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
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
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