Karstbase Bibliography Database
Karstbase Bibliography Database
Hypogene speleogenesis is widespread throughout the Delaware Basin region as evidenced by intrastratal dissolution, hypogenic caves and suites of diagenetic minerals. The world famous carbonate caves of the Capitan reef facies of the Guadalupe Mountains have long been associated with sulfuric acid processes and recently have been associated with semi-confined, hypogene dissolution. However, evaporite karst within Permian backreef and basin-filling facies has been traditionally associated with surficial, epigene processes. On the eastern edge of the Delaware Basin cavernous porosity associated with oil reservoirs in Permian carbonates have been attributed to eogenetic karst processes.
Interbedded (evaporite / carbonate), backreef facies within the mid-Permian Seven Rivers Formation exhibit characteristics of hypogene karst associated with semi-confined dissolution controlled by the eastward migration and entrenchment of the Pecos River. Coffee Cave is a good example of hypogene dissolution, forming a multi-storey, rectilinear maze with abundant distinctive morphologic feature suites (i.e. risers, channels and cupolas) indicative of hypogene speleogenesis. Other caves within the Seven Rivers and Rustler Formations show similar patterns, although often less well developed.
Within the Delaware Basin, Castile Formation evaporites have been extensively modified by hypogene processes. Field mapping coupled with GIS analyses clearly shows that karst development and evaporite calcitization are highly clustered throughout the outcrop area. Individual caves commonly exhibit complex morphologies, including complete suites of morphologic features indicative of intrastratal dissolution. Clusters of hypogene caves are commonly associated with clusters of evaporite calcitization and often occurrences of secondary selenite bodies, suggesting all three are genetically related. Brecciated cores and associated native sulfur deposits indicate that calcitized evaporites are the result of semi-confined sulfate reduction in the presence of ascending hydrocarbons. Hypogene caves are currently being overprinted by epigene processes as surface denudation results in breaching of previously confined solutional conduits. However, calcitized evaporites stand as resistant masses attesting to the widespread importance of hypogene processes within the Castile Formation.
On the southern end of the Central Basin Platform, the spatial distribution of cavernous porosity, secondary mineralization and abundant karst fabrics within the Yates Field carbonate strata provide convincing evidence that karst porosity, at least locally, within the San Andres and overlying Permian strata is the result of hypogene speleogenesis. Porosity development appears to have been enhanced by high geothermal gradients and the addition of sulfuric acid-rich fluids, reminiscent of the same processes that have been proposed for the extensive carbonate caves of the Guadalupe Mountains.
Recognition of the widespread occurrence of hypogene speleogenesis throughout the Delaware Basin region indicates that the regional diagenetic evolution has been significantly affected by confined fluid migration, including not only the development of porosity but also the emplacement of many secondary mineral deposits. Therefore, future natural resource management plans must consider the nature of hypogene karst in site evaluations throughout the region in order to better predict geohazards, potential groundwater contamination and characterize mineral resources.