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Detachment Folding

A detachment fold occurs as layer parallel thrusting along a detachment fault develops without upward propagation of a fault; the accommodation of the strain produced by thrusting results in the folding of the overlying rock units. As a visual aid, picture a rug on the floor. By placing your foot on one end and pushing toward the other, the rug slides across the floor (detachment fault) and folds upward (detachment fold). Detachment faulting and folding may occur in either a compressional or extensional environment; though they serve the same purpose, they are controlled by different modes and thus are defined by these modes. Extensional detachment faulting is essentially defined by a low angle normal fault (dip-slip fault), while detachment folding and faulting in compressional settings result from the accommodation of strain. Figure 1, is a generalized representation of the geometry assumed by a detachment fault. A good example of detachment folding is shown in figure 2, the Canadian Rockies.

Contents:

1.Detachment Systems in a Compressional Environment Definitions Modes of Detachment Folding Detachment Fold Evolution Detachment Faulting

References

1. Princeton Structural Geology Group. (2004). Digital Photograph. Retrieved from http://geoweb.princeton.edu/research/SSG/images/detachmentfold.jpg.

2. Homza T and Wallace W. (1994). Geometric and kinematic models for detachment folds with fixed and variable detachment depths. Journal of Structural Geology, 17/4: 575-588.

3. Hayes M and Hanks C. (2008). Evolving mechanical stratigraphy during detachment folding. Journal of Structural Geology, 30: 548-564.

4. Mitra S. (2003). A unified kinematic model for the evolution of detachment folds. Journal of Structural Geology, 25: 1659-1673.

5. Mitra S. (2002). Structural models of faulted detachment folds. American Association of Petroleum Geologist Bulletin, 86/9: 1673-1694.

6. Stewart S. (1996). Influence of detachment layer thickness on style of thin-skinned shortening. Journal of Structural Geology, 18/10: 1271-1274.

7. Contreras, J. (2010). A model for low amplitude detachment folding and syntectonic stratigraphy based on the conservation of mass equation. Journal of Structural Geology, 32, 566-579.

8. Hardy, S. and Poblet, J. (1994). Geometric and numerical model of progressive limb rotation in detachment folds. Geology, 22, 371-374.

9. Wiltschko, D.V. and Chapple, W. M. (1977). Flow of weak rocks in Appalachian Plateau folds. American Association of Petroleum Geologists Bulletin, 61, 5, 653-669.

10. Dalstrom, C. D. C. (1990). Geometric constraints derived from the law of conservation of volume and applied to evolutionary models for detachment folding. American Association of Petroleum Geologists Bulletin, 75, 3, 336-344.

11. Suppe, J. (1983). Geometry and kinematics of fault-bend folding. American Journal of Science, 283, 684-721.

12. Mitchel, M. M. and Woodward, N. B. (1988). Kink detachment fold in the southwest Montana fold and thrust belt. Geology, 16, 162-165.

13. Poblet, J. and McClay, Ken. (1996). Geometry and kinematics of single-layer detachment folds. American Association of Petroleum Geologists Bulletin, 80, 7, 1085-1109.

14. Fischer, M. and Jackson, P. (1999). Stratigraphic controls on eformation patterns in fault-related folds: a detachment fold example from the Sierra Madre Oriental, northeast Mexico. Journal of Structural Geology, 21,613-633.

15. Hardy, S. and Finch, E. (2005). Discrete-element modeling of detachment folding. Basin Research, 17, 507-520.

16. Mitra, S. (2002). Fold-accommodation faults. American Association of Petroleum Geologists Bulletin, 86, 4, 671-693.

17. Mitra, S. and Namson, J. (1989). Equal-area balancing. American Journal of Science, 289, 563-599.

18. Epard, J. L. and Groshong, R. H., Jr. (1994). Kinematic model of detachment folding including limb rotation, fixed hinges and layer-parallel strain. Tectonophysics 247, 85-103.

19. Storti, F., Salvini, F., and McClay, K. (1997). Fault-related folding in sandbox analogue models of thrust wedges. Journal of Structural Geology, 19, 3-4, 583-602.

20. Dahlstrom, C. D. A. (1969). Balanced cross sections. Canadian Journal of Earth Sciences, 6, 743-757.

21. Bowsworth, W. (1983). Foreland deformation in the Appalachian Plateau, central New York: the role of small-scale detachment structures in regional overthrusting. Journal of Structural Geology, 6, 1-2, 73-81.

22. Zehnder, A. T. and Allmendinger, R. W. (2000). Velocity field for the trishear model. Journal of structural Geology, 22, 1009-1014.