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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 68 (1984)

Issue: 7. (July)

First Page: 938

Last Page: 938

Title: Reactivation of Mesozoic Thrusts as Normal Faults, Humboldt Range, North-Central Nevada: ABSTRACT

Author(s): F. R. Heck, D. C. Demets, R. C. Speed


Some low-angle faults in the Humboldt Range of north-central Nevada may be east-verging Mesozoic thrusts that were reactivated as normal faults with westerly displacement. Early deformation in nappes underlain by such faults produced east-verging asymmetric folds of bedding and moderate to steep northwest-dipping penetrative cleavage. These structures, as well as a shallow southeast-plunging Z finite strain axis in nappe rocks, imply west to east compression. Later deformation has younger over older juxtaposition and west-verging asymmetric folds of first foliation. These folds have shallow easterly dipping axial Previous HitplanesNext Hit whose orientations with respect to adjacent low-angle Previous HitfaultNext Hit Previous HitplanesNext Hit and lineations in the Previous HitfaultNext Hit Previous HitplanesNext Hit indicate westerly displacement. The later deformatio thus implies reactivation of the low-angle faults as normal faults. Though timing of normal Previous HitfaultTop motion is uncertain, it appears reasonable to associate it with Cenozoic extension in the Great Basin. Reactivation of thrust faults as low-angle normal faults provides further evidence in support of thin-skinned crustal extension.

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Copyright 1997 American Association of Petroleum Geologists