Accretion of the Franciscan Complex attending Jurassic-Cretaceous geotectonic development of northern and central California

Abstract

Research Article| September 01, 2011 Accretion of the Franciscan Complex attending Jurassic–Cretaceous geotectonic development of northern and central California W.G. Ernst W.G. Ernst † Department of Geological & Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA †E-mail: wernst@stanford.edu Search for other works by this author on: GSW Google Scholar Author and Article Information W.G. Ernst † Department of Geological & Environmental Sciences, Stanford University, Stanford, California 94305-2115, USA †E-mail: wernst@stanford.edu Publisher: Geological Society of America Received: 08 Aug 2010 Revision Received: 10 Nov 2010 Accepted: 29 Nov 2010 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2011 Geological Society of America GSA Bulletin (2011) 123 (9-10): 1667–1678. https://doi.org/10.1130/B30398.1 Article history Received: 08 Aug 2010 Revision Received: 10 Nov 2010 Accepted: 29 Nov 2010 First Online: 08 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 W.G. Ernst; Accretion of the Franciscan Complex attending Jurassic–Cretaceous geotectonic development of northern and central California. GSA Bulletin 2011;; 123 (9-10): 1667–1678. doi: https://doi.org/10.1130/B30398.1 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 Scattered igneous activity marks the Triassic margin of California, but an Andean volcanic-plutonic arc began to form in the Sierra Nevada–White-Inyo Range and Klamath Mountains at ca. 170 Ma during underflow of the oceanic lithosphere. This calc-alkaline belt supplied volcanogenic erosional debris to the Mariposa-Galice proximal overlap sequence by ca. 165–160 Ma. Transpression also generated high-pressure–low-temperature basaltic eclogites, garnet-blueschists, and amphibolites along the Middle and Late Jurassic convergent plate junction at ca. 170–155 Ma; most of these returned surfaceward as tectonic blocks only during the mid-Cretaceous. The high-grade metamafic (metamorphosed mafic) blocks that formed during construction of the emergent arc and derived Mariposa-Galice strata predate the onset of Franciscan trench deposition. Near the end of Jurassic time, the Klamath salient evidently migrated ∼200 km westward. An earliest Cretaceous westward stepout of the convergent junction apparently formed directly offshore from the Klamath imbricate orogen, but to the south, preexisting oceanic crust–capped lithosphere was trapped landward as the Coast Range ophiolite. Andean arc detritus began to accumulate on this ophiolitic basement within the Great Valley forearc and outboard Franciscan oceanic trench at ca. 145–140 Ma. Because earliest Cretaceous, relatively continuous Great Valley strata were deposited on the stable North American plate, protected from both surface and subcrustal erosion, forearc terrigenous sedimentation also signaled coeval deposition in the outboard trench ∼10–25 m.y. after Middle and Late Jurassic initiation of the continental margin calc-alkaline arc. Voluminous sedimentation and the accretion of Franciscan and San Joaquin sections of Great Valley rocks took place during mid- and Late Cretaceous time after a flare-up in igneous arc activity at ∼125–120 Ma. The youngest Sierran granites have ca. 85 Ma ages, reflecting extinction of the magmagenic zone beneath northern and central California, and presumably reflecting subhorizontal oceanic plate underflow attending the Laramide orogeny. Feebly zeolitized Upper Cretaceous and Lower Tertiary Franciscan Coastal belt rocks, derived from the now-inactive arc, underwent only low-pressure burial metamorphism. Reflecting shallow offloading and/or large-scale transpression, they were not appreciably subducted. Although Coastal belt units are members of the Franciscan lithotectonic assemblage, their origin contrasts with the rest of the subduction complex. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.