In the period from September 25th to October 19th 1979 5,260 km of magnetic, gravity and bathymetric lines and 3,567 km of reflection seismic lines were recovered on the first leg of the VALDIVIA Westafrica-cruise 1979 with the research objective to study similarities and differences in the geological development of physiographically different Northwest African continental margin segments. Test measurements have been carried out during this cruise with an “implosive" seismic sound source. The software for acquisition, calculation and presentation of gravity, magnetic and bathymetric data has been developed so that onboard presentation of free-air anomalies, Bouguer anomalies, anomalies of the earth's magnetic field and of the bathymetry could be achieved. Differences within the regional geological development of the Northwest African continental margin has been confirmed. Parts of the Moroccan continental margin are modified by a Cretaceous epirogenic uplift associated with block—faulting and halokinesis. Tertiary folding of the Western High Atlas extends into the shelf of the Tafelney Plateau segment.