2. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

6. Problem imaging the forelimb… critical for evaluating the structural style

7. Problem imaging fore-limb from seismic… interpretations are commonly strongly model-driven

8. First-pass interp - steep faults..…not in vogue

9. Low-angle thrust (detachment at depth??)

10. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

11. Simple fault-bend fold Suppe model

17. Suppe fault bend folding….. But is this too simplistic a style?

19. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

23. Fault-bend folding Fault-propagation folding Panels of constant-dip strata, folds grow by hinge migration

24. Test kinematic models using growth strata Growth triangles

25. “growth fans” rather than “growth triangles are the usual style…. So are the fault- bend models applicable?

26. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

29. Detachment fold

31. From Sherkati et al. 2004 (Mar. Pet. Geol. )

32. McQuarrie 2004 J. Struct. Geol.

34. Structural styles in the Zagros….. Geomorphologic evolution suggests buckle sheet “detached” on Hormuz salt + minor internal detachments

35. Geomorphological studies of developing folds using Landsat images from the Zagros Mountains, Iran. (Henry Lickorish)

38. Fold collision

39. Fold interactions: Long cylindrical Abrupt plunges Collided folds Merged folds

40. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

41. Fold train initiates If one fold amplifies slightly faster…it will weaken So strain transferred onto that fold - other folds slow down/stop. System experiences stress drop.

42. CONTROLS ON BUCKLE FOLD EVOLUTION?

44. Quantify through modelling by Martin Casey….

45. Buckle fold development Finite element modelling by Martin Casey

46. Viscosity ratio 10:1 Differential stress

50. Stress concentrated in hinge area Differential stress Stress drop on limbs

51. Example….

52. Chevron fold (Hartland Quay) Bed-parallel slip Strain in hinge

53. Structures on limbs shear fibres on bedding fractures in beds More models…..

54. Contrast with higher viscosity ratio...

59. Stress drop throughout

60. Viscosity ratio 10:1 Viscosity ratio 40:1 Longer wavelength (and lower diff stress) for higher viscosity contrast

61. Unloading limbs - can promote fracture here Stress history is complex But can be modelled…..

62. Modelling fracture potential and evolution Timing might be crucial…. Diagenetic “events” Fluid migration “events”

63. Buckling is important Stress history is complex Model in 3D… and…. Fold-thrust complexes

64. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

65. Multilayers?

66. Examples from Champsaur

69. WNW ESE

71. WNW ESE

73. Thrust cuts through Ramp area folds Thrust breaks back ? continuum - localised slip plus distributed deformation

74. WNW ESE

77. Different predictions for sand connectivity Precursor buckling important….

78. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear

82. Strat YES Complex localisation orogenic interiors?

90. Introduction Fault-bend folding Fault-propagation folding Detachment folding Buckles Fold-thrust complexes in multilayers Trishear