STRAIN ACCOMMODATION AND TRANSFER ACROSS THE NORTHERN AND CENTRAL WALKER LANE TRANSITION: KINEMATIC LINKING OF ROTATING AND TRANSLATING CRUST IN AN EVOLVING PLATE BOUNDARY

The Walker Lane is a belt of primarily NW-striking dextral and ENE- to E-striking sinistral fault systems working in concert with the San Andreas fault system to accommodate NW-directed dextral shear along the Pacific-North American plate boundary. At the transition between the central and northern Walker Lane, strain is transferred from translating blocks among the dextral faults of the Walker Lake domain to sinistral faults and oroclinal flexure accommodating vertical-axis rotations in the Carson domain. Detailed geologic mapping and paleomagnetic analysis at the northern end of the Walker Lake domain have identified recent dextral faulting and translation of crustal blocks proximal to the oroclinal flexure. The kinematics and mechanisms of strain transfer at the transition of these disparate fault systems remains enigmatic.

New geologic mapping along this transition shows a narrow ENE-trending, ~2-3 km wide zone with no discrete fault marking the boundary. Dextral faults of the Walker Lake domain abruptly terminate and in part kinematically link with normal faults in the eastern Desert Mountains. Here, the easternmost NNE-striking normal faults transfer strain northeastward into extensional deformation in the central Nevada seismic belt. Farther west in the Desert Mountains, the strike of these normal faults swings ~90° clockwise via oroclinal flexure. The NW-striking dextral faults in the Walker Lake domain project directly into the central part of the orocline and may ramp steeply downward to the brittle-ductile transition, where a middle to lower crustal dextral shear zone may accommodate the clockwise-rotating upper crustal blocks in the orocline. The alignment of the oroclinal flexure with translating blocks bounded by NW-striking dextral faults to both the south and north of the Carson domain suggest a relatively focused and through-going dextral shear zone in the eastern part of the central and northern Walker Lane. This shear zone may ultimately propagate upward through the brittle upper crust and breach the orocline in the Carson domain as this incipient segment of the plate boundary accumulates strain and matures.