Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, North Cascade Range, Washington and British Columbia

Abstract

Research Article| October 01, 1991 Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, North Cascade Range, Washington and British Columbia RALPH A. HAUGERUD; RALPH A. HAUGERUD 1U.S. Geological Survey at Department of Geological Sciences, AJ-20, University of Washington, Seattle, Washington 98195 Search for other works by this author on: GSW Google Scholar PETER VAN DER HEYDEN; PETER VAN DER HEYDEN 2Department of Geological Sciences, University of British Columbia, Vancouver, British Columbia V6T 2B4 Canada Search for other works by this author on: GSW Google Scholar ROWLAND W. TABOR; ROWLAND W. TABOR 3U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar JOHN S. STACEY; JOHN S. STACEY 3U.S. Geological Survey, Menlo Park, California 94025 Search for other works by this author on: GSW Google Scholar ROBERT E. ZARTMAN ROBERT E. ZARTMAN 4U.S. Geological Survey, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information RALPH A. HAUGERUD 1U.S. Geological Survey at Department of Geological Sciences, AJ-20, University of Washington, Seattle, Washington 98195 PETER VAN DER HEYDEN 2Department of Geological Sciences, University of British Columbia, Vancouver, British Columbia V6T 2B4 Canada ROWLAND W. TABOR 3U.S. Geological Survey, Menlo Park, California 94025 JOHN S. STACEY 3U.S. Geological Survey, Menlo Park, California 94025 ROBERT E. ZARTMAN 4U.S. Geological Survey, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1991) 103 (10): 1297–1307. https://doi.org/10.1130/0016-7606(1991)103<1297:LCAETP>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 RALPH A. HAUGERUD, PETER VAN DER HEYDEN, ROWLAND W. TABOR, JOHN S. STACEY, ROBERT E. ZARTMAN; Late Cretaceous and early Tertiary plutonism and deformation in the Skagit Gneiss Complex, North Cascade Range, Washington and British Columbia. GSA Bulletin 1991;; 103 (10): 1297–1307. doi: https://doi.org/10.1130/0016-7606(1991)103<1297:LCAETP>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 The Skagit Gneiss Complex forms a more-or-less continuous terrane within the northern, more deeply eroded part of the North Cascade Range. The complex comprises abundant plutons intruded at mid-crustal depths into a variety of metamorphosed supracrustal rocks of both oceanic and volcanic-arc origin. A plethora of syntectonic pegmatite, small plutons, and granitic dikes gives the complex a migmatitic aspect.U-Pb zircon ages from gneissic plutons within and near the Skagit Gneiss Complex indicate magmatic crystallization between 75 and 60 Ma. Deformation, recrystallization, and migmatization in part postdate intrusion of the 75-60 Ma plutons. This latest Cretaceous and earliest Tertiary plutonism and migmatization may reflect thermal relaxation following early Late Cretaceous orogeny documented else-where in the North Cascades.The complex was ductilely extended northwest-southeast shortly after intrusion of granite dikes at ∼45 Ma, but before emplacement of the earliest (∼34 Ma) plutons of the Cascade arc. Outcrops of Late Cretaceous and earliest Tertiary plutons, migmatites of the Skagit Gneiss Complex, and rocks with young ductile deformation are roughly coextensive, all apparently marking a region of greater middle Eocene unroofing. Unroofing was apparently contemporaneous with east-west extension in the Okanogan region to the east and north-south and northwest-southeast strike-slip faulting within the North Cascades. 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.