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FOLD, BOX, KINKED

When these structures are developed on large scale outcrops or on the mappable scale, they are called monoclines. Two kink-bands in opposite directions may join to form what are known as conjugate kink-bands, or if developed on larger scales, conjugate or box folds. The axial planes of conjugate kink bands occur in pairs and are either inclined towards each other (antiforms) or away from each other (synforms) and the obtuse angle between them faces the direction of maximum shortening in rocks or it faces the direction of maximum principal compressive stress ? . Thus the single or conjugate kink-bands are important in the sense that they allow the orientations of principal stresses to be determined simply by plotting orientations of axial planes on an equal area net as in case of conjugate shear zones. Kink-bands are usually related to late stage movements of an orogenic pulse and therefore developed on a schistosity, slaty cleavage etc. in phyllites or slates developed during a previous episode of deformation and metamorphism. But this is not always true, for kink-bards are also found developed in laminated shales. Kink-bands in single crystals due to lattice dislocations are also found on the scale of an atomic lattice. Since kink-bands are formed by interlayer slip, they are of subclass 1B style i.e. the orthogonal thickness within the kink-band and in the un-deflected layering remains the same