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43979-AC8
Depositional Remanent Magnetization: Toward a Theoretical and Experimental Foundation

Lisa Tauxe, University of California, San Diego

This project supports graduate student, Ritayan Mitra, who just completed his first year of graduate studies with us. He has made wonderful progress on the project and will be giving an invited talk at the Fall Meeting of the AGU. The project concerns how sediments get magnetized. The simplest theory allows computation of the net moment by assuming initially random magnetiztation vectors (m) which, over time, converge on the magnetic field (B). This theory is incomplete, however, neglecting the effect of floculation and hydrodynamic torque. Therefore, we are attempting to modify the theory and test our new formulation with redeposition experiments. Over this past year he has: 1) created a synthetic sediment with carefully controlled components (clay plus single domain magnetite), 2) obtained SEM images of the sediment to constrain grain size distributions, 3) performed many redeposition experiments in which salinity and applied field were controlled, 4) started the process of numerical modelling of the results. His conclusions so far are 1) a confirmation that the strength of the magnetization is strongly effected by floc size distribution and 2) a surprise result that the inclination error is also a strong function of floc size distribution and field strength. He is currently attempting to model the results with a unified theory of DRM which will explain both inclination error and intensity dependence with a simple floculation model of DRM.

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