When to use which strain analysis method
- This depends on the nature of the strain markers.
- The Breddin method is the most limited: it requires abundant, well preserved strain markers (e.g. fossils on a single bedding plane).
- The Fry and Rf/f methods are more widely applicable.
- Fry can be used for markers (e.g. ooids) that may dissolve at their margins during deformation (e.g. via pressure solution), as well as for markers (e.g. phenocrysts, porphyroblasts) in deformed igneous and metamorphic rocks.
- Rf/f can be used on individual grains, pipes, pebbles, etc.
- Remember, for longitudinal strains, it is not often possible to get sufficient data (e.g. boudinaged belemnites) and need at least two known and non-parallel extensions.