IMPACT OF EVAPORITE KARST ON THE LOWER PECOS REGION, SOUTHEASTERN NEW MEXICO: A BLESSING OR A CURSE?

Evaporites make up a substantial portion of the middle and upper Permian stratigraphic section in southeastern New Mexico. Because of the extensive presence of gypsum and halite at the surface and in the subsurface, evaporite karst processes have profoundly shaped the geomorphology of the lower Pecos region on a variety of scales, ranging from individual sinkholes and caves to large subsidence basins and the pirating of major drainage systems. Subsurface dissolution of gypsum and halite have also caused significant geohazards and engineering problems, including the abandonment of an important reservoir on the Pecos River due to leakage through karstic fissures in the underlying bedrock.

Less frequently acknowledged are the beneficial effects of evaporite karst processes on human activity in the greater Delaware Basin region. Subsurface dissolution of interbedded evaporites within the San Andres limestone has produced brecciated intervals that comprise some of the principal water-bearing zones in the Roswell Artesian Basin. The gypsum cenotes at Bottomless Lakes State Park occur at the discharge end of the artesian aquifer system in the Roswell Basin. Overflow from these sinkhole lakes contributes to streamflow in the Pecos River, and ultimately helps New Mexico meet its interstate compact obligation with the downstream state of Texas.