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Normal Faults Extensional Tectonics. Tectonic Settings for Extension Divergent plate motions Gravitational collapse –Over-thickened crust –Continental

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Normal Faults Extensional Tectonics Slide 2 Tectonic Settings for Extension Divergent plate motions Gravitational collapse Over-thickened crust Continental margins Salt Domes Slide 3 Extensional Tectonics Slide 4 Divergent Boundary Normal Faults, rifts Slide 5 Slide 6 Continental Extension Slide 7 Slide 8 Divergent Boundaries Continental Plate Separation East African Rift Valley Somali Subplate African Plate Parallel valleys; volcanoes and earthquakes. Slide 9 Rifts Bounded by normal faults Slide 10 Back Arc extension Slide 11 Slide 12 Extension of the lithosphere 1 Slide 13 Extension of the lithosphere 2 Slide 14 Lithospheric Extension Thinning of the lithosphere Normal faulting at the surface High heat flow (rinsing of the isotherms) Thermal subsidence - > sedimentary basins Slide 15 Slide 16 North Sea Extensional Basin Slide 17 Pure shear vs. simple shear systems Slide 18 Gravitational Collapse of Mt. Belts Slide 19 Basin and Range Province Slide 20 Slide 21 New Mountains-Active Fault Basin and Range Province Slide 22 Two modes of extension Slide 23 Slide 24 Sandbox- Block rotation Sand above plasticine Slide 25 Block Rotation Slide 26 Domino block rotation in the Basin and Range Slide 27 Listric (curved) Faults- roll over anticlines Slide 28 Slide 29 Small roll-overs Slide 30 Sedimentation during faulting Growth faulting AnimationAnimation by R. Allmendinger http://www.geo.cornell.edu/geology/faculty/RWA/movies/ Slide 31 Curved faults Block rotation Growth Strata 3 km 0 Slide 32 Gulf of Mexico Slide 33 Passive Margin Slide 34 Gulf of Mexico Salt Slide 35 Extension Above Salt Diapir Slide 36 Transfer zone in a rift Slide 37 Slide 38 Slide 39 Older faults rotate and become inactive New faults cross-cut them Result= large magnitude extension Successive generations of normal faults Slide 40