Geometry, kinematics and age of the northern half of the White Mountain shear zone, eastern California and Nevada
Sullivan, Walter Andrew
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The White Mountain shear zone (WMSZ) is a zone of intense penetrative deformation that lies along the western front of the northern White-Inyo Range in eastern-most California and western-most Nevada. The northern half of the WMSZ is characterized by a NNE to NNW-striking steeply dipping foliation and associated shallowly plunging NNE to NW-trending stretching lineations. S-C fabrics observed in outcrop, microstructural shear sense indicators and kilometer-scale foliation geometry all indicate dextral movement. Localized discrete zones of coeval steeply plunging stretching lineations are present in the northern half of the WMSZ. Microstructural data from these domains indicate a high component of pure shear within a separate coeval kinematic framework and hence a transpressional history. The WMSZ appears to be tectonically related to both the Sierra Crest shear system to the west and the Santa Rita shear system to the south. Correlation between the WMSZ and the Santa Rita shear system indicates that Late Cretaceous dextral transpression may extend up to ~120 km along the western front of the White-Inyo Range. Cross-cutting relationships with Late Cretaceous plutons bracket the age of the WMSZ at between 72-92 Ma. A lack of annealing recrystallization in deformed quartz and the presence of high temperature crystallographic fabrics near the margins of the ca. 72 Ma Boundary Peak pluton indicate significant strain accumulation within the WMSZ subsequent to emplacement of the Boundary Peak pluton. These observations extend the duration of Late Cretaceous dextral transpression in eastern California to at least as recent as 72 Ma.
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