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• 61. [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

• 62. [Article] Biochemical Description of a Lava Tube Lake in Southeast Oregon

  A Pleistocene lava tube cave in southeast Oregon has a seasonally fluctuating lake occupying the last 1200 to 2000 feet. Three endemic invertebrate species inhabit the lake: Kenkia rynchida Hyman; Asellus ...

  Citation × Citation Citation Abstract Copy Title: Biochemical Description of a Lava Tube Lake in Southeast Oregon Author: Palmer, John Edward Year: 1975 A Pleistocene lava tube cave in southeast Oregon has a seasonally fluctuating lake occupying the last 1200 to 2000 feet. Three endemic invertebrate species inhabit the lake: Kenkia rynchida Hyman; Asellus sp.; and stygobromus hubbsi. Shoemaker. Little is known however, about their environment. The purpose of this study was to describe various physical and chemical parameters of Malheur Cave Lake. Title: Biochemical Description of a Lava Tube Lake in Southeast Oregon Author: Palmer, John Edward Year: 1975 A Pleistocene lava tube cave in southeast Oregon has a seasonally fluctuating lake occupying the last 1200 to 2000 feet. Three endemic invertebrate species inhabit the lake: Kenkia rynchida Hyman; Asellus sp.; and stygobromus hubbsi. Shoemaker. Little is known however, about their environment. The purpose of this study was to describe various physical and chemical parameters of Malheur Cave Lake. Close

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

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

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

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

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

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

• 65. [Article] Late Pleistocene and Holocene Aged Glacial and Climatic Reconstructions in the Goat Rocks Wilderness, Washington, United States

  Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred ...

  Citation × Citation Citation Abstract Copy Title: Late Pleistocene and Holocene Aged Glacial and Climatic Reconstructions in the Goat Rocks Wilderness, Washington, United States Author: Heard, Joshua Andrews Year: 2012 Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 ºC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 ºC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 ºC with no change in precipitation. Title: Late Pleistocene and Holocene Aged Glacial and Climatic Reconstructions in the Goat Rocks Wilderness, Washington, United States Author: Heard, Joshua Andrews Year: 2012 Eight glaciers, covering an area of 1.63 km2, reside on the northern and northeastern slopes of the Goat Rocks tallest peaks in the Cascades of central Washington. At least three glacial stands occurred downstream from these glaciers. Closest to modern glacier termini are Little Ice Age (LIA) moraines that were deposited between 1870 and 1899 AD, according to the lichenometric analysis. They are characterized by sharp, minimally eroded crests, little to no soil cover, and minimal vegetation cover. Glacier reconstructions indicate that LIA glaciers covered 8.29 km2, 76% more area than modern ice coverage. The average LIA equilibrium line altitude (ELA) of 1995 ± 70 m is ~150 m below the average modern ELA of 2149 ± 76 m. To satisfy climate conditions at the LIA ELA, the winter snow accumulation must have been 8 to 43 cm greater and mean summer temperatures 0.2 to 1.3 ºC cooler than they are now. Late Pleistocene to early Holocene (LPEH) aged moraines are located between 100 and 400 m below the LIA deposits. They have degraded moraine crests, few surface boulders, and considerable vegetation and soil cover. Volcanic ashes indicate LPEH moraines were deposited before 1480 AD while morphometric data suggest deposition during the late Pleistocene or early Holocene. The average LPEH ELA of 1904 ± 110 m is ~ 240 m and ~90 m below the modern and LIA ELAs, respectively. The climate change necessary to maintain a glacier with an ELA at that elevation for LPEH conditions requires the winter accumulation to increase by 47 to 48 cm weq and the mean summer temperature to cool by 1.4 to 1.5 ºC. Last glacial maximum (LGM) moraines are located more than 30 km downstream from modern glacial termini. They are characterized by hummocky topography, rounded moraine crests, complete vegetation cover, and well developed soil cover. Moraine morphometry, soil characteristics, and distance from modern glacial termini indicate that deposition occurred at least 15 ka BP during an expansive cooling event, the last being the LGM. The LGM ELA of 1230 m is ~920 m below the modern ELA. The climate change necessary to maintain a glacier with an ELA at that elevation for LGM conditions requires the mean summer temperature to cool by 5.6 ºC with no change in precipitation. Close

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

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

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

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

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

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

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

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

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

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

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

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

• 70. [Article] Moletrack scarps to mountains: Quaternary tectonics of the central Alaska Range

  xvi, 121 p. : ill. (some col.), maps (some col.) Also includes two large-scale maps in two separate pdf files. A print copy of this thesis is available through the UO Libraries. Search the library catalog ...

