of Franklin and Dyrness (1973) but with special reference to the Artemisia/Agropyron association. Impacts of native and domestic grazing animals and of cultural burning are traced from the distant past into recent history. During the Pleistocene Epoch North America supported a wide diversity of large mammals. Toward the end of the Pleistocene, many of these fauna became extinct, perhaps as a result of post-glacial climatic change, perhaps also under the influence of incoming primitive hunting cultures and their broadcast burning practices. Some question exists about the intensity of native grazing in the northern Great Basin during the last few thousand years. Actual levels of bison populations and the duration of their residence in the study area have not been determined. The character of indigenous vegetations, however, indicates that native grazing was relatively light for an extended period primevally. Twenty-four references to native cultural burning at the time of European contact were found in historical journals. Though the antiquity of these customs is uncertain, an analysis of Native American fire myths demonstrates the depth of native cultural perceptions of the relationship between man and fire, and supports the likelihood that fire was used primevally in the northern Great Basin as it was used by aboriginal peoples elsewhere in North America. With the influx of European culture during the 19th century, misapprehensions about fire among whites distorted the influence of native cultural burning. Exotic flora and fauna were introduced, and ecosystems began to change. Large herds of livestock depleted native herbaceous populations. Early irresponsible burning by whites became associated with declining rangeland resources, and efforts toward total fire suppression became incorporated in developing conservation policies. Native woody flora and exotics began to invade open rangeland communities. Climatic flux during the period of European settlement in the northern Great Basin may have exacerbated the impacts of intensified grazing and elimination of burning. Early photographs of rangelands in east-central Oregon were gathered; their dates range from 1880 to the early 1930's. Sites represented in these pictures were re-photographed in 1976. Photo-set comparisons show expansion of western juniper (Juniperus occidentalis) populations into rangeland ecosystems, demonstrating the consequences of cultural disturbances during the last 150 to 200 years. Title: Man and the land : an ecological history of fire and grazing on eastern Oregon rangelands Author: Shinn, Dean Allison Ecological and historical information are combined in examining the environmental influence of fire and grazing on rangelands in eastern Oregon through time. Competitive relationships between herbaceous and woody flora in the northern Great Basin are discussed, focusing broadly on the shrubsteppe regions 'of Franklin and Dyrness (1973) but with special reference to the Artemisia/Agropyron association. Impacts of native and domestic grazing animals and of cultural burning are traced from the distant past into recent history. During the Pleistocene Epoch North America supported a wide diversity of large mammals. Toward the end of the Pleistocene, many of these fauna became extinct, perhaps as a result of post-glacial climatic change, perhaps also under the influence of incoming primitive hunting cultures and their broadcast burning practices. Some question exists about the intensity of native grazing in the northern Great Basin during the last few thousand years. Actual levels of bison populations and the duration of their residence in the study area have not been determined. The character of indigenous vegetations, however, indicates that native grazing was relatively light for an extended period primevally. Twenty-four references to native cultural burning at the time of European contact were found in historical journals. Though the antiquity of these customs is uncertain, an analysis of Native American fire myths demonstrates the depth of native cultural perceptions of the relationship between man and fire, and supports the likelihood that fire was used primevally in the northern Great Basin as it was used by aboriginal peoples elsewhere in North America. With the influx of European culture during the 19th century, misapprehensions about fire among whites distorted the influence of native cultural burning. Exotic flora and fauna were introduced, and ecosystems began to change. Large herds of livestock depleted native herbaceous populations. Early irresponsible burning by whites became associated with declining rangeland resources, and efforts toward total fire suppression became incorporated in developing conservation policies. Native woody flora and exotics began to invade open rangeland communities. Climatic flux during the period of European settlement in the northern Great Basin may have exacerbated the impacts of intensified grazing and elimination of burning. Early photographs of rangelands in east-central Oregon were gathered; their dates range from 1880 to the early 1930's. Sites represented in these pictures were re-photographed in 1976. Photo-set comparisons show expansion of western juniper (Juniperus occidentalis) populations into rangeland ecosystems, demonstrating the consequences of cultural disturbances during the last 150 to 200 years. Close

• 82. [Article] Contrasting geomorphic responses to climatic, anthropogenic, and fluvial change across modern to millennial time scales, Clackamas River, Oregon

  Geomorphic change along the lower Clackamas River is occurring at a millennial scale due to climate change; a decadal scale as a result River Mill Dam operation; and at an annual scale since 1996 due to ...

  Citation × Citation Citation Abstract Copy Title: Contrasting geomorphic responses to climatic, anthropogenic, and fluvial change across modern to millennial time scales, Clackamas River, Oregon Author: Wampler, Peter J. Geomorphic change along the lower Clackamas River is occurring at a millennial scale due to climate change; a decadal scale as a result River Mill Dam operation; and at an annual scale since 1996 due to a meander cutoff. Channel response to these three mechanisms is incision. Holocene strath terraces, inset into Pleistocene terraces, are broadly synchronous with other terraces in the Pacific Northwest, suggesting a regional aggradational event at the Pleistocene/Holocene boundary. A maximum incision rate of 4.3 mm/year occurs where the river emerges from the Western Cascade Mountains and decreases to 1.4 mm/year near the river mouth. Tectonic uplift, bedrock erodibility, rapid base-level change downstream, or a systematic decrease in Holocene sediment flux may be contributing to the extremely rapid incision rates observed. The River Island mining site experienced a meander cutoff during flooding in 1996, resulting in channel length reduction of 1,100 meters as the river began flowing through a series of gravel pits. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. The knick point from the meander cutoff migrated 2,290 meters upstream between 1996 and 2003, resulting in increased bed load transport, incision of 1 to 2 meters, and rapid water table lowering. Ninety-six percent of the total migration distance occurred during the first winter following meander cutoff. Hydrologic changes below River Mill Dam, completed in 1911, are minimal but a set of dam-induced geomorphic changes, resulting from sediment trapping behind the dam, have occurred. Degradation for 3 km below the dam is reflected by regularly spaced bedrock pools with an average spacing of 250 m, or approximately 3.6 channel widths. Measurable downstream effects include: 1) surface grain-size increase; 2) side channel area reduction; 3) gravel bar erosion and bedrock exposure; 4) lowering of water surface elevations; and 5) channel narrowing. Between 1908 and 2000, water surface elevation dropped an average of 0.8 m for 17 km below the dam, presumably due to bed degradation. Title: Contrasting geomorphic responses to climatic, anthropogenic, and fluvial change across modern to millennial time scales, Clackamas River, Oregon Author: Wampler, Peter J. Geomorphic change along the lower Clackamas River is occurring at a millennial scale due to climate change; a decadal scale as a result River Mill Dam operation; and at an annual scale since 1996 due to a meander cutoff. Channel response to these three mechanisms is incision. Holocene strath terraces, inset into Pleistocene terraces, are broadly synchronous with other terraces in the Pacific Northwest, suggesting a regional aggradational event at the Pleistocene/Holocene boundary. A maximum incision rate of 4.3 mm/year occurs where the river emerges from the Western Cascade Mountains and decreases to 1.4 mm/year near the river mouth. Tectonic uplift, bedrock erodibility, rapid base-level change downstream, or a systematic decrease in Holocene sediment flux may be contributing to the extremely rapid incision rates observed. The River Island mining site experienced a meander cutoff during flooding in 1996, resulting in channel length reduction of 1,100 meters as the river began flowing through a series of gravel pits. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. The knick point from the meander cutoff migrated 2,290 meters upstream between 1996 and 2003, resulting in increased bed load transport, incision of 1 to 2 meters, and rapid water table lowering. Ninety-six percent of the total migration distance occurred during the first winter following meander cutoff. Hydrologic changes below River Mill Dam, completed in 1911, are minimal but a set of dam-induced geomorphic changes, resulting from sediment trapping behind the dam, have occurred. Degradation for 3 km below the dam is reflected by regularly spaced bedrock pools with an average spacing of 250 m, or approximately 3.6 channel widths. Measurable downstream effects include: 1) surface grain-size increase; 2) side channel area reduction; 3) gravel bar erosion and bedrock exposure; 4) lowering of water surface elevations; and 5) channel narrowing. Between 1908 and 2000, water surface elevation dropped an average of 0.8 m for 17 km below the dam, presumably due to bed degradation. Close

• 83. [Article] Cosmogenic ¹°Be chronology for the last deglaciation of the southern Scandinavian Ice Sheet

  The goal of this dissertation is to develop a chronology of the retreat of the southern margin of the Scandinavian Ice Sheet (SIS) during the late Pleistocene using surface exposure dating with cosmogenic ...

