Gulf of Mexico
This a chromatogram of oil that came from the Gulf of Mexico, but you can readily see that it is different from oil that came from Santa Barbara, Calif. (slide 2) or a different reservoir in the Gulf: the Macondo well (slide 3).
(Photos courtesy of Bob Nelson, Woods Hole Oceanographic Institution)
Specific compounds provide clues to what types of organisms and conditions went into making the oil. Bisnorhopanes show that this oil formed in low-oxygen ocean sediments. But oleanane reveals that some of the oil came from land sources.
The tall peaks on the left are diasteranes: bulky, nonpolar compounds that resist breaking down in the environment. A high fraction of trisnorneohopane indicates that the Macondo oil underwent a lot of heating during its formation.