Early Cretaceous Pacific palaeomagnetic pole from Ontong Java Plateau basement rocks
Published:January 01, 2004
Peter Riisager, Stuart Hall, Maria Antretter, Xixi Zhao, 2004. "Early Cretaceous Pacific palaeomagnetic pole from Ontong Java Plateau basement rocks", Origin and Evolution of the Ontong Java Plateau, J. Godfrey Fitton, John J. Mahoney, Paul J. Wallace, Andrew D. Saunders
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We present new palaeomagnetic data from Ocean Drilling Program Site 1184 on the eastern salient of the Ontong Java Plateau (OJP) where 337.7 m of Early Cretaceous (c. 120 Ma) volcaniclastic rocks were drilled. Alternating field and thermal demagnetizations were equally effective in removing secondary components, allowing the characteristic remanent magnetization directions from a total of 173 samples (out of 183) to be defined. All samples have negative inclinations (normal polarity), and by treating each sample as an independent reading of the palaeomagnetic field a site-mean inclination of −53.9° (N = 173; α95 = 1.0°, k = 109) was obtained. The corresponding palaeo-colatitude is in excellent accordance with previously published time-averaged palaeo-colatitudes from contemporaneous basalts drilled at OJP and the Nauru Basin. Based on the intersection of the seven palaeo-colatitudes a new Early Cretaceous (c. 120 Ma) Pacific palaeomagnetic pole was obtained with co-ordinates 63.0°N, 10.1°E (95% confidence ellipse with a minor semi-axis of 2.9° with an azimuth of 32° and a major semi-axis of 47.7° with an azimuth of 122°). This pole is far more easterly than previously published Early Cretaceous Pacific palaeomagnetic poles. Based on published Pacific palaeogeographic reconstructions in the fixed hot-spot reference frame we were able to calculate different Pacific true polar wander (TPW) poles. All Pacific TPW poles are found to be statistically different from contemporaneous TPW poles obtained in the Indo-Atlantic realm, illustrating motion between the two groups of hot spots.
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Origin and Evolution of the Ontong Java Plateau
The Cretaceous submarine Ontong Java Plateau, in the western Pacific Ocean, is the most volumnous of the world’s large igneous provinces (LIPs), and represents the largest known magmatic event on Earth. LIPs are the products of basaltic volcanism on a scale and at an effusion rate not seen on Earth at the present time, and their formation may have had significant effects on the Earth's climate and biosphere. The currently favoured explanation for LIP formation is the rapid decompression and melting of anomalously hot mantle in the heads of newly ascended mantle plumes. This volume summarizes the results of research aimed principally at testing the plume-head hypothesis for the formation of the Ontong Java Plateau, and presents the results of integrated studies following recent basement drilling on the plateau by the Ocean Drilling Program. Nineteen papers cover topics as diverse as petrology, geochemistry, tectonics, volcanology, paleomagnatism and biostratigraphy.