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Abstract: The Carboniferous-Permian (Late Paleozoic) Hydrocarbon System, Rocky Mountains. U.S. Region, with Analysis of Evidence for Origin of the Central Utah Tar and Heavy Oil Deposits


Carboniferous-Permian rocks are hydrocarbon-productive in several basins of the Rocky Mountains. U.S. region, including the northern Great Plains Williston basin (mainly Miss. intra-Madison and Bakken source); Sweetgrass Arch area of northcentral Montana (Bakken-Exshaw source); the Bighorn and Wind River basins (Permian Phosphoria source), and the Powder River basin (mainly Pennsylvanian source) of Wyoming; the Uinta basin of Utah

and the NW Colo. basins (Phosphoria source); and the Paradox basin of the Four Corners area (Pennsylvanian Paradox Fm. source).

Additional major resources within and stratigraphically related to this system are the central Utah tar and heavy oil sand deposits in Permian and Lower Triassic sand reservoirs, arguably the largest original petroleum accumulation of the lower U.S. 48 states. Possible source of these hydrocarbons includes the Miss. Manning Canyon Shale., Permian Phosphoria Fm., Lower Triassic Moenkopi Fm., and Proterozoic shales. Regional and local palinspastic studies, including stratigraphic, sedimentary facies, paleotectonic, organic-rich potential source rock and reservoir facies distribution, and burial depth-fluid migration history indicate strongly that the Permian Phosphoria organic-rich shales (Meade Peak & Retort) are the probable primary source.

The estimated volume of total original hydrocarbons generated and accumulated in these Late Paleozoic rocks elevates this system to the probable highest rank in the Rocky Mountains. U.S. region.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado