Abstract: Constraints on the Origin of Upheaval Dome, Paradox Basin, Utah

D. D. Schultz-Ela, M. P. A. Jackson, M. R. Hudec, R. C. Fletcher, M. L. Porter, I. A. Watson

Upheaval Dome is a breached, subcircular Mesozoic dome underlain by Permian Paradox evaporites in Canyonlands National Park. Hypotheses for its structural origin include rise of an underlying salt dome, meteorite impact, and, as newly proposed here, the stem pinch-off below an overhanging diapiric bulb or salt extrusion removed by erosion. Stratigraphic and structural evidence acquired during our recent detailed mapping constrains the type of deformation and its timing, and supports the hypothesis of diapiric pinch-off. Ubiquitous constriction in the center of the dome and an early protracted deformation history rule out the hypotheses of simple deformation in a salt dome roof or by meteorite impact.

The dome is rimmed by a monoclinal kink bending sharply into a gentle rim syncline. Overall, dips increase inward from the synclinal trace to less than, or equal to 60°, elevating strata above their regional elevation. In the rim syncline, the Wingate Sandstone and overlying Kayenta Formation are severely thinned by circumferential ramp-flat extensional faults that dip mostly inward but also outward. Nearer the center, centripetal thrust duplexes thicken the flaggy Kayenta. Within the eroded center of the dome, the deeper Moenkopi Formation is complexly deformed by subradial thrusts closing like a camera diaphragm, accompanied by subradial folds and injected by clastic dikes.

Sedimentary and deformation structures indicate that protracted and noncatastrophic events affected Upheaval Dome but not its surroundings. The Wingate and Kayenta show primary thickness changes and erosional truncations resulting from structurally related relief. Tight, disharmonic growth folds of anomalously short wavelength without microfracturing require deformation of the thick, massive Wingate before cementation.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994