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doi:10.2204/iodp.proc.303306.215.2011

Introduction

Knowledge of deepwater ocean currents is crucial to determining the transportation system of ocean floor sediments. Velocities of present-day deepwater currents are generally high enough to transport sediments (Stow and Holbrook, 1984), for instance, 20 cm/s in the Hatton-Rockall Basin north of Ireland, 30 cm/s in the Greenland-Iceland-Faeroes Ridge section north of Scotland, and 5–20 cm/s on the continental slopes of North America.

Bottom current deposits as a drift in the North Atlantic lead to the formation of sites with high sedimentation rates. The Eirik Drift, located at the foot of the continental slope off the southern margin of Greenland (Chough and Hesse, 1984), is the largest of such thick sediment accumulation sites (Stow and Holbrook, 1984). This drift is an indicator of the North Atlantic paleocurrent system, especially that of the Western Boundary Undercurrent (WBU), at the millennium timescale.

The paleocurrent directions of ocean bottom sediments were analyzed using anisotropy of magnetic susceptibility (AMS) (e.g., Rees, 1965), both on the Norwegian Sea sediments (Kissel et al., 1998) and on the Nova Scotia continental rise (Shor et al., 1984). AMS can give us a paleocurrent history of sediments by preferred orientation of magnetic minerals parallel (or perpendicular) to the current direction (e.g., Rees, 1965), but those of the Eirik Drift have not been examined yet.

In this paper, we report the AMS of siliciclastic sand and detrital carbonate layers recovered in drill cores from Integrated Ocean Drilling Program (IODP) Site U1305. Site U1305 is located at the south margin of the Eirik Drift (Fig. F1). Furthermore, we examined constituent magnetic minerals contributing to AMS using rock magnetic methods.

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