Geological Record on the Ocean Floor* 



GUSTAF ARRHENIUS 



Scripps Institution of Oceanography, University of California, La Jolla, California 



GEOLOGICAL events with worldwide or large-regional effects 

 such as climatic change, volcanic activity, evolution of the ocean, 

 and interaction with outer space are often recorded on the deep 

 ocean floor far away from the continents, in a manner that makes 

 this record advantageous for quantitative interpretations. The 

 Pacific basin (Fig. 1) has some characteristics that make it 

 particularly well suited as a recipient of representative sedimentary 

 sequences. 



The marginal trenches and ridges effectively bar turbidity 

 currents from the central basins; the lack of such protection in 

 exceptional cases such as along the coast of the northern United 

 States and Canada has resulted in widespread detrital deposits 

 over adjacent areas of the deep ocean floor. On account of the 

 approximately isometric shape and the large dimensions of the 

 Pacific Ocean, several of its topographically protected basins are 

 separated by several thousand kilometers from the continental 

 sources of windborne detritus, and the eolian component of the 

 sediment thus is largely attenuated. 



Another important feature of the Pacific Ocean is that its vast 

 open area extends into high latitudes both in the Northern and the 

 Southern Hemispheres. This makes it possible for the wind-driven 

 circulation to develop without interference from land masses in a 

 far more pronounced way than in the Atlantic and Indian oceans. 

 At the equator, the forces arising from the rotation of the earth, 

 cause cold, deep water, rich in nutrients, to ascend to the surface 

 where the sunlight makes photosynthesis possible (Fig. 2, middle 

 graph). The resulting zone of highly increased organic productivity 



Contribution from Scripps Institution of Oceanography, New Series. 



129 



