Abstract
Deformation and mineral alteration adjacent to a 2 km long segment of the Kern Canyon fault near Lake Isabella, California are studied to characterize the internal structure of the fault zone and to understand the development of fault structure and constitution and the mechanical and chemical processes responsible for them. The 140 km long Kern Canyon fault (KCF) is a fault of 15 km right-lateral separation exhumed from seismogenic depth that cuts batholithic and metamorphic rocks of the southern Sierra Nevada. The fault consists of at least three distinct phases: an early phase of lower-greenschist-grade ductile shear with an S-C' phyllonite, a subsequent, dominant phase of brittle faulting characterized by a through-going zone of cataclastic rock, and a late stage of minor faulting along discontinuous, thin, hematitic gouge zones. The S-C' fabric and subsidiary fault-slip data indicate that both the phyllonitic and cataclastic zones are approximately vertical and strike-slip; slip lineations within the hematitic gouge suggest oblique-slip. The phyllonite zone trends N20-40E and accommodated ~175 m of separation. The cataclastic zone cuts the phyllonite, trends N21E, and consists of foliated and non-foliated cataclasites; it accommodates the majority of displacement along the fault. Abundant veins and fluid-assisted alteration in the rock surrounding the fault zone attest to the presence of fluids of evolving chemistry during both ductile and brittle faulting. Mass balance calculations indicate quartz loss during phyllonite faulting and imply that the fault system was open and experienced a negative change in volume during phyllonite faulting. Mesoscale and microscale fracture intensities decrease with log distance from the foliated cataclasites and approach a relatively low level at approximately 500 m. The internal structure of the Kern Canyon fault is similar to other large displacement faults in that it consists of a broad zone of fractured and altered rock and a narrow zone of intense cataclasis.
Neal, Leslie Ann (2002). Internal structure of the Kern Canyon Fault, California: a deeply exhumed strike-slip fault. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -2002 -THESIS -N43.