1) Although limited by a number of simplifications and assumptions, kinematic forward modelling of refold structures is a powerful tool in teaching, learning and exploring the enormous complexity and variability of interference patterns. Especially the presented animations help to understand the transitions of complex three-dimensional geometries (structure-movies) and their intersections on planar orthogonal faces (pattern-movies).
2) As already suggested in previous works, the interference patterns are not indicative for a relative spatial orientation of superposed folds. Therefore refold structures are distinguished by their three-dimensional geometry described by the angles between the kinematic axes of the initial and superposing fold. These kinematic axes, which are defined as an orthogonal triplet of directions corresponding to the fold axis, the pole to the axial plane and the normal to these axes, can be plotted in a refold-stereoplot, which is simply a stereographic projection where the initial fold axis is oriented W-E and the pole to the axial plane N-S.
3) Although Type 0 refold structures have been previously described their importance and their classification in three different end-members have been mainly ignored. Although Type 0 refolds fail to produce interference patterns on sections perpendicular to the kinematic axes of the initial fold, kinematic modelling shows by means of orthogonal marker planes established after initial folding, that the three Type 0 end-members are markedly different. Slight deviations of the end-member geometries result in complex interference patterns, which are considerable different for the three Type 0 end-members. Importantly only the ñclassicalî Type 0 refold structures is plane strain and sections perpendicular to the fold axis of the initial fold are clearly non-plane strain for the two other Type 0 refolds.
4) Therefore we suggest to distinguish Type 1, Type 2, Type 3, Type 01, 02 and 03 refold structures.