Bulletin 117—Geology of Carlsbad Cavern and other caves in the Guadalupe Mountains, New Mexico and Texas

By C. A. Hill, 1987, 150 pp., 31 tables, 131 figs., 16 color plates, 1 index, 9 sheets.

The origin of Carlsbad Cavern and other caves in the Guadalupe Mountains has been one of the great mysteries of speleogenesis. Geomorphically, Guadalupe caves bear little resemblance to other great cave systems of the world, which are thought to have formed by carbonic-acid dissolution at the water table. Rooms are huge, yet passages are not long and terminate abruptly. The caves seem unrelated to surface topography or to ground-water-flow routes. Especially enigmatic are the large deposits of gypsum and the colorful waxy clay in the caves. This book is the result of a lengthy investigation that has utilized observational, stratigraphic, geochemical, and isotopic-dating techniques. It is divided into two parts: speleogenesis and mineralogy. The author attempts to answer questions about the origin of the caves and specifics of their mineralogy: Why are Guadalupe speleothems so large? Why are they so profuse? 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?

For over 30 years the prevailing theory has been that Guadalupe caves formed similarly to other caves; that is, by carbonic-acid dissolution at the water table. Within the past 10 years three new theories of origin have been proposed, all of which differ significantly from one another and from the earlier theory. All of these four theories are based mainly on field observations, despite the pertinence of a number of analytical techniques to speleogenesis problems. This paper is a summary of a lengthy investigation which has utilized observational, stratigraphic, geochemical, dating, and isotopic techniques. The purpose of Part I is to describe cave deposits and discuss speleogenesis events for Permian time to the present.

This bulletin is intended for a variety of readers. It is meant for the geologist who wants to understand caves in the Guadalupe Mountains from a regional perspective; for the speleologist who wants to understand how these caves differ from other caves; for the caver who wants to better appreciate what he or she is seeing in Guadalupe caves; and for the visitor to Carlsbad Cavern as an interpretive guide to its geology and mineralogy. Such a multipurpose intent has its problems. Only the experienced speleologist has the background to understand all parts of this bulletin. Geologists will not necessarily be familiar with the specifics of cave geology or with the speleological terms. Cavers will recognize much of the speleological jargon, but will not necessarily realize the full geological significance of what is being discussed. Cave visitors may be interested in learning only about certain aspects of the caves, e.g. the travertine formations in Carlsbad Cavern. Because of such problems, the paper has been organized so as to be helpful to all readers. It is divided into two parts, speleogenesis and mineralogy. These parts are interrelated, but are presented in such a way that they can be read and understood separately. In both the speleogenesis and mineralogy sections, pictures have been included of most types of cave deposits and speleothems so that the caver can use the publication as a guide to a number of caves in the Guadalupe Mountains. For the visitor to Carlsbad Cavern, specific reference is made to a number of deposits and speleothems that can be seen along the trail.