No. 76: Jul-Aug 1991
Geologists maintain that most of the oil they pump out of the ground was formed tens and hundreds of millions of years ago from biological debris. But in the Guaymas Basin, in the Gulf of California, the oil seeping out of the sediments is only 4240 years old! Actually, it could be even 500-3000 years younger than that for two reasons: (1) The organic debris that was C-14-dated may have taken many years to become incorporated in the sediments; and (2) The dating may be skewed by older material in the sediments. By subtraction, the oil might be as young as 1240 years!
The picture geologists draw of the Guaymas Basin is that of a spreading center covered by perhaps a half kilometer of sediments. Spewing up from the spreading center is hot water at 300-350°C, which "cracks" the organic material in the sediments, converting it into petroleum only 10-30 meters below the sea floor. (Hecht, Jeff; "Youngest Oil Deposit Found below Gulf of California," New Scientist, p. 19, April 6, 1991.)
Comment. Since spreading centers are really cracks in the earth's crust, it is possible that some of the feed materials for this modern "petroleum factory" in the Guaymas Basin could consist of abiogenic, primordial methane and other organics seeping up from deep within the earth.
Reference. Many questions remain about the origin and migration of oil. Many of these are discussed in ESC13 in our catalog: Anomalies in Geology. Details here.