The Pineview field, discovered in 1975, started the recent expansion of exploration in the Overthrust belt and produces mainly from the Jurassic Nugget and Twin Creek formations. Mass spectra, gas chromatographs, and carbon isotopes show that oils from the two formations are geochemically similar, which suggests that they were generated in the same or similar source rock. Source evaluation data indicate that Cretaceous shales and the Phosphoria Formation are the best potential source rocks in this part of the Overthrust belt. An oil-to-source correlation shows that the Pineview oils are related to the Cretaceous source rocks rather than the Phosphoria. A Cretaceous source is geologically reasonable at Pineview because Cretaceous shales of the subthrust section underlie th Jurassic reservoirs. The geochemistry of the different Cretaceous formations is quite similar, probably because of their generally similar depositional environments. Therefore, it is not possible to determine which Cretaceous formation is actually the source of the Pineview oils.

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