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A relationship between strike-slip faults and the process of drape folding of layered rocks

Robert A. Cook
Robert A. Cook
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January 01, 1978

The origin of strike-slip faults in the Rocky Mountains foreland is somewhat of an enigma; these faults occur in an area where the basement deformation has primarily involved vertical movements. Some of these faults may have originated not from lateral shifts within the crystalline basement, but from an interaction of detached and laterally shifting layers within the sedimentary pile and from the dynamics of drape folding.

The folds and related structures of Dinosaur National Monument of Colorado and Utah suggest such an origin for some strike-slip faults. These folds and related features evolved with the uplift and brittle deformation of the Uinta Mountains. Uplift, tilting, and extension along the south flank of this range ruptured the basement core into an array of rigid blocks. During this deformation, the Weber Formation became detached and slid between 1,000 and 1,500 m southward. Where the formation encountered rising steps (fault blocks) in the basement surface that were aligned normal to the sliding direction, it became draped and often thickened. Where steps did not exist, the lateral sliding was accommodated by buckle-type folding. In one region, however, the combination of lateral sliding, drape folding, and the effects of a low, inclined ramp structure caused the Weber Formation to tear in a small strike-slip fault with possibly 1,000 to 1,500 m of offset.

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GSA Memoirs

Laramide Folding Associated with Basement Block Faulting in the Western United States

Vincent Matthews, III
Vincent Matthews, III
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Geological Society of America
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Publication date:
January 01, 1978




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