Kinematics of Franciscan Complex exhumation: New insights from the geology of Mount Diablo, California

This is the authors' abstract. We don't add key points for this paper.

Research Article| May 01, 2008 Kinematics of Franciscan Complex exhumation: New insights from the geology of Mount Diablo, California Kerstin Schemmann; Kerstin Schemmann † 1Institut für Geologische Wissenschaften, Freie Universität Berlin, Malteser Str. 74-100, 12249 Berlin, Germany †Corresponding author. Present address: Geo-forschungszentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany. Tel.: +49-331-288-1315; Fax: +49-331-288-1370; E-mail: kschem@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Jeffrey R. Unruh; Jeffrey R. Unruh § 2William Lettis and Associates, 1777 Botelho Drive, Suite 262, Walnut Creek, California 94596, USA §E-mail: unruh@lettis.com Search for other works by this author on: GSW Google Scholar Eldridge M. Moores Eldridge M. Moores # 3Department of Geology, University of California, One Shields Avenue, Davis, California 95616-8605, USA #E-mail: moores@geology.ucdavis.edu Search for other works by this author on: GSW Google Scholar GSA Bulletin (2008) 120 (5-6): 543–555. https://doi.org/10.1130/B26056.1 Article history received: 12 Jun 2006 rev-recd: 18 Jul 2007 accepted: 19 Jul 2007 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kerstin Schemmann, Jeffrey R. Unruh, Eldridge M. Moores; Kinematics of Franciscan Complex exhumation: New insights from the geology of Mount Diablo, California. GSA Bulletin 2008;; 120 (5-6): 543–555. doi: https://doi.org/10.1130/B26056.1 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 Three major lithotectonic units of an ancient arc-trench system are present in western California. In ascending structural order, they include: the Franciscan Complex, a remnant accretionary prism partly including high-pressure (blueschist-facies) metamorphic rocks in a subduction mélange; the relatively unmetamorphosed Coast Range ophiolite; and the Great Valley Group forearc sediments. In the Mount Diablo study area east of San Francisco, the subduction complex and ophiolite are juxtaposed across the Coast Range fault, and together they represent a structurally attenuated section through the ancestral forearc crust exposed by uplift and folding of the late Cenozoic Mount Diablo anticline. The Coast Range fault is locally associated with a sheared zone in the lower part of the attenuated ophiolite. Shear-sense indicators in the serpentinite, such as S-C fabrics, rotated clasts, and slick-enfibers, record the deformation kinematics and consistently indicate that the ophiolite moved down in a normal sense relative to the Franciscan rocks in the modern reference frame. Based on these kinematic relations and metamorphic facies contrasts between the Franciscan and the Coast Range Ophiolite, as much as 6–18 km structural attenuation has occurred along the Coast Range fault. After restoration of vertical axis rotation and late Cenozoic fold deformation, the Coast Range fault dips at a low angle toward the northeast, and shear-sense data restore to top-to-the-northeast motion on the Coast Range fault, implying normal displacement of the ophiolite with respect to the structurally underlying Franciscan Complex. These relations are consistent with the hypothesis that the Franciscan rocks were exhumed by crustal attenuation along a low-angle fault system. These data suggest that the Coast Range fault dominantly accommodated normal displacement and ductile thinning, and that these processes were primarily responsible for the structural exhumation of high-pressure assemblages in the Franciscan Complex relative to the structurally overlying forearc crust. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.