Restriction of the seawater exchanges between the Atlantic and the Mediterranean during the Messinian: contribution of the tephrochronology of the Melilla-Nador area (northeastern Rif, Morocco)

Thirty-eight volcanic layers have been found, from the littoral carbonate p latform to the basin, interbedded within the Neogene deposits of the Melill a-Nador area. Ten of them, whose stratigraphic location and geographic exte nsion have been established, were petrographically and mineralogically stud ied. They have been used as markers to establish an overall platform/basin correlation sketch. Together with these correlations and a synthesis of ava ilable ages, we show that the sedimentation areas, and thus the oceanic cir culations, progressively restricted in this region between 6.5 and 5.77 Ma as a consequence of tectono-magmatic activity of the Gourougou magmatic fie ld. (C) 2001 Academie des sciences / Editions scientifiques ct medicales El sevier SAS.