Evidence for a Late Tortonian Wedge-Top Basin in the Northern Rif Belt (Morocco)

We report on new stratigraphic data concerning Middle - Upper Miocene deposits outcropping in the Northern Rif Belt. We analyzed sections located in the Dar Zhiro-Bougdour and Saf Lahmam-Seguedla areas, 30 km to the south of Tanger City. In these regions, sandy-clayey deposits unconformably overlie the Numidian and like-Numidian (quartz-lithic arenites) successions pertaining to the Massylian and the External Tanger Intrarif sub-domains, respectively. In turn, the Massylian sub-domain belongs to the Maghrebian Flysch Basin (MFB), whereas the External Tanger Intrarif is part of the External Rif domain (ER). The tectono-stratigraphic features of the studied areas, e.g. the basal unconformity and the slight compressional deformation with respect to the substratum, let us to refer them to a wedge-top basin recording the compressional deformation of MFB and ER domains. Dar Zhiro-Bougdour and Saf Lahmam-Seguedla sections are both represented mainly by dm-thick turbiditic strata interbedded with light-colored and bluish/pinkish marls. These successions show sulfur nodules, glauconie, and ichnofacies pointing to a deep marine environment. Biostratigraphic quantitative analyses, performed on calcareous nannofossil assemblages, provided ages ranging from latest Serravallian to Tortonian for Saf Lahmam-Seguedla areas, and late Tortonian for Dar Zhiro-Bougdour. The new stratigraphic results are a major constraint for the closure timing of the Maghrebian Flysch Basin and its tectono-sedimentary evolution, which is coeval with the internal part of the Intrarif sub-domain. Particularly, they point out the latest collisional and docking stages of the whole Rif nappe-stack onto the African plate in the Gibraltar Arc system.