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FUTURE DIRECTIONS IN OCEAN SCIENCES 87 



plume had major geological consequences, including considerable 

 increases in eustatic sea level, paleotemperature, oil generation, 

 black shale deposition, and species diversification of phytoplank- 

 ton and zooplankton. Such an event has profound implications 

 for our understanding of mantle dynamics, oceanic plateau forma- 

 tion, and global environmental change. 



Structure and Composition of Oceanic Crust 



An understanding of crust formation cannot be achieved in 

 the absence of better knov/ledge of the composition of the total 

 ocean crust. This information would allow solution of a host of 

 long-standing controversies, including the relationship between 

 crustal structure and spreading rate, the origin of the seismically 

 defined stratigraphy of the oceanic crust, the total magnetization 

 of the crust and how it is distributed with depth, and' the depth 

 and nature of hydrothermal interaction in the crust. 



Knowledge of Stresses Acting on Oceanic Lithosphere and 

 Intraplate Deformation 



The observational basis for plate motions is well established, 

 but the relative importance of the forces (ridge-push, trench-pull, 

 and plate-drag) that act on the plates and cause them to move is 

 unresolved. In addition, the stresses that act upon the oceanic 

 lithosphere at or near plate boundaries are poorly understood. 

 Determining the stresses required to create these structures is 

 key to understanding the tectonics of these environments (Zoback 

 et al., 1985). 



Ocean Margins 



Continental margins are a principal site of lithospheric defor- 

 mation, sediment accumulation, and mass flux on Earth and the 

 site of substantial and chemically distinctive magmatism. Under- 

 standing their nature and origin will provide knowledge of the 

 history of the ocean basins, and because the margins are progres- 

 sively incorporated into the continental mass by plate interac- 

 tions, the knowledge is also essential to our understanding of the 

 mechanisms of continental evolution. In the next several years, 

 the opportunity exists for researchers to develop a fundamentally 

 new understanding of margins, a leap that may parallel that brought 

 about by the plate tectonic revolution some 25 years ago. 



