The Guadalupe Mountains are part of one of the finest examples of an ancient marine fossil reef on Earth. Geologists come here from around the world to marvel at this extraordinary natural phenomenon, which formed approximately 250 million years ago in the geologic period know as the Permian.
During this time a vast tropical ocean full of various forms of life covered portions of Texas and New Mexico. Over millions of years, calcareous sponges and algae combined with other lime-secreting marine organisms and vast quantities of lime that precipitated directly from the seawater to form the 400-mile-long, horseshoe-shaped Capitan Reef.
Eventually the sea evaporated, the reef subsided, and a thick blanket of sediments and mineral salts buried the reef. The reef was entombed for millions of years until a mountain-building uplift in this region exposed a part of the fossil reef in the Guadalupe Mountains.
Geology of the Western Escarpment
The Western Escarpment has played an important role in revealing the story of the Permian Period of geologic time in North America. These exposures present one of the finest cross-sections of rocks in the world, showing transitions from shallow-water deposits to deep-water deposits. Abrupt changes in rock types are caused by this change in depth from shallow submerged areas to the deep waters of the Permian Sea. Some two miles of Permian strata are exposed in and adjacent to the Guadalupe Mountains due to faulting which uplifted this section through the ancient fossil reef.
Exposures on the lower section of the western escarpment have been studied intensely by geologists. A portion of these lower layers has been proposed as a world-wide type section for middle Permian strata referred to as the Guadalupian. A type section serves as a defining unit of rock to which all other units of the same age can be compared. These exposures have been preserved so geologists can continue to study and learn about this ancient fossil reef and for the public to enjoy. Collecting of any materials from the park is prohibited.
Frijole Ranch area
In and near the Guadalupe Mountains, very small to medium springs flow from the Permian sandstones and gravel at the foot of the mountains. Springs are spillways through which overflow or surplus groundwater passes. Near Frijole Ranch, which at one time was called Spring Hill Ranch, are five of the park's major springs.
One is Smith Spring, located in Smith Canyon. Smith Spring is among the highest springs in Texas and flows from the Bell Canyon sandstone at 5,955 feet above sea level. This spring water collects in the higher elevations to the northwest where rainfall is greater. The water then percolates down through a complex system of joints in the limestone and sandstone layers.
The Cherry Canyon sandstone is the major water-bearing sandstone layer from which most springs in the park flow. Smith Spring flows from the Bell Canyon sandstone because it is higher in elevation than the other springs in the park.
Water from Smith Springs disappears underground then reemerges from the gravel below to form Manzanita Spring which is 0.3 miles east of Frijole Ranch. The Smith Spring Trail (2.3 miles) gives an excellent view of both Smith Spring and Manzanita Spring.
Pine Springs area
This area is named for Pine Springs, a spring that was historically used by Indians, then served as a stop for the Butterfield Overland Mail Line.
The springs are reported to have failed on August 16, 1931 during an earthquake. There was probably some movement in the fault in the Cherry Canyon sandstone from which the water flowed causing blockage of flow. A fault is a fracture in the earth's crust along which rocks on one side have been displaced relative to the rock on the other side. The fault can be seen below the top exposures of the Capitan Limestone where the limestone beds have been offset; the right side of this fault has been moved up and the left has moved down. This is one of numerous faults that cut this area causing the rock layers to be displaced by a few to several hundred feet.
Visitor Center area
This is an excellent place to view the role of erosion on the Guadalupe Mountains from the formation of the reef until present time. Looking to the far left at El Capitan, this now erosion-resistant cliff was in Permian time eroded by wave action on the seaward-facing side. This caused blocks of the reef to roll down into the sea basin forming a slope of debris at the base of the reef which now makes up some of the lower limestone layers.
Hunter Peak, with its fractured and rugged cliffs, has layers that look almost vertical compared to El Capitan's horizontal layering of rock. Hunter Peak looks so much different due to the faulting that occurred in that area in late Mesozoic time. The rock layers were pushed up by the fault which caused the layers to fracture allowing them to erode more easily. In more recent time, stream- and groundwater erosion have removed softer sediment forming calcium-rich soils in which vegetation has grown.
The most striking feature of Guadalupe Mountains National Park is the thousand-foot high El Capitan, which can be seen from miles around. Early settlers used it as a landmark on the route through Guadalupe Pass.
