HR: 11:35h
AN: GP12A-06    [Abstracts]
TI: Depositional Remanent Magnetization: Toward a Theoretical and Experimental Foundation
AU: * Tauxe, L
EM: ltauxe@ucsd.edu
AF: Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA 92093-0220 United States
AU: Harris, A
GP12A-06 AF: Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA 92093-0220 United States
AU: Steindorf, J L
EM: jlsteindorf@ucsd.edu
AF: Scripps Institution of Oceanography, Geosciences Research Division, La Jolla, CA 92093-0220 United States
AB: A complete knowledge of the behavior of the geomagnetic field in the past relies on interpretation of the sedimentary record. Under certain laboratory conditions, sediments have been shown to acquire a remanence that is linearly related to the applied field and the assumption behind sedimentary relative paleointensity studies is that the depositional remanent magnetization carried by detrital grains, DRM, is a linear function of applied field B under natural conditions as well. DRM is of course also a strong function of mineralogy, concentration and grain size of the magnetic phases and properties of the non-magnetic matrix, hence DRM is quite a complex process. The experimental and theoretical basis for depositional remanent magnetization is therefore relatively undeveloped. Nonetheless, the currently accepted model for how depositional remanence is aquired (rotation of magnetized particles in a viscous medium) can make predictions that are in principle testable in controlled laboratory experiments. We will present a brief tour of DRM theory and show results of a numerical model which includes the equation of motion of magnetic particles in viscous fluid and thermal agitation by Brownian motion. We will explore simulations of DRM under various conditions of viscosity, magnetization, particle size, and applied field, etc. Model results will be compared to carefully controlled laboratory redeposition experiments using natural and synthetic materials. The most profound conclusion from our work is that DRM intensity is only linearly related to the applied field in the Earth field region under certain circumstances and that it is likely that DRM intensity is not linearly related to the Earth's field under many natural conditions.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1521 Paleointensity
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005