<p>Faulted gyprock from the Permian of New Mexico, USA. (field of view 2.4 centimeters across)
</p><p>Faults are quite common in orogenic belts.  Faults are defined as fractures in rocks along which differential displacement has occurred.  Dip-slip faults are those involving movement of rocks in non-horizontal directions.  Strike-slip faults involve movement of rocks in horizontal directions.
</p><p>The two common types of dip-slip faults are normal faults and reverse faults.
</p><p>The rock shown above is a sample of gyprock (rock gypsum), consisting of interlaminated whitish gypsum and dark brown calcite.  There is a small-scale reverse fault going through the center of the sample.  Reverse faults result from compressional stress, and involve upward movement of the hanging wall and downward movement of the footwall.
</p><p>Stratigraphy: Castile Formation, upper Upper Permian
</p>
Locality: State Line outcrop, roadcut on either side of Rt. 180/Rt. 62, between Carlsbad Caverns National Park and Guadalupe Mountains National Park, immediately north of the Texas border, southern Eddy County, southeastern New Mexico, USA (32° 00' 34.2" North latitude, 104° 29' 55.0" West longitude)
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
CC BY 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/15159863205/">Reverse fault in gyprock (Castile Formation, Upper Permian; State Line outcrop, southern Eddy County, New Mexico, USA)</a>