Geological Survey Professional Paper 446 Geology of the Guadalupe Mountains, New Mexico

PURPOSE

After the discovery of oil in Permian rocks in Winkler County, Tex., in 1920, petroleum exploration intensified in adjacent parts of western Texas and southeastern New Mexico. Almost immediately unusual stratigraphic complexities were discovered in the Permian rocks. Thus began a long period of stratigraphic investigations, chiefly reconnaissance studies, of the Permian rocks of the Guadalupe Mountains of Texas and New Mexico. Before 1930 some of the complexities began to be resolved as several geologists almost simultaneously recognized the great barrier reef of Capitan age which separates rocks of radically different character. To the northwest is a great sequence of rocks deposited on a platform area, whereas to the southeast lie the rocks of the Delaware basin. The relations of the basin rocks to the rocks of the reef zone were lucidly described by P. B. King (1942, 1948), but confusion and differences of opinion continued about the relations of the shelf rocks to their correlatives in the basin. The present investigation is an attempt, by means of detailed areal mapping, to resolve the relations of the shelf-rock units to one another and to the reef and basin rocks and to clarify the confusing stratigraphic nomenclature.

PREVIOUS WORK

The first geologist to visit the Guadalupe Mountains was G. G. Shumard (1858), who in 1854, as a member of Capt. John Pope's railroad survey party, examined the part of the mountains that lie in Texas. Fossils collected by Shumard were recognized by his brother, B. F. Shumard (1858), as resembling those of the Permian System in Europe. The next geologist to report on the Guadalupes was Jenney (1874, p. 27), who expressed his belief in a Carboniferous age for the rocks exposed there. In 1890 Tarr (1892) visited the Guadalupes in Texas and New Mexico, and he expressed the same opinion. In 1901 Girty (1902, 1908) made the fossil collections which were the basis of his report on the Guadalupe fauna and which established the Permian age of the rocks of the southern Guadalupe Mountains. Richardson (1910) and Beede (1910) reported further on the part of the mountains that lie in New Mexico. Baker (1920) first recognized the Yeso Formation and San Andres Limestone there. His report was followed by that of Darton and Reeside (1926) who made the first geologic observations in Last Chance Canyon.

The second phase of geological study in the Guadalupe Mountains began as a result of interest created during the development of oil fields in Permian rocks to the northeast. The results of field conferences of petroleum geologists and reconnaissance studies of individual geologists were published in papers by Lloyd (1929), Crandall (1929), Blanchard and Davis (1929), and Cartwright (1930). These papers led to a better understanding of the facies relationships, but they still left many questions unanswered. Fiedler and Nye (1933), as a result of a ground-water study north of the Guadalupe Mountains, introduced new names for rocks in the shelf area, and more nomenclatorial additions and changes were made by Lang (1937). Numerous papers based on reconnaissance studies of the Guadalupe Mountains or detailed studies in limited areas of the mountains were published in the next decade. All of these contributed valuable information and worthwhile ideas, but it was P. B. King (1942, 1948) who first presented the results of a detailed mapping project in a critical area. His publications clearly describe the stratigraphic relations of the rock units of the Delaware basin to the reef zone in the Guadalupes in Texas. Of the many interesting papers published since 1948 on various aspects of the geology of the Guadalupe Mountains, the most outstanding has been the detailed paleoecologic study by Newell and others (1953) on the rocks of the reef complex. The work of Boyd (1958), and Motts (1962), and the present investigation have produced the first published detailed geologic maps of the Guadalupe Mountains in New Mexico.

PRESENT INVESTIGATION AND ACKNOWLEDGMENTS

This report is based on fieldwork done intermittently between 1952 and 1957. Geology of the Carlsbad Caverns East quadrangle was mapped in the summer of 1952 during which time Bennett T. Gale, geologist of the U.S. National Park Service, assisted on several occasions. R. L. Koogle assisted in the mapping of the Carlsbad Caverns West quadrangle in the spring of 1955. The rest of the mapping was done in the spring and summer of 1956. The late Jerry Doty assisted in the mapping for 6 weeks and R. L. Harbour for 2 weeks. Brief periods were also spent in the field on several other occasions. On one of these, Curt Teichert aided in measuring stratigraphic sections, and on another, G. O. Bachman gave similar aid. On another occasion George W. Moore and personnel of the National Park Service assisted in the mapping of caves. Geologic mapping was done on vertical aerial photographs of various scales and was transferred to the topographic base, primarily by inspection after elevations of points on contacts were determined by altimeter or hand level. Supplemental mapping of small local areas was done by planetable. Stratigraphic sections were measured on relatively steep slopes by clinometer and tape. The mapping of caves was done by Brunton compass and tape traverses. Personnel of the U.S. National Park Service were helpful on many occasions during the course of fieldwork in Carlsbad Caverns National Park. Property owners throughout the mapped area were most courteous in allowing access to their property, and many gave valuable information concerning water wells and springs.

Besides the fieldwork this report is based on considerable laboratory work, including the microscopic examination of more than 55,000 feet of samples taken from oil wells and test holes drilled in the area. Many of these samples, as well as sample logs, drillers' logs, and data on formation depths, were furnished by oil companies, independent operators, and the New Mexico Bureau of Mines and Mineral Resources. In addition, more than 200 thin sections and 25 polished sections of carbonate rocks were examined. The thin sections were prepared by Nathaniel Taylor; James Thomas determined the magnesium content of 83 carbonate rocks.