Geologic Evolution of the Beartooth Mountains, Montana and Wyoming. Part 6. Cathedral Peak Area, Montana

Abstract

Research Article| January 01, 1966 Geologic Evolution of the Beartooth Mountains, Montana and Wyoming. Part 6. Cathedral Peak Area, Montana JAMES ROBERT BUTLER JAMES ROBERT BUTLER Dept. Geology, University of North Carolina, Chapel Hill, North Carolina Search for other works by this author on: GSW Google Scholar Author and Article Information JAMES ROBERT BUTLER Dept. Geology, University of North Carolina, Chapel Hill, North Carolina Publisher: Geological Society of America Received: 10 Aug 1964 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1966, 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 (1966) 77 (1): 45–64. https://doi.org/10.1130/0016-7606(1966)77[45:GEOTBM]2.0.CO;2 Article history Received: 10 Aug 1964 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JAMES ROBERT BUTLER; Geologic Evolution of the Beartooth Mountains, Montana and Wyoming. Part 6. Cathedral Peak Area, Montana. GSA Bulletin 1966;; 77 (1): 45–64. doi: https://doi.org/10.1130/0016-7606(1966)77[45:GEOTBM]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 Cathedral Peak area encompasses 35 square miles in the Precambrian core of the Bear-tooth Mountains in Montana, and is bounded by the Stillwater complex on the northeast. The major rock type is granitic gneiss consisting of quartz-feldspar rocks with a wide range in ratio of plagioclase to microcline and having a color index less than 20. Included in the gneiss are small, generally conformable lenses of biotite schist, amphibolite, and other metamorphic rocks, all having assemblages typical of amphibolite facies. Field relationships suggest that the granitic gneiss was formed by metasomatism. A thick aureole of contact metamorphosed rocks, the inner part graded to pyroxene-hornfels facies, underlies the Stillwater complex. Igneous and metamorphic rocks are altered locally to assemblages of greenschist facies along fault zones.Foliation and compositional layering of metasedimentary rocks (presumably representing original bedding) and foliation of granitic gneiss all show monoclinic symmetry. The macroscopic fabric and outcrop pattern indicate a series of open folds with axes trending north-northwest. Directions of mineral elongation and minor fold axes parallel the B-axis of the major fold system. In the southern part of the area, fold axes plunge 10°–15° N., but the plunge increases to 40 degrees near the base of the Stillwater complex. West of the Cathedral Peak area, the plunge is 10°–15° S.Postulated major events of geologic history are: (1) deposition of a sedimentary sequence, (2) formation of open folds, (3) regional metamorphism, granitization, and pegmatite formation, (4) emplacement of Stillwater complex, (5) regional metamorphism and pegmatite formation about 2700 m.y. ago, (6) intrusion of late Precambrian dolerite dikes, and (7) Laramide orogeny. 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.