Geologic Tour of New Mexico

Organ Mountains–Desert Peaks National Monument is a large, diverse and recently established park. It has four separate geographic areas: the Organ Mountains, the Doña Ana Mountains, the Potrillo Mountains, and the “Desert Peaks." This tour deals only with the Organ Mountains. The geology of the Doña Mountains area is briefly discussed in the tour of Fort Selden–Leasburg Dam. The Potrillo Mountains include the remote Potrillo volcanic field and are covered in the Kilbourne Hole tour. The "Desert Peaks" includes the Robledo Mountains and Sierra de las Uvas. The Robledo region is described in the tour of the "Prehistoric Trackways National Monument" (a separate, but contiguous national monument).

Cerro Pedernal, one of the most recognized landmarks in north-central New Mexico, is located in the northern Jemez Mountains . Cerro Pedernal lies in the transition zone between the Colorado Plateau and the Rio Grande rift. Typical, relatively flat-lying, Colorado Plateau Mesozoic stratigraphy is exposed at the base of the mountain, while younger Cenozoic basin fill sediments underlie the shoulders of the peak. The andesite and basalt flows capping Cerro Pedernal, which give the mountain its distinctive flat top, were erupted from the northern Jemez volcanic field about 8 million years ago. The lava flows and underlying rocks on Cerro Pedernal and on mesas to the southeast have since been faulted and down-dropped to the southeast by as much as 1870 feet (570 m) during Rio Grande rift extension in the last 8 million years.

Ghost Ranch is located approximately 38 miles northwest of the town of Española, New Mexico, just north of U.S. Highway 84, and is run by the Presbyterian Church as a conference center. It has facilities for lodging and camping, as well as paleontology and cultural museums. It lies in the Chama Basin, a broad shallow basin along the eastern margin of the Colorado Plateau in the transition between the Plateau and the Rio Grande rift.

Leasburg Dam State Park is adjacent to Fort Selden State Monument on NM–157 (Fort Selden Road) at the Radium Springs exit on I–25, north of Las Cruces. It is an area rich in both geologic and human history. The location was an ancient Indian campground and a crossing point for Spanish caravans headed across the Jornada del Muerto. Living-history demonstrations of 19th century military life at Fort Selden highlight many weekends during the summer. Wildlife viewing, especially bird watching, is popular at the state park. A bird list is available from the park office. In the winter months many species of ducks, teals, snow geese, cranes, herons, egrets, swans, and pelicans migrate through the southern Rio Grande valley and can be seen at the state park. Numerous raptors, including owls, turkey vultures, eagles, and hawks, can be seen hunting in the area. Small mammals common to the park include rabbits, squirrels, chipmunks, rodents, coyotes, and foxes.

Pancho Villa State Park in Columbus, New Mexico, was established in 1959 “in interest of preservation of the memory of the unique, historical occasion of the last hostile action by foreign troops within the continental United States”. It became the only park in the United States to be named after a foreign invader. The creation of the 60-acre park was a gesture of good will between the United States and Mexico. The town of Columbus has been designated a National Historic Site. Across the street from the park is the privately owned Pancho Villa Museum.

Mount Taylor volcano, a prominent landmark that can be seen on the skyline west of Albuquerque, is located about 15 miles northwest of the town of Grants, New Mexico. Mount Taylor Peak, at an elevation of 11,301 feet, stands approximately one mile above the Rio San Jose 12 miles to the south. Mount Taylor volcano is part of a larger, northeast-trending volcanic field that includes Mesa Chivato, a broad plateau located northeast of the cone, and Grants Ridge, located southwest of the cone. Basalt that caps Mesa Chivato and other mesas surrounding Mount Taylor makes up about 80% of the volume of the volcanic field. The Mount Taylor volcanic field lies on the southern flank of the San Juan Basin on the Colorado Plateau and straddles the extensional transition zone between the Colorado Plateau and the Rio Grande rift. The Mount Taylor volcanic field is considered to be part of the Jemez Lineament, a zone of young (< 5 million years old) volcanism aligned along an ancient suture in the 1.7 to 1.6 billion year old Proterozoic basement.

