Rates of extension along the Fish Lake Valley Fault and transtensional deformation in the Eastern California shear zone-Walker Lane Belt

The oblique-normal-dextral Fish Lake Valley fault accommodates the majority of Pacific-North America plate-boundary deformation east of the San Andreas fault in the northern part of the Eastern California shear zone. New rates for the extensional component of fault slip, determined with light imaging and detection (LiDAR) topographic data and 10Be geochronology of four offset alluvial fans, indicate a northward increase in extension rate. The surface exposure ages of these fans range from ca. 71 ka at Perry Aiken Creek and Indian Creek to ca. 94 ka and ca. 121 ka at Furnace Creek and Wildhorse Creek, respectively. These ages, combined with the measured vertical components of slip at each site, an assumed 60° fault dip, and a N65°E extension direction, yield calculated late Pleistocene-Holocene horizontal extension rates of 0.1±0.1, 0.3±0.2, 0.7 +0.3/-0.1, and 0.5 +0.2/-0.1 mm/yr at Furnace Creek, Wildhorse Creek, Perry Aiken Creek, and Indian Creek, from south to north, respectively. Comparison of these rates with geodetic measurements of ∼1 mm/yr of N65°E extension across the northern Eastern California shear zone indicates that the Fish Lake Valley fault accommodates approximately half of the current rate of regional extension. When summed with published rates of extension for faults at the same latitude, the Fish Lake Valley fault data indicate that long-term geologic deformation rates are commensurate with short-term geodetic extension rates. The northward increase in Pleistocene extension rates is opposite the northward decrease in dextral slip rate trend along the Fish Lake Valley fault, likely reflecting a diffuse extensional transfer zone in northern Fish Lake Valley that relays slip to the northeast across the Mina Deflection and northward into the Walker Lane belt.