Five Ocean Drilling Program sites (657-661), which form a north-south transect off the western periphery of the Sahara, were selected. Nearshore mean flux of opal off Cap Blanc (21°N) showed an abrupt increase about 3 Ma that appears to reflect the main onset of coastal upwelling fertility and enhanced trade winds. At the same time, the input of river-borne clay strongly decreased, suggesting a dry up of the central Saharan rivers. Later, marked short-lived spikes of clay and opal may indicate ongoing ephemeral pulses of fluvial runoff linked to peak interglacial stages. Aridification of the south Sahara and Sahel increased in several steps: at 4.6, 4.3 and especially at 4.0, 3.6 and 2.1 Ma, and again, at 0.8 Ma. The late Miocene and earliest Pliocene were humid. Central and north Sahara climate appears to be linked to the glaciation history of the Northern Hemisphere. Spatial distribution of quartz accumulation suggests that the dust outbreaks linked to the Intertropical Convergence Zone during summer did not shift in latitude back to 4.0 Ma, at least. Short-term variations of dust output over the last 0.5 my followed orbital scale pulses with a strong precessional signal, showing a link of Sahelian humidity changes to the variation of sea-surface temperature and evaporation in the tropical Atlantic. -from Authors