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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:: 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...
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Full Text:: focused on mid-ocean ridge environments [e.g., Klein and Langmuir , 1987; Johnson et al. , 1990] and not

Creator:: White, William M., McBirney, Alexander R., and Duncan, Robert A.
Abstract:: We report new major element, trace element, isotope ratio, and geochronological data on the Galapagos Archipelago. Magmas erupted from the large western volcanos are generally moderately fractionated tholeiites of uniform composition; those erupted on other islands are compositionally diverse, ranging from tholeiites to picritic basanitoids. While these volcanoes do not...
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Full Text:: atomic absorption spectrophotometry. Approximately 5 g of the crushed rock was loaded into a Mo-crucible

Creator:: Wheat, C. Geoffrey, McManus, James, Dymond, Jack, Collier, Robert W., and Whiticar, Michael
Abstract:: We present evidence for pore water flow through the sediment of Crater Lake, Oregon based on systematic variations in pore water chemical compositions and thermal gradients. Pore water was extracted from sediment by centrifugation and diffusive exchange using a gravity corer deployed from a surface vessel and a box corer...
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Full Text:: Research, University of Victoria, Victoria, British Columbia, Canada Abstract. We present evidence for

Creator:: Cane, Mark A., Kaplan, Alexey, Miller, Robert N., Tang, Benyang, Hackert, Eric C., and Busalacchi, Anthony J.
Abstract:: The well-known fact that tropical sea level can be usefully simulated by linear wind driven models recommends it as a realistic test problem for data assimilation schemes. Here we report on an assimilation of monthly data for the period 1975-1992 from 34 tropical Pacific tide gauges into such a model...
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Full Text:: Sciences, University of Victoria, Victoria, British Columbia, Canada. 4Hughes STX Corporation, Lanham

Creator:: Duncan, Robert A., Hooper, P. R., Rehacek, J., Marsh, J. S., and Duncan, A. R.
Abstract:: A volcanic event of immense scale occurred within a relatively short period in early Jurassic time over large regions of the contiguous Gondwana supercontinent. In southern Africa, associated remnants of thick volcanic successions of lava flows and extensive dike and sill complexes of similar composition have been grouped together as...
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Full Text:: planet, environmental change, and punctuated evolution. Acknowledgments. We thank L. G. Hogan and C. w

Creator:: Egbert, Gary D., Booker, John R., and Schultz, Adam
Abstract:: Eleven years (1932-1942) of electric potential and magnetic measurement at the Tucson observatory represent a unique very long period magnetotelluric (MT) data set. We report here on a careful reanalysis of this data using modern processing techniques. We have developed and used novel methods for separating out the quasi-periodic daily...
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Full Text:: • 10 ø • 10 -• •g: lO 3 ¸ lO 2 lO 1 lO o lO-• B e 0 2 4 6 8 10 12 FREQUENCY (cpd

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...
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Full Text:: --0.5 mm size fraction, and ultrasonically washed in distilled water. A split 0-5 g) was then powdered

Creator:: Denman, Kenneth L. and Abbott, Mark R.
Abstract:: We have selected square subareas (110 km on a side) from coastal zone color scanner (CZCS) and advanced very high resolution radiometer (AVHRR) images for 1981 in the California Current region off northern California for which we could identify sequences of cloud-free data over periods of days to weeks. We...
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Full Text:: Band A 50 - 1 O0 km 90•g 70 • O. 75 z o:: o. 50 0 O. 25 Band B 25 - 50 km -e-9o

Creator:: Lippmann, T. C. and Holman, R. A.
Abstract:: The spatial and temporal variability of nearshore sand bar morphology is quantified using a unique data set spanning 2 years. The data consist of daily time exposure images of incident wave breaking on an open coast sandy beach which may be used to infer bar morphology (Lippmann and Holman, 1989)....
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Full Text:: period using g•z x - (1) (•2 where g is gravitational acceleration, [5 is beach slope, Z is a

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