Title: Normal Faults Extensional Tectonics
1Normal FaultsExtensional Tectonics
2Tectonic Settings for Extension
- Divergent plate motions
- Gravitational collapse
- Over-thickened crust
- Continental margins
- Salt Domes
3Extensional Tectonics
4Divergent BoundaryNormal Faults, rifts
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6Continental Extension
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8Divergent Boundaries Continental Plate Separation
Parallel valleys volcanoes and earthquakes.
East African Rift Valley
Somali Subplate
African Plate
9Rifts
Rifts Bounded by normal faults
10Back Arc extension
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12Extension of the lithosphere 1
13Extension of the lithosphere 2
14Lithospheric Extension
- Thinning of the lithosphere
- Normal faulting at the surface
- High heat flow (rinsing of the isotherms)
- Thermal subsidence - gt sedimentary basins
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16North Sea Extensional Basin
17Pure shear vs. simple shear systems
18Gravitational Collapse of Mt. Belts
19Basin and Range Province
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21New Mountains-Active Fault Basin and Range
Province
22Two modes of extension
23Out crop- domino blocks
24Sandbox- Block rotation
Sand above plasticine
25Block Rotation
26Domino block rotation in the Basin and Range
27Listric (curved) Faults- roll over anticlines
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29Small roll-overs
30Sedimentation during faultingGrowth faulting
Animation by R. Allmendinger http//www.geo.cornel
l.edu/geology/faculty/RWA/movies/
31Curved faults Block rotationGrowth Strata
0
3 km
32Gulf of Mexico
33Passive Margin
34Gulf of MexicoSalt
35Extension Above Salt Diapir
36Transfer zone in a rift
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39Successive generations of normal faults
- Older faults rotate and become inactive
- New faults cross-cut them
- Result large magnitude extension
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