  Citation × Citation Citation Abstract Copy Title: Cosmogenic ¹°Be chronology for the last deglaciation of the southern Scandinavian Ice Sheet Author: Rinterknecht, Vincent R. The goal of this dissertation is to develop a chronology of the retreat of the southern margin of the Scandinavian Ice Sheet (SIS) during the late Pleistocene using surface exposure dating with cosmogenic 10Be. A sequence of seven prominent moraines in northeastern Europe (the Leszno Moraine, the Pomeranian Moraine, the Middle Lithuanian Moraine, the North Lithuanian Moraine, the P andivere Moraine, the Palivere Moraine, and the Salpausselka I Moraine) indicates a potential millennialscale record of climate variability. However, there are no direct dating constraints on the timing of this ice sheet retreat. Surface exposure dating using cosmogenic nuclide elements produced by secondary high-energy particles in the upper part of the lithosphere allows for direct dating of moraines deposited by the SIS. Cosmogenic 10Be concentrations were measured in quartz sampled from erratic boulders deposited on top of the moraines. The SIS margin withdrew from its maximum extent at 17,9 ± 2,4 10Be ka, which is correlative to the end of the Last Glacial Maximum period (23,0 to 19,0 ka). Following a recessional period, the ice readvanced to the Pomeranian Moraine. Deglaciation from this moraine is dated at 14,1 ± 1,8 10Be ka, and subsequent deglaciation is marked by the Middle Lithuanian Moraine (13,1 ± 1,7 "Be ka), the North Lithuanian Moraine (13,1 ± 1,7 10Be ka), the Pandivere Moraine (13,0 ± 1,1 10Be ka), the Palivere Moraine (10.0 ± 1,3 10Be ka), and the Salpausselka I Moraine (12,5 ± 1,5 10Be ka). This new chronology is compared to abrupt climate variability recorded in the North Atlantic region during the late Pleistocene. Paleo air temperatures recorded from the GISP2 ice core and paleo sea surface temperatures recorded from the North Atlantic region display warmings at the end of the Last Glacial Maximum period, during the Balling-Allerod interstadial, and at the end of the Younger Dryas stadial. These records also display abrupt coolings during the Oldest Dryas and the Younger Dryas stadials. Based on the 10Be chronology, the margin of the SIS responded to climate changes that occurred in the North Atlantic region. This new chronology contributes the first direct evidence of climate forcing on the southern margin of the SIS. Title: Cosmogenic ¹°Be chronology for the last deglaciation of the southern Scandinavian Ice Sheet Author: Rinterknecht, Vincent R. The goal of this dissertation is to develop a chronology of the retreat of the southern margin of the Scandinavian Ice Sheet (SIS) during the late Pleistocene using surface exposure dating with cosmogenic 10Be. A sequence of seven prominent moraines in northeastern Europe (the Leszno Moraine, the Pomeranian Moraine, the Middle Lithuanian Moraine, the North Lithuanian Moraine, the P andivere Moraine, the Palivere Moraine, and the Salpausselka I Moraine) indicates a potential millennialscale record of climate variability. However, there are no direct dating constraints on the timing of this ice sheet retreat. Surface exposure dating using cosmogenic nuclide elements produced by secondary high-energy particles in the upper part of the lithosphere allows for direct dating of moraines deposited by the SIS. Cosmogenic 10Be concentrations were measured in quartz sampled from erratic boulders deposited on top of the moraines. The SIS margin withdrew from its maximum extent at 17,9 ± 2,4 10Be ka, which is correlative to the end of the Last Glacial Maximum period (23,0 to 19,0 ka). Following a recessional period, the ice readvanced to the Pomeranian Moraine. Deglaciation from this moraine is dated at 14,1 ± 1,8 10Be ka, and subsequent deglaciation is marked by the Middle Lithuanian Moraine (13,1 ± 1,7 "Be ka), the North Lithuanian Moraine (13,1 ± 1,7 10Be ka), the Pandivere Moraine (13,0 ± 1,1 10Be ka), the Palivere Moraine (10.0 ± 1,3 10Be ka), and the Salpausselka I Moraine (12,5 ± 1,5 10Be ka). This new chronology is compared to abrupt climate variability recorded in the North Atlantic region during the late Pleistocene. Paleo air temperatures recorded from the GISP2 ice core and paleo sea surface temperatures recorded from the North Atlantic region display warmings at the end of the Last Glacial Maximum period, during the Balling-Allerod interstadial, and at the end of the Younger Dryas stadial. These records also display abrupt coolings during the Oldest Dryas and the Younger Dryas stadials. Based on the 10Be chronology, the margin of the SIS responded to climate changes that occurred in the North Atlantic region. This new chronology contributes the first direct evidence of climate forcing on the southern margin of the SIS. Close

• 84. [Article] Structural evolution of the Russell Ranch oil field and vicinity, southern Coast Ranges, California

  The Russell Ranch oil field is located in the southern Coast Ranges west of Bakersfield, California. Detailed subsurface mapping shows that a northwest-oriented right-lateral wrench-fault system was active ...

  Citation × Citation Citation Abstract Copy Title: Structural evolution of the Russell Ranch oil field and vicinity, southern Coast Ranges, California Author: Nevins, Barbara B. The Russell Ranch oil field is located in the southern Coast Ranges west of Bakersfield, California. Detailed subsurface mapping shows that a northwest-oriented right-lateral wrench-fault system was active from possibly latest Oligocene to Pliocene time. The effects of Quaternary thrusting were superimposed on, and influenced by, structures associated with the older wrench tectonic regime. The right-lateral shear system produced a complex pattern of right-stepping en echelon folds, dip-slip faults with normal separation, and strike-slip faults with both normal and reverse separation. Deformation along the wrench system began during deposition of the late Oligocene-early Miocene Soda Lake Shale and Painted Rock Sandstone members of the Vaqueros Formation, producing elongate en echelon submarine troughs and highs. Northerly trending growth faults of early Miocene age caused thickening of the late Saucesian-early Relizian Saltos Shale Member of the Monterey Formation and may have initiated growth of the Russell Ranch anticline. Northeast- to northwest-trending normal faults and northwest-trending strike-slip faults of the Russell fault system were active during deposition of a sequence tentatively correlated with the Branch Canyon Sandstone and Santa Margarita Formation of middle and late Miocene age. Strike-slip faulting produced a complex interleaving of fault slices and juxtaposed slices of contrasting lithologies and orientations. Subsequent minor movement along the wrench system folded the base of the Morales Formation, of Pliocene-Pleistocene age, into elongate en echelon folds. The north-dipping Whiterock and Morales thrusts brought Miocene and younger strata southward over deposits as young as late Pleistocene. The Whiterock thrust changes southward from a southeasterly to an easterly strike. The upper plate was thrust southward, and structures in the lower plate apparently controlled the geometry of the developing fault plane. The thrust ramps as it overrides the normal and strike-slip faults of middle Miocene age; rootless folds similar to those found in the Caliente Range are present in the upper thrust plate above the tectonic ramps. Wrench-related faulting in the Cuyama basin predates similar movement along the San Andreas fault to the northeast and may represent a strand of the proto-San Andreas fault. Quaternary thrusting in the basin was influenced by and now obscures the structures of the older wrench fault system; thrusting activity was probably contemporaneous with thrust faulting in the Transverse Ranges to the south. Title: Structural evolution of the Russell Ranch oil field and vicinity, southern Coast Ranges, California Author: Nevins, Barbara B. The Russell Ranch oil field is located in the southern Coast Ranges west of Bakersfield, California. Detailed subsurface mapping shows that a northwest-oriented right-lateral wrench-fault system was active from possibly latest Oligocene to Pliocene time. The effects of Quaternary thrusting were superimposed on, and influenced by, structures associated with the older wrench tectonic regime. The right-lateral shear system produced a complex pattern of right-stepping en echelon folds, dip-slip faults with normal separation, and strike-slip faults with both normal and reverse separation. Deformation along the wrench system began during deposition of the late Oligocene-early Miocene Soda Lake Shale and Painted Rock Sandstone members of the Vaqueros Formation, producing elongate en echelon submarine troughs and highs. Northerly trending growth faults of early Miocene age caused thickening of the late Saucesian-early Relizian Saltos Shale Member of the Monterey Formation and may have initiated growth of the Russell Ranch anticline. Northeast- to northwest-trending normal faults and northwest-trending strike-slip faults of the Russell fault system were active during deposition of a sequence tentatively correlated with the Branch Canyon Sandstone and Santa Margarita Formation of middle and late Miocene age. Strike-slip faulting produced a complex interleaving of fault slices and juxtaposed slices of contrasting lithologies and orientations. Subsequent minor movement along the wrench system folded the base of the Morales Formation, of Pliocene-Pleistocene age, into elongate en echelon folds. The north-dipping Whiterock and Morales thrusts brought Miocene and younger strata southward over deposits as young as late Pleistocene. The Whiterock thrust changes southward from a southeasterly to an easterly strike. The upper plate was thrust southward, and structures in the lower plate apparently controlled the geometry of the developing fault plane. The thrust ramps as it overrides the normal and strike-slip faults of middle Miocene age; rootless folds similar to those found in the Caliente Range are present in the upper thrust plate above the tectonic ramps. Wrench-related faulting in the Cuyama basin predates similar movement along the San Andreas fault to the northeast and may represent a strand of the proto-San Andreas fault. Quaternary thrusting in the basin was influenced by and now obscures the structures of the older wrench fault system; thrusting activity was probably contemporaneous with thrust faulting in the Transverse Ranges to the south. Close

• 85. [Article] Evaluation of seismic hazards from the Median Tectonic Line, Japan and blind thrust faults in the Los Angeles metropolitan area, California

  This thesis analyzes active geologic structures in densely populated areas in Japan and southern California based on geological, geophysical, and paleoseismological observations. Chapter 2 discusses segmentation ...

  Citation × Citation Citation Abstract Copy Title: Evaluation of seismic hazards from the Median Tectonic Line, Japan and blind thrust faults in the Los Angeles metropolitan area, California Author: Tsutsumi, Hiroyuki This thesis analyzes active geologic structures in densely populated areas in Japan and southern California based on geological, geophysical, and paleoseismological observations. Chapter 2 discusses segmentation and paleoseismology of the Median Tectonic Line, Japan. We identified 12 geometric segments along the Median Tectonic Line separated by discontinuities such as en echelon steps, bends, changes in strike, and gaps in the surface trace. The recurrence interval and surficial offset for surface-rupturing earthquakes at four individual sites on the Median Tectonic Line in Shikoku Island are 1000-3000 years and 5-8 in, respectively. Part of the fault zone ruptured most recently during or after the 16th century A.D.; this rupture may be correlated to the 1596 Keicho-Kinki earthquake. Chapter 3 discusses active and late Cenozoic tectonics of the northern Los Angeles fault system, California. We mapped the subsurface geology of the northern Los Angeles basin from the City of Santa Monica eastward to downtown Los Angeles, based on an extensive set of oil-well data. The northern Los Angeles fault system developed through an early to late Miocene extensional regime and a Plio-Pleistocene contractional regime. The uplift of the oxygen isotope substage 5e marine terrace at Pacific Palisades and an estimated dip greater than 45° suggest a dip-slip rate as large as 1.5 mm/yr for the Santa Monica Mountains blind thrust fault, a rate considerably smaller than a previous estimate. Chapter 4 discusses the geologic setting of the 1971 San Fernando and 1994 Northridge earthquakes, two of the most devastating earthquakes in southern California history. We mapped the subsurface geology of the northern San Fernando Valley that lies at the updip projection of the two earthquake faults. The San Fernando Valley is underlain by a series of north-dipping blind thrust faults. The thick accumulation of the Robert S. ''eats Plio-Pleistocene Saugus Formation in the Sylmar basin and Merrick syncline is a surface expression of the south-dipping 1994 Northridge thrust that is overlain by the northdipping 1971 San Fernando fault at a depth of -5 km. Title: Evaluation of seismic hazards from the Median Tectonic Line, Japan and blind thrust faults in the Los Angeles metropolitan area, California Author: Tsutsumi, Hiroyuki This thesis analyzes active geologic structures in densely populated areas in Japan and southern California based on geological, geophysical, and paleoseismological observations. Chapter 2 discusses segmentation and paleoseismology of the Median Tectonic Line, Japan. We identified 12 geometric segments along the Median Tectonic Line separated by discontinuities such as en echelon steps, bends, changes in strike, and gaps in the surface trace. The recurrence interval and surficial offset for surface-rupturing earthquakes at four individual sites on the Median Tectonic Line in Shikoku Island are 1000-3000 years and 5-8 in, respectively. Part of the fault zone ruptured most recently during or after the 16th century A.D.; this rupture may be correlated to the 1596 Keicho-Kinki earthquake. Chapter 3 discusses active and late Cenozoic tectonics of the northern Los Angeles fault system, California. We mapped the subsurface geology of the northern Los Angeles basin from the City of Santa Monica eastward to downtown Los Angeles, based on an extensive set of oil-well data. The northern Los Angeles fault system developed through an early to late Miocene extensional regime and a Plio-Pleistocene contractional regime. The uplift of the oxygen isotope substage 5e marine terrace at Pacific Palisades and an estimated dip greater than 45° suggest a dip-slip rate as large as 1.5 mm/yr for the Santa Monica Mountains blind thrust fault, a rate considerably smaller than a previous estimate. Chapter 4 discusses the geologic setting of the 1971 San Fernando and 1994 Northridge earthquakes, two of the most devastating earthquakes in southern California history. We mapped the subsurface geology of the northern San Fernando Valley that lies at the updip projection of the two earthquake faults. The San Fernando Valley is underlain by a series of north-dipping blind thrust faults. The thick accumulation of the Robert S. ''eats Plio-Pleistocene Saugus Formation in the Sylmar basin and Merrick syncline is a surface expression of the south-dipping 1994 Northridge thrust that is overlain by the northdipping 1971 San Fernando fault at a depth of -5 km. Close

