Reconstruction Of Holocene Paleoenvironmental Changes Along Northern Coast Of Sfax: Analysis Of Foraminiferal Associations

Late Pleistocene-Holocene evolution of El Merdassia sebkha (Sfax Northern coast, Gabes Gulf, Tunisia) was deduced on the basis of the analysis of sediment cores and coastal outcrops. The environmental changes were established by means of foraminifera assemblages, diversity index and biocenotic parameters complemented by sedimentological analyses. A shallow marine environment, rich in warm Senegalese fauna, allowed the deposition of quartz sands in Late Pleistocene age. After an important stratigraphic gap, a major modification of the environmental characters was recognized. The dominance of coastal foraminifera such as Elphidium crispum, Quinqueloculina seminula and Ammonia beccarii coupled with the high values of species richness and the two diversity index (H and E) characterize the settlement of a widely opened lagoon. This lagoon is subjected to the action of the longshore drifts which are responsible for the buildup of sand spit, the closure and the genesis of the present sebkhas. Two transgressive events, overlying the marine Late Pleistocene are dated at 2018-2419 and 1001-1804 a cal BP. Sudden changes, toward 0-502 a cal BP, in the structure populations and sedimentological trend argues in favor of a high energy event and the settlement of a peculiar environment.