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• 121. [Article] Postglacial Relative Sea-Level History of the Prince Rupert Area, British Columbia, Canada

  This paper presents a history of relative sea level (RSL) change for the last 15,000 years in the Prince Rupert region on the northern coast of British Columbia, Canada. One hundred twenty-three radiocarbon ...

  Citation × Citation Citation Abstract Copy Title: Postglacial Relative Sea-Level History of the Prince Rupert Area, British Columbia, Canada Author: Letham, Bryn, Martindale, Andrew, Macdonald, Rebecca, Guiry, Eric, Jones, Jacob, Ames, Kenneth Year: 2016 This paper presents a history of relative sea level (RSL) change for the last 15,000 years in the Prince Rupert region on the northern coast of British Columbia, Canada. One hundred twenty-three radiocarbon ages of organic material from isolation basin cores, sediment sequence exposures, and archaeological sites having a recognized relation to past sea levels constrain postglacial RSL. The large number of new measurements relating to past sea-level provides a well constrained RSL curve that differs in significant ways from previously published results. After deglaciation following the Last Glacial Maximum, the region experienced an isostatically-induced rapid RSL drop from as much 50 m asl to as low as −6.3 m asl in as little as a few centuries between 14,500 BP and 13,500 BP. After a lowstand below current sea level for about 2000 years during the terminal Pleistocene, RSL rose again to a highstand at least 6 m asl after the end of the Younger Dryas. RSL slowly dropped through the Holocene to close to its current position by 2000-1500 BP, with some potential fluctuations between 3500 and 1500 BP. This study highlights variation in RSL histories across relatively short distances, which must be accounted for by local RSL reconstructions such as this one. This RSL curve aided in the identification of an 8000–9000 year old archaeological site on a 10–12 m asl terrace, which is currently the earliest dated archaeological site in the area, and it provides guidance for searching for even older archaeological remains. We highlight the utility and potential of this refined RSL history for developing surveys for other archaeological sites associated with paleoshorelines. Title: Postglacial Relative Sea-Level History of the Prince Rupert Area, British Columbia, Canada Author: Letham, Bryn, Martindale, Andrew, Macdonald, Rebecca, Guiry, Eric, Jones, Jacob, Ames, Kenneth Year: 2016 This paper presents a history of relative sea level (RSL) change for the last 15,000 years in the Prince Rupert region on the northern coast of British Columbia, Canada. One hundred twenty-three radiocarbon ages of organic material from isolation basin cores, sediment sequence exposures, and archaeological sites having a recognized relation to past sea levels constrain postglacial RSL. The large number of new measurements relating to past sea-level provides a well constrained RSL curve that differs in significant ways from previously published results. After deglaciation following the Last Glacial Maximum, the region experienced an isostatically-induced rapid RSL drop from as much 50 m asl to as low as −6.3 m asl in as little as a few centuries between 14,500 BP and 13,500 BP. After a lowstand below current sea level for about 2000 years during the terminal Pleistocene, RSL rose again to a highstand at least 6 m asl after the end of the Younger Dryas. RSL slowly dropped through the Holocene to close to its current position by 2000-1500 BP, with some potential fluctuations between 3500 and 1500 BP. This study highlights variation in RSL histories across relatively short distances, which must be accounted for by local RSL reconstructions such as this one. This RSL curve aided in the identification of an 8000–9000 year old archaeological site on a 10–12 m asl terrace, which is currently the earliest dated archaeological site in the area, and it provides guidance for searching for even older archaeological remains. We highlight the utility and potential of this refined RSL history for developing surveys for other archaeological sites associated with paleoshorelines. Close

• 122. [Article] Cultural Responses to Climate Change in the Holocene

  Variable Holocene climate conditions have caused cultures to thrive, adapt or fail. The invention of agriculture and the domestication of plants and animals allowed sedentary societies to develop and are ...

  Citation × Citation Citation Abstract Copy Title: Cultural Responses to Climate Change in the Holocene Author: Prentice, Richard Year: 2009 Variable Holocene climate conditions have caused cultures to thrive, adapt or fail. The invention of agriculture and the domestication of plants and animals allowed sedentary societies to develop and are the result of the climate becoming warmer after the last glaciation. The subsequent cooling of the Younger Dryas forced humans to concentrate into geographic areas that had an abundant water supply and ultimately favorable conditions for the use of agriculture and widespread domestication of plants and animals. Population densities would have reached a threshold and forced a return to foraging, however the end of the Younger Dryas at 10,000 BP allowed agrarian societies to grow in number and expand spatially. The Norse took advantage of the favorable climate conditions of the medieval warm period (800 to 1300 CE) to establish settlements off the coast of Greenland, but the onset of the Little Ice Age (1350-1850 CE) caused sea ice to block trade routes with China and led to their demise. The long and cold winters of the Little Ice Age inspired works of art and literature, and were celebrated in London, but also caused crop failures, famine and disease. The Dust Bowl drought of the 1930’s only lasted six years but caused the most devastating ecological, sociological, agricultural, and economic disaster in United States history. Multicentury and multidecadal droughts led to the collapse of the Akkadian, Classic Maya, Mochica, and Tiwanaku civilizations. The primary factors affecting global climate variations include changes in thermohaline circulation, solar irradiance, and the effects of active volcanoes. Complex societies are not completely powerless nor fully adaptive to climate change. Modern society should use knowledge of past abrupt climate changes to better prepare for the future. Title: Cultural Responses to Climate Change in the Holocene Author: Prentice, Richard Year: 2009 Variable Holocene climate conditions have caused cultures to thrive, adapt or fail. The invention of agriculture and the domestication of plants and animals allowed sedentary societies to develop and are the result of the climate becoming warmer after the last glaciation. The subsequent cooling of the Younger Dryas forced humans to concentrate into geographic areas that had an abundant water supply and ultimately favorable conditions for the use of agriculture and widespread domestication of plants and animals. Population densities would have reached a threshold and forced a return to foraging, however the end of the Younger Dryas at 10,000 BP allowed agrarian societies to grow in number and expand spatially. The Norse took advantage of the favorable climate conditions of the medieval warm period (800 to 1300 CE) to establish settlements off the coast of Greenland, but the onset of the Little Ice Age (1350-1850 CE) caused sea ice to block trade routes with China and led to their demise. The long and cold winters of the Little Ice Age inspired works of art and literature, and were celebrated in London, but also caused crop failures, famine and disease. The Dust Bowl drought of the 1930’s only lasted six years but caused the most devastating ecological, sociological, agricultural, and economic disaster in United States history. Multicentury and multidecadal droughts led to the collapse of the Akkadian, Classic Maya, Mochica, and Tiwanaku civilizations. The primary factors affecting global climate variations include changes in thermohaline circulation, solar irradiance, and the effects of active volcanoes. Complex societies are not completely powerless nor fully adaptive to climate change. Modern society should use knowledge of past abrupt climate changes to better prepare for the future. Close

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

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

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

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

  copyrighted by American Geophysical Union

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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