• 86. [Article] Geology of the Clarno Basin Mitchell quadrangle, Oregon

  In the area surrounding Clarno, Oregon, pre-Cretaceous metamorphics, Cretaceous marine sediments, and a varied assemblage of Tertiary volcanic rocks are known. The oldest exposures are of an homogeneously ...

  Citation × Citation Citation Abstract Copy Title: Geology of the Clarno Basin Mitchell quadrangle, Oregon Author: Taylor, Edward M., 1933- In the area surrounding Clarno, Oregon, pre-Cretaceous metamorphics, Cretaceous marine sediments, and a varied assemblage of Tertiary volcanic rocks are known. The oldest exposures are of an homogeneously fine-grained, mildly metamorphosed, limy shale to which the term "Muddy Ranch phyllite" is applied. Non-metamorphosed, Cretaceous marine shales and graywackes, approximately 1500 feet thick, exist beneath the surface at Clarno. The beginning of Tertiary vulcanism is recorded in the Clarno formation of probable lower Eocene to lower Oligocene age. This is succeeded unconformably by upper Oligocene to lower Miocene tuffs and welded tuffs of the John Day formation. Middle Miocene lavas of the Columbia River basalt formation were the last major products of igneous activity in the area. Unconsolidated Pleistocene and Recent deposits occur along drainage channels. The Clarno Basin was a depository of volcanic sediments from nearby centers of igneous activity throughout Clarno time. Study of these rocks reveals the following succession: The lower two-thirds of the Clarno formation consists of a colorful series of volcanic conglomerates and breccias indicating widespread conditions of mudflow. While dominant in volume, these sediments record only brief interruptions of a prevailing fine-grained lacustrine and floodplain deposition. Andesitic and basaltic lavas of widely varying types were frequently spread over the Basin near the mid-point of mudflow development. This first stage of Clarno vulcanism was brought to a close by the eruption of distinctive white and yellow leucoandesites. A time of quiescence is recorded in a widespread sheet of very fine tuff which was deeply weathered as it accumulated. A flow of basaltic lava poured over this surface, creating a lake in which a jungle-like flora was preserved. When the "fossil soil" had become nearly 200 feet thick at Clarno, a blanket of welded tuff reached the Basin from a probable point of origin near' the Horse Heaven amines. This was followed, after prolonged weathering, by the eruption of pyroxene basalt which eventually rivalled the inter inter-mudflow lavas in thickness and distribution. As Clarno vulcaniscr, diminished, the terrane was reduced to a low relief and thick, tuffaceous soil again accumulated. A recent and remarkable discovery of lower Oligocene mammal remains was made in this horizon. The extravasation of an unusually gas-rich andesite entombed this surface beneath a resistant cap of ignimbrite. With the appearance of another welded tuff sheet, probably from the northeast, Clarno activity ceased. A regional trend of northeast-southwest folds was first developed during the late Cretaceous or Paleocene and was accentuated during lower or middle Oligocene time. This structural system strongly influenced the distribution of rocks formed within it. At the beginning of the Tertiary, Cretaceous sediments were deeply eroded from the anticlines, exposing older rocks. Clarno volcanics were deposited unconformably on this surface. Post-Clarno uplift accelerated erosion of Clarno rocks from the same anticlinal regions. Because structure also determined topographic character, John Day tuffs were concentrated in the synclines. A gentle warping of the older folds during Pliocene time involved the Columbia River basalts and is in part responsible for their superior preservation in synclinal areas. Present-day relief features in the Clarno Basin have been in process of formation since the upper Miocene. Two distinct periods of rejuvenation are recorded, one during the upper Pliocene, another during the later Pleistocene. The Pliocene warping was not a necessary factor in rejuvenation but may have been contemporaneous, increasing its effect in places, decreasing it in others. Title: Geology of the Clarno Basin Mitchell quadrangle, Oregon Author: Taylor, Edward M., 1933- In the area surrounding Clarno, Oregon, pre-Cretaceous metamorphics, Cretaceous marine sediments, and a varied assemblage of Tertiary volcanic rocks are known. The oldest exposures are of an homogeneously fine-grained, mildly metamorphosed, limy shale to which the term "Muddy Ranch phyllite" is applied. Non-metamorphosed, Cretaceous marine shales and graywackes, approximately 1500 feet thick, exist beneath the surface at Clarno. The beginning of Tertiary vulcanism is recorded in the Clarno formation of probable lower Eocene to lower Oligocene age. This is succeeded unconformably by upper Oligocene to lower Miocene tuffs and welded tuffs of the John Day formation. Middle Miocene lavas of the Columbia River basalt formation were the last major products of igneous activity in the area. Unconsolidated Pleistocene and Recent deposits occur along drainage channels. The Clarno Basin was a depository of volcanic sediments from nearby centers of igneous activity throughout Clarno time. Study of these rocks reveals the following succession: The lower two-thirds of the Clarno formation consists of a colorful series of volcanic conglomerates and breccias indicating widespread conditions of mudflow. While dominant in volume, these sediments record only brief interruptions of a prevailing fine-grained lacustrine and floodplain deposition. Andesitic and basaltic lavas of widely varying types were frequently spread over the Basin near the mid-point of mudflow development. This first stage of Clarno vulcanism was brought to a close by the eruption of distinctive white and yellow leucoandesites. A time of quiescence is recorded in a widespread sheet of very fine tuff which was deeply weathered as it accumulated. A flow of basaltic lava poured over this surface, creating a lake in which a jungle-like flora was preserved. When the "fossil soil" had become nearly 200 feet thick at Clarno, a blanket of welded tuff reached the Basin from a probable point of origin near' the Horse Heaven amines. This was followed, after prolonged weathering, by the eruption of pyroxene basalt which eventually rivalled the inter inter-mudflow lavas in thickness and distribution. As Clarno vulcaniscr, diminished, the terrane was reduced to a low relief and thick, tuffaceous soil again accumulated. A recent and remarkable discovery of lower Oligocene mammal remains was made in this horizon. The extravasation of an unusually gas-rich andesite entombed this surface beneath a resistant cap of ignimbrite. With the appearance of another welded tuff sheet, probably from the northeast, Clarno activity ceased. A regional trend of northeast-southwest folds was first developed during the late Cretaceous or Paleocene and was accentuated during lower or middle Oligocene time. This structural system strongly influenced the distribution of rocks formed within it. At the beginning of the Tertiary, Cretaceous sediments were deeply eroded from the anticlines, exposing older rocks. Clarno volcanics were deposited unconformably on this surface. Post-Clarno uplift accelerated erosion of Clarno rocks from the same anticlinal regions. Because structure also determined topographic character, John Day tuffs were concentrated in the synclines. A gentle warping of the older folds during Pliocene time involved the Columbia River basalts and is in part responsible for their superior preservation in synclinal areas. Present-day relief features in the Clarno Basin have been in process of formation since the upper Miocene. Two distinct periods of rejuvenation are recorded, one during the upper Pliocene, another during the later Pleistocene. The Pliocene warping was not a necessary factor in rejuvenation but may have been contemporaneous, increasing its effect in places, decreasing it in others. Close

• 87. [Article] The leafhopper genus Tiaja Oman (Homoptera:Cicadellidae), with a contribution to the biosystematics of the group

  The genus Tiaja Oman consists of eight known species of flightless leafhoppers of the subfamily Megophthalminae found along the western coast of North America between British Columbia and northern Mexico. ...

