The geometry of folded tectonic shear sense indicators

The geometry of refolding of early stretching lineations and associated sen se of shear indicators is often not fully considered and can potentially le ad to grossly incorrect tectonic interpretations of orogens and orogenic ev ents. Sense of shear is not inverted or 'flipped' in all cases of refolding by folds with closure angle < 90 degrees. The geometry of inversion of 'fl ipping' of shear sense is determined entirely by the angle (phi) between th e stretching lineation and the latter fold axes. Folding around an axis ort hogonal to the stretching lineation (phi = 90 degrees) does not result in s hear sense inversion. This is a special case; if there is any degree of obl iquity (phi < 90 degrees) between fold axis and stretching lineation, there is a change in the orientation of the stretching lineation on alternate li mbs and if phi < 45 degrees the sense of shear is inverted in alternate lim bs. (C) 1998 Elsevier Science Ltd. All rights reserved.