Lincoln State Monument encompasses most of the community of Lincoln, New Mexico and commemorates the lives of many of the key players in the Lincoln County War (1878-1881). Lincoln, which is located in south-central New Mexico, can be access via U.S. Highway 380. The community was originally named La Placita del Rio Bonito (village of the pretty river); the stream that runs along the north side of the village is called the Rio Bonito. The legislature of the territory of New Mexico, encouraged by local citizenry, renamed the village Lincoln in 1869, in honor of President Lincoln, who was assassinated 4 years earlier.

The main visitor’s center for the monument is located near the east end of town on the north side of the highway. The Lincoln County Courthouse Museum, which highlights the escapades and legal troubles of William H. Bonney (Billy the Kid), is the other main attraction associated with the monument. The courthouse is on the west end of town on the south side of the highway. Admission tickets ($5 for adults, children under 16 free) may be purchased at the visitor’s center or at the courthouse. Other buildings that can be visited as part of the tour include the Montaño store, the San Juan mission, the torreon, the post office and Turnstall Museum, and Dr. Wood’s home.

Ute Lake State Park was established in 1964 at a cost of approximately $5 million and was named after Ute Creek, one of the tributaries of the Canadian River that is impounded by a dam. The small town of Logan is on the east side of the lake, and the lake extends upstream in both the Ute and Canadian Rivers. It is 25 miles northeast of Tucumcari on US–54, NM–39, and NM–540 and is approximately 20 miles west of the Texas–New Mexico state line. Most of the land surrounding Ute Lake is private. All the water is open to the public. The park is in the Pecos Valley section of the Great Plains physiographic province. It lies on the north edge of the Llano Estacado or “staked plains.”

Kasha-Katuwe Tent Rocks National Monument is on the southeast side of the Valles and Toledo calderas, large collapse features that formed during voluminous eruptions in the Jemez Mountain volcanic field 1.61 and 1.25 million years ago. Tent Rocks encompasses a fascinating landscape in the southeastern Jemez Mountains. Kasha-Katuwe means 'white cliffs' in Keresan, the traditional language of the nearby Pueblo de Cochiti. Delicately layered sand, gravel, volcanic ash, and tuff of the Peralta Tuff Member of the Bearhead Rhyolite and sand and gravel of the Cochiti Formation, which are older units (2 to 6 Ma) in the Jemez Mountain volcanic field, have been erodedinto fragile to robust spires with balanced rocks perched on top. The hoodoos, erosional cones, and pedestal rocks that characterize Tent Rocks form as the result of differential erosion.

Lake Valley was a silver-manganese mining district during the late 19th century. Silver was discovered in 1876, and the area was extensively mined until the silver crash in 1893. The Lake Valley district includes the famed Bridal Chamber, which was found in 1881. The Bridal Chamber was among the richest silver deposits ever mined. The spectacular Bridal Chamber ore body composed of silver chlorides and silver bromides was nearly two hundred feet long and 25 feet thick. Chlorargyrite (cerargyrite; AgCl), the main high-grade ore taken from the Bridal Chamber, was mined out by the late 1880s. Manganese minerals, mainly manganite and pyrolusite, were mined in the Lake Valley district during and after World War II. No significant mining activity has occurred in the area since 1959.

Apache Hill, located about 1.5 miles north of the ghost town of Lake Valley on the east side of New Mexico Highway 27, is one of the best fossil collecting sites in southern New Mexico. The fossils are in the Mississippian Lake Valley Limestone. Good outcrops are located just below the top of the hill. Intact fossils, including brachipods, bryozoans, crinoid plates and calyxes, and horn corals, weather out of the shaly limestone in this particular area. Other fossils that can be found include gastropods, pelecypods, cephalopods, and trilobites.