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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

• 14. [Article] Origins of Late- Pleistocene Coastal Dune Sheets, Magdalena and Guerrero Negro, from Continental Shelf Low-stand Supply (70-20 ka), under Conditions of Southeast Littoral- and Eolian-Sand Transport, in Baja California Sur, Mexico

  Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja ...

  Citation × Citation Citation Abstract Copy Title: Origins of Late- Pleistocene Coastal Dune Sheets, Magdalena and Guerrero Negro, from Continental Shelf Low-stand Supply (70-20 ka), under Conditions of Southeast Littoral- and Eolian-Sand Transport, in Baja California Sur, Mexico Author: Peterson, Curt D., Murillo-Jiminez, Janette, Stock, Errol, Price, David M., Hostetler, Steve W., Percy, David Year: 2017 Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m in height) in the dune sheet interiors trend southeast and are generally of late Pleistocene age (∼70-20 ka). The late Pleistocene dune deposits reflect eolian transport of marine sand across the emerged continental shelf (30-50 km southeast distance) from low-stand paleo-shorelines (-100 ± 25 m elevation), which were locally oriented nearly orthogonal to modeled deep-water wave directions (∼300° TN). During the Holocene marine transgression, onshore and alongshore wave transport delivered remobilized shelf-sand deposits to the nearshore areas of the large dune sheets, building extensive barrier islands and sand spits. Submerged back-barrier lagoons generally precluded marine sand supply to dune sheet interiors in middle to late Holocene time, though exceptions occur along some ocean and lagoon shorelines. Reactivation of the late Pleistocene dune deposits in the dune sheet interiors lead to generally thin (1-3 m thickness), but widespread, covers of Holocene dune deposits (0.41 ± 0.05 to 10.5 ± 1.6 ka). Mechanical drilling will be required to penetrate indurated subsoil caliche layers to reach basal Pleistocene dune deposits. Title: Origins of Late- Pleistocene Coastal Dune Sheets, Magdalena and Guerrero Negro, from Continental Shelf Low-stand Supply (70-20 ka), under Conditions of Southeast Littoral- and Eolian-Sand Transport, in Baja California Sur, Mexico Author: Peterson, Curt D., Murillo-Jiminez, Janette, Stock, Errol, Price, David M., Hostetler, Steve W., Percy, David Year: 2017 Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m in height) in the dune sheet interiors trend southeast and are generally of late Pleistocene age (∼70-20 ka). The late Pleistocene dune deposits reflect eolian transport of marine sand across the emerged continental shelf (30-50 km southeast distance) from low-stand paleo-shorelines (-100 ± 25 m elevation), which were locally oriented nearly orthogonal to modeled deep-water wave directions (∼300° TN). During the Holocene marine transgression, onshore and alongshore wave transport delivered remobilized shelf-sand deposits to the nearshore areas of the large dune sheets, building extensive barrier islands and sand spits. Submerged back-barrier lagoons generally precluded marine sand supply to dune sheet interiors in middle to late Holocene time, though exceptions occur along some ocean and lagoon shorelines. Reactivation of the late Pleistocene dune deposits in the dune sheet interiors lead to generally thin (1-3 m thickness), but widespread, covers of Holocene dune deposits (0.41 ± 0.05 to 10.5 ± 1.6 ka). Mechanical drilling will be required to penetrate indurated subsoil caliche layers to reach basal Pleistocene dune deposits. Close

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

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

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

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

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

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

• 17. [Article] Coastal Eolian Sand-Ramp Development Related to Paleo-Sea-Level Changes during the Latest Pleistocene and Holocene (21–0 ka) in San Miguel Island, California, U.S.A.

  Coastal eolian sand ramps (5–130 m elevation) on the northern slope (windward) side of the small San Miguel Island (13 km in W-E length) range in age from late Pleistocene to modern time, though a major ...

