Geologic Tour of New Mexico — Physiographic Provinces

El Vado (“the ford”) Lake lies upstream of a place along the Rio Chama in north central New Mexico where a resistant sandstone ledge in the upper part of the Cretaceous Dakota Sandstone crosses the river. The narrow canyon through this sandstone ledge facilitated passage across the Rio Chama prior to construction of El Vado dam. The Middle Rio Grande Conservancy District completed the construction of El Vado dam in 1935 to store irrigation water in order to honor Native American water rights of the six Middle Rio Grande Pueblos. The dam was updated in 1953-1954 and the outlets were modified in 1965-1966 to accommodate increased flows associated with San Juan-Chama Project.

Storrie Lake State Park is located four miles north of Las Vegas, New Mexico, and can be reached via New Mexico Highway 518. The 1400-foot long earthen dam that retains the water in Storrie Lake was built under the direction of Robert C. Storrie starting in 1916. Water from the Gallinas River, a southeasterly-flowing river with its headwaters in the Sangre de Cristo Mountains and the main water supply for the community of Las Vegas, is diverted for storage in Storrie Lake. The park offers camping, boating, fishing, beaches, and other water-related activities.

Storrie Lake State Park lies on the boundary between two important physiographic provinces, the Southern High Plains and the Southern Rocky Mountains. The lake is on the High Plains just east of the Rincon Range portion of the Sangre de Cristo Mountains, a sub-province of the Southern Rocky Mountains.

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.

Sumner Lake State Park is approximately 16 miles northwest of Fort Sumner on US-84 and NM-203 at the junction between the Pecos River and Alamogordo Creek. It was established in 1960 as Alamogordo Reservoir; the name was changed in 1974 to avoid confusion with the growing town of Alamogordo in south-central New Mexico. Sumner Lake was named after nearby Fort Sumner, which honors Col. Edmund Vose Sumner, who commanded the 9th Military District and built Forts Craig, Union, Thorn, and Fillmore (Julyan, 1996). Alamogordo (Spanish for big cottonwood) Creek was named after the abundant, large cottonwood trees along the river valleys.

Pecos National Historical Park lies in the extreme western portion of San Miguel County, in the broad valley of the Pecos River where the river leaves its deep canyon in the Sangre de Cristo Mountains. The timeless cycles of geologic history are on display in the ancient and modern river deposits in the park. The spectacular cliffs of sedimentary rocks on Glorieta Mesa to the south and the rugged mountains to the north provide a beautiful geologic setting for the ruins and contain rocks that record shifting shorelines and the birth and erosion of mountains.

The site is of enormous cultural and historical significance. The pueblo here was occupied at least as early as 1450. The Coronado Expedition passed through here in 1541 en route to the Great Plains. Spanish missionaries followed soon thereafter. In 1621 the Franciscans built the adobe church whose ruins tower over the park today. In 1680 the Pueblo Revolt put an end to the efforts of the church throughout northern New Mexico; the priest at Pecos was killed and the church laid waste. The site was occupied by the Pecos Indians until 1838.

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.

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.

The Gilman Tunnels are on NM 485 along the Rio Guadalupe in the southwestern Jemez Mountains, approximately 5 miles northwest of the intersection of NM 4 and NM 485. Two narrow and unusually high tunnels were cut through Precambrian granite in the 1920s to facilitate passage of logging trains through this particularly rugged and constricted section of Guadalupe Canyon, known as the Guadalupe Box. Logs that were harvested in the western Jemez Mountains in the 1920s were taken by narrow-gauge railroad to a sawmill in Bernalillo. The tunnels were enlarged in the 1930s to accommodate logging trucks. Logs were hauled out of the mountains and then loaded on trains at Gilman logging camp, which was established in 1937 about two miles south of the tunnels. The railroad was shut down by flooding along the Jemez and Guadalupe Rivers in 1941. The highway now occupies the old railroad bed. Aside from providing access to the Guadalupe Box itself, NM 485 provides an unparalleled view of the stratigraphy of Guadalupe Canyon.

The Prehistoric Trackways National Monument is located in the Robledo Mountains just northwest of Las Cruces in Dona Ana County, south-central New Mexico. It contains rocks of Permian age, from the Late Paleozoic Era. They are composed of sediments deposited about 280 million years ago, before the age of the dinosaurs. These rocks contain major deposits of fossilized footprints made by numerous amphibians, reptiles, insects, and crustaceans, as well as plants and petrified wood. Some scientists have called these features the most scientifically significant Permian tracksites in the world. These fossils provide important information about animal behavior in this ancient tropical environment on the edge of the supercontinent Pangea.

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.