REVERSE FAULTS

Anderson's Classification of Reverse Faults

Compressional or Contractional faults-

Develop in response to shortening

      Tend to repeat stratigraphic units

      Hanging Wall over Footwall

        Displaces older rock over younger rocks

  Reverse Fault Geometry:

Planar                    

Listric                    

Thrust

Transpressional Faults: oblique slip

Thrust- reverse fault with dip angles less than 45⁰.

           Flats and Ramps

Thrust Faults:

         Cut up section,

        (unless fault develops in already folded rock)

         Propagate in direction of motion

         Transport old rock up against younger rock 

         Footwall Imbrication

          Younger thrusts develop towards foot wall

          Older thrusts are carried �piggy back�

Fault Terrain Terms:

                Allochthon

                Autochton

                Window

                Klippe

                Hinterland

                Foreland

Thrust Systems: 

Duplex structures-

Animation:             http://www.geo.lsa.umich.edu/~vdpluijm/animations/thrustduplex_ani.gif

Imbricate fans-

   imbricate faults sole into basal Floor thrust  

X-section illustrating imbricate thrusting in   

      Himalayas (courtesy of USGS)

Thin Skin Thrusting-

Platform sedimentary rocks

Thin uplifted sheet 

Thick Skin Thrusting-

Basement Involved

Thick uplifted sheet

Foreland Basins-

Isostatic loading due to �telescoping�

Fault Related Folds:  

Check out animations at:

http://courses.eas.ualberta.ca/eas421/thrustanimations.html

            Break Thrust Folds-    

                Folding precedes faulting

Fault Bend Folds-                

   Fault forms before folding

    Hanging wall bends from ramp to flat

           Detachment Folds-

                common in incompetent rock (salt)

           Fault Propagation Fold-

                Fault/Fold synchronous

           Fold Nappes

Fold and Thrust Belt Map Patterns

          Oroclinal-  arcuate bend of thrust belts

http://visibleearth.nasa.gov/cgi-bin/viewrecord?1046

          Salients-  promontories              

         Recesses- embayments

  Radar Image of Appalachians (NASA)

Fold and Thrust Belt Mechanics:

        Gravity Sliding- sliding downslope

Gravity Spreading- of overthickened crust

          Critical Taper Theory

Thrust Sheet Paradox:

          Elevated Fluid Pore Pressures

          Asperities

Inversion Tectonics-

 Involves fault reactivation

 Different tectonic regime

Old normal faults may be reactivated under compression to move in  a reverse sense of motion

Tectonic Occurrence:

Convergent Plate Boundaries

USGS Maps of idealized Convergent boundary (above) and (below) the "Pacific Ring of Fire"

NOAA Gravity Anomaly Map of the Ocean Basins

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