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Five heavy mineral associations occur in the Paleocene and Eocene sediments recovered during Leg 81 of the Deep Sea Drilling Project (DSDP) in the SW Rockall area. Association 1, consisting of augite, iddingsite, and olivine, was derived from the basaltic rocks of the northern part of the Rockall Plateau. Association 2 consists of epidote group minerals, including piedmontite, and amphiboles of actinolite, actinolitic hornblende, and magnesio-hornblende compositions, and was derived from the metamorphic basement of south Greenland. Association 3 comprises garnet, augite, apatite, and edenitic and pargasitic amphiboles and has a provenance in the southern Rockall Plateau. Associations 4 (garnet, apatite, edenitic/pargasitic amphiboles) and 5 (garnet, apatite) are intrastratal solution derivatives of Association 3, with successive removal of first pyroxene and then amphibole with increasing depth of burial. Throughout the SW Rockall Plateau area there is a significant change in the spectrum of the above assemblages in the lower part of the Eocene. This change has been noted at Sites 403, 404, 553, and 555 and is defined by the last appearance of Association 2. This level therefore marks the cessation of sediment supply from southern Greenland and is the result of the final separation of Rockall and Greenland immediately prior to magnetic Anomaly 24. INTRODUCTION Of the four sites drilled during Leg 81 of the Deep Sea Drilling Project (DSDP) SW Rockall Plateau, three (Sites 552, 553, and 555) encountered sand-grade terrigenous sediments of Paleocene to Eocene age (Fig. 1). Previous work on the heavy minerals of Paleogene sediments drilled during DSDP Leg 48 in the same area (Harrison et al., 1979) indicated that major changes in sediment supply took place during the interval related to the onset of seafloor spreading between Rockall and Greenland. The purpose of this study was to discover whether similar heavy mineral changes occur within the Leg 81 sediments, to elucidate more fully the sediment source areas, and to consider the factors controlling heavy mineral distribution.

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Heavy Minerals from Paleogene Sediments, Deep Sea Drilling Project Leg 81: Their Bearing on Stratigraphy, Sediment Provenance, and the Evolution of the North Atlantic