The perisaharan loess: Sedimentological characterization and paleoclimatical significance

The occurrence of peridesert loess in the N Saharan margin (with the well known Matmata loess, S Tunisia) and in a S belt (10–13°N) of W and central Tropical Africa is related to past main deposition of Saharan dusts (especially during the Upper Pleistocene). The sedimentological data of these deposits seem comparable (with particular references to Matmata and N Nigeria regions) and the loess are often coarser than present Saharan dust because of the nearness of some of their desert sources. On the past desert margins, the loess deposition occurred in a peridesert “pluvial” paleoenvironment. This implies that the N perisaharan loess were deposited during a desert retreat (relatively to the present arid bioclimatical conditions of their location), particularly during the Upper Pleistocene “Soltanian” Pluvial; and that, owing to its low latitude, the “tropical” loess deposition took likely place during a desert S advance (Late Pleistocene “Ogolian” period?) nearest to their location in the present wetter tropical zone.