Origins of etioporphyrins in sediments:  evidence from stable carbon isotopes.
In samples of the Julia Creek and Condor oil shales (Australia, Albian, and early Tertiary, respectively) etioporphyrin III is significantly depleted in 13C (4%) relative to porphyrins derived from chlorophylls.  This isotopic difference suggests a large contribution from some independent source.  The haem group found in cytochromes derived from microbial sources is the most likely candidate.
Boreham
C J
CJ
Division of Continental Geology, BMR, Canberra, Australia.
Fookes
C J
CJ
Popp
B N
BN
Hayes
J M
JM
D001315:Australia; D002247:Carbon Isotopes; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D003580:Cytochromes / Q000737:chemistry / Q000378:metabolism; D004783:Environmental Microbiology; D005044:Etioporphyrins / Q000032:analysis* / Q000737:chemistry; D019015:Geologic Sediments / Q000032:analysis / Q000737:chemistry*; D006418:Heme / Q000737:chemistry / Q000378:metabolism*; D009532:Nickel / Q000737:chemistry; D010163:Paleontology; D011166:Porphyrins / Q000032:analysis / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry
D002247:Carbon Isotopes; D003580:Cytochromes; D005044:Etioporphyrins; D011166:Porphyrins; D002734:Chlorophyll; D014638:Vanadates; D006418:Heme; D009532:Nickel