Potassium-Argon Dates of Biotites from Cordilleran Granites

Research Article| May 01, 1961 Potassium-Argon Dates of Biotites from Cordilleran Granites H BAADSGAARD; H BAADSGAARD Dept. Geology, University of Alberta, Edmonton, Alberta, Canada Search for other works by this author on: GSW Google Scholar R. E FOLINSBEE; R. E FOLINSBEE Dept. Geology, University of Alberta, Edmonton, Alberta, Canada Search for other works by this author on: GSW Google Scholar J LIPSON J LIPSON Dept. Geology, University of Alberta, Edmonton, Alberta, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information H BAADSGAARD Dept. Geology, University of Alberta, Edmonton, Alberta, Canada R. E FOLINSBEE Dept. Geology, University of Alberta, Edmonton, Alberta, Canada J LIPSON Dept. Geology, University of Alberta, Edmonton, Alberta, Canada Publisher: Geological Society of America Received: 16 Nov 1959 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1961, 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 (1961) 72 (5): 689–701. https://doi.org/10.1130/0016-7606(1961)72[689:PDOBFC]2.0.CO;2 Article history Received: 16 Nov 1959 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation H BAADSGAARD, R. E FOLINSBEE, J LIPSON; Potassium-Argon Dates of Biotites from Cordilleran Granites. GSA Bulletin 1961;; 72 (5): 689–701. doi: https://doi.org/10.1130/0016-7606(1961)72[689:PDOBFC]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 Biotites from 20 plutons of the Cordillera of North America, principally from British Columbia, have been dated using the potassium-argon method. Samples were selected from well-known intrusive masses in an attempt to compare physically measured dates with relative age established by geological mapping; most dates confirm the geological age interpretations.The Cordillera underwent granitic intrusion or orogeny at five times separated by long periods of quiescence. The earliest orogeny, of Devonian (Acadian) age, occurred 350-360 million years ago and resulted in intrusion of plutons as widely separated as the Ice River syenite of the Rocky Mountains and the Fitton granite of the northern Yukon.Early Mesozoic orogeny resulted in the emplacement of the upper Triassic or lower Jurassic Guichon (186 m.y.) and Topley (163 m.y.) batholiths of central British Columbia. The major Cordilleran intrusion occurred 95–100 million years ago, in about the middle of the Cretaceous, with emplacement of the Coast Range batholith and early phases of the Nelson batholith of British Columbia, and the Cassiar and Itsi batholiths of Yukon. In late Cretaceous time, 80 million years ago, the Bayonne pluton, British Columbia, and Boulder batholith and Marysville stock of Montana were emplaced.During Rocky Mountain orogeny (Eocene), 50–60 million years ago, late phases of the Nelson batholith and a number of plutons such as Coryell were emplaced. Eighteen million years ago, in the Miocene, small granitic bodies intruded the Cascade Range; these are believed to be the youngest exposed batholithic rocks in North America. 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.