Why study geologic structures?


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Why study geologic structures?













Primary Geologic Structures

  • Geometric features developed during formation of a rock body

  • Microscopic to mountain scale

  • Formed in sedimentary or igneous environments

  • Provide clues about environment of rock formation



Sedimentary Structures

  • Bedding

  • Uncomformities

  • Cross bedding

  • Graded bedding

  • Ripple marks

  • Mud cracks

  • Trace fossils

  • Etc.





























Igneous Structures









































Secondary Geologic Structures develop after formation of the rock body





























σ1 horizontal, σ3 vertical — reverse faults

  • σ1 horizontal, σ3 vertical — reverse faults

  • σ1 vertical, σ3 horizontal — normal faults

  • σ1 horizontal, σ3 horizontal — strike-slip faults



Reverse faults: should form at ~30° dip

  • Reverse faults: should form at ~30° dip

  • Normal faults: should form at ~60° dip

  • Strike-slip faults: should form at ~90° dip



Thrust faults — mechanically unfavorable

  • Thrust faults — mechanically unfavorable

  • Low-angle normal faults — mechanically very unfavorable



















































Foliation

























Just how deformed is this rock?






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