HR: 0800h
AN: GP11C-0839    [Abstracts]
TI: Thellier-Thellier Paleointensity and Directional Results From Hawaiian Lava Flows
AU: * Pressling, N J
EM: n.pressling@earth.leeds.ac.uk
AF: School of Earth and Environment, Earth Sciences, The University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AU: Laj, C
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS, Bat 12, Avenue de la Terrase, Gif-sur-Yvette, 91198 France
AU: Kissel, C
AF: Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS, Bat 12, Avenue de la Terrase, Gif-sur-Yvette, 91198 France
AU: Champion, D
AF: US Geological Survey, 345 Middlefield Road, MS-910, Menlo Park, CA 94025 United States
AU: Gubbins, D
AF: School of Earth and Environment, Earth Sciences, The University of Leeds, Woodhouse Lane, Leeds, LS2 9JT United Kingdom
AB: During the last 25,000 years there has been low secular variation in the Pacific region. A large directional dataset for this specific time window already exists but will be enlarged by the inclusion of results from our recent analysis of rocks from Hawaii. In addition to the directional data, we have also obtained paleointensity values for a significant number of the samples studied. This study uses samples that have been collected by the US Geological Survey from 35 lava flows erupted from Kilauea, Mauna Loa and Hualalai volcanoes on the Big Island of Hawaii. All of the flows have been radiocarbon dated and the ages range from 290 to 25,000 years old. Paleomagnetic analysis over a 3 month period was carried out on a total of 216 half-size samples at the Laboratoire des Sciences du Climat et de l'Environnement in Gif-sur-Yvette, France. Thellier-Thellier paleointensity experiments were performed in two large capacity furnaces that have been designed to specifically reduce any oxidation of samples. A new, strict selection criteria based on the analysis of Arai, Zijderveld and stereo plots has also been applied to improve the reliability and robustness of the results. Failure to meet the selection criteria is generally found to be due to to the alteration of the sample and the sample's capacity to record magnetic fields during the heating process. Despite this rigorous selection criteria, a high success rate of 62% has been achieved, well above the average of 30% usually reported for this method. The resulting new paleointensities and directions will be presented within the context of augmenting the secular variation record and improving the dating of lava flows. Interpretion with reference to theories on the secular variation of the Pacific will also be discussed.
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting