| The Olinghouse fault zone cuts a well-exposed section of Oligocene-Miocene volcanic and sedimentary rocks in the eastern Truckee River Canyon in west-central Nevada. It lies within the northern Walker Lane, part of a larger, northwest-striking zone of dextral shear (Walker Lane-eastern California shear zone) that accommodates 15-25% of Pacific-North America plate motion several hundred kilometers inboard of the San Andreas transform. The Olinghouse fault is ∼35 km long, ∼6 km wide, strikes east-northeast, and accommodates primarily left-lateral motion. Similar transcurrent left-lateral and oblique faults and fault systems populate regions within the Walker Lane-eastern California shear zone and San Andreas fault systems. The Olinghouse fault is the best exposed left-lateral fault in the northern Walker Lane, which is the youngest and least developed part of the Pacific-North American plate boundary. Understanding its kinematic development may therefore elucidate the kinematic role of other sinistral fault systems within this right-lateral transform plate boundary.; To assess the kinematic role of the Olinghouse fault zone, ∼90 km 2 of the eastern portion of the fault zone were mapped (1:24,000), and kinematic data were collected on ∼80 fault surfaces. Most fault strands strike ∼067° and dip subvertically. Displacement across the fault strands is dominantly left-lateral with a small normal component. About 1-3 km of left-lateral offset and 1.4-3 km of vertical separation are documented, though total displacement is poorly constrained due to a lack of piercing lines or distinct lithologies. Fault-parallel folds are interpreted to be extensional in origin, whereas folds that trend west-northwest are parallel to the regional least principal strain axis and are interpreted as transtensional. Normal faulting began ∼12-11 Ma as documented by tilt fanning. Regional relations suggest that strike-slip faulting began after ∼8 Ma.; Four non-exclusive models have been proposed to explain left-lateral faulting in a dextral shear zone: (1) extensional transfer zone, (2) conjugate Riedel shear, (3) strike-slip transfer zone, and (4) vertical-axis block rotation. Most of the fault strands are interpreted to have formed -12-11 Ma as north-northeast-striking Basin and Range normal faults. Around 8 Ma, the northernmost strand of the Olinghouse fault zone formed as a secondary Riedel shear within the broad dextral shear zone of the Walker Lane. Shortly thereafter (perhaps coevally), the Olinghouse fault zone began accommodating the clockwise rotation of fault blocks. About 3 Ma, the fault began to serve as a transfer zone between the east-dipping normal faults at the northern end of the Sierra Nevada frontal fault system and northerly striking normal fault systems within the northwestern Great Basin. |
