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>Evolution of a highly dilatant fault zone in the grabens of Canyonlands National Park, Utah, USA – integrating fieldwork, ground-penetrating radar and airborne imagery analysis
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Evolution of a highly dilatant fault zone in the grabens of Canyonlands National Park, Utah, USA – integrating fieldwork, ground-penetrating radar and airborne imagery analysis
The grabens of Canyonlands National Park are a young and active systemof sub-parallel, arcuate grabens, whose evolution is the result of saltmovement in the subsurface and a slight regional tilt of the faulted strata.We present results of ground-penetrating radar (GPR) surveys in combination withfield observations and analysis of high-resolution airborne imagery. GPRdata show intense faulting of the Quaternary sediments at the flat grabenfloors, implying a more complex fault structure than visible at the surface.Direct measurements of heave and throw at several locations to infer faultdips at depth, combined with observations of primary joint surfaces in theupper 100 m, suggest a highly dilatant fault geometry.Sinkholes observed in the field as well as in airborne imagery give insightsin local dilatancy and show where water and sediments aretransported underground. Based on correlations of paleosols observed inoutcrops and GPR profiles, we argue that either the grabens in Canyonlands NationalPark are older than previously assumed or that sedimentation rateswere much higher in the Pleistocene.
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