Index Catalog // ScholarsArchive@OSU

Creator:: Duncan, Robert A. and Helgason, J.
Abstract:: A succession of basaltic lavas, volcaniclastic sediments, and lignite beds in the Holmatindur region of eastern Iceland provides the means for tying magnetic reversal stratigraphy and a record of major North Atlantic cooling to a precise radiometric timescale. A prominent part of the section is the Holmatindur classic bed, which...
Resource Type:: Article
Full Text:: lava sections that cover many millions of years of activity [McDougall et al., 1976, 1984; Watkins and

Creator:: Roperch, Pierrick and Duncan, Robert A.
Abstract:: We report the behavior of the earth's magnetic field for a transition recorded in lavas at the volcanic island of Huahine in French Polynesia, south-central Pacific Ocean. Detailed intermediate fields are observed that record an apparent N-N excursion. The available K-Ar ages indicate that most volcanic rocks of the southern...
Resource Type:: Article
Full Text:: . volcanic lineament [Duncan and McDougall, 1976]. These Hawaiian type volcanoes are composed mostly of

Creator:: Chauvin, Annick, Roperch, Pierrick, and Duncan, Robert A.
Abstract:: A volcanic sequence almost 700 meters thick has been sampled in the Punaruu valley on the island of Tahiti, southern central Pacific Ocean. Detailed paleomagnetic results have been obtained from 123 sites. Three reversals are recorded in this sequence. Age determinations (K-Ar) indicate that the youngest reversal corresponds to the...
Resource Type:: Article
Full Text:: WNW-ESE direction delineating the Pacific plate motion during the last 5 m.y. [Duncan and McDougall

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:: 4øAr/39Ar total fusion and conventional K-Ar radiometric dating methods [McDougall and Harrison, 1988

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
Full Text:: Previous results of K-Ar age determinations from the islands of the Marquesas [Duncan and McDougall, 1974

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
Full Text:: Jarrard, 1973; Jarrard and Clague, 1977; Duncan and McDougall, 1976; McDougall and Duncan, 1980; Duncan

Creator:: Duncan, Robert A., Fisk, Martin R., White, William M., and Nielsen, Roger L.
Abstract:: The island of Tahiti, the largest in French Polynesia, comprises two major volcanoes aligned NW-SE, parallel with the general trend of the Society Islands hotspot track. Rocks form this volcanic system are basalts transitional to tholeiites, alkali basalts, basanites, picrites, and evolved lavas. Through K-Ar radiometric dating we have established...
Resource Type:: Article
Full Text:: 11 cm/yr [Duncan and McDougall, 1976]. The orientation of the chain and the age distribution of the

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...
Resource Type:: Article
Full Text:: ........... .......... • , , , • ....... ........... ........... ::::::::::: ......... ":;Q this study - ß

ScholarsArchive@OSU