  Citation × Citation Citation Abstract Copy Title: Coastal Eolian Sand-Ramp Development Related to Paleo-Sea-Level Changes during the Latest Pleistocene and Holocene (21–0 ka) in San Miguel Island, California, U.S.A. Author: Peterson, Curt D., Erlandson, Jon M., Stock, Errol, Hostetler, Steve W., Price, David M. Year: 2017 Coastal eolian sand ramps (5–130 m elevation) on the northern slope (windward) side of the small San Miguel Island (13 km in W-E length) range in age from late Pleistocene to modern time, though a major hiatus in sand-ramp growth occurred during the early Holocene marine transgression (16–9 ka). The Holocene sand ramps (1–5 m measured thicknesses) currently lack large dune forms, thereby representing deflated erosional remnants, locally covering thicker late Pleistocene sand-ramp deposits. The ramp sand was initially supplied from the adjacent island-shelf platform, extending about 20 km north of the present coastline. The sand-ramp deposits and interbedded loess soils were 14C dated using 112 samples from 32 archaeological sites and other geologic sections. Latest Pleistocene sand ramps (66–18 ka) were derived from across-shelf eolian sand transport during marine low stands. Shoreward wave transport supplied remobilized late Pleistocene sand from the inner shelf to Holocene beaches, where dominant NW winds supplied sand to the sand ramps. The onset dates of the sand-ramp deposition in San Miguel are 7.2 ± 1.5 ka (sample n = 14). The internal strata dates in the vertically accreting sand ramps are 3.4 ± 1.7 ka (n = 34). The sand ramps in San Miguel show wide-scale termination of sand supply in the latest Holocene time. The sand-ramp top dates or burial dates are 1.7 ± 0.9 ka (n = 28). The latest Holocene sand ramps are truncated along most of the island's northern coastline, indicating recent losses of nearshore sand reserves to onshore, alongshore, and, possibly, offshore sand sinks. The truncated sand ramps in San Miguel Island and in other sand-depleted marine coastlines provide warnings about future beach erosion and/or shoreline retreat from accelerated sea-level rise accompanying predicted global warming. Title: Coastal Eolian Sand-Ramp Development Related to Paleo-Sea-Level Changes during the Latest Pleistocene and Holocene (21–0 ka) in San Miguel Island, California, U.S.A. Author: Peterson, Curt D., Erlandson, Jon M., Stock, Errol, Hostetler, Steve W., Price, David M. Year: 2017 Coastal eolian sand ramps (5–130 m elevation) on the northern slope (windward) side of the small San Miguel Island (13 km in W-E length) range in age from late Pleistocene to modern time, though a major hiatus in sand-ramp growth occurred during the early Holocene marine transgression (16–9 ka). The Holocene sand ramps (1–5 m measured thicknesses) currently lack large dune forms, thereby representing deflated erosional remnants, locally covering thicker late Pleistocene sand-ramp deposits. The ramp sand was initially supplied from the adjacent island-shelf platform, extending about 20 km north of the present coastline. The sand-ramp deposits and interbedded loess soils were 14C dated using 112 samples from 32 archaeological sites and other geologic sections. Latest Pleistocene sand ramps (66–18 ka) were derived from across-shelf eolian sand transport during marine low stands. Shoreward wave transport supplied remobilized late Pleistocene sand from the inner shelf to Holocene beaches, where dominant NW winds supplied sand to the sand ramps. The onset dates of the sand-ramp deposition in San Miguel are 7.2 ± 1.5 ka (sample n = 14). The internal strata dates in the vertically accreting sand ramps are 3.4 ± 1.7 ka (n = 34). The sand ramps in San Miguel show wide-scale termination of sand supply in the latest Holocene time. The sand-ramp top dates or burial dates are 1.7 ± 0.9 ka (n = 28). The latest Holocene sand ramps are truncated along most of the island's northern coastline, indicating recent losses of nearshore sand reserves to onshore, alongshore, and, possibly, offshore sand sinks. The truncated sand ramps in San Miguel Island and in other sand-depleted marine coastlines provide warnings about future beach erosion and/or shoreline retreat from accelerated sea-level rise accompanying predicted global warming. Close

• 18. [Article] Chronology and Ecology of Late Pleistocene Megafauna in the Northern Willamette Valley, Oregon

  This study is an investigation of the timing of extinction of late Pleistocene, large bodied mammalian herbivores (megafauna) and of the environment in which they lived. The demise of the megafauna near ...

