n-Alkane and pollen reconstruction of terrestrial climate and vegetation for N.W. Africa over the last 160 kyr

Proxy environmental records have been obtained for the last 160 kyr from the well-studied ODP Site 658, ca. 200 km West of Cap Blanc, N.W. Africa (20°5′N, 18°35′W; 2263 m water depth). This collective assessment of several terrigenous proxies (lithogenic fraction, n-alkane content and δ13C values, and pollen counts) provides a better understanding of the climate and vegetation history of the N.W. African hinterland. The results indicate that, for this site beneath the main dust pathway of the Saharan Air Layer (SAL), the dust flux increased during dry glacial periods but the amounts of pollen and n-alkanes delivered were lower, in accord with the decreased density of vegetation cover of their source areas. The % ‘C4 pollen’ was also very low, but the heavy δ13C values of the n-alkanes accorded with a mainly C4 plant origin. Evidently, the load of SAL-pollen was much reduced, but not the SAL wind strength.