Seabed Assessment Program 



This program funds basic research that focuses on the geo- 

 logical processes along continental margins, midocean ridges, 

 and deep-sea basins. In the last decade, Earth scientists began 

 to recognize the subtle relationship between the movements of 

 the Earth's crust and the active processes in the world's oceans 

 and their bearing on the origin and development of hydrocarbon 

 and metallic ore deposits. 



The projects supported by Seabed Assessment are broadly 

 grouped as Continental Margin Studies, Plate Tectonics and 

 Metallogenesis, and the Manganese Nodule Program. Projects 

 currently supported include: 



1. Southwest Atlantic Continental Margin 



2. Galapagos Rift Hydrothermal Processes 



3. Nazca Plate Study 



4. Studies in East Asia Tectonics and Resources (SEATAR) 



5. Manganese Nodule Program (MANOP) 



Projects of this large a scale require cooperation among sev- 

 eral institutions, disciplines, and nations. 



Once IDOE accepts a project it is supported for 4 years to 

 8 or 9 years. Support typically includes dedicated ships and the 

 development of new technology. 



The project usually requires three phases: synthesis of avail- 

 able data, field programs for the acquisition of new data, and 

 finally, synthesis and publication of results. More than one 

 topic may be investigated in the same geographic area, and 

 conversely, one topic can be investigated in different ocean 

 environments. For example, the Nazca Plate and SEATAR 

 projects address the plate tectonic cycle from spreading center, 

 plate movement, metallogenesis, and hydrocarbons genesis. In 

 MANOP, the processes of manganese nodule origin and dis- 

 tribution are studied in various ocean environments. 



Seabed Assessment General Bibliography 



Byrne, D. A. 



1977. Ocean bottom seismometer gimbal systems. Exposure 

 5:2-11, Univ. Hawaii. 



Joint ad hoc Panel of the Ocean Sciences Board, Assembly 

 of Mathematical and Physical Sciences (National Research 

 Council) and the Marine Board, Assembly of Engineering 

 (NRC), Aug. 1976. A report on selected issues of the Inter- 

 national Decade of Ocean Exploration program of the Na- 

 tional Science Foundation. 10 p. 



National Academy of Sciences. 



1972. Understanding the Mid-Atlantic Ridge, a comprehen- 

 sive report. Ocean Sci. Board, Wash., D.C., 131 p. 

 1976. Multichannel seismic reflection system needs of the 

 U.S. academic community. Ocean Sci. Board, Wash DC 

 30 p. " ' " 



Continental Margin Studies 



The continental margin is being studied to better understand 

 54 



the rifting of continental land masses and the effects of the rift- 

 ing on the margins. Continental margins are broadly divided 

 between passive (pull-apart) and active (compressive) types. 

 The margins around the Atlantic are almost all passive; those 

 around the Pacific are active. At the beginning of the decade, 

 knowledge of the origin and structure of margins was poorly 

 known and very uneven. 



Southwest Atlantic Continental Margin 



IDOE supported major investigations of the passive margins 

 around the South Atlantic and active margins off western South 

 America and in East Asia. Field studies off the coast of 

 Argentina and Brazil were completed in 1976. Results are avail- 

 able in two sets of comprehensive geophysical and bathymetric 

 maps issued by the American Association of Petroleum Geolo- 

 gists (AAPG), Box 979, Tulsa, OK 74101. One set of maps 

 covers the continental margins of Argentina; the other, the 

 margins of Brazil. (See fig. 37.) Each set includes four maps: 

 bathymetry, sediment isopach, gravity, and magnetics, all at a 

 scale of 1 inch equals 1 degree of longitude. In addition, all 

 maps include an interpretational text, sources of data, and data- 

 gathering techniques. These results provided a substantial data 

 base for selection of drifting sites on International Program of 

 Ocean Drilling (IPOD) Legs 36, 37, 39, 40, 41, and 42. 



Detailed studies on the interrelationship between sedimenta- 

 tion and structure of the Brazilian continental margin, especially 

 the Amazon cone, have been completed through cooperative 

 studies by Woods Hole Oceanographic Institution and Brazilian 

 scientists. (See table 10.) 



Continental Margin Data 



Continental Margin data received during the period of this 

 report are available from NGSDC as follows: 



University of Texas at Galveston— J. Watkins, 150 nmi of 

 multichannel (24-track) seismic data profiles on mylar base. 

 University of Texas at Galveston— J. Watkins 1,510 nmi of 

 digital navigation for multichannel seismic data collected in 

 the Gulf of Mexico. 



Continental Margin Bibliography 



Fodor, R. V., J. W. Husler, and N. Kumar. 



1977. Petrology of volcanic rocks from an aseismic rise: 

 implications for the origin of the Rio Grande Rise, South 

 Atlantic Ocean. Earth Planet, Sci. Lett. 35:225-233. 



Gorini, M. A., and G. M. Bryan. 



1976. The tectonic fabric of the equatorial Atlantic and ad- 

 joining continental margins: Gulf of Guinea to northeastern 

 Brazil. An. Acad. bras. Cienc. 48 (Suplemento):101-1 19. 



Houtz, R. E. 



1977. Sound-velocity characteristics of sediment from the 



