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 redeposited 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.

Influence of bottom currents on the sedimentary processes at the western tip of the Gulf of Corinth, Greece

“…AMS has been widely used to determine the direction of bottom-currents (e.g. Rees, 1961;Ellwood, 1980;Flood et al, 1985;Parés et al, 2007;Singsoupho et al, 2015). K max axes generally are oriented parallel to the current direction, but the grains may evolve into a flow-transverse orientation if the flow velocity is high enough to displace the grains on the seafloor after their initial deposition (Ledbetter and Ellwood, 1980;Taira, 1989;Tauxe, 1998;Baas et al, 2007).…”

Oligo‐Miocene magnetostratigraphy and rock magnetism of the Xishuigou section, Subei (Gansu Province, western China) and implications for shallow inclinations in central Asia

“…At Subei the AMS shape parameter (T) appears to vary systematically with depth ( Figure 10b Table 1 The relationships between sedimentation, magnetic remanence directions, and fabric acquisition have been much studied [Rees, 1961[Rees, , 1964 Table 3), including Subei. In conclusion, it appears that the remanent inclinations in the Subei section are lithology independent and that significant postdepositional reorientation of them, either by compaction or by shear, is unlikely.…”

Preferred mineral orientation of a chloritoid-bearing slate in relation to its magnetic fabric

“…minerals to be the primary cause for the observed magnetic fabrics in fine-grained siliciclastic metasedimentary rocks (Graham, 1954;Rees, 1961;Fuller, 1964), Fe-bearing phyllosilicates often are the main magnetic carriers contributing to the magnetic fabric (e.g. Coward and Whalley, 1979;Borradaile et al, 1986;Rochette, 1987).…”