290 



Sediments 



' Values for carbonate and organic carbon by T. A. Rafter, New Zealand Department of Scientific and Industrial 

 Research, Lower Hutt; other values by Silverman and Epstein (1958) and Silverman (personal communication). 



that the C'^ content of plant lipids (hydro- 

 carbons, terpenes, fatty acids, and other 

 ether soluble components) are about 10%o 

 lighter than the rest of the plant. The typi- 

 cal oxidation and loss to the sediment of 

 carbohydrates and proteins at a rate faster 

 than for lipids must then result in a decrease 

 of the C'VC^- ratio, in agreement with the 

 observed progressive change from plants and 



animals to sediments at the surface to sedi- 

 ments at depth to petroleum. According to 

 a single analysis of a natural gas by Silver- 

 man and Epstein (1958), the sequence may 

 continue beyond petroleum to oil field gas. 

 This whole sequence accords with the belief 

 that petroleum is derived from fatty acids 

 (Brooks, 1952) or hydrocarbons in plankton 

 (Smith, 1954), rather than that fractionation 



