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The origin of Variscan kink bands: a study from the Dungarvan Syncline, southern Ireland

Published online by Cambridge University Press:  01 May 2009

F. X. Murphy
Affiliation:
Department of Geology, University College, Cork, Ireland

Abstract

Kink bands formed due to the rotation of cleavage are very common within the Irish Variscides. A detailed examination of those within the Dungarvan Syncline has enabled the recognition of three categories based on kink fold axis orientation; the subvertical, those parallel to first or second order fold axes and those with subhorizontal randomly trending axes. The subvertical variety were formed by strike-parallel compression within a hinge depression in the Dungarvan Syncline and modified by later north–south dextral shear stresses to produce cataclasis of the kink-band boundaries, tension-gashes within the kinked segment and over-rotation. Those, whose axes are parallel to major or minor fold axes, formed as accommodation structures during folding due to extension in the be plane. Those, with subhorizontal randomly trending axes formed due to a relaxation in the northward compression which allowed a reorientation of the principal stress directions, σ1 became vertical and kink bands were generated as a consequence of the increased overburden due to fold tightening and thrusting. It is considered that kink bands throughout the Irish Variscides may be divisible into similar categories.

Type
Articles
Copyright
Copyright © Cambridge University Press 1988

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