  Citation × Citation Citation Abstract Copy Title: Chronology and Ecology of Late Pleistocene Megafauna in the Northern Willamette Valley, Oregon Author: Gilmour, Daniel McGowan Year: 2011 This study is an investigation of the timing of extinction of late Pleistocene, large bodied mammalian herbivores (megafauna) and of the environment in which they lived. The demise of the megafauna near the end of the Pleistocene remains unexplained. Owing to potential human involvement in the extinctions, archaeologists have been particularly concerned to understand the causes for faunal losses. Our current lack of understanding of the timing and the causes of the extinctions in North America may result from a deficiency in understanding the histories of each individual species of extinct animal on a local level. Detailed regional chronologies of fauna are necessary for comparison with paleoenvironmental and archaeological data to help sort out causes for extinction. The Willamette Valley of western Oregon has long been noted for finds of megafauna, though records have not been synthesized since the early 20th century and these materials have remained largely unstudied. In this thesis, I first create a catalog of extinct megafauna recovered from the Willamette Valley. Next, using material from the northern valley, I employ AMS radiocarbon dating, stable isotope δ¹³C and δ¹⁵N analyses, and gross inferences based on the dietary specializations and habitat preferences of taxa in order to reconstruct environments and to develop a local chronology of events that is then arrayed against archaeological and paleoenvironmental data. The results of this study indicate that megafaunal populations in the northern Willamette Valley were contemporaneous with the earliest known human populations of the Pacific Northwest, as well as later populations associated with the Clovis Paleoindian Horizon. Consistent with the overkill hypothesis, radiocarbon ages span the length of the Clovis window, but no ages are younger than Clovis. Moreover, all radiocarbon ages are older than or contemporaneous to the onset of the Younger Dryas Stadial. No age ranges fall exclusively within the Younger Dryas. Comparison of megafaunal ages and paleoenvironmental records support the view that climate change contributed to local animal population declines. Prior to ~13,000 cal BP, the Willamette Valley was an open environment; herbivores mainly consumed C₃ vegetation. The timing of the loss of megafauna coincides with increased forested conditions as indicated by regional paleoenvironmental reconstruction. As the timing of megafaunal decline correlates with Clovis, the onset of the Younger Dryas, and increased forested conditions, it is not possible with the data currently available to distinguish the cause of extinction in the Willamette Valley. The age ranges of the fauna coupled with taphonomic and geologic context indicate that the fauna are autochthonous to the Willamette Valley; they do not represent ice rafted carcasses or isolated skeletal elements transported from elsewhere during late Pleistocene glacial outburst floods. Title: Chronology and Ecology of Late Pleistocene Megafauna in the Northern Willamette Valley, Oregon Author: Gilmour, Daniel McGowan Year: 2011 This study is an investigation of the timing of extinction of late Pleistocene, large bodied mammalian herbivores (megafauna) and of the environment in which they lived. The demise of the megafauna near the end of the Pleistocene remains unexplained. Owing to potential human involvement in the extinctions, archaeologists have been particularly concerned to understand the causes for faunal losses. Our current lack of understanding of the timing and the causes of the extinctions in North America may result from a deficiency in understanding the histories of each individual species of extinct animal on a local level. Detailed regional chronologies of fauna are necessary for comparison with paleoenvironmental and archaeological data to help sort out causes for extinction. The Willamette Valley of western Oregon has long been noted for finds of megafauna, though records have not been synthesized since the early 20th century and these materials have remained largely unstudied. In this thesis, I first create a catalog of extinct megafauna recovered from the Willamette Valley. Next, using material from the northern valley, I employ AMS radiocarbon dating, stable isotope δ¹³C and δ¹⁵N analyses, and gross inferences based on the dietary specializations and habitat preferences of taxa in order to reconstruct environments and to develop a local chronology of events that is then arrayed against archaeological and paleoenvironmental data. The results of this study indicate that megafaunal populations in the northern Willamette Valley were contemporaneous with the earliest known human populations of the Pacific Northwest, as well as later populations associated with the Clovis Paleoindian Horizon. Consistent with the overkill hypothesis, radiocarbon ages span the length of the Clovis window, but no ages are younger than Clovis. Moreover, all radiocarbon ages are older than or contemporaneous to the onset of the Younger Dryas Stadial. No age ranges fall exclusively within the Younger Dryas. Comparison of megafaunal ages and paleoenvironmental records support the view that climate change contributed to local animal population declines. Prior to ~13,000 cal BP, the Willamette Valley was an open environment; herbivores mainly consumed C₃ vegetation. The timing of the loss of megafauna coincides with increased forested conditions as indicated by regional paleoenvironmental reconstruction. As the timing of megafaunal decline correlates with Clovis, the onset of the Younger Dryas, and increased forested conditions, it is not possible with the data currently available to distinguish the cause of extinction in the Willamette Valley. The age ranges of the fauna coupled with taphonomic and geologic context indicate that the fauna are autochthonous to the Willamette Valley; they do not represent ice rafted carcasses or isolated skeletal elements transported from elsewhere during late Pleistocene glacial outburst floods. Close

• 19. [Article] Ancient Cataclysmic Floods in the Pacific Northwest: Ancestors to the Missoula Floods

  Ancient Cataclysmic Floods were the Ice Age Floods that left erosional and depositional features and preceded the Missoula Floods (15-18,000 ka) in the Pacific Northwest of the United States (Allen et ...

