A slow environmental transition derived from changes in sedimentology and pollen assemblages in the Senegal River Delta about 6000 yrs BP

Palynological and mineralogical data from sections located in the N'Diael r egion, (Senegal River Delta) and exhibiting a peaty lever overlain by reddi sh sands, are presented. First they give the opportunity to confirm the rad iocarbon dated sedimentological transition of peat mangrove facies to elast ic continental beds at ca. 6600-6400 yrs BP. Secondly, because the pollen a ssemblage of the sandy sediments overlying the mangrove peat level is chara cterized by a high percentage of Poaceae and the absence of marine palynomo rphs a dry, continental environment appears to have replaced the coastal ti dal lagoon one; moreover, the clay mineral association of sandy levels poin ts to a elastic origin by reworking of the surrounding ferralitic cover. Th e overall data allow to conclude to the gradual setting in of continental c onditions and aridification of the studied area that seems to have begun so on after 6400 yrs BP and have reached a maximum ca. 5000 yrs BP.