One of the major objectives of Ocean Drilling Program (ODP) Leg 172 was obtaining high-resolution records of North Atlantic late Neogene paleoceanographic and climate variability made possible by the high sedimentation rates on the Blake Outer Ridge (BOR) and Bermuda Rise sediment drifts. Anisotropy of magnetic susceptibility (AMS) has been used as a parameter to determine the degree of alignment of sediment particles in deep-ocean sediments by currents, and the current direction (e.g., Ledbetter and Ellwood, 1980; Bulfinch et al., 1982; Joseph et al., 1998). The effect of deep-water currents on sediment characteristics such as particle size has been demonstrated on the BOR (Haskell and Johnson, 1993) and other settings (Ledbetter, 1984) and used to produce paleocirculation records (e.g., Johnson et al., 1988; Haskell et al., 1991). One objective of this study is to place magnetic fabric into a current-influenced depositional context by comparing AMS data with visibly distinct depositional events in cores. Most cores collected during Leg 172 exhibited no visible current-related structures, but there are some decimeter-scale events displaying laminae, limited bioturbation suggesting rapid deposition, abrupt color changes, and sometimes scoured bases (for examples see the "Lithostratigraphy" sections in chapters of Keigwin, Rio, Acton, et al., 1998a). Eight depositional events were sampled from various sites on the Blake and Blake-Bahama Outer Ridges.
A second objective of this study is to assess, using magnetic fabric analysis, changes in circulation at Sites 1057 and 1061 on the BOR spanning marine isotopic Stages (MISs) 10-12. This interval encompasses some climatic and oceanographic extremes for the last 750,000 yr (Crowley, 1985; Sarnthein and Tiedemann, 1990; Pirazzoli et al., 1993; Bassinot et al., 1994). During Termination V at the MIS 11/12 boundary, North Atlantic Deep Water (NADW) production went from a last-750,000-yr minimum during Stage 12 (Raymo et al., 1990) to the highest flux in the Southern Ocean of any interglacial stage in the past 750,000 yr (Oppo et al., 1990). NADW comprises a notable component of the Western Boundary Undercurrent (WBUC) that plays a key role in sedimentation on the BOR (Markl et al., 1970), and sediment cores should reflect changes in NADW characteristics.