Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment

Abstract

Research Article| March 01, 1996 Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment Bruce C. Beaudoin; Bruce C. Beaudoin 1Department of Geophysics, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Nicola J. Godfrey; Nicola J. Godfrey 1Department of Geophysics, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Simon L. Klemperer; Simon L. Klemperer 1Department of Geophysics, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar Christof Lendl; Christof Lendl 2Department of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Anne M. Trehu; Anne M. Trehu 2Department of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331 Search for other works by this author on: GSW Google Scholar Timothy J. Henstock; Timothy J. Henstock 3Department of Geology and Geophysics, Rice University, Houston, Texas 77251 Search for other works by this author on: GSW Google Scholar Alan Levander; Alan Levander 3Department of Geology and Geophysics, Rice University, Houston, Texas 77251 Search for other works by this author on: GSW Google Scholar James E. Holl; James E. Holl 4Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania 18015 Search for other works by this author on: GSW Google Scholar Anne S. Meltzer; Anne S. Meltzer 4Department of Earth and Environmental Sciences, Lehigh University, Bethlehem, Pennsylvania 18015 Search for other works by this author on: GSW Google Scholar James H. Luetger; James H. Luetger 5U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Walter D. Mooney Walter D. Mooney 5U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar Geology (1996) 24 (3): 195–199. https://doi.org/10.1130/0091-7613(1996)024<0195:TFSTSR>2.3.CO;2 Article history first online: 02 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 Bruce C. Beaudoin, Nicola J. Godfrey, Simon L. Klemperer, Christof Lendl, Anne M. Trehu, Timothy J. Henstock, Alan Levander, James E. Holl, Anne S. Meltzer, James H. Luetger, Walter D. Mooney; Transition from slab to slabless: Results from the 1993 Mendocino triple junction seismic experiment. Geology 1996;; 24 (3): 195–199. doi: https://doi.org/10.1130/0091-7613(1996)024<0195:TFSTSR>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 SocietyGeology Search Advanced Search Abstract Three seismic refraction-reflection profiles, part of the Mendocino triple junction seismic experiment, allow us to compare and contrast crust and upper mantle of the North American margin before and after it is modified by passage of the Mendocino triple junction. Upper crustal velocity models reveal an asymmetric Great Valley basin overlying Sierran or ophiolitic rocks at the latitude of Fort Bragg, California, and overlying Sierran or Klamath rocks near Redding, California. In addition, the upper crustal velocity structure indicates that Franciscan rocks underlie the Klamath terrane east of Eureka, California. The Franciscan complex is, on average, laterally homogeneous and is thickest in the triple junction region. North of the triple junction, the Gorda slab can be traced 150 km inboard from the Cascadia subduction zone. South of the triple junction, strong precritical reflections indicate partial melt and/or metamorphic fluids at the base of the crust or in the upper mantle. Breaks in these reflections are correlated with the Maacama and Bartlett Springs faults, suggesting that these faults extend at least to the mantle. We interpret our data to indicate tectonic thickening of the Franciscan complex in response to passage of the Mendocino triple junction and an associated thinning of these rocks south of the triple junction due to assimilation into melt triggered by upwelling asthenosphere. The region of thickened Franciscan complex overlies a zone of increased scattering, intrinsic attenuation, or both, resulting from mechanical mixing of lithologies and/or partial melt beneath the onshore projection of the Mendocino fracture zone. Our data reveal that we have crossed the southern edge of the Gorda slab and that this edge and/or the overlying North American crust may have fragmented because of the change in stress presented by the edge. 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.