File:Banded gyprock with nodular gypsum (Castile Formation, Upper Permian; State Line outcrop, southern Eddy County, New Mexico, USA) (8280546955).jpg

Banded gyprock with nodular gypsum in the Permian of New Mexico, USA. (geology hammer for scale)

This is the famous (& 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. The whitish, irregularly-shaped masses above the geology hammer is nodular gypsum. Spectacular crinkling, small-scale folding, and small-scale faulting are present at this site. The folds and faults formed as a result of early Cenozoic structural deformation, not gypsum-to-anhydrite (or vice-versa) transformations (see Anderson & 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)

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