Saharan dust and desert loess: effect on surrounding soils

Abstract

Only specific desert environments are significant suppliers of the millions of tons of dust blown out annually from the Sahara to its fringes and across the seas. The major dustsource is weathered debris detrained by fluvial transport and redeposited on alluvial fans, in wadis and terminal basins. Rocky gravel and wet sebha surfaces are the only effective dust traps in the desert. Thick loess mantles accumulate on the fringes of the desert after medium or long distance transport where the rate of accretion exceeds 50 g m −2 per year over long a period. At lower deposition rates the dust becomes incorporated and assimilated by the local ground soil (or ocean sediment). Such additions have affected distant areas in southern Europe and Africa and have contributed to their fertility. More desert loess-derived or affected soils are likely to be recognized in the future.