Magnetic susceptibility of eastern Mediterranean marine sediments as a proxy for Saharan dust supply?

Abstract

Interpretations of magnetic susceptibility variations in circum-Saharan marine sediments have suggested a close relationship with Saharan dust supply, which assumes that dust dominates over the potential contributions from a variety of other sources and processes. To evaluate the importance of Saharan dust supply versus that of other potential sources of variability in magnetic susceptibility, we compile magnetic susceptibility data from eastern Mediterranean Plio-Pleistocene sequences at Ocean Drilling Program (ODP) sites 964, 966, 967 and 969, for comparison with other paleoclimatic and paleoceanographic proxy data for the same intervals. Our results demonstrate that magnetic susceptibility variations are linked to the supply of Saharan dust through some parts of the studied intervals, but seem to be predominantly controlled by the discharge of suspended matter from Eurasian rivers and the Nile. Depositional and diagenetic processes in the stratigraphic vicinity of ash layers and sapropels also affect magnetic susceptibility values. We conclude that magnetic susceptibility records can only be used as a proxy for Saharan dust supply in eastern Mediterranean sediments, and likely also in other peri-Saharan marine sediments, when this has been demonstrated by further analyses to be the only (or predominant) source of magnetic susceptibility variability.