Abstract

Long-term deformation along the Fish Springs fault in Owens Valley, California, is recorded by offset landforms, including a previously dated cinder cone (39Ar/40Ar, 314 ± 36 ka, 2σ), several debris-flow fans and levees deposited by Birch Creek, stream channels, and lava flows of nearby Crater Mountain. The 10Be and 26Al model exposure ages (n = 68) delimit fan ages and suggest that deposition stopped after ca. 136, 15, 13, and 8 ka. One fan remains active and has undergone deposition throughout the Holocene. Soil development on three fans, where boulders were sampled for 10Be and 26Al analysis, also indicates distinct ages. Together, soil development and cosmogenic isotope data suggest that fan deposits correlate with the Tahoe and late Tioga glaciations. Soil profile development index values from Fish Springs are low compared with those determined elsewhere, suggesting relatively slow rates of soil formation for fan surfaces at Fish Springs and/or modification of soil profiles by surface processes during or following soil 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.–1 for the Fish Springs fault over the past 300 k.y.

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