53 



Figure 27. Research vessel Atlantis II. 



the West African continental margin similar to those that have been pub- 

 lished for eastern North America : free-air and Bouguer gravity anomalies, 

 trends of geomagnetic anomalies, and depths to mantle, basement, and 

 Horizon A (vi^here present). The construction of numerous structural 

 cross sections and isopach maps also will be possible. All of these materials 

 taken together should provide answers to the following questions : 



(1) How and when did the South Atlantic Ocean open, and how did 

 the process differ from that of the North Atlantic? 



(2) How nearly is the oceanic basement off northwestern Africa a 

 mirror image of that off eastern North America? 



(3) How favorable is the sedimentary pattern to the discovery of 

 large, economically important deposits of oil and gas? 



(4) How do the sediment thicknesses and characteristics reflect the 

 very different water masses on opposite sides of the ocean? 



(5) What remnants of structures that lie at an angle to the coastal 

 trends can be found in the continental margins of once-joined 

 continents ? 



(6) Is the general absence of known tectonic dams at the edge of the 

 continental shelf off Africa merely a consequence of the absence 

 of adequate data? If the dams are present, what is their nature? 



