Structural geology and kinematic history of rocks formed along low-angle normal faults, Death Valley, California

Research Article| October 01, 2003 Structural geology and kinematic history of rocks formed along low-angle normal faults, Death Valley, California Darrel S. Cowan; Darrel S. Cowan 1Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA Search for other works by this author on: GSW Google Scholar Trenton T. Cladouhos; Trenton T. Cladouhos 2Department of Earth and Space Sciences, University of Washington, and WebPE, Edmonds, Washington 98020, USA Search for other works by this author on: GSW Google Scholar Julia K. Morgan Julia K. Morgan 3Department of Geology and Geophysics, Rice University, Houston, Texas 77005, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Darrel S. Cowan 1Department of Earth and Space Sciences, University of Washington, Seattle, Washington 98195-1310, USA Trenton T. Cladouhos 2Department of Earth and Space Sciences, University of Washington, and WebPE, Edmonds, Washington 98020, USA Julia K. Morgan 3Department of Geology and Geophysics, Rice University, Houston, Texas 77005, USA Publisher: Geological Society of America Received: 26 Aug 2002 Revision Received: 16 Feb 2003 Accepted: 12 Mar 2003 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2003) 115 (10): 1230–1248. https://doi.org/10.1130/B25245.1 Article history Received: 26 Aug 2002 Revision Received: 16 Feb 2003 Accepted: 12 Mar 2003 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Darrel S. Cowan, Trenton T. Cladouhos, Julia K. Morgan; Structural geology and kinematic history of rocks formed along low-angle normal faults, Death Valley, California. GSA Bulletin 2003;; 115 (10): 1230–1248. doi: https://doi.org/10.1130/B25245.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Several late Cenozoic low-angle normal, or detachment, faults on the western flank of the Black Mountains are each characterized by the following, in descending structural order: (1) a hanging wall of upper Tertiary to Quaternary sedimentary and volcanic strata that displays little evidence for fault-related damage other than widely spaced planar or listric normal faults; (2) a sharp, planar, and locally striated principal slip plane forming the lower boundary of the hanging wall; (3) an upper zone—zone I—of very fine grained, fault-generated rocks composed dominantly of gouge; (4) a lower zone—zone II—of coarser-grained fault rocks consisting chiefly of foliated breccia; and (5) a variably damaged footwall, consisting of partly mylonitic Precambrian units or Tertiary plutonic rocks, that has been exhumed from depths of 10–12 km since late Miocene time. The fault rocks, which were mostly derived from the footwalls, preserve evidence for cataclastic and particulate flow. Fault rocks contain authigenic minerals but lack the cyclically deformed, mineral-filled syntectonic veins that are abundant in some other late Cenozoic high-angle and strike-slip faults.Meso- and microscale fabrics in zones I and II indicate that finite shear strains increase progressively upward, toward the principal slip plane. In a conceptual kinematic model of a shear box, displacements of the hanging wall produced a shearing flow in the fault rocks below. Some of the slip on the principal slip plane was also partitioned into localized slip on discrete sliding surfaces in zones I and II. Since 770 ka, during the latest stages of incremental deformation in the brittle shear zones, distributed flow in the fault rocks alternated with slip that was chiefly localized on the principal slip planes. In this respect, the detachment faults differ from inactive segments of the San Andreas system, along which displacements were progressively and irreversibly localized onto a single principal slip surface. The strain gradients and corresponding changes in grain size in the shear zones resemble those in mylonitic shear zones except in their symmetry. Strain gradients in the Black Mountains are notably asymmetric: they are present only below the principal slip planes, not above. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.