A Displaced Neritic Diatom (Delphineis-Karstenii) in Pelagic Sediments of the Southeast Atlantic

This paper documents the occurrence of Delphineis karstenii, a neritic diatom, in pelagic sediments of the northern Cape and southern Angola Basins (southeast Atlantic Ocean). Maximum abundances are found in the southern Angola Basin, although the source area appears to be the diatomaceous sediments which blanket much of the Namibian continental shelf. The observed pattern implies large-scale displacement of D. karstenii valves first northward along the continental margin, and then westward into deep waters. Transport evidently occurs in the surface waters of the Benguela Current, which flow northward along the Namibian coast and then turn westward, away from the coast of Angola and out into the Angola Basin. These observations suggest that Delphineis valves, and perhaps other shallow-water diatom valves, may be displaced downslope on other continental margins. Failure to recognize such displacement could lead to incorrect ecological and paleoecological interpretations.