ABSTRACT
Petroleum samples from the Michigan Basin have been analyzed by capillary gas chromatography, combined gas chromatography-mass spectrometry, and carbon isotope mass spectrometry to compare their geochenical characteristics and to detect evidence of their origins. Oils from the Ordovician-age Trenton and Devonian-age Dundee formations have similar, mature biomarker characters. Both contain distributions of n-alkanes, steranes, and hopanes typical of oils generated from clay-bearing source rocks containing marine organic matter. Because they are reservoired in carbonate rocks having relatively low geothermal temperatures, the Trenton and Dundee oils probably were generated deeper in the Basin and migrated to their present locations. Smaller concentrations of steranes in the Dundee oils suggest somewhat lower maturity and are evidence of earlier generation and migration away from their source beds. Silurian-age Niagaran reefs contain oils having hydrocarbon patterns different from the Trenton and Dundee Oils. They are typical of thermally mature oils from carbonate source-rocks and appear to contain major contributions from land-derived organic matter.