  Citation × Citation Citation Abstract Copy Title: Moletrack scarps to mountains: Quaternary tectonics of the central Alaska Range Author: Bemis, Sean Patrick, 1979- Year: 2010 xvi, 121 p. : ill. (some col.), maps (some col.) Also includes two large-scale maps in two separate pdf files. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Title: Moletrack scarps to mountains: Quaternary tectonics of the central Alaska Range Author: Bemis, Sean Patrick, 1979- Year: 2010 xvi, 121 p. : ill. (some col.), maps (some col.) Also includes two large-scale maps in two separate pdf files. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. Close

• 71. [Article] Paleo-archaic broad spectrum adaptations at the Pleistocene-Holocene boundary in Far Western North America

  xx, 463 p. : ill., maps. Two print copies of this title are available through the UO Libraries under the call number: KNIGHT E61 .W72 1989

  Citation × Citation Citation Abstract Copy Title: Paleo-archaic broad spectrum adaptations at the Pleistocene-Holocene boundary in Far Western North America Author: Willig, Judith A. (Judith Ann), 1953- Year: 2009, 1989 xx, 463 p. : ill., maps. Two print copies of this title are available through the UO Libraries under the call number: KNIGHT E61 .W72 1989 Title: Paleo-archaic broad spectrum adaptations at the Pleistocene-Holocene boundary in Far Western North America Author: Willig, Judith A. (Judith Ann), 1953- Year: 2009, 1989 xx, 463 p. : ill., maps. Two print copies of this title are available through the UO Libraries under the call number: KNIGHT E61 .W72 1989 Close

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

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

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

• 73. [Image] Hydrogeology and paleohydrology in the Williamson River basin, Klamath County, Oregon

