The Mazagan (El Jadida) plateau and escarpment constitute the seaward extension of the Moroccan Meseta. Sedimentary sequence began at least as long ago as the Triassic. A very dense seismic reflection survey (32 profiles at 1 n. mile spacing) and information from 18 Cyana dives on the Mazagan the construction of isochrom map of the depth of the acoustic basement constituted either by jurassic platform carbonates or by Paleozoic granodiorite to Precambrian (?) crystalline basement, and a detailed structural map. The carbonate platform is structured in a succession of tilted blocks from the plateau to the foot of the escarpment. During early Cretaceous times, an important phase of vertical structuration is marked by the denudation of the escarpment. Transgressive sediments of late Cretaceous age cover unconformably the carbonate platform along the outer edge of the Mazagan Plateau. Deformation observed within the sedimentary cover suggests vertical tectonism from late Cretaceous up to the Present.