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The central Wassuk Range of western Nevada is ideally located to investigate the interplay of Basin and Range extension and Walker Lane dextral deformation on the margin of the Basin and Range province. To elucidate the Cenozoic evolution of the range, the author conducted geologic mapping, structural data collection and analysis, geochemical analysis of igneous lithologies, and geochronology. This research delineates a three-stage deformational history for the range. A ~15 Ma pulse of ENE-WSW directed extension at high strain rates (~8.7 Ma) was immediately preceded by the eruption of andesites and was accommodated by high-angle, closely spaced (1-2 km), east-dipping normal faults which rotated and remained active to low angles as extension continued. A post-12 Ma period of extension at low strain rates was accommodated by a second generation of normal faults and two prominent dextral strike slip faults which strike NW, subparallel to the dextral faults of the Walker Lane at this latitude. A new pulse of extension began at ~4 Ma and continues today. The increase in the rate of range-bounding fault displacement has resulted in impressive topographic relief on the east flank of the Wassuk Range and supports a shift in extension direction from ENE-WSW during the highest rates of Miocene extension to WNW-ESE today. The total extension accommodated across the central Wassuk Range since the Middle Miocene is > 200%, with only a brief period of dextral fault activity during the Late Miocene. Data presented here suggest a local geologic evolution intimately connected to regional tectonics, from intra-arc extension in the Middle Miocene, to Late Miocene dextral deformation associated with the northward growth of the San Andreas fault, to a Pliocene pulse of extension and magmatism likely influenced by both the northward passage of the Mendocino triple junction and possible delamination of the crustal root of the southern Sierra Nevada.

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Taylor & Francis Group

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International Geology Review