Ocean Drilling Program, United States

During Leg 175, we propose to drill between eight and ten advanced hydraulic piston and extended core barrel core sites off the western coast of Africa (Angola and Namibia) to reconstruct the late Neogene history of the Benguela Current and the associated upwelling regime between 5 degrees S and 32 degrees S. The Angola/Namibia system contains one of the great upwelling regions of the world. Like the systems off Peru and California, which were studied during recent Ocean Drilling Program legs, it is characterized by organic-rich sediments that contain an excellent record of productivity history, which can be read on a very fine scale. In addition, this environment provides an excellent setting for natural experiments in diagenesis. The individual transects reflect a compromise between geographic coverage, accessibility, and time constraints. We aim to study specific "end-member" environments, which collectively comprise one of the most active areas of ocean productivity. One of the major goals is to reconstruct the evolution of the Benguela Current system and its relationship with the onset of glacial cycles in the northern hemisphere. Most of the proposed sites are expected to have high sedimentation rates, offering an opportunity to develop detailed paleoceanographic records, and all proposed sites will extend and refine the partial record of the paleoceanographic and paleoclimatic changes for the late Neogene that was provided by Deep Sea Drilling Project Sites 362 and 532. Sediments will be largely diatomaceous and carbonate-rich clays with variable, and occasionally very high organic carbon contents.