GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 215-2
Presentation Time: 1:45 PM


CRADDOCK, John P.1, MALONE, David2, WARTMAN, Jakob1, KELLY, Megan1, LIU, Junlai3, BUSSOLOTTO, Maura4, INVERNIZZI, Chiari5, KNOTT, Jeffrey R.6 and PORTER, Ryan C.7, (1)Geology, Macalester College, 1600 Grand Avenue, St. Paul, IL 55105, (2)Department of Geology, Illinois State University, Campus Box 4400, Bloomington, IL 61701, (3)China University of Geosciences, Beijing, 100083, China, (4)Université Paris Sud XI, Dépt. Sciences de la Terre,, UMR 7072 - Tectonique, Dynamique des systèmes faillés,, Orsay Cedex, 91405, France, (5)Dip. Scienze della Terra,, Università di Camerino,, Camerino, Italy, (6)Department of Geological Sciences, MH 327B, California State University, Fullerton, Fullerton, CA 92831, (7)School of Earth Sciences and Environmental Sustainability, Northern Arizona University, PO Box 4099, Flagstaff, AZ 86011-4099

We have evaluated the stress-strain behavior of calcite precipitated and mechanically twinned in small-offset strike-slip (5 sites), normal (7 sites) and thrust faults (7 sites) of a variety of ages and from a variety of tectonic settings (n=3001 twinned grains) on 6 continents. For each strike-slip fault system the twinning shortening strain (e1) is horizontal and at an angle of 0°-60° to the respective fault plane (dextral or sinistral) although in the majority of cases the shortening axis is parallel to fault strike. In each normal fault example, dip-slip kinematic striations dominate the faulted surface yet the orientation of the maximum principal compressive stress (s1) and shortening strain axis (e1) are not 45° to the fault plane as predicted but are sub-horizontal and either strike-parallel or strike-normal. Thrust faults preserve shortening strain axes (e1) parallel to the dip-slip kinematic direction, within the fault plane (plane strain) and not at 45° to the principal plane. None of the fault stress-strain field results reported here support the Andersonian or Mohr-Coulomb criteria for stress-strain relations predicted along faults.