Incontrast to buckling in which case folds are generated as periodic waveforms when compression is applied parallel or at small angle (<45 degrees) to the layer boundaries. In case of bending, there is no such instability generated and folds form as a result of bending by force normal to layers or torsional forces. The folds generated are no periodic waveforms and are chaotic structures. They do not throw any light on the mechanical properties of the layers deformed.
BENDING FOLDS formed by a buckling instability and no competence contrast is necessary to produce these folds. The periodic or irregular motion does not go parallel to layering but normal to it. There are nothing like contact strain zones and since folding involves compression in the outer arc region, the folding zone is of greater width in the inner arc area. Any type of stress pattern may be able to produce bending folds. The contact strain that produces bending folds around competent inclusions does not penetrate very far into the surroundings.