GEOLOGIC MAPPING OF THE STANSBURY RANGE, UTAH, AND IMPACTS FOR HYDROLOGY OF THE REGION

Catastrophic wildfires in 1991 on the east slope of the Onaqui Mountains removed 25-50+ year-old Utah junipers from upland regions and subsequently 68 springs emerged from two small watersheds. The Clover Creek Coordinated Resource Management Planning Unit was developed for long-term, watershed-scale studies. Geologic mapping of the Deseret Peak East Quadrangle is part of this effort; in addition, urban development requires identification of the watershed components before development. The region consists of Cambrian through Pennsylvanian quartzites, carbonates, and shales that have been deformed during Mesozoic compression and Cenozoic extension. These events have created a broad anticline trending N5°E with 30°W and 60°-overturned east dipping limbs; a large thrust fault cutting diagonally across steeply dipping beds on both blocks, striking N12°W-N11°E dipping 45°-55°E with a flat-ramp-flat geometry from south to north, indicating a pre-existing footwall structure. A major syncline and at least two small asymmetrical sub-parallel folds mapped on the east side of the range with vertical to strongly overturned dips along the western flank and 30°-45°SW dips along the eastern flank trending N20°W and plunging steeply to the south. Associated with this deformation a variety of normal faults both within the range and at the range-basin margin are abundant with fractures rocks throughout the study area. Large areas of Quaternary colluvial deposits unrelated to Pleistocene glaciation are contained in relatively high regions of the range, burying drainages and mantling hillslopes. The area is dominated by bedrock springs and seeps at base of Quaternary units. The influence of bedrock on groundwater flow paths and stream baseflow is suggested by local anecdotal reports that high snowfall in the Deseret Peak East area of the Stansbury Mountains north of the study area generates high discharge to the south in Clover Creek though they are not in the same drainage basin.