42 



BROECKER 



5 13 C 

 PLANKTONIC 



0.5 1.0 



Q. 



LU 



Q 



1.5 -3.0 



6 18 

 FORAM G. RUBER 



-2.0 -1.0 



-0.0 



-127 — 



O 



< 



11 — 



V-12 - 122 

 VAN DONK 

 L.D.G.O. 



290- 



220 



CARBON-TO-PHOSPHORUS RATIO, TEMPERATURE AND ICE VOLUME 



DEEP SEA 



Fig. 6 The 6 ' 3 C and <5 ' 8 O ratio as a function of depth and age in a sediment core from the 

 Caribbean Sea. 



The difference of 2 per mil between surface and deep water is recorded by 

 the forams that grow in these two reservoirs. Shells that grow in surface water 

 record the C in the surface ocean; shells that grow in deep water record l 3 C at 

 the bottom of the ocean. The difference between their I3 C contents is a 

 reflection of the difference in the carbon isotope ratios in the dissolved carbon 

 in the ocean. And that depends on the ratio of the phosphorus to carbon 

 dissolved in the sea (Fig. 6). 



One of the key factors in understanding paleochemistry is to ascertain the 

 ratios of nutrient elements, one to another. First we will consider the calcium 



