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Development of Chevron Folds
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1974
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Exploration GeophysicsEngineeringGeometryOrigami MetamaterialsFoldable StructureComputer-aided DesignEarth ScienceChevron FoldsRegional GeologySuspension StructureCompetent Layer ThicknessGeological DataGeochronologyGeometric ModelingGeological EngineeringGeographyGeology3D PrintingTectonicsFlexible ElectronicsStructural GeologyNatural SciencesExploration GeologyEconomic GeologyEarth SciencesPetrology
Research Article| November 01, 1974 Development of Chevron Folds JOHN G. RAMSAY JOHN G. RAMSAY 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT England Search for other works by this author on: GSW Google Scholar Author and Article Information JOHN G. RAMSAY 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT England Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1974) 85 (11): 1741–1754. https://doi.org/10.1130/0016-7606(1974)85<1741:DOCF>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation JOHN G. RAMSAY; Development of Chevron Folds. GSA Bulletin 1974;; 85 (11): 1741–1754. doi: https://doi.org/10.1130/0016-7606(1974)85<1741:DOCF>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 Multilayered rock complexes with regular alternations of competent and incompetent layers of thickness t1 and t2, respectively, and with high ductility contrast form folds of the chevron style when subjected to compression along the layering. The geometric forms of progressively developing chevron folds are analyzed using a model whose properties are based on the geometric forms of naturally deformed rock layers. It is found that the chevron fold style is only stable where no strongly marked variations in competent layer thickness t1 exists. The thickness of the incompetent layer exerts no influence on fold model stability. Slight variations of competent layer thickness can be accommodated by local modifications of the fold style, such as limb faults, bulbous hinge zones, or layer boudinage, but if any strongly marked variation exists, the fold limbs become curved. The chevron model involves dilation at the hinge zones, and saddle reef formation, incompetent layer flow into the hinge, or slow hinge collapse generally results from actual or potential dilation. The speed of development of chevron folds is calculated under conditions of constant stress and of constant load. Folding starts slowly but rapidly accelerates; the later stages are characterized by a progressive slowing in shortening rate and fold growth, leading either to a stage of locking up of the fold or to modification of its geometry by limb thinning and hinge thickening; toward a more similar geometric style. The strains in the hinge zone region are related to the rates of shear taking place in the fold limbs; the geometric model is not completely stable throughout the fold development, and complex progressive strain increments can occur in the hinge zones and lead to the development of superposed small-scale structures indicating reversals of principal axes of incremental strain. 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.