Abstract

Oil wells drilled on Bowes Dome have provided data to help interpret some rather unusual structural features noted in this area. Bowes Dome is a gentle, symmetrical structure several miles in diameter with closure of more than 100 ft. A great many normal faults cut the shallow strata on the dome, but they do not extend to depth and thus do not involve the strata underlying the upper part of the Colorado Shale [Upper Cretaceous]. The normal faults cause a NE.-SW.-trending graben across the crest of the dome, where the strata have parted as a result of gravity sliding down the flanks. At least 1000 ft of separation occurs across this feature but the sliding involves only strata above a well-defined slippage plane in the upper part of the Colorado Shale. This unusual structure supports Frank Reeves' hypothesis regarding the nature of thrust faults in this area. Presumably the strata which have slid down the flanks of Bowes Dome have caused shallow thrust faults around it. Bowes Dome is thus a small-scale model and the Bearpaw uplift a larger-scale example of a type of shallow subsidiary deformation caused primarily by gravity sliding.

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