Index Catalog // ScholarsArchive@OSU

Creator:: Desonie, Dana L. and Duncan, Robert A.
Abstract:: Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has the temporal but not the isotopic characteristics usually attributed to a mantle plume. The earlier volcanic products of the hotspot, from eight volcanoes in the Cobb-Eickelberg seamount (CES) chain, show a westward age progression away from...
Resource Type:: Article
Full Text:: University, Corvallis Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has

Creator:: Duncan, Robert A. and Richards, M. A.
Abstract:: Persistent, long‐lived, stationary sites of excessive mantle melting are called hotspots. Hotspots leave volcanic trails on lithospheric plates passing across them. The global constellation of fixed hotspots thus forms a convenient frame of reference for plate motions, through the orientations and age distributions of volcanic trails left by these melting...
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Full Text:: Oregon State University, Corvallis M. A. Richards Department of Geology University of California

Creator:: Sinton, Christopher W., Christie, David M., and Duncan, Robert A.
Abstract:: Lavas from seamounts of the central Galápagos Platform and the Carnegie Ridge increase in age with distance from the western edge of the platform, consistent with a hotspot model for the generation of these features. The areal distribution of seamount ages suggests that the pattern of dispersed volcanism seen on...
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Full Text:: seamounts Christopher W. Sinton, David M. Christie, and Robert A. Duncan College of Oceanic and

Creator:: Pyle, D. G., Christie, David M., Mahoney, J. J., and Duncan, Robert A.
Abstract:: Within the Australian-Antarctic Discordance (AAD), a boundary exists between isotopically defined “Pacific-type” and “Indian-type” mid-ocean ridge basalt (MORB) erupted along the Southeast Indian Ridge (SEIR). This boundary has migrated westward beneath the easternmost AAD spreading segment at a minimum rate of 25 mm/yr since 4 Ma; however, its long-term history...
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Full Text:: seafloor D. G. Pyle and D. M. Christie College of Oceanic and Atmospheric Sciences, Oregon State

Creator:: Hall, L. S., Mahoney, J. J., Sinton, J. M., and Duncan, Robert A.
Abstract:: Lavas of the Rano Rahi seamount field define a Nd-Pb-Sr isotopic array that connects, and substantially overlaps, the arrays of the nearby East Pacific Rise axis and 5.6–28 Ma lavas of the Pukapuka ridge system, situated between the seamount field and French Polynesia. Dating of Rano Rahi samples by ⁴⁰Ar-³⁹Ar...
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Full Text:: , and J. M. Sinton School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu

Creator:: Konrad, Kevin, Graham, David W., Thornber, Carl R., Duncan, Robert A., Kent, Adam J.R., and Al-Amri, Abdullah M.
Abstract:: Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed ³He/⁴He, and He, CO₂ and trace element concentrations...
Full Text:: , Robert A. Duncan a, Adam J.R. Kent a, Abdullah M. Al-Amri c a College of Earth, Ocean, and Atmospheric

Creator:: Tréhu, Anne Martine, Stakes, Debra S., Bartlett, Cindy D., Chevallier, Johanna, Duncan, Robert A., Goffredi, Shana K., Potter, Susan M., and Salamy, Karen A.
Abstract:: Seismic data and seafloor samples indicate the presence of free gas, gas hydrate, and fluid seeps south of the Gorda Escarpment, a topographic feature that marks the eastern end of the Gorda/Pacific transform plate boundary southwest of Cape Mendocino, California. In spite of high sedimentation rates and high biological productivity,...
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Full Text:: hydrates, and fluid seeps on the transform margin offshore Cape Mendocino Anne M. Tréhu,1 Debra S

Creator:: Duncan, Robert A. and Hogan, L. G.
Abstract:: Determination of reliable crystallization ages by K-Ar methods for young (<1 Ma), fresh basalts from the seafloor has been frustrated by several effects. The small amounts of radiogenic ⁴⁰Ar developed over these timescales in such low-K rocks are difficult to resolve from predominantly atmospheric ⁴⁰Ar. An additional concern is that...
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Full Text:: MORB glasses near the Juan de Fuca, Gorda and Endeavour Ridges implying ages between 0 and 350 ka

Creator:: Verplanck, Emily P. and Duncan, Robert A.
Abstract:: New K-Ar age determinations on basalts, basaltic andesites, and ash flow tuffs from the central Western Cascades in Oregon range in age from 32 to 3 Ma. The ages decrease from west to east and with increasing elevation. Volcanism has been continuous throughout the evolution of the Western Cascades, with...
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Full Text:: Juan factor of 6 from 35 Ma to the present. The de Fuca (Farallon) plate beneath the eruption rates

Creator:: Chaytor, Jason D., Keller, Randall A., Duncan, Robert A., and Dziak, Robert P.
Abstract:: Full-coverage multibeam bathymetric mapping of twelve seamounts in the Gulf of Alaska reveals that they are characterized by flat-topped summits (rarely with summit craters) and by terraced, or step-bench, flanks. These summit plateaus contain relict volcanic features (e.g., flow levees, late-stage cones, and collapse craters) and as such must have...
Resource Type:: Article
Full Text:: extending from the Explorer-Juan de Fuca Ridge offshore Washington and British Columbia to the Aleutian

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