CONTINENTAL MARGINS OF THE WORLD 



E] POORLY KNOWN 



MODERATELY KNOWN 



Figure 15 



BEST KNOWN 



Program of Work 



Major studies of the continental margins 

 along the South Atlantic are now under way. 

 One study off west Africa extends from South 

 Africa to Portugal; another along the east 

 coast of South America extends from Argen- 

 tina to Brazil. The African studies were ini- 

 tiated in January 1972 when scientists from 

 the Woods Hole Oceanographic Institution 

 began a systematic study extending from Port 

 Elizabeth, South Africa to the Congo River. 

 Although survey tracks concentrated on the 

 continental margin, a few tracks were ex- 

 tended out to the Mid-Atlantic Ridge. A total 

 of 50,000 km of seismic reflection, gravity and 

 magnetic data were recorded. Precision bathy- 

 metric data were also obtained, and seismic 

 refraction data, using sonobuoys, were rou- 

 tinely recorded. Location of lines at sea was 

 controlled by satellite navigation. In 1973 the 

 second and final cruise extended the study 

 from the Congo River to Lisbon (Figure 16]. 



African Atlantic Assessment 



Preliminary findings from the 1972 work in- 

 dicated two potential sources of oil accumu- 

 lation, one in a thick sedimentary section off 

 the delta of the Orange River in southwest 

 Africa, and another in a large diapiric salt 

 basin off Angola. The areal extent and thick- 

 ness of both deposits were outlined using geo- 

 physical methods, and their internal structure 

 has been analyzed using seismic reflection and 

 refraction data. K. O. Emery, the Principal 

 Investigator from Woods Hole, concluded 

 that: "Within the delta are probably numerous 

 stratigraphic traps capable of retaining oil and 

 gas if they are present and within the diapir 

 field are many structural traps caused by the 

 upward movement of the salt. The landward 

 side of both features underlies the outer con- 

 tinental shelf or the upper continental slope, 

 but the major parts lie much deeper. Nearly 

 all of both features lie within 200 nautical 

 miles ... of the adjacent coasts. While depths 



28 



