1. Classroom presentations to accompany Understanding Earth, 3rd edition prepared by Peter Copeland and William Dupré University of Houston Chapter 10 Folds, Faults, and Other Records of Rock Deformation

2. Deformation of Rocks

3. Deformation of rocks Folds and faults are geologic structures. Structural geology is the study of the deformation of rocks and the effects of this movement.

4. Phil Dombrowski Fig. 10.1 Small-scale Folds

5. Small-scale Faults Tom Bean Fig. 10.2

6. Orientation of deformed rocks We need some way to describe the distribution of geologic structures. Strike Strike: bearing of a line defined by the intersection of the plane in question and the horizontal Dip Dip: acute angle between the plane and the horizontal, measured perpendicular to strike.

7. Fig. 10.4

9. Dipping Sedimentary Beds Chris Pellant Fig. 10.3

10. P.L. Kresan Cockscomb Ridge, S. Utah

11. Dip Strike P.L. Kresan

12. Geologic Map and Cross Section Fig. 10.5

13. Stress (force per unit area) Types of directed stresses include: Compression Extension Shear

14. Compression Action of coincident oppositely directed forces acting towards each other

15. Tension Action of coincident oppositely directed forces acting away from each other

16. Shear Action of coincident oppositely directed forces acting parallel to each other across a surface in a couple

17. Strength Ability of an object to resist deformation Compressive or tensile

18. Strain Any change in original shape or size of an object in response to stress acting on the object

19. Types of deformation Elastic Ductile (plastic) Brittle (rupture)

20. Elastic deformation Temporary change in shape or size that is recovered when the deforming force is removed

21. Ductile (plastic) deformation Permanent change in shape or size that is not recovered when the stress is removed Occurs by the slippage of atoms or small groups of atoms past each other in the deforming material, without loss of cohesion

22. Brittle deformation (rupture) Loss of cohesion of a body under the influence of deforming stress Usually occurs along sub-planar surfaces that separate zones of coherent material

23. Factors that affect deformation Temperature Pressure Strain rate Rock type The variation of these factors determines if a rock will fault or fold.

24. Effects of rock type on deformation Some rocks are stronger than others. competent: competent: rocks that deform only under great stresses incompetent: incompetent: rocks that deform under moderate to low stresses

25. Tectonic Forces and Resulting Deformation Fig. 10.6

26. Experimental Deformation of Marble M.S. Patterson Fig. 10.7 Brittle Deformation Ductile Deformation

27. Types of folds Types of folds (bent planar structures) anticline anticline: older rocks on the inside syncline syncline: older rocks on the outside (scale (scale - from mm to tens of km)

28. Anticlines and Synclines Fig. 10.9

29. Fold terms axial Plane: the plane of mirror symmetry dividing the fold into two limbs axis: line formed by the intersection of the axial plane and a bedding plane horizontal fold: where the fold axis is horizontal plunging fold: where the fold axis is not horizontal

30. Fold Terminology Fig. 10.10

31. Bill Evarts Fig. 10.11

32. Symmetrical, Asymmetrical and Overturned Folds Fig. 10.12

33. Bill Evarts Axial plane Anticline Fig. 10.11

34. Breck Kent Asymmetric Folds AntiformSynform

35. Phil Dombrowski Fig. 10.1 Overturned Folds

36. Overturned Syncline, Israel Geological Survey of Israel Fig. 10.13

37. Map View of Plunging Folds Fig. 10.14

38. Oil Field at crest of Plunging Anticline Kurt N. Coonstenius

39. Axial Trace of Plunging Anticline* * Note Landers Oil Field on crest of anticline Kurt N. Coonstenius

40. Valley and Ridge Province P. L. Kresan

41. J. Shelton, Geology illustrated Fig. 10.15 Plunging Folds in the Valley and Ridge

42. Valley and Ridge Province of the Appalachian Mountains Fig. 10.19

43. Raplee Anticline, S.E. Utah

44. Raplee Anticline on the San Juan River, Utah

45. Domes and Basins Fig. 10.16

46. John S. Shelton Fig. 10.17 Sinclair Dome, Wyoming

47. Syncline Fig. 10.18

48. Drape Fold over Reverse Fault, WY George Davis

49. Columns Formed by Joint- controlled Weathering Terry Englander Fig. 10.20

50. Joint-controlled Landscape, S.E. Utah

51. Faults Fractures in rocks created by earthquakes (hanging wall, footwall, displacement) Dip-slip faults — normal — reverse Strike-slip faults Oblique-slip faults

52. Faults may be "reactivated" History of a fault may be very long. Previously developed weakness is the most likely place to break. Reactivation may have opposite sense as before. Active = 10,000 to 100,000 years Very important for dams and reactors

53. Dip-slip faults Motion of the fault blocks, parallel to the dip direction.

54. Classification of Faults hanging wall footwall cross section

55. Classification of Faults hanging wall footwall cross section

56. Normal Fault footwall hanging wall cross section

57. Reverse Fault footwall hanging wall cross section

58. Thrust Fault footwall hanging wall cross section Thrust faults are low-angle reverse faults.

59. Fig. 10.22

60. Fig. 10.22a

61. Normal Dip-slip Fault

62. Fig. 10.22b

63. Reverse Dip-slip Fault

64. Strike-slip faults Motion of the fault blocks, parallel to the strike direction.

65. Left-lateral Strike Slip Fault map view

66. Right-lateral Strike Slip Fault map view

67. Fig. 10.22c

68. Gudmundar E. Sigvaldason Fig. 10.21 Strike- slip Fault

69. Fig. 10.22d

70. Large-scale Overthrust Sheet Fig. 10.23

71. Keystone Thrust Fault, S. Nevada John S..Shelton Fig. 10.24 Cambrian Limestone Jurassic Sandstone

72. Lewis Thrust, Sawtooth Range, Wyoming Kurt N. Coonstenius

73. French Thrust, Wyoming Cretaceous Shale Mississippian Limestone Kurt N. Coonstenius

74. Fig. 10.25 Rift Valley Formed by Extension

75. Wildrose Graben, Southern California

76. NASA/TSADO/Tom Stack Fig. 10.26

77. Stages in the Development of the Basin and Range Province in Nevada and Utah Fig. 10.27

78. Stages in the Development of the Basin and Range Province in Nevada and Utah Fig. 10.27

79. 1872 Fault Scarp, Southern California

80. 1988 Armenian Earthquake Fault Scarp Fig. 10.28 Armando Cisternas

81. 1992 Landers Earthquake Fault Scarp

82. Dating the order of deformation Use geometry: Inclusions Cross-cutting relationships Combine with fossils and radiometric dating