Numerical simulation of inclination shallowing by rolling and slipping of spherical particles

We report algorithms for two- and three-dimensional numerical simulations of settling spherical magnetic particles with prescribed size-distributions. Particles roll, or roll and slip, on the substrate, which causes their magnetic moments to rotate. These models are applied to the problem of inclination shallowing, which is repeatedly encountered in paleomagnetic studies of sedimentary rocks, where the recorded inclination is less than the expected field inclination. Simulations of equal-sized assemblages of magnetic spheres yield shallowing factors of 0.6, similar to that found in nature and in laboratory redeposition experiments. Comparable results are obtained when varying the size distributions of the spheres. Inclination shallowing is more pronounced when the smaller particles are magnetic and the larger ones are non-magnetic. Our study shows that rolling and/or slip (translation) of spherical particles can significantly contribute to inclination shallowing.