El Capitan is composed of Capitan Limestone, which is the Permian-aged limestone reef deposit. A reef is a submerged resistant mound or ridge formed by the accumulation of plant and animal skeletons. The Capitan Limestone is a massive, fine-grained fossiliferous limestone that formed by growth and accumulation of invertebrate skeleton of algae, sponges, and tiny colonial animals called bryozoans. These skeletons were stabilized by encrusting organisms that grew over and cemented the solid reef rock, unlike modern reefs built by mainly a rigid framework of corals.
Below this massive cliff of Capitan Limestone you can see a prominent sandstone ledge of the Brushy Canyon sandstone which formed when the off-shore basin began to slowly subside.
Because of the Capitan's greater resistance to erosion, it forms this cliff which looms majestically above the horizon for us all to see.
The same Capitan Limestone exposed on the top of the Patterson Hills, is also exposed on the top of the Western Escarpment. There is, however, a 3,000 foot difference in elevation between the two due to faulting that began about 26 million years ago. A series of branching faults runs close to the base of the Western Escarpment. The fault block comprising the Guadalupe Mountains was uplifted more than two miles from its original position below sea level.
Turnaround Area and William's Ranch
As you make your way toward William's Ranch, the entire face of the Western Escarpment comes into view. Now you can see from El Capitan all the way to Shumard Peak; El Capitan and Guadalupe Peak dominate the view. Guadalupe Peak, the highest peak in Texas at 8,749 feet, is also composed mostly of Capitan Limestone.
The very top of Guadalupe Peak, about 4,000 feet above road level, is composed of back-reef deposits of Seven Rivers Dolomite, which was deposited in a quiet, shallow, underwater lagoon between the reef and the shoreline. The slopes below these cliffs consist of Cherry Canyon siltstones and sandstones and Brushy Canyon sandstones. The El Capitan Trail in Shumard Canyon has exposures of ripple marks in these sandstones. The more resistant, brown-weathering ledges in the middle of the slope below El Capitan are the upper-most Brushy Canyon sandstones that were deposited as sediment filled in sub-marine channels in the basin.
William's Ranch sits on the Bone Springs Limestone at the head of the Bone Canyon alluvial fan. An alluvial fan is an outspread, gently sloping mass of material deposited by a stream.
Behind the ranch is Bone Canyon. Its cliffs and slopes are formed of the oldest rocks in the Guadalupes. These rocks are the Victorio Peak limestone, the Cutoff Formation, and the Bone Spring limestone, which make up the lower portion or "bank-ramp complex" of the Western Escarpment. The bank-ramp complex formed from unbound carbonate sediments which were deposited as broad banks stretching 10-20 miles, creating a gentle ramp dipping only one or two degrees toward the basin. These shallow carbonate ramps lack the binding organisms that are prominent components of the reef complex. These limestones are well bedded in contrast to the massive reef deposits, and are exposed on the lower canyon walls.
The reef complex, which consists of Capitan limestone and underlying Goat Seep limestone, form the upper portion of the Western Escarpment. Shumard Peak, also composed of Capitan limestone and the second highest peak in the park at 8,615 feet, can be seen looking north from the ranch house porch.
The Brushy Canyon sandstone holds the water that was pumped through a pipeline two miles from Bone Spring to the ranch.
During Late Permian time, the Capitan Reef stretched some 400 miles around the edge of the Delaware Basin. Only a small part of the reef towers above the Texas desert in the Guadalupe Mountains. Other parts are exposed in the Apache- and the Glass Mountains.
The General park map handed out at the visitor center is available on the park's map webpage.For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.
A fire photo album for this park can be found here.For information on other photo collections featuring National Park geology, please see the Image Sources page.
Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.
Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
9" x 10.75", paperback, 550 pages, full color throughout
The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!
Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.
For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.
The NPS maintains a searchable data base of research needs that have been identified by parks.
A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.
NPS Geology and Soils PartnersAssociation of American State Geologists
Geological Society of America
Natural Resource Conservation Service - Soils
U.S. Geological Survey
Currently, we do not have a listing for any park-specific geology education programs or activities.
General information about the park's education and intrepretive programs is available on the park's education webpage.For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.