424 



86 



OCEANOGRAPHY IN THE NEXT DECADE 



Normal 

 Reversed 



10 20 30 40 50 60 70 80 90 100 110 120 130 



MILUONS OF YEARS 



FIGURE 3-2 Combined plot of magmatic reversal stratigraphy; world 

 crustal production; high-latitude, sea surface paleotemperatures; long-term 

 eustatic sea level; times of black shale deposition; and world oil resourc- 

 es plotted on the geologic time scale. Note that increased volcanic activ- 

 ity in the Cretaceous is associated with eustatic sea levels, high sea 

 surface temperatures, and black shale production. Thus, this may be a 

 link between mantle processes (volcanism) and global climate. (Com- 

 piled from a variety of sources; Larson, 1991.) 



