Observations from active sulfuric karst systems: Is the present the key to understanding Guadalupe Mountain speleogenesis?
— Louise D. Hose and Jennifer L. Macaladt

Field investigations in active sulfide-rich cave systems in Mexico, Italy, and the United States have documented a three-step process of speleogenesis that includes an early sulfide-rich phreatic phase forming incipient karst conduits, a secondary sulfide-rich vadose-phreatic phase of chemical stoping, and a tertiary sulfide-depleted vadose phase of epigenic speleogenesis. The vadose-phreatic phase produces many geologic and biological characteristics unique to caves formed in sulfidic and hypogenic mixing environments. The tertiary vadose phase may destroy most of the evidence linking an ancient cave to a sulfidic origin. Commonly preserved evidence of previous sulfide-driven speleogenesis includes horizontal levels of large passages connected by vertical rifts, abruptly terminating passages, major passages formed parallel to axial planes, gypsum crusts on walls and ceiling, piles of gypsum sediments on the floor, subterranean rills, and speleosols. Caves in the Guadalupe Mountains prominently display all of these features. The robust microbial communities in vadose-phreatic phase sulfide-rich caves also impart characteristic isotopic, mineralogical, and lipid signatures that deserve further study in both active and ancient sulfidic cave environments.