ABSTRACT

In the absence of direct evidence from the source beds of Gulf of Mexico oils, detailed biomarker analysis can provide information on the nature and thermal history of the orgainc matter from which the oils were generated. Thermal maturity of the oils increases from west to east, indicating that source beds of eastern oils are older than those of western oils. Oils produced from the eastern offshore region were probably generated from Early to Middle Miocene sediments. The depocenter was located to the northwest, and the deposition of oil-generating sediments, enriched in marine organic matter, took place in deep water. Oils produced from the western offshore region were probably generated from Pliocene sediments. The depocenter was located close to where the oils are found today, hence the oils are enriched in components derived from land plants which were deposited in oxygenated sediments. Oils produced from two locations close to the present day shelf edge are significantly different from the other offshore oils. These were probably generated from Middle to Late Miocene sediments which were deposited in anoxic basins with high bacterial input.