The purpose of this page and associated pages is to describe the classification used and to explain how these models can be generated; it does not provide a review of superposed folding and associated references. However, I refer to the literature that I used for creating these models which should give students unfamiliar with classification and computer programs of refolded folds a good starting point.

Please feel free to contact me if you have any suggestions of how to improve the script or if you think it would be very useful to add some other models!

Martin Schöpfer

Email: martin@fag.ucd.ie

The reference axes of the folds shown in the figure above are:

x

x

x

where the primed axes labels are the reference axes of the superposed folds.

Each papermodel also contains information about the amplitude and wavelength of the two fold systems. Folds are idealised using the following plane-strain equations (see p. 955 in:

$x$

y

z

where x

Because there are six end-members and 15 possible intermediate types the papermodels are grouped using the same scheme as in

- End Members:
Six end members of refold structures are distinguished. The reference axes of the initial and the superposed folds are either perpendicular or parallel to each other. Type 0
_{1}and Type 0_{2}do not generate interference patterns but are included in the table for completeness; the 0_{1}and 0_{2}models basically illustrate the geometry of the first fold.

- Intermediate Types - Parallel Rotation:
Nine intermediate types that can be obtained by rotation around one of the fold reference axes are possible. For example the intermediate Type 1 ↔ 2 is obtained by a rotation around x
_{2}of the refold fold (see figure above). All the intermediate type papermodels available under the heading 'parallel rotation' are forms that were obtained by a rotation of 45^{o}around the appropriate reference axis. Note that Type 0_{1}↔ 0_{2}does not modify the first fold and that Type 0_{2}↔ 0_{3}only leads to an increase in fold amplitude, but are included in the table for the sake of completeness.

- Intermediate Types - Oblique Rotation:
Six intermediate types that can be obtained by rotation around an axis which is oblique to the reference axes. The rotation axis makes an angle of 55
^{o}(more precisely cos^{-1}(3^{-1/2})) with all three (mutually perpendicular) reference axes. A rotation of 120^{o}around this axis leads to the transition from one reference axes orientation to the other (e.g. Type 1 ↔ 3). Because all end member papermodels have refold fold reference axes which are N-S, E-W and vertical, the plunge direction and plunge of (one possible) rotation axis is 045/35 (whether the rotation is clockwise or anti-clockwise depends on the transition). All the intermediate type papermodels available under the heading 'oblique rotation' are forms that were obtained by a rotation of 60^{o}around this rotation axis.

Instructions of how to use and modify the script can be found here.

The script and associated functions can be downloaded here.

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