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Geologic structures

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This document discusses geologic structures and how they are recorded and studied. It describes how rocks behave under stress and strain, and how their structural features can provide information about geological history. Specifically, it defines different types of folds like anticlines and synclines, and fractures like joints, faults, and different categories of faults including normal, reverse, thrust, and strike-slip faults. Field methods are discussed for observing and recording these structural features on geologic maps and cross sections.

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GEOLOGIC STRUCTURES • “Architecture of bedrock” • Structural Geology– shapes, – arrangement, – interrelationships of bedrock – units & forces that cause them

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Geologic structures

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Geologic structures

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Behavior of rocks to stress & strain • Elastic – Elastic limit • Plastic • Brittle Stress Strain

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Geologic structures

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Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section

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Geologic structures

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Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section

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Geologic structures

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Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section

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Geologic structures

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Geologic structures

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FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin

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Geologic structures

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FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin

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Geologic structures

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FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin

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Geologic structures

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Geologic structures

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FOLDS • Interpreting folds – Open fold – Isoclinal fold – Overturned fold – Recumbent fold

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Geologic structures

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Geologic structures

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Geologic structures

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Geologic structures

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Fractures in rock • Joints – Columnar jointing – Sheet jointing – Joint set • Faults – Dip-slip faults- normal and reverse • Footwall vs. hanging wall – Normal fault • Graben; Rift • Horst ; fault-block mountain range

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Geologic structures

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Geologic structures

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Fractures in rock • Joints – Columnar jointing – Sheet jointing – Joint set • Faults – Dip-slip faults- normal and reverse • Footwall vs. hanging wall – Normal fault • Graben; Rift • Horst ; fault-block mountain range

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Geologic structures

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Geologic structures

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Fractures in rock • Faults – Reverse fault • Thrust fault- low angle reverse fault – Strike-Slip fault • Left-lateral vs. right-lateral

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Geologic structures

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Fractures in rock • Faults – Reverse fault • Thrust fault- low angle reverse fault – Strike-Slip fault • Left-lateral vs. right-lateral

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Geologic structures

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Geologic structures

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Geologic structures

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Geologic structures

  • 1. GEOLOGIC STRUCTURES • “Architecture of bedrock” • Structural Geology– shapes, – arrangement, – interrelationships of bedrock – units & forces that cause them
  • 4. Behavior of rocks to stress & strain • Elastic – Elastic limit • Plastic • Brittle Stress Strain
  • 6. Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section
  • 8. Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section
  • 10. Structures as a Record of the Geologic Past • Geologic maps and field methods – Observations of outcrops – Geologic map – Strike and dip • • • • • Original horizontality Strike Angle of dip Direction of dip Symbols – Geologic cross section
  • 13. FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin
  • 15. FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin
  • 17. FOLDS • Anticline vs. syncline – Hinge line (axis) – Limb – Axial plane • Plunging fold • Structural dome • Structural basin
  • 20. FOLDS • Interpreting folds – Open fold – Isoclinal fold – Overturned fold – Recumbent fold
  • 25. Fractures in rock • Joints – Columnar jointing – Sheet jointing – Joint set • Faults – Dip-slip faults- normal and reverse • Footwall vs. hanging wall – Normal fault • Graben; Rift • Horst ; fault-block mountain range
  • 28. Fractures in rock • Joints – Columnar jointing – Sheet jointing – Joint set • Faults – Dip-slip faults- normal and reverse • Footwall vs. hanging wall – Normal fault • Graben; Rift • Horst ; fault-block mountain range
  • 31. Fractures in rock • Faults – Reverse fault • Thrust fault- low angle reverse fault – Strike-Slip fault • Left-lateral vs. right-lateral
  • 33. Fractures in rock • Faults – Reverse fault • Thrust fault- low angle reverse fault – Strike-Slip fault • Left-lateral vs. right-lateral