The tectonic evolution of the Zoumi Sandstone, western Moroccan Rif

Abstract

The Zoumi Sandstone is an Oligo-Miocene syn-tectonic flysch sequence, deposited on the back of the Mesorif thrust sheet, whose sediment source was from the foreland to the south. Variations within the Zoumi Sandstone from thick to thin bedded turbidite lobes are explained as the result of deposition in small, confined basins or larger, more extensive basins, respectively. Formation of small basins is related to contractional deformation in the underlying Mesorif thrust sheet. Propagation of the Zoumi thrust through the developed basin with areas of relative uplift and subsidence produced complex hanging-wall cutoff geometry. A complicated footwall geometry exists because deformation in the more external Mesorif thrust sheet preceded the final displacement of the more internal, Intrarif thrust sheet. The latter incorporated the Zoumi Sandstone into its leading edge and thrust it over the Mesorif during the Miocene. This deformation sequence of two or more simultaneously active thrust sheets is described as synchronous thrusting.