HR: 10:20h
AN: GP12A-01 INVITED     [Abstracts]
TI: On the use of Anhysteretic Remanent Magnetization (ARM) in Paleointensity Determination
AU: * Yu, Y
EM: yjyu@ucsd.edu
AF: Scripps Institution of Oceanography, 9500 Gilman Drive, La Jolla, CA 92122 United States
AU: Dunlop, D J
EM: dunlop@physics.utoronto.ca
AF: University of Toronto, 60 St. George Street, Toronto, ON M5S 1A7 Canada
AB: Anhysteretic remanent magnetization (ARM) is produced by the combination of a slowly decaying alternating-field (AF) and a steady unidirectional field. ARM is important because of its analogy to thermoremanent magentization (TRM), and it has been widely used in geomagnetic field intensity determination on sediments. However, compared to TRM, fundamental properties of ARM are still poorly known. We investigated the fundamental properties of partial anhysteretic remanent magnetizations (pARMs), including additivity, independence, and reciprocity of neighboring pARMs, in order to provide a fundamental rationale for the use of the pseudo-Thellier technique. Additivity was verfied for all the samples, whatever the domain state or composition. Violation of reciprocity in coarse-grained magnetites results in convex-down curves of ARM remaining versus partial ARM gained. Independence in particular was approached in a novel way by orthogonally superimposing pARMs on ARM so that the demagnetization of both components could be tracked separately. We observed that violation of independence causes systematic underestimation of paleointensities.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005