ABSTRACT

Upper Devonian and lower Carboniferous deposits exposed along the north flank of the Tindouf Basin in southern Morocco are assigned to 12 sedimentary facies belonging to four interacting depositional environments: progradational deltaic, marine shelf, beach and tidal flat. These environments together form an ancient delta system which records regressive-transgressive episodes due to phases of constructive and destructive delta building. The constructive phase of delta building occurs when an actively depositing fluvial system progrades a platform of deltaic plain deposits onto a marine shelf, without significant contemporaneous reworking of sediment by marine processes. The first destructive phase of delta building occurs when a less actively depositing fluvial system enables marine p ocesses of a microtidal and moderate wave energy sea, to build a beach on the margin of the deltaic plain. The final destructive phase of delta building occurs when detrital influx is almost absent and the deltaic plain converts to a back-barrier tidal flat which is eventually transgressed by the barrier beach and marine shelf.