Active buckling and rotation enhances formation of sheath folds. They may look similar but are not the same as crenulation cleavages, which normally develop normal to shortening. Develops early in shear zone formation. Mantle is not the same as pressure shadow or pressure fringe With high strain, mantles can get stretched to form wings. Flow field and amount of mantle material determine geometry of mantled porphyroclasts.
Upward step is in shear direction.