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Flattening strain during coordinated slip on a curved fault array, Rhodes Salt Marsh extensional basin, central Walker Lane, west-central Nevada

By
Luigi Ferranti
Luigi Ferranti
Dipartimento di Scienze della Terra, Università Federico II, Napoli, 80138, Italy
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John S Oldow
John S Oldow
Department of Geosciences, University of Texas at Dallas, Richardson, Texas 75080-3021, USA
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John W Geissman
John W Geissman
Department of Earth and Planetary Sciences, MSC03 2040, University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
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Mark M Nell
Mark M Nell
Department of Geological Sciences, University of Idaho, Moscow, Idaho 83844-3022, USA
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Published:
April 01, 2009

Integrated mapping, fault-kinematic, paleomagnetic, and gravity analyses around the Rhodes Salt Marsh extensional basin, located within the east-west–trending Mina deflection of the central Walker Lane, reveal that from 8.0 to 9.0 km of late Cenozoic displacement was accommodated on a curved array of faults. The dominant slip on the faults systematically varies from left-oblique, to normal, and to right-oblique as fault strike changes from east, to north-northeast, and to north-northwest, respectively. Kinematic consistency of fault slickenline rakes, preservation of displacement budget, and paleomagnetic data from a pluton and volcanic rocks in the fault-system hanging wall indicate that the curved fault geometry is primary and not due to superposition of two fault systems nor to later vertical-axis rotation. Large-magnitude extension was localized at the apex of the curved faults and resulted in the formation of an ~3.0-km-deep prismatic basin beneath Rhodes Salt Marsh. The offset geologic structures and geophysical basin models indicate that hanging-wall displacement diverged around the curved fault array and resulted in finite flattening, with primary and secondary extensional axes oriented west-northwest and north-northeast, respectively. Fault-slip inversion yields two directions of extension consistent with the finite strain axes, and slickenlines with mutually crosscutting relations indicate formation during incremental flattening. Although broadly contemporaneous, extension parallel to the primary and secondary extension axes alternated at periods ranging from months to as much as several hundred thousand years. Large through-going structures sustained extension directions recorded geodetically and seismologically through multiple seismic cycles. In contrast, the alternation between primary and secondary extension directions recorded by a strainmeter suggests that, on small structures contained within fault-bounded blocks, the two extension directions alternated over time scales of as little as 2 yr.

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Contents

GSA Special Papers

Late Cenozoic Structure and Evolution of the Great Basin-Sierra Nevada Transition

John S. Oldow
John S. Oldow
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Patricia H. Cashman
Patricia H. Cashman
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Geological Society of America
Volume
447
ISBN print:
9780813724478
Publication date:
April 01, 2009

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