Unconfined hypogene evaporite karst: West Texas and southeastern New Mexico, USA

Abstract

Abstract:Diverse karst phenomena occur throughout the Gypsum Plain where the Castile Formation crops out over ~1800 km 2 in West Texas and southeastern New Mexico. Hypergene karst is extensive and widespread, while traditional hypogene karst manifestations (both caves and intrastratal dissolution) occur in high frequency in the western outcrop region where surface denudation has been the greatest so as to induce surficial breaching. Unconfined hypogene karst occurrences have been recently identified, including two general variations: 1) artesianlike discharge features; and 2) venting structures. Artesian-like discharge features arise at surficially-breached hypogene caves and through high permeability regions on the margins of breccia pipes; these occur when aquifer pressures within the underlying Bell Canyon siliciclastics are sufficiently elevated subsequent to anomalously high precipitation events. Venting structures associated with condensation corrosion-like processes coupled with ascending moisture-rich vapor occur as fracture vents and hydration buckles; fracture vents develop along near-vertical joint sets and hydration buckles form at intermittent zones of high permeability within the core regions of breccia pipes. All venting structures form highly porous, low density, secondary sulfate mineralization at the land surface, creating local topographic highs decimeters to a meter in scale that preclude interception of meteoric waters into these unconfined hypogene karst features. The Gypsum Plain hosts complex karst phenomena that present unique engineering challenges as variable geohazard occurrences ranging from shallow, hypergene caves to deep, complex, hypogene features both formed in semi-confined and unconfined speleogenetic conditions.

Morphology of Dome- and Tepee-Like Landforms Generated by Expansive Hydration of Weathering Anhydrite: A Case Study at Dingwall, Nova Scotia, Canada

“…Occurrences of hydration forms and caves have been documented in many places around the world, both in natural (e.g., Woodward Co. in Oklahoma, Ottawa Co. in Ohio, Culberson Co. in Texas, and Eddy Co. in New Mexico in the USA, Alberta in Canada, and Tripolitania in Libya) and artificial exposures of anhydrite rocks [3,4,[15][16][17]19,22,[39][40][41][42][43][44][45][46][47][48][49][50]. However, so far, only four places are known with remarkable amounts of these forms creating spectacular hydration landscape: most notably at environs of Walkenried at the south margin of Harz Mts.…”