Sediments recovered at DSDP Sites 362 and 532 on Walvis Ridge Abutment Plateau and 530 in the southeastern Angola Basin record long-term waxing and waning of upwelling. The amounts of opaline silica and organic carbon in the sediments increase from latest Miocene to latest Pliocene then decline to present. During the late Pliocene, opaline silica accumulated ten times faster than during the late Pleistocene. If the area of accumulation also expanded to include the Abutment Plateau, this region would have been the global silica sink, consuming the equivalent of the entire silica output of the present ocean. The sediments contain light-dark cycles; the dark cycles contain more terrigenous material and on this basis have been interpreted as representing glacials. Before the Pliocene the maximum biological productivity in this region occurred during the glacials, but since then it has occurred during the interglacials, an effect of sea-level change on productivity opposite to that in most parts of the world. The most important factors causing the changes in sedimentation are judged to be threefold.