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

Purpose

Carlsbad Cavern is well known for the beauty and immensity of its "speleothems," a term used to denote secondary mineral deposits in caves. Stalactites and stalagmites are two of the most common speleothem types, examples of which are the huge Rock of Ages and Crystal Dome stalagmites of the Big Room, the tall, thin, totem-pole stalagmites of the Main Corridor, and the war-club-shaped stalactites of the War Club Room. Other, less common speleothem varieties are those shaped like draperies, grapes, popcorn, clouds, pearls, shields, balloons, lily pads, coke tables, cotton, flowers, needles, and rope. Two bizarre and interesting speleothems are helictites, which twist in any direction like contorted inchworms, and moonmilk, a cream-cheese-like pasty substance composed of a variety of carbonate minerals. All of these and other speleothem types are found in various parts of Carlsbad Cavern (Fig. 95), and also in other caves of the Guadalupe Mountains.

FIGURE 95—Location of best examples of various kinds of speleothems, Carlsbad Cavern. (click on image for a PDF version)

The purpose of Part II of this study is to describe the speleothems of Guadalupe caves and to relate their origin to geologic factors influencing their deposition. Basic questions that the mineralogy discussion will attempt to answer are: Why are Guadalupe speleothems so large? Why are they so profuse? Why are there so many types of speleothems in Guadalupe caves? Why is there so much popcorn-like decoration in the caves? Why is there an abundance of carbonate speleothems but relatively few sulfate speleothems? Why are most of the speleothems dry and inactive?

Previous work

The mineralogical wonders of Carlsbad Cavern were first introduced to the world by Willis T. Lee in two articles in the National Geographic Magazine (Lee, 1924a, 1925b). Lee's popularized description of Carlsbad Cavern brought world-wide recognition to the cave, propelling it quickly to National Monument and then National Park status. The first mineralogical article to appear in a strictly scientific journal was by Hess (1929) on the cave pearls of Carlsbad Cavern. Two more popular articles appeared in 1938, one by Burnet on New Cave, and one by Nymeyer, who briefly described the mineralogy of Hidden Cave, Hell Below Cave, Cottonwood Cave, and 19 other caves in the Guadalupe Mountains. Nothing further was written on the mineralogy of Guadalupe caves until the early 1950's, when Donald M. Black, a Park employee, published a number of articles on the cave pearls, rafts, and rimstone dams of Carlsbad Cavern (Black, 1951a, b, 1952, 1953), and one on the "Chinese Wall" rimstone dams of New Cave (Black, 1956). In addition, Thrailkill (1953) published a brief note on the popcorn in Manhole Cave.

The 1960's and early 1970's marked a period of short descriptions of Guadalupe speleothems in grotto newsletters or other publications of the National Speleological Society. It was during this time that cavers began to actively explore the caves of the Guadalupe Mountains and these publications were the news outlets for the cavers' findings. Crisman (1960) gave a brief mention of Guadalupe Mountain speleothems in a guidebook published by the National Speleological Society. White (1960), Russell (1961), and Frost (1971) wrote on the sulfate mineralization in Cottonwood Cave, DuChene (1967) described the large spar crystals in Idono Crystal Cave, and Davis (1970) reported to Carlsbad Caverns National Park on his discovery of folia in the Lake of the Clouds area, Carlsbad Cavern. It was also during this time that John Thrailkill did his doctoral dissertation on the carbonate mineralogy of Carlsbad Cavern. Thrailkill went beyond the mainly descriptive efforts of past workers. He identified a number of carbonate minerals by x-ray diffraction, discussed the stability of carbonate minerals in a cave environment where the effect of the magnesium ion is pronounced, and described in specific terms the mode of popcorn deposition (Thrailkill, 1963, 1965a, b, 1968, 1971). Thrailkill's dissertation remains the definitive work on the carbonate mineralogy of Carlsbad Cavern.

In the early 1970's, the Cave Research Foundation's long-term commitment to cave survey and research on federal lands brought about the systematic description and study of speleothems in the caves of the Guadalupe Mountains. In 1972-1973, geologists Carol Hill, Harvey DuChene, Dave Jagnow, and Dwight Deal submitted six reports to Carlsbad Caverns National Park in which they discussed various geological topics and also a number of new speleothem types in Carlsbad Cavern, such as hydromagnesite balloons, mirabilite and epsomite cotton, huntite flowstone, cave rims, and various types of coralloids (DuChene, 1972; Hill, 1972; Hill et al., 1972a, b; Hill et al., 1972; Hill, 1973b). Also during this period, Hill published some of these and other mineralogical findings in technical journals (Hill, 1973a, c, d). Since that time, Hill has described the mineralogy of many Guadalupe caves in numerous short articles in the Annual Reports of the Cave Research Foundation (see References).

Significant advancement in the understanding of how travertine layers grow was made in the middle to late 1970's by two sets of investigators. Folk and Asserto (1976) described the crystal fabric of flowstone collected in Carlsbad Cavern and suggested that variations in fabric are controlled by the chemistry of the depositing solution. Kendall and Broughton (1977) questioned some of Folk and Asserto's findings in a reply that favored the importance of the substrate on carbonate mineral fabrics.