GEOLOGIC MAP OF THE HANGING ROCK CANYON 7.5' QUADRANGLE, INYO COUNTY, CALIFORNIA

The Last Chance Range of northern Death Valley National Park hosts key structural relationships related to pre-subduction contraction along the southwest margin of Laurentia. Elucidating Early Permian tectonism in east-central California is essential for understanding the initial conditions of cordilleran subduction. Located within the modern transtensional Walker Lane, this region is defined by large topographic gradients exposing kilometers of bedrock. Phanerozoic tectonic events are well recorded in the ranges of eastern California, however regionally recognized Permian deformation remains vague due to tectonic overprinting. The Hanging Rock Canyon 7.5-minute quadrangle of the northwest Last Chance Range contains the best exposure of the Early Permian Last Chance thrust. The fault is indicated by Cambrian hanging wall strata in contact with Mississippian rocks in the footwall. The geometry of the thrust is obscured in most areas by intense folds and Cenozoic faults. Rocks of the Last Chance Range are unmetamorphosed and brittlely deformed limiting the application of common analytical techniques to detail a deformation chronology. Thus, detailed structural observations are required to determine the sequence of events. Structural mapping reveals the arenites and carbonates in the hanging wall show minor internal deformation, while Mississippian siltstone and shale of the footwall are intensely deformed. The most notable feature of the Last Chance Range is an overturned recumbent syncline that folds the Last Chance thrust. Upright Mississippian strata are in fault contact with the overturned limb of this fold. In the northeast portion of the map area, the structural style is simpler with upright Carrara Formation and Bonanza King Dolomite thrust over upright Perdido Formation. The disconnect between structural features in the west and east, along with various puzzling structural relationships, point to an overprinting contractional event. The potential for multiple thrusts at the Hanging Rock Canyon locality offers an opportunity to test existing models that call for post-Last Chance thrust Permian deformation. A better understanding of contraction in the Last Chance Range will allow more accurate regional correlations of Early Permian contractional features.