New Evidence for Long-Term, Salt-Related Deformation at Upheaval Dome, Southeast Utah

Abstract

Upheaval Dome is an eroded structural dome that exposes Mesozoic strata along with associated folds, faults and sand injectites in the Paradox basin, SE Utah. Multiple interpretations for its origin have been proposed, but the two remaining viable hypotheses are at opposite ends of the geologic spectrum: one proposing long-term salt-related deformation and growth of the structure, the other a catastrophic meteorite impact. Analysis of stratigraphic field data collected in Triassic to Jurassic-aged strata adjacent to Upheaval Dome reveals: (1) stratigraphic thicknesses from measured sections for the Kayenta Formation (~199 to ~195 Ma) that range from 7 meters to 224 meters, and projected thicknesses in cross section that can exceed 400 meters; (2) distinct changes in facies distributions in relation to mapped structures; (3) localized angular unconformities and stratal-onlap surfaces; (4) blocks of Triassic Chinle Formation encased in younger Jurassic Wingate Sandstone adjacent to thinned, Wingate lobes, that apparently downlap onto the underlying Chinle. Structural analysis at Upheaval Dome reveals: (1) synclinal growth axes and associated depositional centers shift away from the center of the dome throughout the Late Triassic/Early Jurassic; (2) stratigraphic thicknesses increase across normal faults on the scale of meters to tens of meters; (3) thrust faults within the Kayenta Formation verge to the southeast regardless of location around the structure. These structural features and associated growth strata offer compelling evidence for long-term deformation compatible with salt tectonics at Upheaval Dome during the Late Triassic/Early Jurassic. Sparse indicators of catastrophic impact are present in the Kayenta Formation in the form of two shocked quartz grains, orders of magnitude less than would be expected <1 km from a meteorite impact site. We interpret these grains to be detrital and sourced from outside the Paradox basin. In our interpretation of salt-related deformation, we discuss the merits and drawbacks of a model invoking collapse over a buried salt high to a prior model of a pinched-off diapiric feeder to an eroded salt glacier. The possibility that a meteorite impact of Late Permian to Early Triassic age initiated the growth of an isolated salt pillow in the western part of the northern Paradox Basin requires further investigation.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015