  	Abstract An abstract of the thesis of Jeffrey Scott Conaway for the Master of Science in Geology presented December 8, 1999. Title: Hydrogeology and Paleohydrology in the Williamson River Basin, Klamath ...
  	Citation × Citation Citation Abstract Copy Title: Hydrogeology and paleohydrology in the Williamson River basin, Klamath County, Oregon Author: Conaway, Jeffrey Scott Year: 2000, 2008, 2005 Abstract An abstract of the thesis of Jeffrey Scott Conaway for the Master of Science in Geology presented December 8, 1999. Title: Hydrogeology and Paleohydrology in the Williamson River Basin, Klamath County, Oregon. Stress on the water resources of the Williamson River basin has led to their regulation to protect important habitat. Quantification of this resource is required for accurate regulation. A portion of this study is a hydrogeologic reconnaissance that suggests directions for future work. Measured discharge and deuterium isotope data from points above and below the Williamson River canyon indicate that the river receives 99% of its discharge from ground water during periods of low flow. The principle aquifer of the southern Klamath Marsh is a fractured basalt, while continental sediments that are up to 200 m thick provide high artesian yields south of the canyon. The disparity between high precipitation on the basin's western margin and the low and variable discharge of the Williamson River at the Kirk Sill suggests either the presence of a fault zone that interrupts the flow of ground water or deep flow paths that do not surface within Klamath Marsh. Three terraces line the eastern edge of Klamath Marsh at approximate elevations of 1380, 1385, and 1397 m. The lowest terrace is late Holocene and cut into marsh sediment and reworked deposits from the pyroclastic eruptions of Mount Mazama. The middle terrace is planed into bedrock and formed when Pleistocene Lake Chemult occupied this basin. The upper terrace, a strand line, is delineated by a slope break that separates reworked pyroclastic deposits from undisturbed pyroclastic fall. Formation of this terrace occurred when pyroclastic flows from the cataclysmic eruption of Mount Mazama formed a blockage in the Williamson River canyon. Resultant backflooding reworked pyroclastic deposits and rafted pumice up to an approximate elevation of 1400 m. The blockage failed catastrophically from overtopping, draining 5.7 x 109 m3 of water, scouring the canyon and producing an erratic boulder deposit at the mouth of the canyon. Upstream evidence of rapid draining includes linear scour channels incised in pyroclastic-flow deposits and scouring of the broad Pleistocene terrace. Paleohydraulic reconstruction of down stream flooding using a flow-competence equation and a physically based dam-break model yield a peak discharge of 1.3 x 104 m3 s"1. Title: Hydrogeology and paleohydrology in the Williamson River basin, Klamath County, Oregon Author: Conaway, Jeffrey Scott Year: 2000, 2008, 2005 Abstract An abstract of the thesis of Jeffrey Scott Conaway for the Master of Science in Geology presented December 8, 1999. Title: Hydrogeology and Paleohydrology in the Williamson River Basin, Klamath County, Oregon. Stress on the water resources of the Williamson River basin has led to their regulation to protect important habitat. Quantification of this resource is required for accurate regulation. A portion of this study is a hydrogeologic reconnaissance that suggests directions for future work. Measured discharge and deuterium isotope data from points above and below the Williamson River canyon indicate that the river receives 99% of its discharge from ground water during periods of low flow. The principle aquifer of the southern Klamath Marsh is a fractured basalt, while continental sediments that are up to 200 m thick provide high artesian yields south of the canyon. The disparity between high precipitation on the basin's western margin and the low and variable discharge of the Williamson River at the Kirk Sill suggests either the presence of a fault zone that interrupts the flow of ground water or deep flow paths that do not surface within Klamath Marsh. Three terraces line the eastern edge of Klamath Marsh at approximate elevations of 1380, 1385, and 1397 m. The lowest terrace is late Holocene and cut into marsh sediment and reworked deposits from the pyroclastic eruptions of Mount Mazama. The middle terrace is planed into bedrock and formed when Pleistocene Lake Chemult occupied this basin. The upper terrace, a strand line, is delineated by a slope break that separates reworked pyroclastic deposits from undisturbed pyroclastic fall. Formation of this terrace occurred when pyroclastic flows from the cataclysmic eruption of Mount Mazama formed a blockage in the Williamson River canyon. Resultant backflooding reworked pyroclastic deposits and rafted pumice up to an approximate elevation of 1400 m. The blockage failed catastrophically from overtopping, draining 5.7 x 109 m3 of water, scouring the canyon and producing an erratic boulder deposit at the mouth of the canyon. Upstream evidence of rapid draining includes linear scour channels incised in pyroclastic-flow deposits and scouring of the broad Pleistocene terrace. Paleohydraulic reconstruction of down stream flooding using a flow-competence equation and a physically based dam-break model yield a peak discharge of 1.3 x 104 m3 s"1. Close

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

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

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

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

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

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

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

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

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

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

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

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

• 78. [Image] Investigation of Two Areas in New York State which may have Potential for Geothermal Energy. Progress Report, May 1, 1976--September 31, 1976

  	Significant results to date include the following: (1) the present Adirondack Mountains Dome is undergoing rapid contemporary vertical doming; the velocity at the center of the dome is 3.7mm/yr, compared ...
  	Citation × Citation Citation Abstract Copy Title: Investigation of Two Areas in New York State which may have Potential for Geothermal Energy. Progress Report, May 1, 1976--September 31, 1976 Author: Isachsen, Y.W. Year: 1976 Significant results to date include the following: (1) the present Adirondack Mountains Dome is undergoing rapid contemporary vertical doming; the velocity at the center of the dome is 3.7mm/yr, compared to 1mm/yr for the Swiss Alps; (2) post-Pleistocene fault offsets measuring from one to eleven millimeters have been found in the Adirondacks, indicating vertical uplift during the past 10,000 years; (3) the Panther Mountain Circular drainage feature is structurally-controlled and shows a 10 to 20 milligal negative Simple Bouguer gravity anomaly such as might be produced by a buried felsic pluton Title: Investigation of Two Areas in New York State which may have Potential for Geothermal Energy. Progress Report, May 1, 1976--September 31, 1976 Author: Isachsen, Y.W. Year: 1976 Significant results to date include the following: (1) the present Adirondack Mountains Dome is undergoing rapid contemporary vertical doming; the velocity at the center of the dome is 3.7mm/yr, compared to 1mm/yr for the Swiss Alps; (2) post-Pleistocene fault offsets measuring from one to eleven millimeters have been found in the Adirondacks, indicating vertical uplift during the past 10,000 years; (3) the Panther Mountain Circular drainage feature is structurally-controlled and shows a 10 to 20 milligal negative Simple Bouguer gravity anomaly such as might be produced by a buried felsic pluton Close

