Paper No. 3
Presentation Time: 9:30 AM
PRELIMINARY FIELD INVESTIGATION INTO THE RELATIONSHIP BETWEEN HOODOO FORMATION AND FOOTWALL SHEARING OF THE RUBY'S INN THRUST FAULT, BRYCE CANYON, UTAH
The Ruby’s Inn Thrust Fault, located in the Bryce Canyon region, is an uncharacteristic demonstration of a south-directed shortening episode located near the predominately east-directed contractional structures of the Sevier Orogeny. The Paleocene to Eocene Claron Formation in the footwall of the Ruby’s Inn Thrust contains conjugate shear sets and vertical fault planes with slickensides and slickenlines, indicating complex multidirectional shearing. George Davis, in his 1997 Field Guide to the Geologic Structures in the Bryce Canyon Region, Utah, stated that these footwall structures are relatable to the Ruby’s Inn thrusting. Davis also suggested that the formation of the hoodoos in Bryce Canyon may have been caused, in part, by the deformation associated with the faulting and not solely by vertical jointing and differential weathering and erosion. During the 2011 field season, we found that structures within the hoodoo outcrops of the Claron Formation also demonstrate displacement along both vertical and sub-horizontal conjugate shear structures. In this study, we characterized the orientation, intensity, and geographical extent of these conjugate shear structures, vertical fault planes, and slickenlines in the Claron Formation. We found that the deformation was not observed in the hanging wall but is present in the footwall in varying intensities on a roughly north-to-south transect of outcrops about two kilometers outside the western boundary of Bryce Canyon National Park. This deformation begins directly south of the main thrust described by previous researchers. Our research supports the idea that the deformation structures were a significant cause in the formation of hoodoos found in the Claron.