New Estimates of Late Pleistocene Slip Rate Along the Panamint Valley Fault System: Implications for Distributed Shear in Eastern California
Abstract:Despite decades of study, the distribution of fault slip within the eastern California shear zone (ECSZ) remains incompletely understood. Along the Panamint Valley fault system (PVFS), Late Pleistocene - Holocene slip rates are sparse, limited to a single site along the southernmost fault segment (~2-3 mm/yr). However, geodetic results along the Hunter Mountain fault, a strike-slip fault linked to the northern PVFS, suggest slip rates as high as 5-6 mm/yr. Here, we present preliminary results from an investigation of displaced alluvial fan surfaces along the central PVFS, near Jail Canyon. We utilize LiDAR-derived high resolution topography, field mapping, and soil characterization to reconstruct displacement. Comparison of soil characteristics to a calibrated regional soil chronosequence constrains the age of alluvial surfaces; analysis of a depth profile using 10Be cosmogenic isotopes is underway.
The PVFS near the mouth of Jail Canyon is characterized by a ~500 m wide zone of distributed deformation. Dextral offset of channels and associated alluvial surfaces across a N45W strike-slip fault marks lateral displacement, while N-S striking normal faults accomplish E-W extension. We exploit the preservation of a large relict channel to reconstruct the cumulative displacement from these faults. Offset crests of the channel levees suggest 115±10 m of right-lateral displacement, while the sum of extension across the fault zone is 34±3 m. Together, these suggest a cumulative slip of 148±13m oriented in a 310° direction, consistent with dextral-oblique motion across the PVFS. Soil development in alluvial surfaces is consistent with soils dated regionally between 30 – 50 ka. These preliminary results suggest that a minimum slip rate across the central PVFS is 4.1±1.3 mm/yr. Our results imply that the PVFS accomplishes a greater fraction of dextral shear, north of the Garlock fault, than previously thought.