Abstract Title: PAIRED MAGMATIC-TECTONIC EVOLUTION OF THE NORTHERN WALKER LANE 
(NWL), NORTHWESTERN NEVADA AND NORTHEASTERN CALIFORNIA

Abstract Author(s): Henry, Christopher D. (University of Nevada, Reno) - 
Faulds, James E. (University of Nevada, Reno)  

Abstract: The NWL consists of two sets of NW-striking, dextral faults that take 
up much of Pacific-North American plate motion not on the San Andreas system. 
The eastern set, which comprises the traditional Walker Lane, consists of 
three, left-stepping, en-echelon faults over a 30 km width; these developed at 
~3-5 Ma and have accumulated measurable displacements of a few to ~10 km. The 
western faults are seismically active but have not accumulated measurable 
displacement, presumably because they developed only recently. All faults 
developed in a region that had undergone complex magmatism and tectonism that 
prepared the area for strike-slip faulting. An ancestral Cascades arc was 
active at least by 28 Ma in western NV and by 17 Ma was established all along 
the NW-striking belt that was to become the NWL. Arc magmatism continued at 
least until 3 Ma at the latitude of Reno and remains active at Lassen Peak, 75 
km to the NW. Generally E-W extension migrated westward into the region, 
establishing the evolving Sierra Nevada - Basin and Range boundary, with major 
episodes at ~12 and 3 Ma. The eastern NWL faults commonly reactivated major 
extensional faults. The strike-slip faults parallel but are 2-5 km outboard of 
major basin-bounding normal faults. The western limit of extension and area of 
strike-slip faults coincide with the area of ancestral arc magmatism. Magmatism 
presumably heated and therefore weakened the crust. Although extension and 
strike-slip faulting partly avoided the relatively cold and therefore strong 
Sierra Nevada batholith, the NWL cuts through the batholith north of Reno where 
arc magmatism weakened the crust.