FELDSPAR LUMINESCENCE EVIDENCE FOR TWO MIDDLE PLEISTOCENE INTERGLACIAL SEA-LEVEL HIGHSTANDS (MIS 7 AND MIS 9) ALONG THE EASTERN COAST OF TUNISIA (SAHEL)

FELDSPAR LUMINESCENCE EVIDENCE FOR TWO MIDDLE PLEISTOCENE INTERGLACIAL SEA-LEVEL HIGHSTANDS (MIS 7 AND MIS 9) ALONG THE EASTERN COAST OF TUNISIA (SAHEL) The IRSL dating method is applied to alkali feldspar grains (200-250 mu m) from the two sandy marine units of the Douira Formation, a Middle Pleistocene morphostratigraphic marine unit specific to the Tunisian Sahel area. This formation is devoid of Strombus bubonius and ooids. The IRSL ages of both marine units, obtained at El Hajeb, close to the type locality of Douira in the Sahel area, confirm the pre-tyrrhenian age of the Douira Formation. Moreover, they demonstrate, for the first time, the presence of two successive interglacial high sea-level events within the Douira Formation, correlative of MIS 7 and MIS 9. These sandy marine units are separated, at El Hajeb, by a major erosional surface and, at Rejiche, by a continental pedogenised loamy deposit related to a low sea-level event that might be assigned to MIS 8. We therefore suggest herein to subdivide the Douira Formation into two members, a lower and an upper member correlated respectively with MIS 9 and 7. Both high sea-level stands coincide with the development of extensive Middle Pleistocene paleolakes in south-western Tunisia and Libya and the formation of sapropels in the Mediterranean basin.