Les hauts niveaux marins interglaciaires pléistocènes enregistrés dans la région d'Agadir : bilan des données chronologiques

The IRSL dating method has been applied to K-feldspars (150-250 microns) from littoral deposits (marine and dune sands, lagoonal silt) in the Agadir area, belonging to three successive raised Pleistocene paleoshorelines, assigned to the Ouljian (MIS 5), the Agadirian (MIS 7/9?) and the Maarifian (MIS 11?) stages. These IRSL ages are compared with (1) U/Th ages measured on mollusc shells and (2) D/L ratio on Patella. The IRSL ages of the Ouljian sandy marine samples collected at Aghroud (+ 5 m a.s.l) and Tamraght (+ 4 m a.s.l.) are in good agreement with the U-Th ages on molluscs and comfort thereby the MIS 5 age of these marine deposits. The IRSL ages of the marine and dune sand deposits obtained at Agadir Founti (previous “Agadir-Port”), the type locality for the Agadirian formation, demonstrate that the younger Agadirian beach (+ 20-25 m a.s.l.) is correlated with MIS 7, in agreement with the U/Th ages and the amino-acid data. The older Agadirian beach, presently inaccessible, could not be dated by IRSL but mollusc shells previously collected yield a U/Th age which might suggest a correlation with early MIS 9 (?). The preliminary IRSL age of the lagoonal silt deposit collected at Assif Lamahyane suggests a MIS 11 age.