12 
BSH Report No. 56 
Inorganic Carbon 
Marine Limestones 
Atmospheric Carbon Dioxide 
± 
Carbon in Living Organisms 
i i 
Marine Plants, Vertebrates, Invertebrates 
Marine Plankton 
I I 
Land Plants 
Hydrocarbon Source Materials 
tebrates U 
Organic Carbon In 
Recent Sedlmnets 
{ 
Organic Carbon-Clastic Rocks 
Coal 
Hydrocarbons 
Methane 
Marine Щ 
Nonmarine 
siic Rocks ИрЯЬ’ь 
ne Ж 
Petroleum 
Commercial Gas 
Gas Associated with 
OH Generation 
"Deep" Dry Gas 
I Geothermal Methane 
1 —Г 
90 -80 -70 -60 -50 -40 
-30 -20 
10 
3 C content, change from standard, parts/1000 
Fig. 6: d13C Contents of different materials [8].