  Citation × Citation Citation Abstract Copy Title: The leafhopper genus Tiaja Oman (Homoptera:Cicadellidae), with a contribution to the biosystematics of the group Author: Sawbridge, Jane Rosamund The genus Tiaja Oman consists of eight known species of flightless leafhoppers of the subfamily Megophthalminae found along the western coast of North America between British Columbia and northern Mexico. Species occurring from the San Francisco Bay area northward are restricted to a narrow coastal zone within 1 km of the ocean; some of those species that occur farther south may be found inland as well as on the coast. Members of the genus occupy an unusual habitat in that most individuals are found on the undersides of their host plants or in the litter layer beneath them. Flightlessness and the position the insects occupy on their host plants are seen as adaptations to enhance survival in a windswept environment. Life history studies of T. friscana (Ball) and T. arenaria Oman show that nymphs normally pass through five nymphal ins tars although some individuals may have four or six nymphal ins tars. The final nymphal ins tar is of longer duration than any of the preceding ins tars but the length of the developmental period appears to depend on temperature conditions in the rearing chamber. The northernmost species, T. arenaria, is univoltine with obligatory diapause while T. friscana and T. montara Oman, two species of the central California coast, are multivoltine with no diapause under favorable conditions. Other species are presumed to be multivoltine. Host association studies show that members of the genus Tiaja are usually found associated with woody shrubs and that these shrubs may serve as feeding but not necessarily oviposition hosts. The oviposition host of T. arenaria is Fragaria chiloensis (L.) Duch. Infraspecific variation in disjunct populations of T. friscana is examined. These populations lie 550 km apart and the range of another species, T. montara, intervenes. Crossbreeding experiments show that while there is some genetic differentiation as a result of isolation, the populations are similar enough and hybridize to a sufficient extent to be considered members of the same species. Crossbreeding experiments between T. friscana and T. montara show that these allopatric species from the San Francisco Bay area hybridize to some extent when artificially placed together. However, fertility is considerably reduced compared to parental crosses and this is taken as evidence of the reliability of morphological features used for species differentiation in this genus. Factors influencing the success rates of these crosses are discussed. The presence of members of the genus on islands and in populations isolated from the remainder of a species despite the limited mobility of the group is discussed. It is speculated that dispersal of T. arenaria to Vancouver Island subsequent to Pleistocene glaciation, dispersal of T. insula Sawbridge to Santa Barbara Island following its submersion in the late Pleistocene, and the colonization of San Simeon by T. iris cana can be attributed to dispersal by drift of egg-containing host plant material aided by ocean currents and prevailing winds. Taxonomic information includes a discussion of the place of the Megophthalminae within the Cicadellidae, recharacterization of the genus Tiaja, a revised key to the eight known species, and species recharacterizations including morphological data, distributions, seasonal occurrence, and host and habitat information. Criteria for differentiation of nymphal ins tars through setal patterns and wing pad development are discussed and illustrated. It is concluded that further study of the habitats, life history, behavior, and cytogenetics of the Ulopinae and other members of the Megophthalminae will be necessary before current data on Tiaja can be used to help redefine relationships within and between these subfamilies. Title: The leafhopper genus Tiaja Oman (Homoptera:Cicadellidae), with a contribution to the biosystematics of the group Author: Sawbridge, Jane Rosamund The genus Tiaja Oman consists of eight known species of flightless leafhoppers of the subfamily Megophthalminae found along the western coast of North America between British Columbia and northern Mexico. Species occurring from the San Francisco Bay area northward are restricted to a narrow coastal zone within 1 km of the ocean; some of those species that occur farther south may be found inland as well as on the coast. Members of the genus occupy an unusual habitat in that most individuals are found on the undersides of their host plants or in the litter layer beneath them. Flightlessness and the position the insects occupy on their host plants are seen as adaptations to enhance survival in a windswept environment. Life history studies of T. friscana (Ball) and T. arenaria Oman show that nymphs normally pass through five nymphal ins tars although some individuals may have four or six nymphal ins tars. The final nymphal ins tar is of longer duration than any of the preceding ins tars but the length of the developmental period appears to depend on temperature conditions in the rearing chamber. The northernmost species, T. arenaria, is univoltine with obligatory diapause while T. friscana and T. montara Oman, two species of the central California coast, are multivoltine with no diapause under favorable conditions. Other species are presumed to be multivoltine. Host association studies show that members of the genus Tiaja are usually found associated with woody shrubs and that these shrubs may serve as feeding but not necessarily oviposition hosts. The oviposition host of T. arenaria is Fragaria chiloensis (L.) Duch. Infraspecific variation in disjunct populations of T. friscana is examined. These populations lie 550 km apart and the range of another species, T. montara, intervenes. Crossbreeding experiments show that while there is some genetic differentiation as a result of isolation, the populations are similar enough and hybridize to a sufficient extent to be considered members of the same species. Crossbreeding experiments between T. friscana and T. montara show that these allopatric species from the San Francisco Bay area hybridize to some extent when artificially placed together. However, fertility is considerably reduced compared to parental crosses and this is taken as evidence of the reliability of morphological features used for species differentiation in this genus. Factors influencing the success rates of these crosses are discussed. The presence of members of the genus on islands and in populations isolated from the remainder of a species despite the limited mobility of the group is discussed. It is speculated that dispersal of T. arenaria to Vancouver Island subsequent to Pleistocene glaciation, dispersal of T. insula Sawbridge to Santa Barbara Island following its submersion in the late Pleistocene, and the colonization of San Simeon by T. iris cana can be attributed to dispersal by drift of egg-containing host plant material aided by ocean currents and prevailing winds. Taxonomic information includes a discussion of the place of the Megophthalminae within the Cicadellidae, recharacterization of the genus Tiaja, a revised key to the eight known species, and species recharacterizations including morphological data, distributions, seasonal occurrence, and host and habitat information. Criteria for differentiation of nymphal ins tars through setal patterns and wing pad development are discussed and illustrated. It is concluded that further study of the habitats, life history, behavior, and cytogenetics of the Ulopinae and other members of the Megophthalminae will be necessary before current data on Tiaja can be used to help redefine relationships within and between these subfamilies. Close

• 88. [Article] Superposed compressional and extensional strain in Lower Paleozic rocks of the northwestern Grant Range, Nevada

  The Grant Range, in east-central Nevada, is a north-east trending range bounded on the west by a west-dipping normal fault system. Rocks within the range record a complex polyphase Mesozoic ductile compressional ...

  Citation × Citation Citation Abstract Copy Title: Superposed compressional and extensional strain in Lower Paleozic rocks of the northwestern Grant Range, Nevada Author: Camilleri, Phyllis A. The Grant Range, in east-central Nevada, is a north-east trending range bounded on the west by a west-dipping normal fault system. Rocks within the range record a complex polyphase Mesozoic ductile compressional and Cenozoic brittle extensional deformational history. The northwestern Grant Range exposes deformed, regionally metamorphosed and unmetamorphosed, Cambrian to Mississippian carbonate and clastic strata, and minor Tertiary granitic and andesitic dikes. Cambrian and Ordovician rocks are ductilely strained and metamorphosed. Metamorphic grade decreases stratigraphically upwards, generally commensurate with the degree of ductile strain. Two Mesozoic compressional events are recorded in the rocks of the northwestern Grant Range. The first event produced mesoscopic, east-vergent folds with spaced axial-planar cleavage. These folds were overprinted by small-scale, west-vergent thrust faults and folds of the second event. Regional metamorphism began during the first folding event, but outlasted deformation. Static metamorphism was followed by west-vergent deformation, which marked the end of metamorphism. The compressional structures may have been part of an east-vergent anticline or the hanging wall of an east-vergent thrust fault. Ductile Mesozoic compressional structures and fabrics are cut by an arched, imbricate stack of Cenozoic low-angle normal faults of a more brittle character. The low-angle normal faults omit stratigraphic section, and each successively structurally higher fault is generally younger than the one below it. Most faults appear to be west-directed. The age of the low-angle normal fault system is constrained only as late Oligocene to Pleistocene, but could be largely Miocene to Pleistocene. Some granitic and andesitic dikes cross-cut or are cut by low-angle normal faults, indicating that igneous activity is at least in part synchronous with extension. The geometry of the low-angle normal faults suggest that these faults could be rotated, extinct fault segments formed as a result of arching of the upper reaches of the high- to moderate-angle west-dipping normal fault system responsible for the uplift of the Grant Range. This would suggest that the low-angle normal faults are products of progressive Basin and Range extension and do not represent a distinct extensional event. Title: Superposed compressional and extensional strain in Lower Paleozic rocks of the northwestern Grant Range, Nevada Author: Camilleri, Phyllis A. The Grant Range, in east-central Nevada, is a north-east trending range bounded on the west by a west-dipping normal fault system. Rocks within the range record a complex polyphase Mesozoic ductile compressional and Cenozoic brittle extensional deformational history. The northwestern Grant Range exposes deformed, regionally metamorphosed and unmetamorphosed, Cambrian to Mississippian carbonate and clastic strata, and minor Tertiary granitic and andesitic dikes. Cambrian and Ordovician rocks are ductilely strained and metamorphosed. Metamorphic grade decreases stratigraphically upwards, generally commensurate with the degree of ductile strain. Two Mesozoic compressional events are recorded in the rocks of the northwestern Grant Range. The first event produced mesoscopic, east-vergent folds with spaced axial-planar cleavage. These folds were overprinted by small-scale, west-vergent thrust faults and folds of the second event. Regional metamorphism began during the first folding event, but outlasted deformation. Static metamorphism was followed by west-vergent deformation, which marked the end of metamorphism. The compressional structures may have been part of an east-vergent anticline or the hanging wall of an east-vergent thrust fault. Ductile Mesozoic compressional structures and fabrics are cut by an arched, imbricate stack of Cenozoic low-angle normal faults of a more brittle character. The low-angle normal faults omit stratigraphic section, and each successively structurally higher fault is generally younger than the one below it. Most faults appear to be west-directed. The age of the low-angle normal fault system is constrained only as late Oligocene to Pleistocene, but could be largely Miocene to Pleistocene. Some granitic and andesitic dikes cross-cut or are cut by low-angle normal faults, indicating that igneous activity is at least in part synchronous with extension. The geometry of the low-angle normal faults suggest that these faults could be rotated, extinct fault segments formed as a result of arching of the upper reaches of the high- to moderate-angle west-dipping normal fault system responsible for the uplift of the Grant Range. This would suggest that the low-angle normal faults are products of progressive Basin and Range extension and do not represent a distinct extensional event. Close

• 89. [Article] The Deschutes Formation-- High Cascade transition in the Whitewater River area, Jefferson County, Oregon

  The Whitewater River area is located directly east of Mt. Jefferson in the Cascades of central Oregon. Approximately 90 mi2 (230 km2) were mapped (scale 1/24,000) and four new K-Ar ages and 151 major element ...

