Fold Structures

Folding is almost always accompanied by a number of associated minor structures. These include:

• drag folding

  Minor folds with the same plunge and axial plane orientation as the larger fold structure.
  

• axial plane cleavage

  Alignment of platey minerals normal to the major compressive stress responsible for folding and parallel to the axial plane. The intersection of axial plane cleavage with bedding produces a lineation with the same plunge as the fold axis.
  

• boudinage

  Flow of less competent beds around thin competent beds fragmented into blocks by tensile failure.
  

• bedding surface lineations

  Striations developed by shear along bedding surfaces during folding.

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  Faulting Fold Classification Outline

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  (c) Department of Civil and Geological Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, Canada, S7N 5A9