The Pilbera has undergone two significant phases of compression, N-S resulting in E-W folds and NNE-SSW -> NE-SW resulting in ENE-WNW (ish) folding. The overprinting of these two deformations creates some lovely interference patterns. I rather like the M fold in this hillside as erosion and the inclination of the bedding has conspired to turn it into a heart shape. M folds are typically found in a fold hinge of an F1 (first deformation fold) but can form on the limbs of an F1 when it is refolded by D2 (Deformation #2) creating F2 folds which are typically non-cylindrical due to the prior orientation of the bedding.
If you're interested in how interference patterns look with at a variety of orientation, plunge and dips visit the wonderful page by the Fault Analysis Group at the Univeristy College of Dublin.
No comments:
Post a Comment