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Normal Faults Extensional Tectonics

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Bounded by normal faults. Back Arc extension. Extension of the lithosphere 1 ... Sand above plasticine. Block Rotation. Domino block rotation in the Basin and Range ... – PowerPoint PPT presentation

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Title: Normal Faults Extensional Tectonics


1
Normal FaultsExtensional Tectonics
2
Tectonic Settings for Extension
  • Divergent plate motions
  • Gravitational collapse
  • Over-thickened crust
  • Continental margins
  • Salt Domes

3
Extensional Tectonics
4
Divergent BoundaryNormal Faults, rifts
5
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6
Continental Extension
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Divergent Boundaries Continental Plate Separation
Parallel valleys volcanoes and earthquakes.
East African Rift Valley
Somali Subplate
African Plate
9
Rifts
Rifts Bounded by normal faults
10
Back Arc extension
11
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12
Extension of the lithosphere 1
13
Extension of the lithosphere 2
14
Lithospheric Extension
  • Thinning of the lithosphere
  • Normal faulting at the surface
  • High heat flow (rinsing of the isotherms)
  • Thermal subsidence - gt sedimentary basins

15
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16
North Sea Extensional Basin
17
Pure shear vs. simple shear systems
18
Gravitational Collapse of Mt. Belts
19
Basin and Range Province
20
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21
New Mountains-Active Fault Basin and Range
Province

22
Two modes of extension
23
Out crop- domino blocks
24
Sandbox- Block rotation
Sand above plasticine
25
Block Rotation
26
Domino block rotation in the Basin and Range
27
Listric (curved) Faults- roll over anticlines
28
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Small roll-overs
30
Sedimentation during faultingGrowth faulting
Animation by R. Allmendinger http//www.geo.cornel
l.edu/geology/faculty/RWA/movies/
31
Curved faults Block rotationGrowth Strata
0
3 km
32
Gulf of Mexico
33
Passive Margin
34
Gulf of MexicoSalt
35
Extension Above Salt Diapir
36
Transfer zone in a rift
37
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Successive generations of normal faults
  • Older faults rotate and become inactive
  • New faults cross-cut them
  • Result large magnitude extension

40
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