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Structure of the (ultra)high-pressure Western Gneiss Region, Norway: Imbrication during Caledonian continental margin subduction

2017; Geological Society of America; Volume: 130; Issue: 5-6 Linguagem: Inglês

10.1130/b31764.1

1943-2674

D. J. Young,

earthquake and tectonic studies

Research Article| December 14, 2017 Structure of the (ultra)high-pressure Western Gneiss Region, Norway: Imbrication during Caledonian continental margin subduction David J. Young David J. Young † 1School of Earth Sciences, The Ohio State University, Columbus, Ohio 43210, USA †young.2536@osu.edu Search for other works by this author on: GSW Google Scholar GSA Bulletin (2018) 130 (5-6): 926–940. https://doi.org/10.1130/B31764.1 Article history received: 05 Feb 2017 rev-recd: 24 May 2017 accepted: 23 Oct 2017 first online: 14 Dec 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation David J. Young; Structure of the (ultra)high-pressure Western Gneiss Region, Norway: Imbrication during Caledonian continental margin subduction. GSA Bulletin 2017;; 130 (5-6): 926–940. doi: https://doi.org/10.1130/B31764.1 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 A new structural model is presented for the giant Western Gneiss Region (WGR) in western Norway, a part of the Baltica continental margin that was subducted to eclogite-facies conditions during the Silurian–Devonian Caledonian (Scandian) orogeny. The WGR is divided into three tectonostratigraphic subdivisions that are composed largely of felsic orthogneiss, and they are separated from each other by regional shear zones. From structurally lowest to highest, these subdivisions are the Western Gneiss Complex, the Fjordane Complex, and the Tafjord Complex. The Western Gneiss Complex is mainly exposed across the southern extent of the WGR, and it is inferred to reappear again in the north. The Fjordane Complex occupies a shallowly east-plunging synclinorium through the center of the WGR; it is separated from the Western Gneiss Complex by the Sandane shear zone. The Tafjord Complex lies above the Fjordane Complex, across the east-dipping Geiranger shear zone. Both the Sandane and Geiranger shear zones contain top-to-the-foreland shear indicators; the Sandane shear zone is also overprinted toward the western coast by later extensional shear (top-to-the-hinterland). These gneiss sheets resulted from progressive delamination of the frontal and upper sections of the WGR during Scandian collision and subduction from ca. 430 to ca. 405 Ma. Combining the structural model with existing pressure-temperature and geochronological data indicates: (1) the Tafjord Complex likely detached relatively early and stagnated beneath the overlying orogenic pile while the Baltica slab continued sliding underneath; (2) the Fjordane Complex detached later in the eclogite facies, and also likely stalled at these conditions; and (3) the Western Gneiss Complex continued subducting at eclogite-facies depths for perhaps another 5 m.y. before it began to exhume at ca. 405 Ma. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.