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Sheath fold formation around slip surfaces
Author(s) -
Reber Jacqueline E.,
Dabrowski Marcin,
Schmid Daniel W.
Publication year - 2012
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.1365-3121.2012.01081.x
Subject(s) - geology , perpendicular , fold (higher order function) , shear (geology) , slip (aerodynamics) , simple shear , planar , shear zone , perturbation (astronomy) , geometry , mechanics , petrology , seismology , physics , tectonics , mechanical engineering , mathematics , computer graphics (images) , quantum mechanics , computer science , engineering , thermodynamics
Terra Nova, 24, 417–421, 2012 Abstract Sheath folds are associated with shear zones and have been used as high strain indicators. We present results from a three‐dimensional analytical study showing that the flow perturbation around a planar weakness acting as a slip surface, in simple shear leads to the formation of sheath folds at low shear strain. Closed traces of marker layers are exhibited in cross‐sections cut perpendicular to the shear direction in the vicinity of the slip surface tip. In cross‐sections cut parallel to the shear direction and normal to the shear plane, flanking folds are observed. Our model captures the first‐order observations of natural sheath folds, such as diversity of shapes and multiple eye‐structures. Natural equivalents of the planar weaknesses that we model include fractures, veins and rheologically weak layers. Flow perturbation around these zones of weaknesses is proposed as an alternative mechanism of sheath fold formation, which emphasizes the coeval operation of brittle and ductile processes in shear zones.