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Geologic framework of the Northern Great Basin

 

 

 

Neotectonic and paleohydrologic framework, central and southern Walker Lane belt, western Great Basin

The geology of Federal lands in the Walker Lane, western Great Basin are important to land and resource managers at the federal, state and regional levels because of active fault hazards, volcano hazards, geothermal resources, ecologic and water resources, proximity to the high level nuclear waste facility, and recreation. A quarter of the relative motion between the Pacific and North American plates is accommodated along the seismically active western margin of the northern Great Basin, and the Owens Valley is the largest basin within this transtensional shear zone. Owens Valley is a graben bounded by normal oblique-slip faults, but it also contains an active axial-valley strike-slip fault (the Owens Valley fault) with late Quaternary basaltic volcanoes at intermittent locations along the fault system. The timing of faulting that formed the Owens Valley graben is controversial; estimates range from about 12 and 6 Ma and faulting may be time transgressive from south to north. The Owens Valley fault ruptured in a large (M 7.75) earthquake in 1872 and several M 5.0-6.2 earthquakes in the late 1900’s. Two seismically active volcanic centers with geothermal power plants—the Coso volcanic field and the Long Valley caldera— lie at the southern and northern ends of Owens Valley, respectively. The most recent volcanic eruptions in this area occurred only 300-600 years ago, along the Inyo-Mono Craters chain and Mono Lake Islands that extend from the northern edge of Long Valley into Mono Basin. Major problems are to understand the timing and kinematics of slip on major faults and relate their structural development to young volcanic centers, basin formation, and transtensional crustal thinning.

Active and late Pleistocene volcanic systems are of interest to the U.S.G.S Volcano Hazards mission and are associated with geothermal activity currently investigated by the NEHRP Geothermal Assessment Project. Mono Basin, and Long Valley lie along the Sierra Nevada Frontal Fault, which bonds the west margin of the Walker Lane. Other significant geothermal systems lie within the central Walker Lane where active deformation appears to step eastward towards the Columbus Marsh and central Walker Lake area. Quaternary deformation rates have not been established within the stepover zone. Likewise, the Plio-Pleistocene structural evolution of the basins and influence on regional drainage systems remains largely unstudied.

 

   

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