Structural Geology: Lecture 8

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Structural Geology Lecture 8
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Distribution of Cordilleran Metamorphic Core
Complexes
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Tilt domain in the Basin Range Province
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3-D warped Whipple detachment fault

• Mylonitic shear zone.
• A detachment fault
• Highly extended hanging wall
• A breakaway fault.

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J.F. Dunn, 1986.
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Whipple Detachment Fault
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Whipple Detachment Fault
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• Tectonic settings for normal faults
• Mid-ocean ridges (slow spreading centers, 3
  cm/year).
• Continental rifts and extensional provinces
  Basin Range, Rio Grande, Baikal, and east Africa
  rift).
• Back arc basins Japan Sea, South China Sea.
• Collision zones Tibetan plateau.

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Room problems of normal faults and their
implications for kinematics
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Is this cross section possible?
Region with surface observations
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• Basic terminology and concepts
• Simple-shear vs. pure-shear extension
  (Wernicke vs. McKenzie Models for continental
  extension).
• Synthetic vs. antithetic normal faults.
• Historical development of the concept of
  Cordilleran Metamorphic Core Complexes.
  (Armstrong, 1971 Anderson, 1972 Coney, 1980
  Wernicke, 1981 Lister and Davis, 1989).

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Room problem associated with conjugate normal
faults
Unbalanced cross section because it is not
restorable
Not a possible cross section, therefore it must
be wrong?
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rigid
rigid
rigid
Ductile lower crust