Deposition of Franciscan Complex cherts along the paleoequator and accretion to the American margin at tropical paleolatitudes

Abstract

Research Article| June 01, 1993 Deposition of Franciscan Complex cherts along the paleoequator and accretion to the American margin at tropical paleolatitudes JONATHAN T. HAGSTRUM; JONATHAN T. HAGSTRUM 1U S. Geological Survey, Menlo Park California 94025 Search for other works by this author on: GSW Google Scholar BENITA L. MURCHEY BENITA L. MURCHEY 1U S. Geological Survey, Menlo Park California 94025 Search for other works by this author on: GSW Google Scholar Author and Article Information JONATHAN T. HAGSTRUM 1U S. Geological Survey, Menlo Park California 94025 BENITA L. MURCHEY 1U S. Geological Survey, Menlo Park California 94025 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1993) 105 (6): 766–778. https://doi.org/10.1130/0016-7606(1993)105<0766:DOFCCA>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JONATHAN T. HAGSTRUM, BENITA L. MURCHEY; Deposition of Franciscan Complex cherts along the paleoequator and accretion to the American margin at tropical paleolatitudes. GSA Bulletin 1993;; 105 (6): 766–778. doi: https://doi.org/10.1130/0016-7606(1993)105<0766:DOFCCA>2.3.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 Red radiolarian cherts from three localities within the Franciscan subduction complex of northern California contain three components of remanent magnetization which are best isolated by progressive thermal demagnetization. The first component, usually removed by 300 °C, has an in situ direction similar to the present axial-dipole field and is probably a recently acquired thermoviscous overprint. A second component, generally removed between 300 and 630 °C, has constant (normal) polarity and direction within each section and is interpreted to have been acquired by low-temperature chemical alteration during subduction and accretion at the continental margin. The third component, isolated between ∼560 and 680 °C, has both normal and reversed polarities, passes a fold test, and is inferred to have been acquired during or soon after deposition. The available paleomagnetic, biostratigraphic, and geochemical data indicate deposition of these cherts along the paleoequator (0°-2°N or S paleolatitude) between Pliensbachian and Oxfordian time as the oceanic plate moved eastward, relative to North America, beneath the equatorial zone of high biologic productivity. Between Bathonian and Cenomanian time, the chert sequences apparently moved progressively away from the paleoequator (2°-15°N or S), and were soon after accreted to the American continental margin. Plate reconstruction models for the Farallon plate corroborate low-paleolatitude trajectories from ridge crest to subduction zone (for example, from 3°S to 11°N), and they imply subsequent northward translation of the Franciscan Complex (> 4,000 km) by strike-slip faulting related to relative motions between the Farallon, Kula, Pacific, and North American plates. 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.