Tectonic influences on speleogenesis in the Guadalupe Mountains, New Mexico and Texas
Harvey R. DuChene and Kimberley I. Cunningham
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 H2S. 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 (Guadalupian) oil reservoirs, causing biodegradation of petroleum and generating copious H2S. The water table within the Guadalupe Mountains began to fall 14-12 Ma in response to erosion and tectonism. During this time, oxygen-rich meteoric water mixed with H2S water to form sulfuric acid, which enlarged passages and galleries at the water table. Tectonic spasms related to the opening of the Rio Grande Rift caused abrupt drops in the water table, shifting the locus of sulfuric acid dissolution eastward and downward. Cave levels formed by sulfuric acid record the position of the water table at a given time, and the elevation difference between levels may correlate with episodes of Rio Grande Rift tectonism since 12 Ma.
- DuChene, Harvey R.; Cunningham, Kimberley I., 2006, Tectonic influences on speleogenesis in the Guadalupe Mountains, New Mexico and Texas, in: Caves and karst of southeastern New Mexico, Land, Lewis; Lueth, Virgil W.; Raatz, William; Boston, Penny; Love, David L., New Mexico Geological Society, Guidebook, 57th Field Conference, pp. 211-217.