Paper No. 5
Presentation Time: 10:00 AM
STRUCTURAL OBSERVATIONS AND STRATIGRAPHIC VARIABILITY IN JURASSIC STRATA, UPHEAVAL DOME, CANYONLANDS NATIONAL PARK, UTAH, USA
For several decades, numerous scientists have hypothesized and debated the genesis of the Upheaval Dome structure in Canyonlands National Park, Utah. Currently, two viable hypotheses explain the formation of Upheaval Dome: (1) meteorite impact (Boone and Albritton, 1938; Kriens et al., 1999; Huntoon, 2000; Buchner and Kenkmann, 2008); and (2) pinched-off salt diapir (Jackson et al., 1998). Both hypotheses have evidence and data to support their interpretations. Prior this study, however, there has been no attempt made to combine an in depth stratigraphic investigation of exposed, accessible formations with structural and lithologic observations in the Upheaval Dome area. To achieve this, fifteen, meter-scale stratigraphic sections from inside the dome-encircling syncline (DES), near the synclinal axis, and near the dome-encircling monocline (DEM) were measured through the Kayenta Formation; and 6 geologic cross sections were compiled in a radiating fashion around the dome flanks to include the Navajo Sandstone, the Kayenta Formation, the Wingate Sandstone, the Chinle Formation and the Moenkopi Formation. These cross sections extend from the inside of the DES to the outside of the DEM and display stratigraphic thickness changes and offset synclinal axial traces. Structural data and panoramic photographs of pertinent faults and stratigraphic relationships, such as truncation and onlap surfaces, were also collected in the field.
Investigation of field data reveal various noteworthy observations of Jurassic-aged strata including: (1) Stratigraphic thicknesses from measured sections range from 7 meters to 224 meters in the Kayenta Formation, while projected thicknesses in cross sections can exceed 400 meters; (2) Stratigraphic thicknesses across normal faults from hanging to footwall blocks are unequal on the scale of meters to tens of meters; (3) Several angular discordances, both within individual formations and at the contact between two formations, are evident around the flanks of Upheaval Dome. These particular observations imply long-lived deformation in stratigraphic formations that surround Upheaval Dome.