Earth and Planetary Sciences ETDs

Publication Date

1977

Abstract

The purpose of this thesis is to determine the geologic factors that have influenced speleogenesis (origin of caves) in the Capitan reef complex (Permian) exposed along the northeast prong of the Guadalupe Mountains of New Mexico and Texas. This study of 52 caves included mapping caves, joints, and cross sections, determining stratigraphic position, generating joint rose diagrams, and photographing the geologic and hydrologic controls on speleogenesis.

Most Guadalupe caves are strongly controlled by vertical joints that parallel or are nearly perpendicular to the reef escarpment. East of Rattlesnake Canyon, caves generally develop along joint swarms that parallel the reef escarpment; west of Rattlesnake Canyon, caves generally follow joint swarms that parallel the Huapache monocline and the faulted western escarpment. Caves are commonly associated with "blades" of bedrock that probably result from surficial case-hardening by evaporation of mineral bearing solutions. Inward exfoliation is a major breakdown mechanism that modifies the original solutional passages.

Most Guadalupe caves developed by shallow phreatic solution at pre­vious base levels--the most important hydrologic control. Periodic uplift of the Guadalupe Mountains during late Pliocene and Pleistocene produced a series of slightly tilted cave levels. In Carlsbad Caverns, the Left Hand Tunnel base level is tilted l/4° NE, whereas the Guadalupe Room and Bat Cave base levels appear to be tilted nearly 1°W.

The complex structure and stratigraphy of the Capitan reef is responsible for four zones of preferential solution: 1) below the Yates transition into the massive Capitan Limestone, 2) at the contact of the massive and breccia members, 3) at the Artesia Group transition into the massive Capitan Limestone in general, and 4) immediately below the Yates Formation in the more soluble Seven Rivers Formation. Impermeable Yates siltstones provide the major stratigraphic control for distribution of groundwater and resulting solution in the Capitan Reef.

I propose that the sulfuric acid reaction (in addition to carbonic acid) was a major solution reaction during the development of the Guadalupe caves. Large crystals, massive concentrations, and finely disseminated pyrite in the overlying Yates Formation provided the sulfide source for the reaction. Massive beds of gypsum in many Guadalupe caves are the end product of cavern development via sulfuric acid.

Other minor structural controls include solution along sandstone dikes, preferential solution along the axial fractures of tepee struc­tures, and the development of fault caves along the faulted western escarpment. Most caves in the Guadalupe Mountains have developed by prefer­ential solution at the intersection of the geologic and hydrologic features studied.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

J. Paul Fitzsimmons

Second Committee Member

Lee A. Woodward

Third Committee Member

Jonathan L Callender

Fourth Committee Member

Steven G. Wells

Language

English

Document Type

Thesis

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