On resolving shear direction in foliated rocks deformed by simple shear

Abstract

Research Article| September 01, 1990 On resolving shear direction in foliated rocks deformed by simple shear ALLEN J. DENNIS; ALLEN J. DENNIS 1Department of Physical Sciences, University of South Carolina, Aiken, South Carolina 29801 Search for other works by this author on: GSW Google Scholar DONALD T. SECOR, JR. DONALD T. SECOR, JR. 2Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1990) 102 (9): 1257–1267. https://doi.org/10.1130/0016-7606(1990)102<1257:ORSDIF>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation ALLEN J. DENNIS, DONALD T. SECOR; On resolving shear direction in foliated rocks deformed by simple shear. GSA Bulletin 1990;; 102 (9): 1257–1267. doi: https://doi.org/10.1130/0016-7606(1990)102<1257:ORSDIF>2.3.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 We present a three-dimensional model for the formation of crenulations in ductile shear zones, based on compatibility conditions, infinitesimal-displacement equations, and our own field observations. In many shear zones, at least two and probably three mesoscopic slip systems are active. Crenulation slip is interpreted to compensate for the displacement component of foliation slip normal to the shear zone wall. In zones in which foliation slip is an important mode of deformation, foliation and crenulation slip vectors do not necessarily lie in the same plane, nor are they necessarily perpendicular to crenulation axes. Solutions for the orientation of the crenulation plane, crenulation slip vector, and magnitude of the crenulation slip shear strain belong to one of two possible solution sets, given the orientation of slipping foliation, the foliation slip vector, and the magnitude of slip on foliation. Hence, shear sense may be reliably interpreted from composite planar fabrics in ductile shear zones, but more specifically, shear direction cannot. These results have broad implications in the interpretation of the kinematic significance of mineral lineations oblique to crenulation axes, and in the deduction of shear strain from angular relations between planar fabric elements. 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.