The coastal upwelling region off southwestern Africa associated with the Benguela Current in the eastern South Atlantic is one of the great centers of productivity in the world ocean. The goal of Ocean Drilling Program Leg 175 was to recover the materials necessary to reconstruct the Neogene history of upwelling off western Africa, south of the equator. Here we report on a study of the early Quaternary sediments recovered at Site 1085, located well off the Oranje River, south of Luederitz (Namibia) and north of Cape Town (South Africa). Site 1085 has a complex record, including evidence from coastal upwelling, from Oranje River influx, from the Benguela Current itself near the point of its origin, and from the warm water eddies spawned by the Agulhas Retroflection south of the Cape (Fig. F1). Background information on these processes may be found in a symposium on upwelling off southwestern Africa (Summerhayes et al., 1992), in a recent symposium on South Atlantic oceanography (Wefer et al., 1996), and in the Leg 175 Initial Reports volume (Wefer, Berger, Richter, et al., 1998), including the paleoceanographic synthesis (Berger et al., 1998). The role of upwelling in the global carbon cycle is discussed by Schneider and Müller (1995) and other authors in the same symposium (Summerhayes et al., 1995).
Here, we address a single question, one that arose previously from observations on Walvis Ridge, that is, the "Walvis Paradox" (Berger and Wefer, 1996). The paradox juxtaposes evidence for low opal accumulation during glacial periods in the Quaternary (Diester-Haass, 1985) with evidence for intensified upwelling and high general production during glacials (Oberhänsli, 1991). We attempt to establish whether the paradox is valid for the southernmost end of the Namibia upwelling system (and hence, presumably for the entire system from the Oranje River to the Walvis Ridge) for the early Quaternary. We shall present evidence that it is indeed valid, and we comment on the implications for variations in silicate supply and intensity of mixing for the Namibia upwelling system.