An AMS Study of Gulf of Papua Ocean Sediment Cores- Evidence of Deformation Caused by Piston Coring

Abstract:

Anisotropy of magnetic susceptibility (AMS) is a rapid and non-destructive technique used to study rock fabrics. As part of a larger study, we analyzed the AMS for a number of relatively oriented cores collected in the Gulf of Papua. We collected continuous, discrete samples from six pairs of jumbo piston cores (up to 9 meters in length) and their companion trigger cores to use for our study. The trigger cores, which are just gravity cores, show a fabric with a near vertical minimum susceptibility axis and a degree of anisotropy that increases down core. The jumbo piston cores also display the near vertical minimum axis throughout, but the upper portions have a degree of anisotropy that decreases with depth. We attribute this effect, which can be seen up to two meters down core, to the piston coring process, and suggest that AMS be measured when studying sediment cores as a means of identifying portions of the core that have been affected by the collection process. Additionally, we examine the down core variability in AMS data, as well as variability between sets of cores and its relation to sedimentation in the Gulf of Papua.