HR: 10:50h
AN: GP52A-03 INVITED    [Abstracts]
TI: An Alternative View on Absolute Paleointensity Determination
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
AU: Bohnel, H N
EM: hboehnel@geociencieas.unam.mx
AF: Centro de Geociencias, Campus Juriquilla, UNAM, Queretaro, QUE 76230, Mexico
AB: Determination of the so-called absolute paleointensity (absPI) is tedious because many rocks do not satisfy the criteria for Thellier style determination protocols. Recently an entirely new approach was proposed that involves exploring the field dependence of pTRMs rather then its temperature dependence, the ‘multispecimen parallel differential pTRM method' (Dekkers and Böhnel, 2006, EPSL 248, 507-516). The method involves imparting a laboratory pTRM parallel to the original NRM of the rock sample and scaling the intensity difference to the NRM. When the laboratory field is stronger than the original field a stronger composite remanence results, when the laboratory field is weaker the reverse is true. The absPI is the field value where no change occurs. In multidomain grains, previous thermal-magnetic history determines in part the outcome and each treatment is done with a fresh specimen which undergoes only one in-field thermal cycle. Therefore, the specimens must have the same thermomagnetic properties. All magnetic grain sizes can be processed enabling absPI determination on many more flows than otherwise would be possible. We show examples of the approach illustrating its merit and discuss how incipient alteration can be recognized.
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