OUT OF AFRICA – MARINE RECORDS OF DUST AT THE LAST GLACIAL MAXIMUM

Marine sedimentary records from the southern North Atlantic provide evidence of increased transport of dust from northern Africa at the LGM. Lake and pollen-data indicate increased aridity in equatorial and southern Africa. However, changes in dust transport from these areas are poorly constrained. New records from three cores located in the low- to mid-latitude South Atlantic show low dust accumulation rates and no change in flux since the LGM. This implies that there has been no change in wind transport patterns over this region since the LGM. Modern wind patterns off southern Africa confine dust transport and hence deposition to the coastal zone today.

Comparison of our records with marine records from the DIRTMAP database, suggest three regimes underlying atmospheric dust transport out of Africa. In southern Africa, despite increased aridity and decreased vegetation cover, there was no enhanced transport to the Atlantic. In the Sahelian region, however, enhanced transport to the Atlantic can be linked to expanded sources due to increased aridity and concomitant changes in vegetation cover. Increased transport from the Sahara does not reflect changes in vegetation cover. A shift towards coarser grain size suggests a strengthened dust transport reflecting stronger winds.