KINEMATIC EVOLUTION OF THE OLINGHOUSE FAULT IN THE NORTHERN WALKER LANE, WESTERN NEVADA: A LEFT-LATERAL FAULT ZONE IN A REGION OF DEXTRAL SHEAR

The Olinghouse fault zone (OFZ) is an ~35 km-long ~6 km-wide ENE-striking sinistral-normal oblique fault in the northern Walker Lane (NWL) south and east of Reno, NV. NW-striking dextral faults in the NWL accommodate 15-25% of the Pacific-North America plate motion. Similar ENE- to NE-striking transverse faults populate domains within the Walker Lane-eastern California shear zone and San Andreas fault systems. The OFZ is the best exposed left-lateral fault in the NWL, the youngest and least developed part of the Pacific-North America plate boundary. Therefore, understanding its kinematic evolution may elucidate the role of other transverse faults in developing continental transform boundaries.

We used detailed geologic mapping, structural analysis of 80 fault surfaces, and tephrochronologic correlations to constrain the evolution of the OFZ. Tilt fanning and coeval regional basin formation suggest that the OFZ initiated as a NNE-striking normal fault ~12-11 Ma. Regional relations indicate that left slip and associated clockwise rotation of fault blocks began after 8 Ma. About 1-3 km of left-lateral separation and 1-2 km of normal separation are recorded across the fault zone.

Kinematic models that had been proposed for similar sinistral zones in the Pacific-North America transform boundary were tested to develop a model for the kinematic role of the OFZ in the NWL. Most strands of the OFZ are interpreted as forming 12-11 Ma as NNE-striking Basin and Range normal faults. Around 8 Ma, the northernmost strand(s) developed as ENE-striking, conjugate Riedel shears to the northward-propagating dextral shear in the Walker Lane. Fault blocks to the south and their bounding NNE-striking normal faults began clockwise rotation at this time and have since rotated ~45 deg. About 3 Ma, the OFZ began to serve as a sinistral-normal transfer zone between the northern end of E-dipping normal faults of the Sierra Nevada frontal fault zone to the west and northerly striking normal fault systems in the northwestern Great Basin. Thus, the OFZ appears to have served multiple kinematic roles in this rapidly evolving region, implying perhaps a complex history for other sinistral fault zones along the Pacific-North America dextral-transform boundary.