2. Data Report: Carbonate and Organic Carbon Contents of Sediments from Site 1087, Southern Cape Basin¹

Philip A. Meyers² and Rebecca S. Robinson²

INTRODUCTION

Site 1087 is located on the continental rise of southwest Africa at a water depth of 1371 m in the southern part of the Cape Basin. The site is part of the suite of Africa margin locations drilled during Leg 175 to reconstruct the onset and evolution of the elevated biological productivity associated with the Benguela Current upwelling system. Measurements of the amounts of inorganic and organic carbon that have accumulated in sediment under this major coastal upwelling regime are essential to this reconstruction, and these were routinely done for the first 12 sites occupied during Leg 175. However, determinations of calcium carbonate and organic carbon concentrations in sediments from Site 1087 had to be deferred to postcruise analysis because the JOIDES Resolution (JR) entered Cape Town 1 day after completing this site.

Sediment samples were collected at intervals of three per core from Hole 1087A and the lower part of Hole 1087C to provide a survey of the histories of post-Eocene accumulation of calcium carbonate and organic carbon at this site. The samples were freeze-dried on the ship in preparation for subsequent shore-based analysis. Concentrations of calcium carbonate and organic carbon in the sediment samples were measured at the University of Michigan after the cruise. Organic matter atomic C/N ratios were employed to infer the origin of the organic matter contained within the sediments and to explore some of the factors affecting its preservation and accumulation.