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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

Creator:: Watts, A. B., Weissel, J. K., Duncan, Robert A., and Larson, R. L.
Abstract:: We have combined shipboard and Seasat altimeter derived data in an intergrated geological and geophysical study of the Louisville Ridge; a 3500-km-long seamount chain extending from the Tonga trench to the Eltanin Fracture Zone. A break in the smooth trend of the ridge at latitude 37.5°S has been recognized in...
Resource Type:: Article

Creator:: Chauvin, Annick, Duncan, Robert A., Bonhommet, Norbert, and Levi, Saul
Abstract:: We report paleointensity results of the Earth's magnetic field from n Late Pleistocene lava flow (Louchadiere, Central France), which recorded an intermediate geomagnetic field direction (5 sites, mean declination= 114.1°, inclination=58.2°, k=130, α95=6.7°). New K-Ar age determinations confirm that this flow is contemporaneous with the Laschamp and Olby flows, and...
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

Creator:: Duncan, Robert A.
Abstract:: K-Ar and ⁴⁰Ar-³⁹Ar geochronologic data reveal the Paleocene to Eocene eruptive history of volcanic centers which produced the basaltic basement rocks of the Coast Range of Oregon and Washington. Volcanism was short lived at each center and migrated with time from the northern and southern ends toward the center, near...
Resource Type:: Article

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

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