A geochemical and isotopic characterization of a wide selection of the produced oils in the petroleum subprovinces from the Mexican Gulf Coast Basin has revealed five major genetic groups. Their distribution and chemical features appear to reflect multiple sources, fades variations, maturation, and postfilling alteration processes. Each group is correlated with a specific generative source, namely (1) Oxfordian marine marl-dominated, (2) Oxfordian marine carbonate-dominated, (3) Tithonian marine marl-dominated, (4) Cretaceous marine carbonate-evaporitic, and (5) Tertiary marine deltaic siliciclastics.

Biomarker and isotope differences observed in the Tithonian oils can be interpreted in terms of facies variations. The Tithonian generative subsystem has produced more than 80% of all oil reserves from the Mexican Gulf Coast Basin. Oil reserves have accumulated both onshore and offshore and throughout the stratigraphic column from Kimmeridgian to Pleistocene in marine-siliciclastic and carbonate reservoirs, suggesting that vertical pathways are an important secondary migration mechanism.