<p>Structurally crinkled gyprock from the Permian of New Mexico, USA. (8.4 centimeters across at its widest)
</p><p>This is a sample of gyprock (rock gypsum), a finely crystalline-textured, chemical sedimentary rock dominated by the mineral gypsum (CaSO4·2H2O - hydrous calcium sulfate).  The whitish-gray layers are the gypsum.  The dark brown layers are calcite (CaCO3 - calcium carbonate).  Gyprock is an evaporite, which forms by the evaporation of water (usually seawater) and the precipitation of dissolved minerals.  The dark brown calcite layers were originally straight and horizontal.  The fine-scale folding or crinkling seen in this specimen was due to early Cenozoic structural deformation, not gypsum-to-anhydrite (or vice-versa) transformations (see Anderson &amp; Kirkland, 1987).
</p><p>Stratigraphy: Castile Formation, upper Upper Permian
</p><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)
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<hr><p>Reference cited:
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Anderson, R.Y. &amp; D.W. Kirkland.  1987.  Banded Castile evaporites, Delaware Basin, New Mexico.  Rocky Mountain Section of the Geological Society of America, Centennial Field Guide Volume 2: 455-458.
<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/15823222696/">Structurally crinkled gyprock (Castile Formation, Upper Permian; State Line outcrop, southern Eddy County, New Mexico, USA) 3</a>