DIP OF THE SIERRA NEVADA FRONTAL FAULT SYSTEM ADJACENT TO THE HIGHEST ELEVATIONS OF THE SIERRA NEVADA MOUNTAINS NEAR LONE PINE CALIFORNIA

Uplift of the Sierra Nevada Mountains has been debated for over 100 years, yet the orientation of the fault system that accommodates this uplift, the Sierra Nevada Frontal Fault System (SNFFS), is poorly constrained. Most kinematic models of uplift, extension, and slip rates for the Sierra Nevada Mountains assume 60° dipping range-front normal faults. However, analysis of SNFFS faults near Independence, and farther north near Bishop (Phillips and Majkowski, 2011), suggest shallower dips of 25-35° on some fault sections. In this study, we use differential GPS to remap and survey sections of the SNFFS along 20 km of the range front in the vicinity of Lone Pine, adjacent to Mount Whitney and the highest elevations of the Sierra Nevada Mountains. The x-y-z data from these surveys were assessed using plane-fitting software to determine best-fit fault orientations. Survey results show: (1) the 1.5 km long Carroll Creek section strikes N24W and dips 30°E; (2) the 2 km long Diaz Creek section strikes N41W and dips 22°E; (3) the 1 km long Tuttle Creek section strikes N34W and dips 36°E; and (4) the 2 km long Whitney Portal Road section strikes N24W and dips 28°E. Direct dip measurements on fault exposures at Carroll Creek are 30°E and at Independence Creek to the north are 40°E. Shear fractures adjacent to SNFFS faults near Tuttle Creek and Whitney Portal Road show average fracture dips of 37°E and 33°E, respectively. Our new findings are consistent with studies elsewhere in Owens Valley and suggest that shallow dipping SNFFS faults may extend along most of the range front from at least 15 km south of Lone Pine to north of Bishop. A shallow-dipping SNFFS significantly affects calculations of long-term extension and fault slip rates derived from fault profile and/or total basin to range crest vertical offset estimates. For example, long-term extension rates increase by a factor of three to four using 30° dipping faults rather than assuming 60°.