Biological v. Abiotic?
Evaluations of abiotic oil make more sense than biological sources being responsible for its presence. Although more commonly found at subduction zones and fault lines, the deeper the oil is found, the more radioactive it is. This is one method used to determine that the oil slicks all over the Gulf of Mexico, as well as the heavier stuff on the bottom, came from the site of the Deepwater Horizon intentional well blow out of 3-11.