page_title: Fold (geology)
hierarchical_section_title: Fold (geology)
caption_attribution_description: English: Folded gyprock (Castile Formation, Upper Permian; State Line outcrop, southern Eddy County, New Mexico, USA) 7 Folded gyprock in the Permian of New Mexico, USA. This is the famous (&amp; former) State Line outcrop, along Rt. 180/Rt. 62 at the New Mexico-Texas border. The cut contains finely-laminated gyprock (rock gypsum), a finely crystalline-textured, chemical sedimentary rock composed of the mineral gypsum (CaSO4·2H2O - hydrous calcium sulfate). Gyprock is an evaporite, which forms by the evaporation of water (usually seawater) and the precipitation of dissolved minerals. The whitish layers are gypsum. The dark brown layers are calcite. Each gypsum-calcite couplet represents one year's worth of deposition. These layers could be called varves. The calcite-gypsum (or -anhydrite) couplets have been successfully correlated throughout the Delaware Basin. Spectacular crinkling, small-scale folding, and small-scale faulting are present here. The folds and faults formed as a result of early Cenozoic structural deformation, not gypsum-to-anhydrite (or vice-versa) transformations (see Anderson &amp; Kirkland, 1987). This world-class outcrop was destroyed in the late 2000s by the highway department to convert the two-lane highway into a four-lane divided highway. Stratigraphy: Castile Formation, upper Upper Permian 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) Reference cited: 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.
context_page_description: In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets. Synsedimentary folds are those formed during sedimentary deposition.
  Folds form under varied conditions of stress, pore pressure, and temperature gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault, at the tip of a propagating fault, by differential compaction or due to the effects of a high-level igneous intrusion e.g. above a laccolith.
context_section_description: In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation.  Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as fold trains). Synsedimentary folds are those formed during sedimentary deposition.
  Folds form under varied conditions of stress, pore pressure, and temperature gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault (fault bend fold), at the tip of a propagating fault (fault propagation fold), by differential compaction or due to the effects of a high-level igneous intrusion e.g. above a laccolith.
caption: Kink band folds in the Permian of New Mexico, USA
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