Is the Pringle Falls excursion a product of geomagnetic field behaviour or an artefact of sedimentation processes? Insights from anisotropy of magnetic susceptibility (AMS) analyses

Abstract

It is well known that the Earth's magnetic field changes both in direction and magnitude as a function of time. The magnitudes of those changes, and the timescales over which those changes take place, however, are still a matter of some debate. In particular, the record of geomagnetic excursions obtained from sedimentary sequences has been suspected to introduce some noise in the analyses of geomagnetic changes due to disturbances associated with the deposition of the sediments. The range of possible disturbances is large and includes both natural and human-induced factors. In this work, we show that it is possible to assess the extent to which the geomagnetic record might have been influenced by fluctuations in the conditions of deposition of the sediments by combining the measurement of the anisotropy of magnetic susceptibility with remanence measurements. The case of study focuses in the geomagnetic record of the geomagnetic excursion known as the PRINGLE FALLS event, preserved in different locations within the same basin. The various petrofabric signals obtained from the different sections sampled are shown to be independent of the variations of the geomagnetic field. The results presented therefore suggest that, in at least some cases, the observed flips in the orientation of the remanence are actual features of the geomagnetic field rather than being associated to fluctuations in the conditions of deposition of the sediments. © Journal compilation © 2009 RAS.