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dc.contributor.authorSpencer, Jon E.en
dc.contributor.authorReynolds, Stephen J.en
dc.contributor.authorScott, Robert J.en
dc.contributor.authorRichard, Stephen M.en
dc.date.accessioned2017-04-12T17:42:09Z
dc.date.available2017-04-12T17:42:09Z
dc.date.issued2016-12
dc.identifier.citationShortening in the upper plate of the Buckskin-Rawhide extensional detachment fault, southwestern U.S., and implications for stress conditions during extension 2016, 35 (12):3119 Tectonicsen
dc.identifier.issn02787407
dc.identifier.doi10.1002/2016TC004345
dc.identifier.urihttp://hdl.handle.net/10150/623118
dc.description.abstractDetailed geologic mapping in the Buckskin, Rawhide, and Artillery Mountains in western Arizona identified numerous folds in Oligocene-Miocene strata above the Buckskin-Rawhide extensional detachment fault. The folds are above or adjacent to the Harcuvar metamorphic core complex, which was uplifted and exposed by top-northeast normal faulting and penetrative shearing at similar to 27-9 Ma. Strata deposited during extension were folded, and the folds are truncated by the detachment fault, demonstrating that folding occurred during the period of extensional faulting. Fold axes are approximately perpendicular to regional extension direction. In two of the four areas of folding described here, alluvial-fan deposits derived partially from lower plate mylonitic rocks are the stratigraphically highest folded strata. Folding could have occurred above low-angle normal faults with curved or ramp-flat geometries, but fold abundance, large size, high degree of closure, and steep northeastward dips of the northeast limbs of anticlines lead us to consider the possibility that at least some folds reflect local shortening in the same direction as regional extension. Application of critical-taper theory to an extensional wedge with very low basal friction indicates that wedge shortening would be expected if the wedge developed a sufficient surface slope that was downhill away from the wedge tip. Such a slope could have developed late during extension either because core-complex uplift tilted the wedge away from the core complex or because alluvial fans shed off the core complex produced such a slope. In either case, wedge shortening would promote core-complex denudation.
dc.description.sponsorshipCommonwealth Post-graduate Research Award; U.S. Geological Survey National Cooperative Geologic Mapping Program under STATEMAP [G11AC20455]en
dc.language.isoenen
dc.publisherAMER GEOPHYSICAL UNIONen
dc.relation.urlhttp://doi.wiley.com/10.1002/2016TC004345en
dc.rights©2016. American Geophysical Union. All Rights Reserved.en
dc.titleShortening in the upper plate of the Buckskin-Rawhide extensional detachment fault, southwestern U.S., and implications for stress conditions during extensionen
dc.typeArticleen
dc.contributor.departmentUniv Arizona, Dept Geoscien
dc.identifier.journalTectonicsen
dc.description.note6 month embargo; First published: 29 December 2016en
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en
dc.eprint.versionFinal published versionen
dc.contributor.institutionDepartment of Geosciences; University of Arizona; Tucson Arizona USA
dc.contributor.institutionDepartment of Geology; Arizona State University; Phoenix Arizona USA
dc.contributor.institutionARC Centre of Excellence in Ore Deposits; University of Tasmania; Hobart Tasmania Australia
dc.contributor.institutionDepartment of Geosciences; University of Arizona; Tucson Arizona USA
refterms.dateFOA2017-06-30T00:00:00Z
html.description.abstractDetailed geologic mapping in the Buckskin, Rawhide, and Artillery Mountains in western Arizona identified numerous folds in Oligocene-Miocene strata above the Buckskin-Rawhide extensional detachment fault. The folds are above or adjacent to the Harcuvar metamorphic core complex, which was uplifted and exposed by top-northeast normal faulting and penetrative shearing at similar to 27-9 Ma. Strata deposited during extension were folded, and the folds are truncated by the detachment fault, demonstrating that folding occurred during the period of extensional faulting. Fold axes are approximately perpendicular to regional extension direction. In two of the four areas of folding described here, alluvial-fan deposits derived partially from lower plate mylonitic rocks are the stratigraphically highest folded strata. Folding could have occurred above low-angle normal faults with curved or ramp-flat geometries, but fold abundance, large size, high degree of closure, and steep northeastward dips of the northeast limbs of anticlines lead us to consider the possibility that at least some folds reflect local shortening in the same direction as regional extension. Application of critical-taper theory to an extensional wedge with very low basal friction indicates that wedge shortening would be expected if the wedge developed a sufficient surface slope that was downhill away from the wedge tip. Such a slope could have developed late during extension either because core-complex uplift tilted the wedge away from the core complex or because alluvial fans shed off the core complex produced such a slope. In either case, wedge shortening would promote core-complex denudation.


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