190 



L. HILLIS-COLINVAUX 



GREEN ALGAE 



SHALI OW- WATER 

 MOLLUSCS AND \ 



FORAMINIFERA \ \ 



X' 



6 '"0 



(Voo) 



NON-SKELETAL 

 COMPONENTS 



SHALLOW-WATER LIMESTONES 



DEEP- SEA 

 LIMESTONES 



EVAPORITIC 

 DOLOMITES 



HERMATYPIC 



SCLERACTINIAN 



CORALS 



FRESH-WATER 

 LIMESTONES 



METHANE-DERIVED 

 LIMESTONES AND 

 DOLOMITES 



Fig. 57. Comparison of the deviations of ^^O and ^^C in Halimeda (green algae) with 

 those of other calcareous organisms and natural carbonates. (From Milliman (1974), 

 reproduced with permission.) 



organic matrix, and that crystallization was internal in coccolitho- 

 phorids, the crystals subsequently being extruded onto the cell surface. 

 One might, therefore, anticipate a matrix or internal precipitation in 



