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 processes 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.