  Citation × Citation Citation Abstract Copy Title: The Deschutes Formation-- High Cascade transition in the Whitewater River area, Jefferson County, Oregon Author: Yogodzinski, Gene M. The Whitewater River area is located directly east of Mt. Jefferson in the Cascades of central Oregon. Approximately 90 mi2 (230 km2) were mapped (scale 1/24,000) and four new K-Ar ages and 151 major element analyses were obtained in a study of the stratigraphic and magmatic transition from the Miocene - Pliocene Deschutes Formation on the east to the Pliocene - Pleistocene High Cascades on the west. Deschutes strata in the Whitewater River area overlie late Miocene (8-11+ m.y.) andesites, dacites, and rhyodacites along an erosional unconformity. The oldest Deschutes rocks exposed in the Whitewater River area are approximately 6 m.y. old, and the youngest are probably between 4.5 and 5 m.y. old. The oldest High Cascade rocks exposed in the Whitewater River area are approximately 4.3 m.y. old. There is no evidence for a hiatus in volcanic activity between Deschutes and High Cascade time in the Whitewater River area. Late Pleistocene explosive volcanism, probably free Mt. Jefferson, is evidenced in a hornblende rhyodacite pyroclastic-flow deposit which occurs within the glacial stratigraphy and is tentatively thought to be between approximately 60,000 and 20,000 years old. Deschutes strata are dominated by pyroclastic lithologies (mostly ash-flow tuffs) with some lava flows and minor epiclastic sediment. Compositions range mostly between basaltic andesite and dacite. Many Deschutes-age rocks are aphyric, high in Fed, TiO2, and alkalies, and low in MgO, CaO, and A12O3. They define a tholeiitic trend extending at least from basaltic andesite to dacite that can largely be derived through fractional crystallization of plagioclase, olivine, magnetite, and clinopyroxene from a parent magma, probably of basaltic composition. These rocks are compositionally similar to "tholeiitic anorogenic andesites" that are most commonly associated with areas of crustal extension. Rocks of High Cascade age in the Whitewater River area are mostly lava flaws that range in composition from basalt (high-alumina, olivine tholeiite) to rhyodacite. The High Cascade suite forms a calc-alkalic association that is typical of subduction-related magmatic arcs. Fractional crystallization of the basalts leads to iron-enrichment. Fractional crystallization of the basaltic andesites might lead to calc-alkalic compositions, but the mineral phases necessary to deplete the magmas in FeO, TiO2, and CaO (magnetite and clinopyroxene) are not common phenocryst phases in the basaltic andesites or andesites. Two northwest-trending, down-to-the-west normal faults with sane possible strike-slip motion have been mapped in the upper Whitewater River area, directly west of Lion's Head. Motion on these faults occurred after approximately 4 m.y. ago, but probably began prior to that time. There is between 200 and 400 ft (60-120 m) of apparent vertical separation on the western side of these faults. There may be a large, northwest-trending fault running from the south end of Green Ridge, through Bald Peter and the Whitewater River area, but this structure is largely buried by younger volcanic rocks. There is no evidence for a northern extension of the north-trending Green Ridge faults, and there is no evidence for large structural displacement in the lower Whitewater River along north- or northwest-trending structures. The Deschutes Formation - High Cascade transition in the Whitewater River area is marked by a switch in the eruptive style and in the dominant magmatic compositions during Deschutes and High Cascade times. Volcanism in the Whitewater River area does not appear to have been episodic with respect to volume and/or intensity; rather, the character of magmatism has varied with time and with the tectonic style through the period immediately prior to and following the formation of the High cascade graben. Title: The Deschutes Formation-- High Cascade transition in the Whitewater River area, Jefferson County, Oregon Author: Yogodzinski, Gene M. The Whitewater River area is located directly east of Mt. Jefferson in the Cascades of central Oregon. Approximately 90 mi2 (230 km2) were mapped (scale 1/24,000) and four new K-Ar ages and 151 major element analyses were obtained in a study of the stratigraphic and magmatic transition from the Miocene - Pliocene Deschutes Formation on the east to the Pliocene - Pleistocene High Cascades on the west. Deschutes strata in the Whitewater River area overlie late Miocene (8-11+ m.y.) andesites, dacites, and rhyodacites along an erosional unconformity. The oldest Deschutes rocks exposed in the Whitewater River area are approximately 6 m.y. old, and the youngest are probably between 4.5 and 5 m.y. old. The oldest High Cascade rocks exposed in the Whitewater River area are approximately 4.3 m.y. old. There is no evidence for a hiatus in volcanic activity between Deschutes and High Cascade time in the Whitewater River area. Late Pleistocene explosive volcanism, probably free Mt. Jefferson, is evidenced in a hornblende rhyodacite pyroclastic-flow deposit which occurs within the glacial stratigraphy and is tentatively thought to be between approximately 60,000 and 20,000 years old. Deschutes strata are dominated by pyroclastic lithologies (mostly ash-flow tuffs) with some lava flows and minor epiclastic sediment. Compositions range mostly between basaltic andesite and dacite. Many Deschutes-age rocks are aphyric, high in Fed, TiO2, and alkalies, and low in MgO, CaO, and A12O3. They define a tholeiitic trend extending at least from basaltic andesite to dacite that can largely be derived through fractional crystallization of plagioclase, olivine, magnetite, and clinopyroxene from a parent magma, probably of basaltic composition. These rocks are compositionally similar to "tholeiitic anorogenic andesites" that are most commonly associated with areas of crustal extension. Rocks of High Cascade age in the Whitewater River area are mostly lava flaws that range in composition from basalt (high-alumina, olivine tholeiite) to rhyodacite. The High Cascade suite forms a calc-alkalic association that is typical of subduction-related magmatic arcs. Fractional crystallization of the basalts leads to iron-enrichment. Fractional crystallization of the basaltic andesites might lead to calc-alkalic compositions, but the mineral phases necessary to deplete the magmas in FeO, TiO2, and CaO (magnetite and clinopyroxene) are not common phenocryst phases in the basaltic andesites or andesites. Two northwest-trending, down-to-the-west normal faults with sane possible strike-slip motion have been mapped in the upper Whitewater River area, directly west of Lion's Head. Motion on these faults occurred after approximately 4 m.y. ago, but probably began prior to that time. There is between 200 and 400 ft (60-120 m) of apparent vertical separation on the western side of these faults. There may be a large, northwest-trending fault running from the south end of Green Ridge, through Bald Peter and the Whitewater River area, but this structure is largely buried by younger volcanic rocks. There is no evidence for a northern extension of the north-trending Green Ridge faults, and there is no evidence for large structural displacement in the lower Whitewater River along north- or northwest-trending structures. The Deschutes Formation - High Cascade transition in the Whitewater River area is marked by a switch in the eruptive style and in the dominant magmatic compositions during Deschutes and High Cascade times. Volcanism in the Whitewater River area does not appear to have been episodic with respect to volume and/or intensity; rather, the character of magmatism has varied with time and with the tectonic style through the period immediately prior to and following the formation of the High cascade graben. Close

• 90. [Article] Geology, flooding & human activities : establishing a hierarchy of influence for controls on historic channel change, Willamette River, Oregon

  Channel evolution and influences of changing floodplain characteristics, heterogenous bank materials, and altered flow regimes were examined along the Willamette River, a large alluvial river in northwestern Oregon. ...

