Carbon dating crude oil
Michael Moldowan, a research professor at Stanford University.The new dating method is described in the August 5 issue of the journal Science.Notice in the diagram that eight different isotopes of Carbon are illustrated.Three of the Carbon isotopes (C) are found in nature.But "even this crude level of dating can be very useful in petroleum exploration," said Moldowan, who recently moved to Stanford from Chevron.Dating the oil in a given reservoir provides important clues to its source formation, something that often is not obvious because oil can migrate large distances underground.It is called "Carbon-12," which is abbreviated "C." The fact that the atom has six protons is what makes it carbon.
When they obtained these ratios and compared them with the age of their samples and the number of families of angiosperms in the fossil record, they found that, although there were some differences, variations in the level of the biological marker are broadly consistent with the fossil record.
Because the geological processes involved convert the oleanoids in the angiosperms into oleanane, the more oleanane found in a given oil sample, the more recent it is likely to be. Oils of any age can lack oleanane if flowering plants were not part of the material from which it formed.
But lack of oleanane is a significant clue that the oil may have formed in the Jurassic or older times, before angiosperms evolved.
NEWS RELEASE 08/04/94 CONTACT: Stanford University News Service (650) 723-2558 STANFORD -- The Jurassic (180 million to 140 million years ago) was a very good age for oil formation.
So too was the Cretaceous (140 million to 65 million years ago).