The Effect of Water Currents on the Magnetic Remanence and Anisotropy of Susceptibility of Some Sediments

Abstract

This work is a study of the magnetic properties of fine silts deposited in the laboratory. The results are described of a number of experiments in which a naturally occurring sediment was redeposited in an open flume under a range of controlled conditions. Measurements have been made of the directions of remanent magnetism of the re‐deposited sediments and of their principal axes of magnetic susceptibility. It is found that the deviations of the remanence direction and of the direction of maximum susceptibility caused by the movement of water over the bed during deposition can be accounted for by an extension of the theory in which the sediment is considered as an assemblage of quasi‐spherical particles which roll on deposition into hollows in the bed. In the interpretation put forward it is postulated that the effect of a water current is to rotate the particles through an angle p immediately before they touch bottom, the magnitude of p being determined by an equilibrium between the shearing couple and the magnetic restoring couple. A method has been found of correcting for the effects of currents in natural sediments from measurements of their remanence and anisotropy of susceptibility, and a field test of this method is suggested. Copyright © 1961, Wiley Blackwell. All rights reserved