  Citation × Citation Citation Abstract Copy Title: Geology, flooding & human activities : establishing a hierarchy of influence for controls on historic channel change, Willamette River, Oregon Author: Wallick, Jennifer Rose Channel evolution and influences of changing floodplain characteristics, heterogenous bank materials, and altered flow regimes were examined along the Willamette River, a large alluvial river in northwestern Oregon. The Willamette River is composed of a series of geomorphically diverse reaches, which have each evolved uniquely in the century following Euro-American settlement. The river was divided into three large (30-50 km) alluvial reaches according to physiographic characteristics. The historically anastomosing and relatively steep McKenzie Reach (uppermost study reach), extends between the confluences of the McKenzie and Long Tom Rivers. The Willamette along the lower-gradient Santiam Reach (between the confluences of the Santiam and Yamhill Rivers is primarily contained within a single channel and has experienced lower rates of erosion than upper reaches. The Long Tom Reach (extending between the confluences of the Long Tom and Santiam Rivers), acts as a transition between the upper and lower Willamette, as it is here that the channel adopts a single-thread planform and becomes more stable. To assess the role of bank materials on bank-erosion rates, a method for detecting relative differences in erodibility between bank materials along large floodplains was developed. Coupling historic patterns of channel change with a simple model of bank erodibility enabled tracking of relative changes in bank erodibility among time intervals and bank materials. The analysis was applied to the McKenzie Reach for three time periods: 1850-1895, 1895-1932, and 1972-1995, and relative differences in bank erodibility were calculated for Holocene alluvium, partially cemented Pleistocene gravels, and revetments constructed in the 20th century. This simple model of bank erodibility reveals that, for all three periods, banks composed of Holocene alluvium were at least 2-5 times more erodible than banks composed of Pleistocene gravels. Revetment installed in the twentieth century was highly resistant to erosion and was at least 10 times less erodible than Pleistocene gravels. To examine larger-scale controls of geology, flooding, and human intervention on channel stability, rates and styles of historic channel change were determined for the McKenzie, Long Tom and Santiam Reaches and were linked with events or factors that may have triggered the observed patterns of channel change. Effects of anthropogenic activities on channel change were assessed by reviewing historic documents describing settlement patterns, riparian deforestation, channel improvements, and other actions. The role of flooding was assessed by compiling gauge records, anecdotal accounts of flooding, and by comparing stream-power distributions of large historic floods against smaller, post-dam floods with a 2-D flood model. Analyses of these larger-scale controls revealed that between 1850 and 1895, a period marked by the 3 largest floods of record, all reaches experienced numerous avulsions, increases in channel width, and decreases in centerline length. During the interval 1895-1932, a period with frequent, moderate-sized floods, migration rates increased by 50-300%, sinuosity increased and channel width decreased. The interval 1932-1995 was initially marked by rapid migration, but channel stabilization and dam building slowed erosion rates, causing the Long Tom and Santiam Reaches to display similar migration rates as those recorded for 1850-1895. Along the upper Willamette (McKenzie Reach), channel change during 1972 to 1995 was primarily limited to lateral migration along areas unrestricted by revetments and occurred at rates similar to 1850-1895 levels. Channel width decreased along all reaches during the 20th century. It is hypothesized that flooding may have been the primary factor responsible for the large-scale straightening and widening that occurred during 1850-1895. Actions taken to reduce streamside wood and side-channels along the McKenzie and Long Tom Reaches may have also contributed to widening. Along some areas of the floodplain, where the largely straightened and widened 1895 channel flowed through Holocene alluvium, the channel developed small bends that subsequently migrated rapidly downstream, and triggered rapid migration of adjacent bends. This concurrence of events and conditions suggests that accelerated erosion during the period 1895-1932 results from a combination of a "primed" planform, highly erodible bank materials, and a highly erosive flow regime with many moderate-sized floods. Migration rates 1895-1932 may have also increased as a result of land clearing and snag removal, as increasing numbers of settlers occupied floodplain lands in this interval. Anthropogenic activities have no clear effect on planform or erosion rates until the 193 D's, when widespread bank stabilization and dam construction resulted in diminished migration rates, fewer avulsions, and channel narrowing. By the late century, 30-45% of each reach was stabilized with revetments, while naturally resistant bank materials bordered an additional 13-30% of the channel length. Results indicate that revetments, naturally resistant bank materials, and flow regulation restrict migration and channel movement along the modern Willamette River. Efforts aiming to increase lateral migration on the Willamette River might consider removing revetment from bends bordered by Holocene alluvium along higher-gradient areas of the floodplain. However, such efforts may not create the suite of floodplain dynamics displayed by the historic Willamette, as much of the rapid migration, side channel maintenance and avulsions were related to flooding, channel change along adjacent bends, and large wood; all of which are largely absent from the modern floodplain. Title: Geology, flooding & human activities : establishing a hierarchy of influence for controls on historic channel change, Willamette River, Oregon Author: Wallick, Jennifer Rose Channel evolution and influences of changing floodplain characteristics, heterogenous bank materials, and altered flow regimes were examined along the Willamette River, a large alluvial river in northwestern Oregon. The Willamette River is composed of a series of geomorphically diverse reaches, which have each evolved uniquely in the century following Euro-American settlement. The river was divided into three large (30-50 km) alluvial reaches according to physiographic characteristics. The historically anastomosing and relatively steep McKenzie Reach (uppermost study reach), extends between the confluences of the McKenzie and Long Tom Rivers. The Willamette along the lower-gradient Santiam Reach (between the confluences of the Santiam and Yamhill Rivers is primarily contained within a single channel and has experienced lower rates of erosion than upper reaches. The Long Tom Reach (extending between the confluences of the Long Tom and Santiam Rivers), acts as a transition between the upper and lower Willamette, as it is here that the channel adopts a single-thread planform and becomes more stable. To assess the role of bank materials on bank-erosion rates, a method for detecting relative differences in erodibility between bank materials along large floodplains was developed. Coupling historic patterns of channel change with a simple model of bank erodibility enabled tracking of relative changes in bank erodibility among time intervals and bank materials. The analysis was applied to the McKenzie Reach for three time periods: 1850-1895, 1895-1932, and 1972-1995, and relative differences in bank erodibility were calculated for Holocene alluvium, partially cemented Pleistocene gravels, and revetments constructed in the 20th century. This simple model of bank erodibility reveals that, for all three periods, banks composed of Holocene alluvium were at least 2-5 times more erodible than banks composed of Pleistocene gravels. Revetment installed in the twentieth century was highly resistant to erosion and was at least 10 times less erodible than Pleistocene gravels. To examine larger-scale controls of geology, flooding, and human intervention on channel stability, rates and styles of historic channel change were determined for the McKenzie, Long Tom and Santiam Reaches and were linked with events or factors that may have triggered the observed patterns of channel change. Effects of anthropogenic activities on channel change were assessed by reviewing historic documents describing settlement patterns, riparian deforestation, channel improvements, and other actions. The role of flooding was assessed by compiling gauge records, anecdotal accounts of flooding, and by comparing stream-power distributions of large historic floods against smaller, post-dam floods with a 2-D flood model. Analyses of these larger-scale controls revealed that between 1850 and 1895, a period marked by the 3 largest floods of record, all reaches experienced numerous avulsions, increases in channel width, and decreases in centerline length. During the interval 1895-1932, a period with frequent, moderate-sized floods, migration rates increased by 50-300%, sinuosity increased and channel width decreased. The interval 1932-1995 was initially marked by rapid migration, but channel stabilization and dam building slowed erosion rates, causing the Long Tom and Santiam Reaches to display similar migration rates as those recorded for 1850-1895. Along the upper Willamette (McKenzie Reach), channel change during 1972 to 1995 was primarily limited to lateral migration along areas unrestricted by revetments and occurred at rates similar to 1850-1895 levels. Channel width decreased along all reaches during the 20th century. It is hypothesized that flooding may have been the primary factor responsible for the large-scale straightening and widening that occurred during 1850-1895. Actions taken to reduce streamside wood and side-channels along the McKenzie and Long Tom Reaches may have also contributed to widening. Along some areas of the floodplain, where the largely straightened and widened 1895 channel flowed through Holocene alluvium, the channel developed small bends that subsequently migrated rapidly downstream, and triggered rapid migration of adjacent bends. This concurrence of events and conditions suggests that accelerated erosion during the period 1895-1932 results from a combination of a "primed" planform, highly erodible bank materials, and a highly erosive flow regime with many moderate-sized floods. Migration rates 1895-1932 may have also increased as a result of land clearing and snag removal, as increasing numbers of settlers occupied floodplain lands in this interval. Anthropogenic activities have no clear effect on planform or erosion rates until the 193 D's, when widespread bank stabilization and dam construction resulted in diminished migration rates, fewer avulsions, and channel narrowing. By the late century, 30-45% of each reach was stabilized with revetments, while naturally resistant bank materials bordered an additional 13-30% of the channel length. Results indicate that revetments, naturally resistant bank materials, and flow regulation restrict migration and channel movement along the modern Willamette River. Efforts aiming to increase lateral migration on the Willamette River might consider removing revetment from bends bordered by Holocene alluvium along higher-gradient areas of the floodplain. However, such efforts may not create the suite of floodplain dynamics displayed by the historic Willamette, as much of the rapid migration, side channel maintenance and avulsions were related to flooding, channel change along adjacent bends, and large wood; all of which are largely absent from the modern floodplain. Close

• 91. [Article] Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Public Library ...

  Citation × Citation Citation Abstract Copy Title: Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island Author: Betancourt, Julio L., Mead, Jim I., Epps, Clinton W., Wilder, Benjamin T., Crowhurst, Rachel S., Ezcurra, Exequiel To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Public Library of Science and is in the public domain. The published article can be found at: http://www.plosone.org/. Title: Local Extinction and Unintentional Rewilding of Bighorn Sheep (Ovis canadensis) on a Desert Island Author: Betancourt, Julio L., Mead, Jim I., Epps, Clinton W., Wilder, Benjamin T., Crowhurst, Rachel S., Ezcurra, Exequiel To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The article was published by the Public Library of Science and is in the public domain. The published article can be found at: http://www.plosone.org/. Close

• 92. [Article] North Atlantic Paleoceanography: The Last Five Million Years

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: North Atlantic Paleoceanography: The Last Five Million Years Author: Ferretti, Partizia, Kullanek, Denise K., Zhai, Qiumin, Neilsen, Simmon H. H., Stein, Ruediger, Ohno, Masao, Rashid, Harunur, Sierro Sanchez, Francisco J., Judge, Shelley A., Bailey, Ian, Acton, Gary D., Nanayama, Futoshi, Harris, Robert N., Kanamatsu, Toshiya, Higgins, Sean M., Hefter, Jens, Alvarez-Zarikian, Carlos, Aboud, Essam, Akimoto, Kazumi, Bjorklund, Kjell R., Channell, Jim E. T., Evans, Helen, Hatakeda, Kentaro, Gruetzner, Jean, Hagino, Kentaro, Voelker, Antje copyrighted by American Geophysical Union Title: North Atlantic Paleoceanography: The Last Five Million Years Author: Ferretti, Partizia, Kullanek, Denise K., Zhai, Qiumin, Neilsen, Simmon H. H., Stein, Ruediger, Ohno, Masao, Rashid, Harunur, Sierro Sanchez, Francisco J., Judge, Shelley A., Bailey, Ian, Acton, Gary D., Nanayama, Futoshi, Harris, Robert N., Kanamatsu, Toshiya, Higgins, Sean M., Hefter, Jens, Alvarez-Zarikian, Carlos, Aboud, Essam, Akimoto, Kazumi, Bjorklund, Kjell R., Channell, Jim E. T., Evans, Helen, Hatakeda, Kentaro, Gruetzner, Jean, Hagino, Kentaro, Voelker, Antje copyrighted by American Geophysical Union Close

• 93. [Article] Rapid Holocene Deglaciation of the Labrador Sector of the Laurentide Ice Sheet

  Retreat of the Laurentide Ice Sheet (LIS) following the Last Glacial Maximum 21 000 yr BP affected regional to global climate and accounted for the largest proportion of sea level rise. Although the late ...

  Citation × Citation Citation Abstract Copy Title: Rapid Holocene Deglaciation of the Labrador Sector of the Laurentide Ice Sheet Author: Brook, Edward J., Raisbeck, Grant M., Carlson, Anders E., Clark, Peter U. Retreat of the Laurentide Ice Sheet (LIS) following the Last Glacial Maximum 21 000 yr BP affected regional to global climate and accounted for the largest proportion of sea level rise. Although the late Pleistocene LIS retreat chronology is relatively well constrained, its Holocene chronology remains poorly dated, limiting our understanding of its role in Holocene climate change and sea level rise. Here new ¹⁰Be cosmogenic exposure ages on glacially deposited boulders are used to date the final disappearance of the Labrador sector of the LIS (LS-LIS). These data suggest that following the deglaciation of the southeastern Hudson Bay coastline at 8.0 ± 0.2 cal ka BP, the southwestern margin of the LS-LIS rapidly retreated ~600 km in 140 yr and most likely in ~600 yr at a rate of ~900 m yr⁻¹, with final deglaciation by 6.8 ± 0.2 ¹⁰Be ka. The disappearance of the LS-LIS ~6.8 ¹⁰Be ka and attendant reduction in freshwater runoff may have induced the formation of Labrador Deep Seawater, while the loss of the high albedo surface may have initiated the Holocene Thermal Maximum in eastern Canada and southern Greenland. Moreover, the rapid melting just prior to ~6.8 ¹⁰Be ka indicates that the remnant LIS may be the primary source of a postulated rapid rise in global sea level of ~5 m that occurred sometime between 7.6 and 6.5 cal ka BP. Title: Rapid Holocene Deglaciation of the Labrador Sector of the Laurentide Ice Sheet Author: Brook, Edward J., Raisbeck, Grant M., Carlson, Anders E., Clark, Peter U. Retreat of the Laurentide Ice Sheet (LIS) following the Last Glacial Maximum 21 000 yr BP affected regional to global climate and accounted for the largest proportion of sea level rise. Although the late Pleistocene LIS retreat chronology is relatively well constrained, its Holocene chronology remains poorly dated, limiting our understanding of its role in Holocene climate change and sea level rise. Here new ¹⁰Be cosmogenic exposure ages on glacially deposited boulders are used to date the final disappearance of the Labrador sector of the LIS (LS-LIS). These data suggest that following the deglaciation of the southeastern Hudson Bay coastline at 8.0 ± 0.2 cal ka BP, the southwestern margin of the LS-LIS rapidly retreated ~600 km in 140 yr and most likely in ~600 yr at a rate of ~900 m yr⁻¹, with final deglaciation by 6.8 ± 0.2 ¹⁰Be ka. The disappearance of the LS-LIS ~6.8 ¹⁰Be ka and attendant reduction in freshwater runoff may have induced the formation of Labrador Deep Seawater, while the loss of the high albedo surface may have initiated the Holocene Thermal Maximum in eastern Canada and southern Greenland. Moreover, the rapid melting just prior to ~6.8 ¹⁰Be ka indicates that the remnant LIS may be the primary source of a postulated rapid rise in global sea level of ~5 m that occurred sometime between 7.6 and 6.5 cal ka BP. Close

• 94. [Article] Model of late Pleistocene-Holocene variations in rate of sediment accumulation : Panama Basin, eastern equatorial Pacific

  The assumption of constant quartz accumulation for the deep-sea sediment core Y69-106P, taken in the Panama Basin, has been used to date the core and construct a sedimentation rate versus time curve for ...

