Can Magnetic Anisotropy Help Correct for Compaction-induced Decrease in Intensity as Well as Inclination of Remanence? A Case Study Using Plastic Deformation Experiments on Clay-rich Magnetite-bearing Turbidites.

HR: 11:50h
AN: GP12A-07 [Abstracts]
TI: Can Magnetic Anisotropy Help Correct for Compaction-induced Decrease in Intensity as Well as Inclination of Remanence? A Case Study Using Plastic Deformation Experiments on Clay-rich Magnetite-bearing Turbidites.
AU: * Hodych, J P
EM: jhodych@mun.ca
AF: Memorial University of Newfoundland, Department of Earth Sciences, St. John's, NL A1B 3X5 Canada
AU: Bradbury, N V
EM: v34nvb@mun.ca
AF: Memorial University of Newfoundland, Department of Earth Sciences, St. John's, NL A1B 3X5 Canada
AU: Bijaksana, S
EM: satria@fi.itb.ac.id
AF: Department of Physics, Institut Teknologi Bandung, Jalan Ganesa 10, Bandung, 13220 Indonesia
AB: We studied distal clay-rich turbidites on the continental rise off Nova Scotia, Canada, that carry a natural remanence inclined approximately 10° shallower than the 61° inclination of the Earth`s field in which they were deposited. These soft sediments are dominated by pseudo-single-domain magnetite and are magnetically anisotropic with hard axis vertical, perpendicular to bedding. We mixed together small amounts of each of a suite of 22 turbidite samples from core HUD88010-28 to make an isotropic composite sample that was given an anhysteretic remanence (ARM) with a 60° inclination. This composite sample was plastically deformed by compressing vertically, which induced an ARM anisotropy with hard axis (ARM_min) vertical and decreased the intensity as well as the inclination of the remanence. The tangent of the remanence inclination decreased in approximate proportion to ARM_min/ARM_max in the plastic deformation experiments. We used this relationship and the ARM_min/ARM_max values observed in the suite of natural samples, to successfully correct for the inclination shallowing observed in the natural remanence. In addition, we found that remanence intensity decreased in approximate proportion to ARM_min/ARM_max in the plastic deformation experiments. We used this relationship and the ARM_min/ARM_max values observed in the suite of natural samples to estimate how much their natural remanence intensity had decreased due to sediment compaction. The average intensity decrease was estimated to be approximately 36%. This method may help correct for the effect of burial compaction on the paleointensity record in magnetite-bearing soft sediments.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1518 Magnetic fabrics and anisotropy
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005