Transgressive-regressive facies cycles in late Cretaceous calciturbidites from the Mauretanian Series, Béni Ider thrust sheet, northwestern External Rif, Morocco: application of the ‘facies tract-facies sequence’ concept

Abstract

AbstractLate Cretaceous mixed carbonate-siliciclastic, thin-bedded turbidites occur between the two great sandstone packages of the Mauretanian Series (the Tisirène and the Béni Ider sandstone flyschs, of early Cretaceous and late Oligocene-early Burdigalian age, respectively). The application of the facies tract-facies sequence model allows subdivision of the studied calciturbidites into five distinct facies sequences (FS.1–5), which equal five transgressive-regressive facies cycles. These cycles mainly consist of thinning upward calciturbidites, which almost all start with coarse-grained carbonate breccias, and passing upward into a shale-dominated interval. Fe-stained discontinuities, together with sedimentological and ichnological evidence, lead us to assign these two lithological components to a transgressive and a regressive trend, respectively. This result provides new insights into the sequence-stratigraphic interpretation of turbiditic successions.