Slip rates on the Fish Springs fault, Owens Valley, California, deduced from cosmogenic Be-10 and Al-26 and soil development on fan surfaces

Long-term deformation along the Fish Springs fault in Owens Valley, Califor nia, is recorded by offset landforms, including a previously dated cinder c one (Ar-39/Ar-40, 314 +/- 36 ka, 2 sigma), several debris-flow fans and lev ees deposited by Birth Creek, stream channels, and lava flows of nearby Cra ter Mountain. The Be-10 and Al-26 model exposure ages (n = 68) delimit fan ages and suggest that deposition stopped after ca, 136, 15, 13, and 8 ka. O ne fan remains active and has undergone deposition throughout the Holocene. Soil development on three fans, where boulders were sampled for Be-10 and Al-26 analysis, also indicates distinct ages. Together, soil development an d cosmogenic isotope data suggest that fan deposits correlate with the Taho e and late Tioga glaciations. Soil profile development index values from Fi sh Springs are low compared with those determined elsewhere, suggesting rel atively slow rates of soil formation for fan surfaces at Fish Springs and/o r modification of soil profiles by surface processes during or following so il formation. Age estimates and measured offsets of the Fans are consistent with a long-term vertical slip rate of 0.24 +/- 0.04 m k.y.(-l) for the Fi sh Springs fault over the past 300 k.y.