Seabed Assessment Program 



This program has as its objective the resolution of questions 

 concerning geologic processes along continental margins, mid- 

 ocean ridges, and deep-ocean basins. A better understanding of 

 sea-floor processes will help in locating hydrocarbon and metal- 

 lic accumulations and other products of economic significance. 

 The subprograms are broadly grouped as Continental Margin 

 Studies, Plate Tectonics and Metallogenesis Studies, and the 

 Manganese Nodule Study. 



Projects supported by IDOE are, whenever possible, based 

 on recommendations prepared by participants in scientific work- 

 shops sponsored by UNESCO's Intergovernmental Oceano- 

 graphic Commission (IOC). Scientists from universities, gov- 

 ernment, and industry, who are investigating the phenomena of 

 interest, are invited to participate in the workshops. Objectives 

 are to determine the present status of knowledge within the 

 related scientific discipline, identify major gaps in what is 

 known, recommend needed research, and develop a strategy for 

 conducting studies. International cooperation and participation 

 is emphasized. Exchange of personnel among countries is en- 

 couraged, but each country is expected to bear its own share of 

 the cost. 



To carry out the studies, a few large scale projects are 

 supported that require the cooperative efforts of several institu- 

 tions and several nations. In some cases, one topic is investi- 

 gated in a single geographic area, such as continental margin 

 work in the South Atlantic, metallogenesis in the FAMOUS 

 area, and manganese nodule studies in the North Central Pacific. 

 Due to the international nature of continental margin studies 

 and metallogenesis. they are investigated in the same broad 

 geographic areas, e.g. Nazca Plate Studies and Studies in East 

 Asia Tectonics and Resources (SEATAR). Consideration has 

 been given to investigating the occurrence of the same phenom- 

 ena (manganese nodules, subduction zones etc.) in different 

 parts of the world to make comparative studies. This idea 

 has not proven logistically feasible. 



Continental Margin Studies 



Continental margins can be classified as passive and active 

 types. Passive margins characterize the Atlantic Ocean; active 

 margins, the Pacific Ocean rim. Studies of the eastern and south- 

 west Atlantic continental margins were completed in 1976. 

 Of special concern in these programs were the processes and 

 structural features that controlled the distribution of sediments 

 along the margins of the Atlantic Ocean during its early stages 

 of opening. It was during these early stages that conditions were 

 most favorable for the formation and entrapment of oil. 



African Atlantic Margin 



This study is divided into three major phases: 1) South 

 Africa to Walvis Ridge; 2) Angola to Sierra Leone; and 3) 

 Senegal to Portugal. The Senegal to Portugal portion of the 

 study was recently completed (fig. 13). 



Some general conclusions can now be drawn about the 

 origin and development of the African Atlantic Margin. Studies 

 of both the sea floor and land arch suggest that basement struc- 

 ture resulted from the breakup of Gonwanaland and dispersion 

 of fragments to their present position. Most of the disper- 

 sion occurred in the last 150 million years. 



African Atlantic Margin Technical and Data Reports 



Emery, K. O. 1973: Review of the results from the Eastern 

 Atlantic Continental Margin Program of the International 

 Decade of Ocean Exploration, Woods Hole Oceanographic 

 Institution Tech. Rep. Ref. No. WHOI-73-75. 



Rona, Peter A. 1972: Exploration methods for continental shelf: 

 geology, geophysics, geochemistry, NO A A Tech. Rep. ERL 

 238-AOML 8. 47 pp. 



Uchupi, E., K. O. Emery, C. O. Bowin, and J. D. Phillips. 

 1975: The continental margin off Western Africa: Senegal 

 to Portugal, WHOI Contribution No. 3618, Ref. No. 

 WHOI-75-43. 201 pp. 



Southwest Atlantic Continental Margin 



This IDOE project, begun in 1972, complements the work 

 along the East Atlantic to reconstruct the various stages of 

 opening of the South Atlantic Ocean. A team of scientists from 

 Lamont-Doherty Geological Observatory (LDGO) worked 

 from the Scotia Arc at the southern tip of Argentina to the 

 Caribbean off the northeast coast of Brazil. Another group of 

 scientists from Woods Hole Oceanographic Institution (WHOI) 

 investigated the shallow water continental shelf off Brazil. These 

 studies were carried out in cooperation with scientists from 

 Argentina, Brazil, Chile, and the United Kingdom. The in- 

 vestigation of the Scotia Arc involved primarily land work in 

 cooperation with Antarctic investigations by United Kingdom 

 scientists. The participants have sought to determine the struc- 

 ture and early history of the continental margins of both Brazil 

 and Argentina. Researchers prior to this past year have esti- 

 mated the age and evolution of the Amazon cone and struc- 

 tures on the Brazilian continental shelf, explored sedimentation 

 processes on the eastern margins of Brazil, and conducted ex- 

 tensive geological and geophysical studies on the continental 

 rise and slope off Argentina. 



More recent studies have focused on a zone of diapiric 

 structures present within a region of known continental 

 shelf salt and associated evaporities on the margin of eastern 

 Brazil. Lamont-Doherty scientists are attempting to outline the 

 Brazilian diapiric zone and to compare it with a similar zone 

 located on the west African margin in efforts to determine if 

 the west African and Brazilian diapiric zones may have at one 

 time formed a single province prior to the separation of the two 

 continents. Of additional interest in mapping the diapiric zone 

 is the possible association of petroleum deposits with salt 

 diapirs, as is found in other regions like the Gulf of Mexico. 



31 



