Articles | Volume 6, issue 3
Research article
21 Jul 2015
Research article |  | 21 Jul 2015

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

M. Kettermann, C. Grützner, H. W. van Gent, J. L. Urai, K. Reicherter, and J. Mertens

Abstract. The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate grabens, whose evolution is the result of salt movement in the subsurface and a slight regional tilt of the faulted strata. We present results of ground-penetrating radar (GPR) surveys in combination with field observations and analysis of high-resolution airborne imagery. GPR data show intense faulting of the Quaternary sediments at the flat graben floors, implying a more complex fault structure than visible at the surface. Direct measurements of heave and throw at several locations to infer fault dips at depth, combined with observations of primary joint surfaces in the upper 100 m, suggest a highly dilatant fault geometry. Sinkholes observed in the field as well as in airborne imagery give insights in local dilatancy and show where water and sediments are transported underground. Based on correlations of paleosols observed in outcrops and GPR profiles, we argue that either the grabens in Canyonlands National Park are older than previously assumed or that sedimentation rates were much higher in the Pleistocene.

Short summary
This paper combines fieldwork, ground-penetrating radar (GPR) and remote sensing in the jointed and faulted grabens area of Canyonlands National Park, Utah, USA. GPR profiles show that graben floors are subject to faulting, although the surface shows no scarps. We enhance evidence for the effect of preexisting joints on the formation of dilatant faults and provide a conceptual model for graben evolution. Correlating paleosols from outcrops and GPR adds to estimates of the age of the grabens.