  Citation × Citation Citation Abstract Copy Title: Model of late Pleistocene-Holocene variations in rate of sediment accumulation : Panama Basin, eastern equatorial Pacific Author: Pisias, Nicklas G. The assumption of constant quartz accumulation for the deep-sea sediment core Y69-106P, taken in the Panama Basin, has been used to date the core and construct a sedimentation rate versus time curve for it. Stratigraphic control for the calculated time scale includes three carbon-14 measurements, the extinction of the radiolarian Stylatractus universus, and correlation with oxygen isotope curves from other dated cores. The model sedimentation rates and sediment composition data allow the determination of sediment accumulation rates for calcium carbonate, opaline silica, and remaining "detritus". Fluctuations in calcium carbonate accumulation rates correlate closely with variations in oxygen isotope ratios in biogenous carbonate from two other equatorial Pacific sediment cores. High oxygen isotope ratios correlate with high calcium carbonate accumulation rates. Opaline silica accumulation rates reflect changes in the dominance of radiolarian fossil groups which can be related to surface circulation in the Panama Basin. The successive maxima in opal and calcium accumulation rates and the oxygen isotope ratios in Y69-106P suggest that at the end of the last glacial period, the rate of calcium carbonate dissolution increased in the Panama Basin first, to be followed by a decrease in the intensity of the eastern equatorial Pacific upwelling, and finally the volume of continental glaciers decreased. Spectral analysis of the rate of accumulation of calcium carbonate in Y69-106P and of the oxygen isotope record of core V28-238 indicate the presence of a 23,000 year periodicity. Analysis of opal accumulation rate suggest a 100,000 year periodicity. These two periodicities are found in fluctuations in the earth's orbital parameters. The eccentricity of the orbit fluctuates with an average period of 98,000 years and the precession of the equinoxes changes with a 22,000 year period. Title: Model of late Pleistocene-Holocene variations in rate of sediment accumulation : Panama Basin, eastern equatorial Pacific Author: Pisias, Nicklas G. The assumption of constant quartz accumulation for the deep-sea sediment core Y69-106P, taken in the Panama Basin, has been used to date the core and construct a sedimentation rate versus time curve for it. Stratigraphic control for the calculated time scale includes three carbon-14 measurements, the extinction of the radiolarian Stylatractus universus, and correlation with oxygen isotope curves from other dated cores. The model sedimentation rates and sediment composition data allow the determination of sediment accumulation rates for calcium carbonate, opaline silica, and remaining "detritus". Fluctuations in calcium carbonate accumulation rates correlate closely with variations in oxygen isotope ratios in biogenous carbonate from two other equatorial Pacific sediment cores. High oxygen isotope ratios correlate with high calcium carbonate accumulation rates. Opaline silica accumulation rates reflect changes in the dominance of radiolarian fossil groups which can be related to surface circulation in the Panama Basin. The successive maxima in opal and calcium accumulation rates and the oxygen isotope ratios in Y69-106P suggest that at the end of the last glacial period, the rate of calcium carbonate dissolution increased in the Panama Basin first, to be followed by a decrease in the intensity of the eastern equatorial Pacific upwelling, and finally the volume of continental glaciers decreased. Spectral analysis of the rate of accumulation of calcium carbonate in Y69-106P and of the oxygen isotope record of core V28-238 indicate the presence of a 23,000 year periodicity. Analysis of opal accumulation rate suggest a 100,000 year periodicity. These two periodicities are found in fluctuations in the earth's orbital parameters. The eccentricity of the orbit fluctuates with an average period of 98,000 years and the precession of the equinoxes changes with a 22,000 year period. Close

• 95. [Article] Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Seismological ...

  Citation × Citation Citation Abstract Copy Title: Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures Author: Walton, Maureen A. L., Roland, Emily C., Gulick, Sean P. S., Haeussler, Peter J., Tréhu, Anne M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Seismological Society of America and can be found at: http://www.bssaonline.org/. Title: Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures Author: Walton, Maureen A. L., Roland, Emily C., Gulick, Sean P. S., Haeussler, Peter J., Tréhu, Anne M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by the Seismological Society of America and can be found at: http://www.bssaonline.org/. Close

• 96. [Article] A dwarfed population of Catostomus rimiculus (Catostomidae: Pisces) in Jenny Creek, Jackson County, Oregon

  The population of Catostomus rimiculus from Jenny Creek basin is identified as a dwarfed derivative of the normally much larger C. rimiculus from the Klamath and Rogue River systems. C. rimiculus in Jenny ...

  Citation × Citation Citation Abstract Copy Title: A dwarfed population of Catostomus rimiculus (Catostomidae: Pisces) in Jenny Creek, Jackson County, Oregon Author: Hohler, David Berry The population of Catostomus rimiculus from Jenny Creek basin is identified as a dwarfed derivative of the normally much larger C. rimiculus from the Klamath and Rogue River systems. C. rimiculus in Jenny Creek basin are separated from those in the Klamath by a series of 3-10m waterfalls resulting from a Pleistocene lava flow. C. rimiculus in Jenny Creek basin can be distinguished from the Rogue River stock by number of scales above the lateral line, number of pectoral fin rays, number of caudal vertebrae, number of post-Weberian vertebrae and size of the lips. Stocks from Jenny Creek basin and the Klamath can be distinguished on the basis of number of caudal vertebrae. The suckers from Jenny Creek basin mature at approximately 130 mm SL at age II. Only one specimen was older than III. Growth rate appears to be similar in all three stocks of suckers despite the young age of maturity of Jenny Creek suckers. Age at maturity is IV or V for Klamath and Rogue River C. rimiculus. The largest sucker collected from the Jenny Creek basin was 210 mm SL whereas many specimens 250-390 mm SL were collected in the Rogue and Klamath River systems. I hypothesize that fish colonized the Jenny Creek basin by headwater capture in the Skookum-Rocky Creek area. Jenny Creek suckers are opportunistic omnivores. Segregation of foods in the intestine indicate discriminative feeding. Jenny Creek suckers were found in most habitat types in the lower reaches of Jenny, Beaver, Corral, Keene and Johnson Creeks in summer 1979. Sampling throughout the year established a pattern of migration upstream to spawn in spring and movement downstream in fall. Title: A dwarfed population of Catostomus rimiculus (Catostomidae: Pisces) in Jenny Creek, Jackson County, Oregon Author: Hohler, David Berry The population of Catostomus rimiculus from Jenny Creek basin is identified as a dwarfed derivative of the normally much larger C. rimiculus from the Klamath and Rogue River systems. C. rimiculus in Jenny Creek basin are separated from those in the Klamath by a series of 3-10m waterfalls resulting from a Pleistocene lava flow. C. rimiculus in Jenny Creek basin can be distinguished from the Rogue River stock by number of scales above the lateral line, number of pectoral fin rays, number of caudal vertebrae, number of post-Weberian vertebrae and size of the lips. Stocks from Jenny Creek basin and the Klamath can be distinguished on the basis of number of caudal vertebrae. The suckers from Jenny Creek basin mature at approximately 130 mm SL at age II. Only one specimen was older than III. Growth rate appears to be similar in all three stocks of suckers despite the young age of maturity of Jenny Creek suckers. Age at maturity is IV or V for Klamath and Rogue River C. rimiculus. The largest sucker collected from the Jenny Creek basin was 210 mm SL whereas many specimens 250-390 mm SL were collected in the Rogue and Klamath River systems. I hypothesize that fish colonized the Jenny Creek basin by headwater capture in the Skookum-Rocky Creek area. Jenny Creek suckers are opportunistic omnivores. Segregation of foods in the intestine indicate discriminative feeding. Jenny Creek suckers were found in most habitat types in the lower reaches of Jenny, Beaver, Corral, Keene and Johnson Creeks in summer 1979. Sampling throughout the year established a pattern of migration upstream to spawn in spring and movement downstream in fall. Close

• 97. [Article] Geology of the Duke Point-Kulleet Bay area, Vancouver Island, B.C.

  The Duke Point-Kulleet Bay area is located on the southeast coast of Vancouver Island, B.C., approximately 60 miles northwest of Victoria, B.C. and 25 miles west, across the Strait of Georgia, from Vancouver, ...

  Citation × Citation Citation Abstract Copy Title: Geology of the Duke Point-Kulleet Bay area, Vancouver Island, B.C. Author: Rinne, Richard Wyman The Duke Point-Kulleet Bay area is located on the southeast coast of Vancouver Island, B.C., approximately 60 miles northwest of Victoria, B.C. and 25 miles west, across the Strait of Georgia, from Vancouver, B.C. Approximately 2500 feet of Late Cretaceous sedimentary rocks of the Nanaimo Group are exposed within the area of investigation. The rocks were deposited in the Nanaimo Basin by a series of east and northeast flowing streams and rivers carrying sediments from the pre-Pennsylvanian Sicker Group volcanics, metavolcanics, argillites and quartzites, the Late Triassic-Early Jurassic Vancouver Group volcanics, limestones, argillites and greywackes, and the Middle Jurassic granodiorite-gabbro Island Intrusions. Formations within the area are: 1) the Cedar District, mainly marine mudstones with limy concretions and sandstone dikes, and Z) the De Courcy, mainly fluvial to shallow marine arkosic wackes, exhibiting honeycomb weathering and containing concretions and minor conglomerate, During the Late Cretaceous and Tertiary the rocks were differentially uplifted and folded and faulted into a northwest-southeast trending belt. The possibility of later episodes of diastrophism, exists. Two Pleistocene glacial epochs scoured the rocks and left till deposits behind during their retreats. Coal was mined extensively in the Nanaimo Basin from the 1850's to the 1940's and 1950's, but is no longer an economic commodity. Building stone and sand and gravel have been quarried for local use. Petroleum companies have investigated the area, but the results of their exploration have not been made public. Title: Geology of the Duke Point-Kulleet Bay area, Vancouver Island, B.C. Author: Rinne, Richard Wyman The Duke Point-Kulleet Bay area is located on the southeast coast of Vancouver Island, B.C., approximately 60 miles northwest of Victoria, B.C. and 25 miles west, across the Strait of Georgia, from Vancouver, B.C. Approximately 2500 feet of Late Cretaceous sedimentary rocks of the Nanaimo Group are exposed within the area of investigation. The rocks were deposited in the Nanaimo Basin by a series of east and northeast flowing streams and rivers carrying sediments from the pre-Pennsylvanian Sicker Group volcanics, metavolcanics, argillites and quartzites, the Late Triassic-Early Jurassic Vancouver Group volcanics, limestones, argillites and greywackes, and the Middle Jurassic granodiorite-gabbro Island Intrusions. Formations within the area are: 1) the Cedar District, mainly marine mudstones with limy concretions and sandstone dikes, and Z) the De Courcy, mainly fluvial to shallow marine arkosic wackes, exhibiting honeycomb weathering and containing concretions and minor conglomerate, During the Late Cretaceous and Tertiary the rocks were differentially uplifted and folded and faulted into a northwest-southeast trending belt. The possibility of later episodes of diastrophism, exists. Two Pleistocene glacial epochs scoured the rocks and left till deposits behind during their retreats. Coal was mined extensively in the Nanaimo Basin from the 1850's to the 1940's and 1950's, but is no longer an economic commodity. Building stone and sand and gravel have been quarried for local use. Petroleum companies have investigated the area, but the results of their exploration have not been made public. Close

