Geochemical distribution patterns as indicators for productivity and terrigenous input off NW Africa

One hundred and twenty-eight surface-sediment samples collected off North-West Africa were studied geochemically to detect the expressions of different meridional climate regimes and zonal productivity gradients in the surface sediments. This geochemical multi-tracer approach, coupled with additional information on the bulk carbonate and TOC contents makes it possible to characterise the sedimentological regime in detail. Typical terrigenous elements like Al, K and Fe mirror the importance of the humid (fluvial) influence in the north of the study area and the dominance of aeolian input in the south. Furthermore, the distributions of Ti and Fe in the surface sediments serve as tracers for the supply of eolian volcanic material from the Canary Islands. The spatial variability of the TOC contents in the surface sediments closely follows the ocean surface productivity patterns, whereas the CaCO3 contents are mainly controlled by dilution with terrigenous matter. The potential productivity proxy Ba is not a reliable tracer for productivity in this region, since it is mainly supplied by terrigenous input (coupled with aluminosilicates).

► One hundred and twenty-eight surface-sediment samples off NW Africa were studied geochemically.
► TOC distribution reflects the surface water productivity off NW Africa.
► The Ba content mainly reflects the input of Ba adsorbed onto and/or incorporated into aluminosilicates.
► Al, K and Fe mirror the fluvial influence in the north and the dominance of aeolian input in the south.
► Distributions of Ti and Fe serve as tracers for the supply of eolian volcanic material from the Canary Islands.