Tectonic influences on speleogenesis in the Guadalupe Mountains, New Mexico and Texas

A BSTRACT .— Sulfuric acid speleogenesis in the Guadalupe Mountains of New Mexico and Texas is a consequence of the rise of the Alvarado Ridge and subsequent opening of the Rio Grande Rift during Cenozoic time. Uplands of the late Laramide (~38-35Ma) Alvarado Ridge provided an immense recharge area that supplied water to aquifers draining eastward to the Permian basin. Prior to, or during the early stages of the opening of the Rio Grande Rift, hydrostatic head in the Capitan aquifer caused water to flow upward along fractures to artesian springs. This resulted in solutional enlargement of fractures and development of early stage caves that may not have involved H 2 S. Extensional faulting since 29 Ma fragmented the east flank of the ridge, progressively reducing the size of the upland recharge area and reducing hydrostatic head. Fresh water influx also introduced microbes into Artesia Group (