HR: 11:05h
AN: GP52A-04    [Abstracts]
TI: Absolute Paleointensities for the Last 10Kyrs From the Hana Volcanics (East Maui, Hawaii, USA) Determined With the Multispecimen Parallel Differential pTRM Method
AU: * Herrero-Bervera, E
EM: herrero@soest.hawaii.edu
AF: Emilio Herrero-Bervera, SOEST-HIGP 1680 East West Rd University of Hawaii at Manoa, Honolulu, HI 96822, United States
AU: Bohnel, H N
EM: hboehnel@geociencias.unam.mx
AF: Harald N. Bohnel, Centro de Geociencias, Campus Juriquilla, UNAM, Queretaro, QUE 76230, Mexico
AU: Dekkers, M J
EM: dekkers@geo.uu.nl
AF: Paleomagnetic Laboratory 'Fort Hoofddijk', Department of Earth Sciences, Utrecht University, Budapestlaan 17, Utrecht, 3584 CD, Netherlands
AB: We have determined the paleointensity of eight lavas flows that recorded the last 10kyrs of geomagnetic field behavior from the youngest and largest of the two edifices of the island of Maui (i.e. Hana Volcanics, East Maui) with the multispecimen parallel differential pTRM method (Dekkers and Bohnel, EPSL, 248, 508-517, 2006). The flows are characterized by irreversible Curie curves indicating two kinds of magnetic carriers, one almost pure magnetite and the second one Ti-rich magnetite with a possibility of traces of titanomaghemite. The coercivity of remanence (Hcr) suggests that low-coercivity grains carry the NRM. Magnetic minerals from all of these flows are scattered within the PSD range with exception of site HKAM (age 4.07±0.09 ka) that lie in the SD range. The multispecimen method involves giving a laboratory pTRM to pristine specimens in different field strengths parallel to the original TRM; note that all pTRM are given from the same temperature. From an existing sample collection for paleosecular variation studies (Herrero-Bervera and Valet, PEPI, 161, 267-280, 2007) we could process 9 flows for paleointensity determination with this protocol ranging in age from 0.83±0.06 ka to 8.19±0.06 ka. pTRM were given by cooling from 175^oC to avoid alteration, low-field susceptibility variation appeared to be less than 10 percent. Eight flows yielded good quality data; one flow appeared to show erratic and non- interpretable behavior (that flow had a larger susceptibility increase). The paleointensity increases to ~ 46 μTesla at ~ 2.2 ka whereas it drops to ~ 22 μTesla at ~ 3.5 ka, and at ~ 8.2 ka ~ 39 μTesla is obtained, i.e. slightly higher than present-day value (36 μTesla). Our paleointensity results (at least 7 flows) correlate well with the absolute paleointensity global determinations
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
DE: 1530 Rapid time variations
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting