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1 Copyright (c) 2005 Pearson Education Canada, Inc. Chapter 9: Structures & Mountain Building PowerPoint Presentation PowerPoint Presentation Stan Hatfield.

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Presentation on theme: "1 Copyright (c) 2005 Pearson Education Canada, Inc. Chapter 9: Structures & Mountain Building PowerPoint Presentation PowerPoint Presentation Stan Hatfield."— Presentation transcript:

1 1 Copyright (c) 2005 Pearson Education Canada, Inc. Chapter 9: Structures & Mountain Building PowerPoint Presentation PowerPoint Presentation Stan Hatfield. SW Illinois College Stan Hatfield. SW Illinois College Ken Pinzke. SW Illinois College Ken Pinzke. SW Illinois College Charles Henderson. University of Calgary Charles Henderson. University of Calgary Tark Hamilton. Camosun College Tark Hamilton. Camosun College

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3 Chapter 9: Structural Deformation Forces Forces Origin Origin Nomenclature Nomenclature

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5 Copyright (c) 2005 Pearson Education Canada Inc Structural Geology: A Study of Earth’s Architecture Structural Geology: A Study of Earth’s Architecture Earth is a dynamic planet. Some rock units in the Canadian Rockies have been thrust for over 100 kilometres Earth is a dynamic planet. Some rock units in the Canadian Rockies have been thrust for over 100 kilometres Structural geologists study the architecture and processes responsible for deformation of Earth’s crust Structural geologists study the architecture and processes responsible for deformation of Earth’s crust A working knowledge of rock structures is essential to our economic well-being for hazards & resources A working knowledge of rock structures is essential to our economic well-being for hazards & resources

6 Caledonides formed Late Paleozoic with the closing of Iapetus Ocean, forming Pangea

7 Copyright (c) 2005 Pearson Education Canada Inc Deformation Deformation Deformation involves Deformation involves Stress - force applied to a given area Stress - force applied to a given area Types of stress (differential stress that is applied unequally in different directions) Types of stress (differential stress that is applied unequally in different directions) Compressional stress – shortens a rock body Compressional stress – shortens a rock body Tensional stress – tends to elongate or pull apart a rock unit Tensional stress – tends to elongate or pull apart a rock unit Shear stress – produces a motion similar to the slippage that occurs between individual playing cards when the top of the stack is moved relative to the bottom Shear stress – produces a motion similar to the slippage that occurs between individual playing cards when the top of the stack is moved relative to the bottom

8 Compression (convergence) Tension (uplift) Shear (lateral rotation)

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10 Copyright (c) 2005 Pearson Education Canada Inc Deformation How Rocks Deform How Rocks Deform Rocks subjected to stresses greater than their own strength begin to deform usually by folding, flowing, or fracturing Rocks subjected to stresses greater than their own strength begin to deform usually by folding, flowing, or fracturing Weaker rocks deform more easily (lithology, bedding) Weaker rocks deform more easily (lithology, bedding) Fluids and Heat affect lower strength Fluids and Heat affect lower strength Pressure increases rock strength Pressure increases rock strength General characteristics of rock deformation General characteristics of rock deformation Elastic deformation – the rock returns to nearly its original size and shape when the stress is removed Elastic deformation – the rock returns to nearly its original size and shape when the stress is removed Once the elastic limit (strength) of a rock is surpassed, it either flows slowly (ductile deformation) or fractures quickly (brittle deformation) Once the elastic limit (strength) of a rock is surpassed, it either flows slowly (ductile deformation) or fractures quickly (brittle deformation) This depends on Strain Rate and Time/Duration This depends on Strain Rate and Time/Duration

11 Deformed Lacustrine Strata, {Normal Fault} Palmdale, CA

12 Increasing Confining Pressure/Depth Brittle Ductile S max S min S int

13 Shear reorients Foliation

14 Strike: intersection of dipping rock layer with horizontal surface & contact direction on map (azimuth relative to north) Dip: Angle below horizontal

15 Copyright (c) 2005 Pearson Education Canada Inc Folds During crustal deformation rocks are often bent into a series of wave-like undulations called folds During crustal deformation rocks are often bent into a series of wave-like undulations called folds Characteristics of folds Characteristics of folds Most folds result from compressional stresses which shorten & thicken the crust: mountain belts Most folds result from compressional stresses which shorten & thicken the crust: mountain belts Parts of a fold Parts of a fold Limbs – refers to the two sides of a fold Limbs – refers to the two sides of a fold Axis – a line drawn down the points of maximum curvature of each layer Axis – a line drawn down the points of maximum curvature of each layer Axial plane – an imaginary surface that divides a fold more or less symmetrically Axial plane – an imaginary surface that divides a fold more or less symmetrically Asymmetry points in the direction of crustal transport, roll over, vergence Asymmetry points in the direction of crustal transport, roll over, vergence

16 Strike & Dip Permits 3-D Visuals Read the map symbols: Visualize the Cross Sections

17 Copyright (c) 2005 Pearson Education Canada Inc Folds Common types of folds Common types of folds Anticline – upfolded or arched rock layers Anticline – upfolded or arched rock layers Oldest in the middle Oldest in the middle Outwards directed, antithetic dips Outwards directed, antithetic dips Syncline – downfolds or troughs of rock layers Syncline – downfolds or troughs of rock layers Youngest in the middle Youngest in the middle Inwards directed, synthetic dips Inwards directed, synthetic dips Depending on their orientation, anticlines and synclines can be described as Depending on their orientation, anticlines and synclines can be described as Symmetrical, asymmetrical, recumbent (an overturned fold), or plunging Symmetrical, asymmetrical, recumbent (an overturned fold), or plunging Antiform & Synform when age is unknown Antiform & Synform when age is unknown Anticlinorium or Synclinorium for continental size Anticlinorium or Synclinorium for continental size

18 Symmetric Anticline Opposing outwards dips Oldest beds in middle

19 Plunging Anticline Strike wraps around Nose points down plunge

20 East Verging Fold & Thrust Belt  Vergence (transport) Direction 

21 Kink Folds, Sharp Axial Planes: SynclineAnticline

22 Plunging Folds: Tilted or Refolded Fold Belt

23 Doubly Plunging Anticline or Asymmetric Dome

24 Chevrons on flank of Monocline Reverse Fault in Basement Drape Fold Compression

25 Copyright (c) 2005 Pearson Education Canada Inc Folds Common types of folds Common types of folds Monoclines – large, step-like folds in otherwise horizontal sedimentary strata Monoclines – large, step-like folds in otherwise horizontal sedimentary strata Other types of folds Other types of folds Dome Dome Upwarped displacement of rocks Upwarped displacement of rocks Circular or slightly elongated structure Circular or slightly elongated structure Oldest rocks in centre, younger rocks on the flanks Oldest rocks in centre, younger rocks on the flanks Basin Basin Downwarped displacement of rocks Downwarped displacement of rocks Circular or slightly elongated structure Circular or slightly elongated structure Youngest rocks in centre, older rocks on the flanks Youngest rocks in centre, older rocks on the flanks

26 Salt, Intrusion Or Central Uplift

27 Subsidence

28 Black Hills, SD Cretaceous (Laramide Orogeny) Deforms Mesozoic through Precambrian Rocks Pc Pz Mz

29 Late Paleozoic Michigan Basin

30 Copyright (c) 2005 Pearson Education Canada Inc Faults Faults Faults are fractures in rocks along which appreciable displacement has taken place Faults are fractures in rocks along which appreciable displacement has taken place Brittle/Shallow in the upper crust Brittle/Shallow in the upper crust Ductile/Deep in the lower crust Ductile/Deep in the lower crust Sudden movements along faults are the cause of most earthquakes usually deeper than 5 km to about 660 km Sudden movements along faults are the cause of most earthquakes usually deeper than 5 km to about 660 km Along faults, rock is often broken into breccia, pulverized into gouge or polished as slickenslides Along faults, rock is often broken into breccia, pulverized into gouge or polished as slickenslides Faults are classified by their relative orientation & movement which can be Faults are classified by their relative orientation & movement which can be Horizontal, vertical, or inclined Horizontal, vertical, or inclined Strike Slip, Dip Slip or Oblique Slip Strike Slip, Dip Slip or Oblique Slip

31 Normal Fault (Tension)

32 Copyright (c) 2005 Pearson Education Canada Inc Types of Faults Types of Faults Dip-Slip Faults: (Normal, Reverse & Thrust) Dip-Slip Faults: (Normal, Reverse & Thrust) Movement is mainly parallel to the dip of the fault surface Movement is mainly parallel to the dip of the fault surface May form in either compression or tension May form in either compression or tension Normal faults thin the crust & miss out some strata Normal faults thin the crust & miss out some strata Reverse & Thrust Faults thicken the crust & double some strata Reverse & Thrust Faults thicken the crust & double some strata May produce long, low cliffs called fault scarps May produce long, low cliffs called fault scarps Active if fault cuts to surface Active if fault cuts to surface Resequent if erosional & controlled by strata Resequent if erosional & controlled by strata Parts of a dip-slip fault include the hanging wall (rock surface above the fault) and the footwall (rock surface below the fault) Parts of a dip-slip fault include the hanging wall (rock surface above the fault) and the footwall (rock surface below the fault) Faults Faults

33 Normal Fault: (Extension)

34 Hanging Wall Falls Section Thins

35 Copyright (c) 2005 Pearson Education Canada Inc Types of dip-slip faults Normal Faults Hanging wall block moves down relative to the footwall block Hanging wall block moves down relative to the footwall block Accommodate lengthening or extension of the crust Accommodate lengthening or extension of the crust Many are small like landslides with displacements of a metre or so Many are small like landslides with displacements of a metre or so Larger scale normal faults are associated with Mid Ocean Ridges, Rifts & Fault-block mountains, Horsts & Grabens Larger scale normal faults are associated with Mid Ocean Ridges, Rifts & Fault-block mountains, Horsts & Grabens Reverse & Thrust Faults Hanging wall block moves up relative to the footwall block Hanging wall block moves up relative to the footwall block Accommodate shortening or compression of crust Accommodate shortening or compression of crust Larger scale thrust faults are associated with edges of Fold & Thrust Mountain Belts Larger scale thrust faults are associated with edges of Fold & Thrust Mountain Belts Faults Faults

36 Copyright (c) 2005 Pearson Education Canada Inc Faults: Horst & Graben as in Rifts or Basin & Range Diagrammatic sketch of downfaulted (graben) and upfaulted (horst) blocks. Note that there are places where if you drilled there is missing stratigraphy due to extensional faulting.

37 Development of a Normal Fault

38 Most Normal Faults “sole-out” and become Listric with depth.

39 Copyright (c) 2005 Pearson Education Canada Inc Types of dip-slip faults Types of dip-slip faults Reverse and Thrust Faults Reverse and Thrust Faults Hanging wall block moves up relative to the footwall block Hanging wall block moves up relative to the footwall block Reverse faults have dips greater than 45 o and thrust faults have dips less than 45 o Reverse faults have dips greater than 45 o and thrust faults have dips less than 45 o Most thrust faults have flat soles and arise from a common surface called a decollement Most thrust faults have flat soles and arise from a common surface called a decollement Accommodate shortening of the crust Accommodate shortening of the crust Strong compressional forces Strong compressional forces Common in mountain belts like the Alps and Rockies Common in mountain belts like the Alps and Rockies An isolated outlying remnant of a thrust sheet is called a klippe (old rocks surrounded by younger rocks, Teeth point inwards) An isolated outlying remnant of a thrust sheet is called a klippe (old rocks surrounded by younger rocks, Teeth point inwards) Faults: Thrust & Reverse Faults: Thrust & Reverse

40 Reverse Fault: (Compression) Hanging Wall Rises Section Thickens Angle > 15°

41 Thrust Fault: (Compression) Laramide Orogeny Rockies Section thickens Older over younger Thrust Vergence direction

42 Crowsnest Mountain Klippe: Thrust Outlier Paleozoic Limestone Cretaceous Shales

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45 Right Lateral Strike Slip Fault: Like Queen Charlotte & San Andreas

46 Columnar Joints: Thermal Cooling

47 Joints from from Decompression

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