Index Catalog // ScholarsArchive@OSU

Creator:: Duncan, Robert A.
Abstract:: Radiometric ages (K-Ar and ⁴⁰Ar- ³⁹Ar methods) have been determined on dredged volcanic rocks from seven of the New England Seamounts, a prominent northwest-southeast trending volcanic lineament in the northwestern Atlantic Ocean. The ⁴⁰Ar-³⁹Ar total fusion and incremental heating ages show an increase in seamount construction age from southeast to...
Resource Type:: Article
Full Text:: . 288-297, John Wiley, New York, 1967. Houghton, R. L., J. E. Thomas, Jr., R. J. Diecchio, and A

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...
Resource Type:: Article
Full Text:: and Robert A. Duncan College of Oceanography, Oregon State University, Corvallis Abstract. New

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...
Resource Type:: Article

Creator:: Magill, James, Cox, Allan, and Duncan, Robert A.
Abstract:: Paleomagnetic directions from the Eocene Tillamook Volcanic Series of the Oregon Coast Range point 460 clockwise from the expected Eocene field direction. Potassium argon dating of six dikes and flows from this formation yields a mean age of 44.3 ± 0.6 m.y. These results establish that the Oregon coastal block...
Resource Type:: Article
Full Text:: 94305 ROBERT DUNCAN School of Oceanography, Oregon State University, Corvallis, Oregon 97331

Creator:: Sinton, Christopher W., Duncan, Robert A., and Denyer, Percy
Abstract:: The pre-Tertiary oceanic crust exposed on the west coast of Costa Pica has been broadly referred to as the Nicoya Complex. This study was designed to determine the age of the Nicoya Complex in the Nicoya Peninsula, Playa Jaco, and the Quepos Peninsula using Ar-40-Ar-39 radiometric dating and to assess...
Resource Type:: Article
Full Text:: W. Sinton 1 and Robert A. Duncan College of Oceanic and Atmospheric Sciences, Oregon State

Creator:: Koppers, Anthony A. P., Staudigel, Hubert, and Duncan, Robert A.
Abstract:: We report new ⁴⁰Ar/³⁹Ar ages for the oldest Pacific oceanic floor at Ocean Drilling Program Site 801C in the Pigafetta basin and Site 1149D close to the Izu-Bonin subduction zone in the Nadezhda basin. These ages were determined by applying high-resolution incremental heating experiments (including 15–30 heating steps) to better...
Resource Type:: Article
Full Text:: , San Diego, La Jolla, California 92093-0225, USA (akoppers@ucsd.edu) Robert A. Duncan College of

Creator:: Desonie, Dana L., Duncan, Robert A., and Natland, J. H.
Abstract:: The Marquesas archipelago is a short. NW-SE trending cluster of islands and seamounts that formed as a result of volcanic activity over a weak hotspot. This volcanic chain lies at the northern margin of a broad region of warm and compositionally diverse mantle that melts to build several other subparallel...
Resource Type:: Article

Creator:: Shrivastava, J. P., Duncan, Robert A., and Kashyap, Mamta
Abstract:: We present new age determinations, derived from ⁴⁰Ar–³⁹Ar incremental heating experiments, for basaltic lava flows from the Mandla lobe, located on the eastern margin of the main Deccan volcanic province, some ~ 1000 km from the Western Ghats escarpment. The most reliable estimates of crystallization ages come from 5 plateau...
Resource Type:: Article
Full Text:: volcanism J.P. Shrivastava, Robert A. Duncan, Mamta Kashyap PII: S0024-4937(15)00090-0 DOI: doi: 10.1016

Creator:: VanLaningham, Sam, Duncan, Robert A., and Pisias, Nicklas G.
Abstract:: We use Ar-40-Ar-39 incremental heating to fingerprint bulk fluvial sediment entering the northeast Pacific Ocean, with the long-term intent of tracking sediment source and transport changes from the terrestrial system to the marine environment through time. We show reproducible age spectra from individual rivers accounting for the majority of sediment...
Resource Type:: Article
Full Text:: ,1 Robert A. Duncan,1 and Nicklas G. Pisias1 Received 23 May 2006; accepted 8 September 2006

Creator:: Snow, Laura J., Duncan, Robert A., and Bralower, Timothy J.
Abstract:: Rapid eruption of submarine lava flows during formation of the Caribbean plateau correlates closely with ocean anoxic event 2 (OAE2), which bracketed the Cenomanian/Turonian boundary (~93.5 Ma). These events also correspond with a positive excursion in carbon isotopic composition of seawater. Hydrothermal activity associated with large-scale submarine volcanism may have...
Resource Type:: Article
Full Text:: construction and oxygen anoxic event 2 Laura J. Snow1 and Robert A. Duncan College of Oceanic and Atmospheric

ScholarsArchive@OSU