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Abstract: Thermal and Petroleum-Generation History of the Mississippian Eleana Formation and Tertiary Source Rocks, Yucca Mountain Area, Southern Nye County, Nevada

Charles E. Barker

A geochemical and geologic assessment of petroleum potential in the Yucca Mountain area indicates little remaining potential for significant oil and gas generation in the Mississippian Eleana Formation or related Paleozoic rocks, and good but areally restricted potential in Tertiary rocks in Area 8 of the Nevada Test Site. Mesozoic source rocks are not present in the Yucca Mountain area.

The Tertiary source rocks in Area 8 of the Nevada Test Site are typically carbon-rich, and where hydrogen-rich, they are good oil-prone source rocks that are immature to marginally mature with respect to oil and gas generation. A geologically similar occurrence of hydrothermally altered Tertiary source rocks at north Bare Mountain retains little hydrocarbon generation capacity. The implication is that hydrocarbons were generated during hydrothermal alteration and have since migrated out of the source rocks or have been lost during exhumation.

A reconstructed thermal history of the Yucca Mountain area, based on the Eleana Formation, indicates petroleum was generated in the Late Paleozoic and possibly Early Mesozoic and that the oil was lost or metamorphosed to pyrobitumen during later heating, probably related to igneous activity. The Tertiary rocks are still capable of generating oil and gas, but little potential exists for a major hydrocarbon discovery due to the restricted occurrence of good source rocks and their marginal thermal maturity when situated away from intrusions.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada