The results of the chromatography are significant and can be simply stated. Two distinctly different sources are clearly responsible for the Nevada oils.

The oil composition data determined from both the whole oil and saturate fraction gas chromatography indicate that the crude oils from the Blackburn Field in Pine Valley, and the Grant Canyon and Trap Spring Fields in Railroad Valley are very similar. All three oils are distinctly different from the oil found in the Eagle Springs Field in Railroad Valley.

The low pristane/phytane ratio and low carbon preference index in the Eagle Springs oil indicates a source rock deposited in a highly reducing, probably Tertiary lacustrine, environment. The Eagle Springs oil has the lowest thermal maturity and appears to be related to an exinite-rich source.

The two Tertiary lacustrine rocks sampled in outcrop were the Sheep Pass and Elko Formations. The Sheep Pass limestones are so organically lean that they make poor samples for gas chromatography. Sample 278-SP, the best candidate, was selected for chromatography. It showed a very high pristane/phytane ratio, a high carbon preference index, and a completely different normal alkane distribution than the Eagle Springs oil, but is strongly affected by the presence of Recent organic contamination ("root juice") and weathering.

Poole and Claypool (1984) report an acceptable geochemical correlation between saturate extracts from cores of mudstones in the Sheep Pass Formation and the Eagle Springs oil. We accept this correlation but unfortunately could not corroborate it. The organic-rich source facies responsible for the Eagle Springs oil field appears to be restricted to the subsurface of Railroad Valley.

The sample of the Elko Formation, 165-EK, has a high carbon preference index (CPI) value and a low pristane/phytane ratio characteristic of an immature exinite-rich source deposited in a strongly reducing depositional environment. The total extract recovery and pyrolysis S1 value were very high for this sample, which is characteristic of an immature, lacustrine oil source. Although the Elko Formation does not correlate with known Nevada oils, the Elko should yield oil where deeply buried and thermally mature.

The Blackburn, Grant Canyon and Trap Spring oils have a higher thermal maturity and were derived from marine source lithologies containing some terrestrial organic matter (high pristane/phytane ratio, and a carbon preference index above 1).

The dominantly marine kerogen bearing Woodruff, Roberts Mountains, Pilot, Chainman, and Vinini Formations were examined for comparison and correlation with these oils.

Four of these samples, 267-C (Chainman), 260-P (Pilot), 66-Wo? (Woodruff), and 46-Vi (Vinini) show a full range of normal alkanes, CPI values near 1.0 and relatively few napthenes, characteristic of thermally mature crude oils (0.8 to 1.4 Ro range). All have the potential to generate oil where thermally mature.

Samples 84-RM (Roberts Mountains), 69-Wo (Woodruff) and 59-Vi (Vinini) had low S1 pyrolysis values and gave low total extract recoveries. They are strongly affected by the presence of Recent contamination.

One sample of the Chainman Formation, sample 71-C from the Carlin-Pinon Range, shows a strong chromatographic correlation with whole oil as well as saturate fraction extracts of the Trap Spring, Pine Valley and Grant Canyon crude oils. The oils and Chainman sample show very similar normal alkane distributions and CPI values, with the oils ranging from 1.12 to 1.30 and the Chainman sample showing a CPI of 1.17. The pristane/phytane ratio for the Chainman sample is higher, 2.07, suggesting a more significant terrestrial organic component than the oils that range from 1.38 to 1.65; a slightly different, perhaps deeper water facies may have been responsible for generating the oils.

The Mississippian Chainman Formation correlates well with the Trap Spring, Grant Canyon and Blackburn oils and appears to be the source or parent responsible for generating the oil in these fields. This result coupled with the conclusions of the surface geochemistry show that the regionally extensive Chainman Formation is certainly the most prospective source candidate in northeastern Nevada.