New Mexico Bureau of Mines & Mineral Resources Bulletin 117 Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas

(1) Guadalupe speleothems are large because: (a) a sulfuric-acid mode of dissolution created huge chambers in which speleothems could grow large; (b) the caves are very old and, therefore, there has been sufficient time for speleothems to grow large; and (c) wet climatic episodes earlier in the Pleistocene provided the moisture necessary for the growth of large speleothems.

(2) The profuseness of speleothems in Guadalupe Mountain caves is related to the fact that ground water easily descends everywhere into underground chambers through the jointed and bedded Tansill and Yates Formations and the porous reef.

(3) A variety of speleothem types occur in Guadalupe caves because a variety of factors have influenced the diversity of speleothem form: permeability, bedding, and jointing differences in the various limestone facies; dolomitic as well as calcitic rock; and evaporation as well as carbon-dioxide loss. Dolomitic rock supplies magnesium to the high-magnesium carbonate minerals hydromagnesite, huntite, and dolomite; evaporation causes these minerals to precipitate and also affects the morphology of speleothems such as bell canopies, popcorn, and tower coral. Jointing and bedding favor dripstone and flowstone speleothems, whereas high porosity and permeability of bedrock favor popcorn growth.

(4) The dominance of popcorn-type speleothems in Guadalupe caves relates to the porous and massive nature of the Capitan reef core facies, to condensation-corrosion processes, and to the lower humidity and high rate of evaporation in the caves. Water seeping through porous limestone results in thin films of water necessary for popcorn growth. High rate of evaporation turns flowstone-depositing or condensation water into slowly moving films of popcorn-depositing water.

(5) Most of the speleothems in Guadalupe caves are composed of carbonate rather than sulfate minerals. Sulfur-isotope data suggest that the sulfate minerals derived from pyrite in the overburden; the general lack of sulfate speleothems in these caves is due to the relative scarcity of pyrite in the Guadalupe Mountains. The exception to this rule is Cottonwood Cave which lies directly below a pyrite rich section of the Yates Formation, and consequently has abundant gypsum and epsomite speleothems in its Gypsum Passage.

(6) Speleothems in Guadalupe caves are, for the most part, dry and inactive because the present climate in the Guadalupe Mountains is semiarid. Most travertine in the caves formed earlier in the Pleistocene when the climate was more humid and moist than it is today.