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Grabens in Canyonlands National Park, Utah, began extending above a layer of evaporites when the Colorado River cut through the overburden. Two-dimensional finite element models simulate the effects of geometry and rock properties on graben configuration and spacing. Only those models having a progressively increasing slope or no slope mimicked the natural upslope graben propagation. Typical rock properties produced the most realistic fault patterns: an initial friction angle of 31°, a cohesion of 1 MPa, and strain weakening comprising cohesion loss and decrease of friction angle to 26°. A tensile stress limit narrowed the grabens and reproduced the vertical upper portion of the natural faults. The viscous salt...
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Results of numerical models and field observations of regularly spaced grabens in Canyonlands National Park, Utah, demonstrate that salt flow beneath a brittle overburden accommodated recent and ongoing westward gravity spreading. Erosion of the Colorado River canyon differentially loaded the underlying viscous salt. In our models, the overlying brittle strata flexed downward toward the canyon, initiating faults near the surface that propagated downward toward the salt contact. Modeled grabens developed sequentially away from the canyon (eastward) as salt was expelled from beneath undeformed strata. After their eastern boundary faults broke through, horst blocks tilted in the opposite direction of initial flexure,...
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