Abstract

The Garlock fault is an integral part of the plate-boundary deformation system inboard of the San Andreas fault (California, USA); however, the Garlock is transversely oriented and has the opposite sense of shear. The slip history of the Garlock is critical for interpreting the deformation of the through-going dextral shear of the Walker Lane belt–Eastern California shear zone. The Lava Mountains–Summit Range (LMSR), located along the central Garlock fault, is a Miocene volcanic center that holds the key to unraveling the fault slip and development of the Garlock. The LMSR is also located at the intersection of the NNW-striking dextral Blackwater fault and contains several sinistral WSW-striking structures that provide a framework for establishing the relationship between the sinistral Garlock fault system and the dextral Eastern California shear zone. New field mapping and geochronology data (40Ar/39Ar and U-Pb) show five distinct suites of volcanic-sedimentary rock units in the LMSR overlain by Pliocene exotic-clast conglomerates. This stratigraphy coupled with fifteen fault slip markers define a three-stage history for the central Garlock fault system of 11–7 Ma, 7–3.8 Ma, and 3.8–0 Ma. Pliocene to recent slip occurs in a ∼12-km-wide zone and accounts for ∼33 km or 51% of the total 64 km of left-lateral offset on the Garlock fault in the vicinity of the LMSR since 3.8 Ma. This history yields slip rates of 6–9 mm/yr for the younger stage and slower rates for older stages. The LMSR internally accommodates northwest-directed dextral slip associated with the Eastern California shear zone–Walker Lane belt via multiple processes of lateral tectonic escape, folding, normal faulting, and the creation of new faults. The geologic slip rates for the Garlock fault in the LMSR match with and explain along-strike variations in neotectonic rates.

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