Geological Society of America

T215 Structure and Tectonic Studies, from Outcrop to Supercontinent II: In Honor of Ian Dalziel

Tuesday, 24 September 2019
1:30 PM - 5:30 PM
Room 229A, North Building

TWINNING STRAINS FROM SYN-FAULTING CALCITE GOUGE: SMALL-OFFSET STRIKE-SLIP, NORMAL AND THRUST FAULTS

Paper number: T215-2
Program: Technical Sessions
Time: 1:45 PM – 2:00 PM

Authors

John P. Craddock Presenting Author
Macalester College, St. Paul, IL
David Malone
Illinois State University, Bloomington, IL
Jakob Wartman
Macalester College, St. Paul, IL
Megan Kelly
Macalester College, St. Paul, IL
Junlai Liu
Beijing
Maura Bussolotto
Dépt. Sciences de la Terre,, Orsay Cedex
Chiari Invernizzi
Università di Camerino,, Camerino
Jeffrey Knott
California State University, Fullerton, Fullerton, CA
Ryan C. Porter
Northern Arizona University, Flagstaff, AZ

Abstract

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.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-338487

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