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Fault-related folds

Fault-related folds. Fault Bend folds-Ramp anticlines. Could also relate to fault propagation. Folds related to blind thrust faults. Fault-tip folds. Detachment folds. Fault-detachment folds evolve into fault-tip folds and fault – bend folds. Fault-Bend Fold (assumes bed parallel shear).

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Fault-related folds

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  1. Fault-related folds

  2. Fault Bend folds-Ramp anticlines Could also relate to fault propagation

  3. Folds related to blind thrust faults Fault-tip folds Detachment folds Fault-detachment folds evolve into fault-tip folds and fault –bend folds

  4. Fault-Bend Fold (assumes bed parallel shear) • Fault Bend Folds (FBF) • throughgoing faults - slip is conserved. • Fold amplitude is determined by the thickness above the lower hanging wall flat. • Once the fold has achieved maximum amplitude, it only grows in width.

  5. Fault-bend folding (Rich, 1934)… Flat: Fault is parallel to bedding Ramp: Fault cuts trough bed

  6. Fault-bend folding (Rich, 1934)… The non planar fault has a flat-ramp-flat geometry. Translation of the thrust sheet along that fault requires axial surfaces. Note the difference between the active and passive axial surfaces

  7. Duplex system

  8. Fault-bend-folding +Imprication/Duplex…

  9. Balanced cross-section across the Pine Mountain (Southern Appalachians) (Suppe, 1983)

  10. Balanced cross-section Across the Pine Mountain (Southern Appalachians) (Mitra, 1988)

  11. Structural elevation in balanced cross sections:the problem of filling space

  12. Structural elevation in balanced cross sections:the problem of filling space

  13. (Caer et al, J. Struct. Geol, 2015)

  14. (Caer et al, J. Struct. Geol, 2015)

  15. (Caer et al, J. Struct. Geol, 2015)

  16. Klippe (Robinson, Geosphere, 2008)

  17. The  Move software Midland Valley Ltd.  MOVE is the core product of the Move Suite providing a powerful structural modelling environment.  Move provides data integration, 2D cross-section construction and 3D model building and is the base for the specialist structural modules for 2D and 3D kinematic, geomechanical, fracture and sediment modelling. 2D MOVE - removes deformation to restore the present day interpretation to its un-deformed state, adhering to line length and area balancing structural geology principles and taking into account the importance of geological time and its impact on the structure of today.

  18. II. Balanced cross sections • Principles • Fault-related folds: • Fault-bend folds • Fault-tip folds

  19. Fault-tip Folds Detachment fold (folding is always non-parallel) Fault-tip fold (non-parallel fold) Fault-propagation Fold (parallel fold)

  20. Fault-Propagation Fold • Fault Propagation Folds (FPF) • fault slip is not conserved. Fault displacement is taken up by folding • Fault tip is marked by a ductile ‘process zone’. • Ideally, FPF’s evolve into FBF’s (Suppe and Medwedeff, 1984)

  21. (Hughes&Shaw, 2014)

  22. Let’s practice…

  23. Describe: from: http://earth.leeds.ac.uk/learnstructure/index.htm from: http://www.stmarys.ca/academic/science/geology/structural/

  24. similar fold parallel fold from: http://earth.leeds.ac.uk/learnstructure/index.htm from: http://www.stmarys.ca/academic/science/geology/structural/ Recumbent tight similar syncline and anticline Upright open parallel syncline

  25. try to sketch: shallowly plunging, upright, tight, similar syncline Assume fold axis plunges toward N45E

  26. Example from the Argentinian Cordillera

  27. What is it?

  28. Primary strucure due to cross-bedding stratification. Not related to deformation

  29. Fault related Folds all from: http://earth.leeds.ac.uk/learnstructure/index.htm http://earth.leeds.ac.uk/learnstructure/index.htm

  30. Fault related Folds Fault-tip Fold Fault-bend Fold http://earth.leeds.ac.uk/learnstructure/index.htm

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