Research Article| May 01, 2000 Clast-fabric development in a shearing granular material: Implications for subglacial till and fault gouge Thomas S. Hooyer; Thomas S. Hooyer 1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa 50011, USA Search for other works by this author on: GSW Google Scholar Neal R. Iverson Neal R. Iverson 1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa 50011, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Thomas S. Hooyer 1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa 50011, USA Neal R. Iverson 1Department of Geological and Atmospheric Sciences, Iowa State University, Ames, Iowa 50011, USA Publisher: Geological Society of America Received: 17 Sep 1998 Revision Received: 06 Apr 1999 Accepted: 15 Jun 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (5): 683–692. https://doi.org/10.1130/0016-7606(2000)112<683:CDIASG>2.0.CO;2 Article history Received: 17 Sep 1998 Revision Received: 06 Apr 1999 Accepted: 15 Jun 1999 First Online: 01 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 Thomas S. Hooyer, Neal R. Iverson; Clast-fabric development in a shearing granular material: Implications for subglacial till and fault gouge. GSA Bulletin 2000;; 112 (5): 683–692. doi: https://doi.org/10.1130/0016-7606(2000)112<683:CDIASG>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 Elongate clasts in subglacial till and in fault gouge align during shearing, but the relation between clast-fabric strength and cumulative shear strain for such materials is effectively unknown. This relation was explored in experiments with a large ring-shear device in which a till and a viscous putty that contained isolated clasts were sheared to high strains. As expected, rotation of clasts in the putty is closely approximated by the theory of G.B. Jeffery, who derived the orbits of rigid ellipsoids in a slowly shearing fluid. Clast rotation in the till, however, is strikingly different. Rather than orbiting through the shear plane as predicted by Jeffery, most clasts rotate into the shear plane and remain there, resulting in strong fabrics regardless of the aspect ratios and initial orientations of clasts. This divergent behavior is likely due to slip of the till matrix along the surfaces of clasts, which is a natural expectation in a granular material but violates the no-slip condition of Jeffery's model. These results do not support the widespread belief that subglacial till deformation results in weak clast fabrics. Thus, many tills with weak fabrics thought to have been sheared subglacially to high strains, like many basal tills of the Laurentide Ice Sheet, may have been sheared only slightly with little effect on either ice-sheet dynamics or sediment transport. In addition, these results indicate that in simple shear the rotation of clasts in till and in fault gouge is best analyzed with the model of A. March, who treated inclusions as passive markers. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.