Age models of sediment cores from the continental margin of northwest Africa

Off this region, coastal upwelling is well developed under the influence of the NE trade winds. Variations in diatom abundance in these cores are inferred to represent changes caused by varying degrees of the upwelling fertility.

Times of high productivity are marked by high relative frequencies of Chaetoceros, while low productivity is marked by the dominance of Aulacoseira granulata. Upwelling increased during glacial episodes (isotopic stages 2-4 and 6) relative to isotopic stages 1 and 5. During the late Holocene, primary productivity levels are similar to those for Stage 5, but in the early Holocene upwelling intensities seem to have been weaker than today.