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Strain localization in sandstone during embryonic stages of shear‐zone evolution
Author(s) -
Katz Yoram,
Weinberger Ram
Publication year - 2005
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.2005.00615.x
Subject(s) - geology , shear (geology) , deformation (meteorology) , shear zone , simple shear , geometry , strain (injury) , flow (mathematics) , geotechnical engineering , petrology , seismology , tectonics , anatomy , mathematics , medicine , oceanography
Geometric analysis of nested Riedel structures was used to identify and quantify strain localization processes within faulted Navajo sandstone. The analysis shows systematic deviation from the basic Riedel geometry complying with the Mohr–Coulomb criterion. Using cross‐cutting relations amongst deformation bands within the Riedel structures, and comparing the orientations of the deformation bands to theoretical strain calculations, we identify two coupling deformation mechanisms involved in the early stages of shear‐zone evolution, namely, granular flow and discrete faulting. Both mechanisms localize during strain accumulation, and the granular flow facilitates considerable change in the initial geometry of the Riedel structures. The analysis demonstrates a systematic sequence, by which new Riedel structures form after a constant amount of shear strain takes place in the sandstone. Analysis further indicates that granular flow is the major deformation mechanism during early stages of shear‐zone evolution and discrete faulting is the dominant mechanism during later deformation stages.