  Citation × Citation Citation Abstract Copy Title: Ancient Cataclysmic Floods in the Pacific Northwest: Ancestors to the Missoula Floods Author: Medley, Erica Year: 2012 Ancient Cataclysmic Floods were the Ice Age Floods that left erosional and depositional features and preceded the Missoula Floods (15-18,000 ka) in the Pacific Northwest of the United States (Allen et al., 2009). All previously studied ancient sites were visited (14) and new sites (11) were found; four Missoula Flood quarries were also visited; a total of 29 sites were studied in this thesis. The use of calcrete paleosols to provide relative age dates for flood deposits was analyzed in this thesis. Missoula Flood gravel pits were sampled in order to examine the degree of calcrete development in flood deposits of known ages. All of the Missoula Flood deposits tested contain Stage 1 calcrete soil development. Calcrete paleosols at sites with evidence for older floods were all analyzed. Eight sites have paleosols with Stage II development (3-12% CaCO3): Rulo Outcrop, Potholes Coulee, Leslie Road, Benge, E. Callaway Road, Collier Coulee, Palouse, and Connell. Five sites have paleosols with Stage II+ development (12-17% CaCO3): Brown Road, Leslie Road, Benge, Reese Coulee, and Connell. Fourteen sites have paleosols with Stage III development (17-35% CaCO3): The Dalles, Rulo Outcrop, Winans Road 1, Poplar Heights, Yakima Bluffs, Canal Outcrop, Othello Canal, Reese Coulee, Potholes Coulee, E. Callaway Road, Frenchmen Coulee, Macall, Ritzville, and East Connell. One site has a paleosol with Stage III+ development (35-50% CaCO3): Othello Canal. Ancient Cataclysmic flooding initiated in the Early Pleistocene, at least 1.5 Ma. Sixteen field sites show evidence for Early Pleistocene flooding, preserved in all six provinces: Othello Channels, Columbia River Gorge, Cheney-Palouse Scabland, Quincy Basin, Pasco Basin, and the Walla Walla Valley. There are 26 field sites with evidence for Middle Pleistocene flooding, present in all regions except Othello Channels. Eleven of those 26 sites also show evidence for Early Pleistocene floods. Evidence for Early and Middle Pleistocene floods is present over a wide distribution of elevations from 117 to 524 meters. Title: Ancient Cataclysmic Floods in the Pacific Northwest: Ancestors to the Missoula Floods Author: Medley, Erica Year: 2012 Ancient Cataclysmic Floods were the Ice Age Floods that left erosional and depositional features and preceded the Missoula Floods (15-18,000 ka) in the Pacific Northwest of the United States (Allen et al., 2009). All previously studied ancient sites were visited (14) and new sites (11) were found; four Missoula Flood quarries were also visited; a total of 29 sites were studied in this thesis. The use of calcrete paleosols to provide relative age dates for flood deposits was analyzed in this thesis. Missoula Flood gravel pits were sampled in order to examine the degree of calcrete development in flood deposits of known ages. All of the Missoula Flood deposits tested contain Stage 1 calcrete soil development. Calcrete paleosols at sites with evidence for older floods were all analyzed. Eight sites have paleosols with Stage II development (3-12% CaCO3): Rulo Outcrop, Potholes Coulee, Leslie Road, Benge, E. Callaway Road, Collier Coulee, Palouse, and Connell. Five sites have paleosols with Stage II+ development (12-17% CaCO3): Brown Road, Leslie Road, Benge, Reese Coulee, and Connell. Fourteen sites have paleosols with Stage III development (17-35% CaCO3): The Dalles, Rulo Outcrop, Winans Road 1, Poplar Heights, Yakima Bluffs, Canal Outcrop, Othello Canal, Reese Coulee, Potholes Coulee, E. Callaway Road, Frenchmen Coulee, Macall, Ritzville, and East Connell. One site has a paleosol with Stage III+ development (35-50% CaCO3): Othello Canal. Ancient Cataclysmic flooding initiated in the Early Pleistocene, at least 1.5 Ma. Sixteen field sites show evidence for Early Pleistocene flooding, preserved in all six provinces: Othello Channels, Columbia River Gorge, Cheney-Palouse Scabland, Quincy Basin, Pasco Basin, and the Walla Walla Valley. There are 26 field sites with evidence for Middle Pleistocene flooding, present in all regions except Othello Channels. Eleven of those 26 sites also show evidence for Early Pleistocene floods. Evidence for Early and Middle Pleistocene floods is present over a wide distribution of elevations from 117 to 524 meters. Close

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

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

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