• 79. [Image] The 1980-1982 Geothermal Resource Assessment Program in Washington

  	Since 1978, the Division of Geology and Earth Resources of the Washington Department of Natural Resources has participated in the U.S. Department of Energy's (USDOE) StateCoupled Geothermal Resource Program. ...
  	Citation × Citation Citation Abstract Copy Title: The 1980-1982 Geothermal Resource Assessment Program in Washington Author: Korosec, M. A. Year: 1983 Since 1978, the Division of Geology and Earth Resources of the Washington Department of Natural Resources has participated in the U.S. Department of Energy's (USDOE) StateCoupled Geothermal Resource Program. Federal and state funds have been used to investigate and evaluate the potential for geothermal resources, on both a reconnaissance and area-specific level. Preliminary results and progress reports for the period up through mid-1980 have already been released as a Division Open File Report (Korosec, Schuster, and others, 1981). Preliminary results and progress summaries of work carried out from mid-1980 through the end of 1982 are presented in this report Title: The 1980-1982 Geothermal Resource Assessment Program in Washington Author: Korosec, M. A. Year: 1983 Since 1978, the Division of Geology and Earth Resources of the Washington Department of Natural Resources has participated in the U.S. Department of Energy's (USDOE) StateCoupled Geothermal Resource Program. Federal and state funds have been used to investigate and evaluate the potential for geothermal resources, on both a reconnaissance and area-specific level. Preliminary results and progress reports for the period up through mid-1980 have already been released as a Division Open File Report (Korosec, Schuster, and others, 1981). Preliminary results and progress summaries of work carried out from mid-1980 through the end of 1982 are presented in this report Close

• 80. [Image] Petrographic Analysis and Correlation of Volcanic Rocks in Bostic 1-A Well near Mountain Home, Idaho

  	Detailed examination of volcanic rock cuttings from the Bostic I-A well near Mountain Home, Idaho, provides data that correlate the stratigraphy of the well with the regional stratigraphy of the western ...
  	Citation × Citation Citation Abstract Copy Title: Petrographic Analysis and Correlation of Volcanic Rocks in Bostic 1-A Well near Mountain Home, Idaho Author: Arney, B. H. Year: 1984 Detailed examination of volcanic rock cuttings from the Bostic I-A well near Mountain Home, Idaho, provides data that correlate the stratigraphy of the well with the regional stratigraphy of the western Snake River Plain. The Bostic I-A well penetrates basalt of the Middle Pleistocene Bruneau Formation and underlying sedimentary rocks of the Upper Pliocene Glenns Ferry Formation. Basalt underlying the Glenns Ferry Formation is most likely Banbury Basalt of Middle Pliocene age or Banbury equivalent. A 350-ft interval of felsic volcanics is then intersected above another 600 ft of basalt. The well bottoms in altered felsic volcanics Title: Petrographic Analysis and Correlation of Volcanic Rocks in Bostic 1-A Well near Mountain Home, Idaho Author: Arney, B. H. Year: 1984 Detailed examination of volcanic rock cuttings from the Bostic I-A well near Mountain Home, Idaho, provides data that correlate the stratigraphy of the well with the regional stratigraphy of the western Snake River Plain. The Bostic I-A well penetrates basalt of the Middle Pleistocene Bruneau Formation and underlying sedimentary rocks of the Upper Pliocene Glenns Ferry Formation. Basalt underlying the Glenns Ferry Formation is most likely Banbury Basalt of Middle Pliocene age or Banbury equivalent. A 350-ft interval of felsic volcanics is then intersected above another 600 ft of basalt. The well bottoms in altered felsic volcanics Close