• 98. [Article] Structure and seismic hazards of the offshore Cascadia forearc and evolution of the Neogene forearc basin

  The Cascadia subduction zone has been characterized as a typical Chilean-type subduction zone based on qualitative comparisons of plate age and convergence rate, with simple forearc structure. However, ...

  Citation × Citation Citation Abstract Copy Title: Structure and seismic hazards of the offshore Cascadia forearc and evolution of the Neogene forearc basin Author: McNeill, Lisa C. The Cascadia subduction zone has been characterized as a typical Chilean-type subduction zone based on qualitative comparisons of plate age and convergence rate, with simple forearc structure. However, the discovery of unusual structural styles of deformation, variations in the morphology of the forearc, and its absence of seismic activity suggest differences from the Chilean analog. The manuscripts presented here (McNeill et al., 1997, in press, submitted) illustrate this complexity and provide examples of contrasting deformation throughout the offshore forearc. The Washington and northern Oregon shelf and upper slope are characterized by extension in the form of listric normal faults. These faults have been active since the late Miocene and are driven by detachment and extension of the underlying overpressured mélange and broken formation. This region of the forearc is partly to wholly decoupled from convergence-driven compression which dominates deformation elsewhere in the forearc. One exception to convergence-driven compression is a region of N-S compression of the inner shelf and coastal region which reflects the regional stress field. N-S compressional structures apparently influence the positions of coastal lowlands and uplands and may contribute to the record of coastal marsh burials interepreted as the result of coseismic subsidence during subduction zone earthquakes. Modeling of subduction zone earthquake characteristics based on marsh stratigraphy is likely to be inaccurate in terms of rupture zone position, magnitude, and recurrence interval. The Cascadia shelf and upper slope are underlain by a sequence of deformed basinal strata which reflects the tectonic evolution of the margin. The surface of a regional late Miocene angular unconformity (7.5-6 Ma: a global hiatus) indicates deformation by uplifted submarine banks and subsided synclines (coincident with low recent uplift onshore), which control the current shelf break position. The basin is currently filled behind a N-S-trending outer-arc high, which uplifted in the early-middle Pliocene following truncation and erosion of the seaward edge of the basin. Breaching of the outer-arc high occurred in the early Pleistocene leading to the formation of the Astoria Submarine Fan and increased growth rates of the accretionary wedge. Title: Structure and seismic hazards of the offshore Cascadia forearc and evolution of the Neogene forearc basin Author: McNeill, Lisa C. The Cascadia subduction zone has been characterized as a typical Chilean-type subduction zone based on qualitative comparisons of plate age and convergence rate, with simple forearc structure. However, the discovery of unusual structural styles of deformation, variations in the morphology of the forearc, and its absence of seismic activity suggest differences from the Chilean analog. The manuscripts presented here (McNeill et al., 1997, in press, submitted) illustrate this complexity and provide examples of contrasting deformation throughout the offshore forearc. The Washington and northern Oregon shelf and upper slope are characterized by extension in the form of listric normal faults. These faults have been active since the late Miocene and are driven by detachment and extension of the underlying overpressured mélange and broken formation. This region of the forearc is partly to wholly decoupled from convergence-driven compression which dominates deformation elsewhere in the forearc. One exception to convergence-driven compression is a region of N-S compression of the inner shelf and coastal region which reflects the regional stress field. N-S compressional structures apparently influence the positions of coastal lowlands and uplands and may contribute to the record of coastal marsh burials interepreted as the result of coseismic subsidence during subduction zone earthquakes. Modeling of subduction zone earthquake characteristics based on marsh stratigraphy is likely to be inaccurate in terms of rupture zone position, magnitude, and recurrence interval. The Cascadia shelf and upper slope are underlain by a sequence of deformed basinal strata which reflects the tectonic evolution of the margin. The surface of a regional late Miocene angular unconformity (7.5-6 Ma: a global hiatus) indicates deformation by uplifted submarine banks and subsided synclines (coincident with low recent uplift onshore), which control the current shelf break position. The basin is currently filled behind a N-S-trending outer-arc high, which uplifted in the early-middle Pliocene following truncation and erosion of the seaward edge of the basin. Breaching of the outer-arc high occurred in the early Pleistocene leading to the formation of the Astoria Submarine Fan and increased growth rates of the accretionary wedge. Close

• 99. [Article] Subsurface geology of the Santa Clara Avenue oil field and the Las Posas area, Ventura basin, California

  In the Santa Clara Avenue oil field, the nonmarine Sespe Formation of Oligocene age has produced 4 million barrels of oil trapped by a Miocene mafic igneous intrusion that cuts across bedding. Throughout ...

  Citation × Citation Citation Abstract Copy Title: Subsurface geology of the Santa Clara Avenue oil field and the Las Posas area, Ventura basin, California Author: Richards, Matthew E. In the Santa Clara Avenue oil field, the nonmarine Sespe Formation of Oligocene age has produced 4 million barrels of oil trapped by a Miocene mafic igneous intrusion that cuts across bedding. Throughout most of the oil field, the Miocene and older beds dip about 15° northwest. The intrusion may be related to the outpouring of Conejo Volcanics throughout much of the southern Ventura basin. The Pacific Farms #1 well penetrated 1000 feet of igneous rocks below 5100 feet, whereas wells less than 500 feet to the northwest penetrated Sespe Formation over this interval. The western wall of the intrusion is located by 10 wells which pass repeatedly through the Sespe-intrusive contact. Structure contours on the intrusive contact with the Sespe on the northwest show Redacted for Privacy that the contact varies from N20°E,80°SE in the southern portion of the field, to N90°E,85°S in the northern end of the field. The southeast wall of the intrusion is not cut by wells, but its location is controlled by a well about 1200 feet southeast of the northwest wall. If the intrusive contact is rotated to its position when it was intruded prior to tilting of the middle and late Miocene Modelo Formation, the Sespe overhangs the igneous body along a contact with a paleo-dip of 80°NW. Lateral closure in the field may be due to early Miocene normal faulting of the Sespe Formation. In the Las Posas area, two faults are documented. Both faults cut the entire Miocene section but do not cut the Pliocene-Pleistocene Pico Formation. The Miocene Vaqueros is found only on the south side of the Las Posas fault. Intra-Sespe correlations show that the upthrown block of the Las Posas fault lost to erosion 1000 feet of Sespe in addition to the Vaqueros Formation. The Epworth syncline and Beryiwood anticline were folded prior to the deposition of the Pico Formation. Title: Subsurface geology of the Santa Clara Avenue oil field and the Las Posas area, Ventura basin, California Author: Richards, Matthew E. In the Santa Clara Avenue oil field, the nonmarine Sespe Formation of Oligocene age has produced 4 million barrels of oil trapped by a Miocene mafic igneous intrusion that cuts across bedding. Throughout most of the oil field, the Miocene and older beds dip about 15° northwest. The intrusion may be related to the outpouring of Conejo Volcanics throughout much of the southern Ventura basin. The Pacific Farms #1 well penetrated 1000 feet of igneous rocks below 5100 feet, whereas wells less than 500 feet to the northwest penetrated Sespe Formation over this interval. The western wall of the intrusion is located by 10 wells which pass repeatedly through the Sespe-intrusive contact. Structure contours on the intrusive contact with the Sespe on the northwest show Redacted for Privacy that the contact varies from N20°E,80°SE in the southern portion of the field, to N90°E,85°S in the northern end of the field. The southeast wall of the intrusion is not cut by wells, but its location is controlled by a well about 1200 feet southeast of the northwest wall. If the intrusive contact is rotated to its position when it was intruded prior to tilting of the middle and late Miocene Modelo Formation, the Sespe overhangs the igneous body along a contact with a paleo-dip of 80°NW. Lateral closure in the field may be due to early Miocene normal faulting of the Sespe Formation. In the Las Posas area, two faults are documented. Both faults cut the entire Miocene section but do not cut the Pliocene-Pleistocene Pico Formation. The Miocene Vaqueros is found only on the south side of the Las Posas fault. Intra-Sespe correlations show that the upthrown block of the Las Posas fault lost to erosion 1000 feet of Sespe in addition to the Vaqueros Formation. The Epworth syncline and Beryiwood anticline were folded prior to the deposition of the Pico Formation. Close

• 100. [Article] Phylogeny and Biogeography of Primula sect. Parryi (Primulaceae)

  This is the publisher’s final pdf. The published article is copyrighted by The University of Chicago Press and can be found at: http://www.press.uchicago.edu/ucp/journals/journal/ijps.html

  Citation × Citation Citation Abstract Copy Title: Phylogeny and Biogeography of Primula sect. Parryi (Primulaceae) Author: Weitemier, Kevin, Beardsley, Paul M., Kelso, Sylvia This is the publisher’s final pdf. The published article is copyrighted by The University of Chicago Press and can be found at: http://www.press.uchicago.edu/ucp/journals/journal/ijps.html Title: Phylogeny and Biogeography of Primula sect. Parryi (Primulaceae) Author: Weitemier, Kevin, Beardsley, Paul M., Kelso, Sylvia This is the publisher’s final pdf. The published article is copyrighted by The University of Chicago Press and can be found at: http://www.press.uchicago.edu/ucp/journals/journal/ijps.html Close