Measurements of anisotropy of magnetic susceptibility (AMS) provide information about petrofabric: the orientation of principal axes and the shape represented by parameters calculated by normed principal susceptibilities. In this study, the AMS method was applied to investigate downhole petrofabric changes and paleocurrent directions. AMS in sediments may be developed in two stages, during deposition and after deposition. The first stage occurs during settling of grains on the bottom. During deposition, each grain's minimum length axis falls perpendicular to the bedding plane. As a result, the fabric (well-developed foliation) forms an oblate shape. In cases where water currents are present, the alignment of grains is affected by hydraulic forces. The AMS method has been applied to identify current-induced fabric (e.g., Shor et al., 1984). Lithostratigraphic Unit I at Leg 149 sites consists of terrigenous turbidites, and lithostratigraphic Unit II consists of calcareous turbidites and contourites (Sawyer, Whitmarsh, Klaus, et al., 1994). The inference of current direction can provide information useful for determining the history of sedimentation.
After deposition, the fabric may be affected by compaction, tectonic deformation, bioturbation, and/or migration of fluid and gas. Thus, studies of the fabric can also provide information about postdepositional processes.