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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