CASTILE KARST OF THE DELAWARE BASIN, WEST TEXAS AND SOUTHEASTERN NEW MEXICO

Permian Castile evaporites of the Delaware Basin host abundant karst development that exhibits complex, polygenetic origins which have been sculpted by regional climate, upward migration of hydrocarbons, mixing of meteoric and basinal fluids, evolution of the Pecos River and denudation of the Gypsum Plain. Karst features range from subtle closed depressions and laterally-limited epigene caves to vertically-extensive breccia pipes, subsidence troughs and complex hypogene caves. Over 10,000 individual karst features are estimated to exist in outcrop across the Gypsum Plain based on spatial analyses. Currently, extensive development of petroleum resources underlying the Permian evaporites has placed greater interest on these potential geohazards for drilling operations and pipeline installation.

Small caves and karren features are associated with rapid solution kinetics of epigene development coupled to intense monsoonal precipitation patterns. Hypogene caves form isolated voids and complex, inversely-branched morphologies; they are coupled to insufficient drainage areas for primary porosity development by epigene processes that currently overprint them. Evaporite calcitization, the result of upward migration of hydrocarbons that fueled sulfate reduction are widespread and often associated with sulfur mineralization, selenite replacement and hypogene karsting. Vertical breccia pipes penetrate thick evaporite sequences throughout the Delaware Basin, while laterally-extensive blanket breccias are associated with horizontal migration of confined fluids. Eastward migration of the Pecos River has promoted extensive denudation of the Gypsum Plain and provided a major potentiometric driver for upward fluid migration, resulting in large-scale, sediment-filled, subsidence troughs. While often considered insignificant compared to nearby Guadalupe Mountains carbonate karst development, gypsum karst within the Castile Formation attests to the complex diagenetic evolution of the greater Delaware Basin.