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Abstract: Geologic Differences with Structural Similarities: A Comparison of the Green River and Strawn Basins


Both the Green River and Strawn Basins are elongate structural features that owe their configurations primarily to regional thrust systems. Geologic differences between the two basins are significant. First, the Green River Basin is bounded on three sides by basement thrusts. The Strawn Basin is bounded only on one side by a thrust that does not involve basement. Secondly, the Green River Basin mainly produces gas from Cretaceous to Paleocene age clastic reservoirs. In contrast, the Strawn Basin is most known for oil production from Ordovician age carbonates. Third, while both horizontal and vertical displacements are important in the Green River Basin, horizontal displacement is predominant in the Strawn Basin. In addition, geophysical imaging of the Wind River Thrust is best accomplished by aeromagnetics, while the Ouachita Thrust is better seen by gravity.

Despite all of these differences, however, there are analogous structural styles in front of both of the thrust systems. Most notable of these similarities is a pattern of cross-cutting features normal to the trends of the two thrust systems. These crosscutting lineaments have been interpreted from aeromagnetic and gravity data as the result of slip due to differential compression on adjoining segments of the thrust belts. Structurally, these lineaments are believed to be near-vertical tear faults. Well control supports this interpretation. Although there are significant geologic differences, exploration programs in basins bounded by thrust systems should consider the existence of fault systems with considerable displacement normal to the thrust zone.

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