Mesozoic California and the Underflow of Pacific Mantle

Abstract

Research Article| December 01, 1969 Mesozoic California and the Underflow of Pacific Mantle WARREN HAMILTON WARREN HAMILTON U.S. Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information WARREN HAMILTON U.S. Geological Survey, Denver, Colorado 80225 Publisher: Geological Society of America Received: 08 Apr 1969 Revision Received: 03 Jun 1969 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1969, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1969) 80 (12): 2409–2430. https://doi.org/10.1130/0016-7606(1969)80[2409:MCATUO]2.0.CO;2 Article history Received: 08 Apr 1969 Revision Received: 03 Jun 1969 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation WARREN HAMILTON; Mesozoic California and the Underflow of Pacific Mantle. GSA Bulletin 1969;; 80 (12): 2409–2430. doi: https://doi.org/10.1130/0016-7606(1969)80[2409:MCATUO]2.0.CO;2 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 The Mesozoic evolution of California is interpreted as dominated by the underflow of oceanic mantle beneath the continental margin. Underflow during part of Late Cretaceous time of more than 2000 km of the eastern Pacific plate seems required by the marine magnetic data. Correspondingly, varied oceanic environments—abyssal hill, island arc, trench, oceanic crust, and upper mantle, perhaps also continental rise and abyssal plain—appear to be represented in the eugeosynclinal terranes of California. The rock juxtapositions accord with the concept that these materials were scraped off against the continent as the oceanic plate slid beneath it along Mesozoic Benioff seismic zones, which are now seen as serpentine belts separating profoundly different rock assemblages.The chaotic Franciscan Formation of coastal California consists of deep-ocean Late Jurassic to Late Cretaceous sedimentary, volcanic, crustal, and mantle materials. As open-ocean abyssal oozes and the oceanic crust beneath them were swept into the Benioff-zone trench at the continental margin, they were covered by terrigenous clastic sediments, and the entire complex was carried beneath the correlative continental-shelf and continental-slope deposits (Great Valley sequence) and the older Mesozoic complexes.The other eugeosynclinal terranes of California can be interpreted, albeit with less confidence, in similar terms of underflow of Pacific mantle. In the Klamath Mountains and northern Sierra Nevada, for example, Ordovician and Silurian ocean-floor materials, overlain by or juxtaposed against an Upper Silurian to Permian island arc, were swept in first to the continent, along with a large fragment of oceanic crust and mantle and another fragment of an old orogenic belt. This debris was followed by Permian and Triassic ocean-floor deposits. Late Triassic and Jurassic volcanic products from stocks and batholiths forming in the welded complexes lapped across both landward and oceanward sides of the region.Reversal of Cenozoic extension, strike-slip faulting, and volcanic crustal growth in the western United States reveals a Cretaceous tectonic pattern strikingly like the modern pattern of the Andes, so the paleotectonic setting of North America can be inferred from the South American present. The Mesozoic batholiths of North America, like the late Cenozoic volcanic belt of the central Andes, are products of the same rapid motion of oceanic plates that carried oceanic sediments against the continent to form eugeosynclinal terranes. Magmas generated in the Benioff zones formed the batholiths and the volcanic fields which initially capped them. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.