716 



AKRHENIUS 



[chap. 25 



matter higher than average and thus an overestimate for the extrapolated age. 

 These conditions ilhistrate the desirabihty of stratigraphic control in sequences 

 where absolute age determinations are attempted. 



Methods similar to those applied in the equatorial Pacific have been used by 

 Emiliani (1955) and Broecker et al. (1959) to determine the absolute age 

 relations of the Upper Pleistocene climatic stages in the Atlantic Ocean. 



Depth 

 m 



57 



Core number 



56 5 5 54 



G> 



5 — 



53 

 —J— 



52 



51 



UATERNARY 



iPl^iOr-ENE] 



50 





PLIOCENE 



130° 



120" w 





<30 



50-!30 

 >130 

 X \0~' 



MIOCENE 



PaOs 





20° 



!0°N 



Fig. 40. Stratigraphy of the present north equatorial clay facies in the Pacific on the basis 

 of phosphate content of the sediment. The phosphate is due to skeletal debris of 

 pelagic fish, and the concentration appears to be inversely proportional to the rate 

 of accumulation of terrigenous components. Concentrations are given in g/g. 



Vertical lines correspond to the sediment cores indicated by numbers in the graph 

 and in the map insert. The lower detached parts of the figure show older sediments 

 now near the surface below unconformities of various age. 



C indicates the heterochronous calcium carbonate compensation surface, separating 

 calcareous from non-calcareous deposits. This boundary moved south past approxi- 

 mately latitude 15°N in the Upper Miocene and appears to have arrived near its 

 present position (cf. Fig. 36) in Pliocene times. (After Arrhenius, 1952.) 



Emiliani assumes a low variability in time for both the inorganic and biotic 

 sedimentary components. The stratigraphic subdivision used by Emiliani is 

 based on changes in ocean surface temperature, whereas the stratification in the 

 equatorial Pacific, as mentioned above, is presumably caused by productivity 

 changes, induced by variations in trade-wind intensity. Since certainly both 

 equatorial Pacific circulation and equatorial Atlantic surface temperature were 

 controlled by Pleistocene climatic changes, one would expect agreement in 

 phase but not necessarily in amplitude between the Pacific and Atlantic records. 



