Research Article| October 01, 2002 Proterozoic Farwell Mountain–Lester Mountain suture zone, northern Colorado: Subduction flip and progressive assembly of arcs A.R. Tyson; A.R. Tyson 1Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar E.A. Morozova; E.A. Morozova 2Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar K.E. Karlstrom; K.E. Karlstrom 3Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA Search for other works by this author on: GSW Google Scholar K.R. Chamberlain S.B. Smithson K.G. Dueker; K.R. Chamberlain S.B. Smithson K.G. Dueker 4Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA Search for other works by this author on: GSW Google Scholar C.T. Foster C.T. Foster 5Department of Geology, University of Iowa, Iowa City, Iowa 52242, USA Search for other works by this author on: GSW Google Scholar Author and Article Information A.R. Tyson 1Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA E.A. Morozova 2Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA K.E. Karlstrom 3Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA K.R. Chamberlain S.B. Smithson K.G. Dueker 4Department of Geology and Geophysics, University of Wyoming, Laramie, Wyoming 82071, USA C.T. Foster 5Department of Geology, University of Iowa, Iowa City, Iowa 52242, USA Publisher: Geological Society of America Received: 07 Mar 2002 Revision Received: 03 Jun 2002 Accepted: 21 Jun 2002 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2002) 30 (10): 943–946. https://doi.org/10.1130/0091-7613(2002)030<0943:PFMLMS>2.0.CO;2 Article history Received: 07 Mar 2002 Revision Received: 03 Jun 2002 Accepted: 21 Jun 2002 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 A.R. Tyson, E.A. Morozova, K.E. Karlstrom, K.R. Chamberlain S.B. Smithson K.G. Dueker, C.T. Foster; Proterozoic Farwell Mountain–Lester Mountain suture zone, northern Colorado: Subduction flip and progressive assembly of arcs. Geology 2002;; 30 (10): 943–946. doi: https://doi.org/10.1130/0091-7613(2002)030<0943:PFMLMS>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 SocietyGeology Search Advanced Search Abstract This paper considers the amalgamation of arc and oceanic terranes to be the main mechanism of ca. 1.8–1.6 Ga continental crustal growth in southwestern Laurentia. On the basis of geologic and seismic reflection data and teleseismic images, we propose the Farwell Mountain–Lester Mountain suture zone as the northernmost Paleoproterozoic arc-arc suture. North-dipping (Farwell Mountain) seismic reflections project from 18 km depths to the surface and are interpreted to represent conjugate thrusting as the 1.79–1.77 Ga Green Mountain arc was partially underthrust beneath the Archean craton. We speculate that a north-dipping high-velocity mantle “slab” in the teleseismic image is a continuation of this thrust zone. South-dipping (Lester Mountain) reflections project from 22 km depths to the surface and are interpreted to be a thrust zone between the Green Mountain arc and the 1.76–1.72 Ga Rawah block. Surface features of the Farwell Mountain–Lester Mountain suture zone are (1) marble, chert, rock with sillimanite pods, ultramafic rocks, sulfide deposits, and pillow basalts, which we interpret to be a dismembered accretionary complex; (2) an axial-planar fabric to north-verging isoclinal folds (F2), which we interpret to be part of a north-vergent fold-and-thrust system; and (3) a metamorphic break between ∼500 °C rocks to the north and ∼610 °C rocks to the south, which we attribute to reactivation of the zone. Movement on the Farwell Mountain backthrust is inferred to relate to Cheyenne belt suturing at 1.78–1.75 Ga. We correlate suturing in the Farwell Mountain–Lester Mountain suture zone to S1/D1 (1.746–1.74 Ga) in the Soda Creek–Fish Creek shear zone. We attribute the complexity of this broad suture zone to initial conjugate thrusting, plus overprinting and steepening of accretionary structures by subsequent tectonism. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.