Seismic reflection study of Upheaval Dome, Canyonlands National Park, Utah

The origin of Upheaval Dome, in Canyonlands National Park of southeastern U tah, has been a topic of controversy among geologists and planetary scienti sts. The structure has long been thought to have been created by salt diapi rism from the underlying Paradox Formation. Recent studies have suggested t hat impact could have formed the dome. To test the various hypotheses, we a cquired, processed, and interpreted seismic reflection data within and adja cent to the structure. Both conventionally stacked and prestack-migrated im ages show <100 m relief in the Paradox Formation, contrary to salt diapiris m hypotheses. Further, we have identified features within the images typica l of impact structures, such as listric normal faults having displacements toward the center of the dome. Deformation occurs in two depth ranges, with the faulting that created the central uplift appearing only above the Herm osa Formation, in the upper 800 m of the structure. The images also suggest limited fracturing of the Hermosa and salt flow in the Paradox Formation, perhaps due to gravitational relaxation of the crater form. Our image of a nearly flat top of the Paradox salt strongly favors an impact origin for Up heaval Dome.