The bulk of the oil in the southern Tampico-Misantla Basin is contained in Upper Cretaceous oil reservoirs of the Golden Lane and Poza Rica Trend. where additional production comes from Upper Jurassic and Eocene reservoirs. The nature of the source rocks that gave rise to these oils has not been well understood. This study presents results of the geochemical characterizations of oil and source rocks from across the Tertiary, Cretaceous, and Upper Jurassic formations of the study area. Oil-oil and oil source rock correlations are based on gas chromatography, carbon stable isotopes, and biomarker analyses of oils and rock extracts.

The data suggest that the oils have a common origin, and that they were generated from an organic-rich marine carbonate source rock deposited in a reducing environment. The physical and chemical differences among oils can be explained by migration effects, thermal maturity differences, changes of the organic facies of the source rock, and migration-contamination. Oils display geochemical similarities to Upper Jurassic carbonate source rocks. The upper Jurassic and Cretaceous rocks both display good source rock potential, and reside in the early stages of oil generation. However, it is difficult to correlate oils and source rocks in the study area. Therefore, it is possible that the studied Upper Jurassic-Cretaceous section has not contributed significantly to the oils entrapped locally. These data imply that oils have migrated from a deeper water facies downdip of the study, most likely from offshore Gulf of Mexico.

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