Last updated: June 14, 2024
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NPS Geodiversity Atlas—Coronado National Memorial, Arizona
Geodiversity refers to the full variety of natural geologic (rocks, minerals, sediments, fossils, landforms, and physical processes) and soil resources and processes that occur in the park. A product of the Geologic Resources Inventory, the NPS Geodiversity Atlas delivers information in support of education, Geoconservation, and integrated management of living (biotic) and non-living (abiotic) components of the ecosystem.
Introduction
Coronado National Memorial (CORO) is situated along the U.S.–Mexico border in Cochise County, southeastern Arizona. Originally authorized by Congress as an international memorial on August 18, 1941, the park unit was redesignated on July 9, 1952. The national memorial includes approximately 1,954 hectares (4,830 acres) and commemorates the first major European exploration of the American Southwest by Francisco Vásquez de Coronado in 1540–1542 and affirms the ties that bind the United States to Mexico and Spain (National Park Service 2016a). The Coronado Expedition brought to the region profound and lasting changes in areas such as language, technology, religion, livestock, agriculture, and food. CORO offers panoramic views of the U.S.–Mexico border and the San Pedro River Valley, the route believed to have been taken by the Coronado Expedition in their search for the “Seven Cities of Gold” (National Park Service 2016c).
Geologic Setting
The landscape of CORO is underlain by a complex assemblage of igneous and sedimentary rocks spanning the last 300 million years. The geology of the memorial reflects cataclysmic volcanic eruptions that occurred during the Jurassic (~201–143 Ma) and formed several calderas including the Montezuma caldera (Graham 2011a). Jurassic tuffs and associated granitic intrusions (Huachuca Granite) dominate the rugged topography in northern CORO, while the southwestern portion of the memorial contains a chaotic group of rock units that includes volcanic tuff, lava flows, limestone, sandstone, and shale (mudstone) overlain by the Jurassic Glance Conglomerate. The oldest bedrock mapped within CORO is in the middle of the memorial and consists of Permian strata of the Naco Group. Young surficial deposits are predominantly located in southeastern CORO and include Pleistocene–Holocene terrace gravels, alluvium, colluvium, and debris flow deposits.
Geologic Features and Processes
The memorial preserves a magnificent landscape created by dynamic geologic processes acting over the past 300 million years. Principal among these processes was a cataclysmic volcanic eruption in the southern Huachuca Mountains that left a great hole in the ground, called the Montezuma Caldera, and generated landslides, earthquakes, and a complex geology consisting of exceptionally large blocks of broken and shattered strata.
Most surface exposures in Coronado National Memorial consist primarily of Jurassic-aged rocks, and most of these are associated with igneous activity that formed the Montezuma Caldera. The complex geology in the memorial and southern Huachuca Mountains involves volcanic rocks, granitic intrusions and related mineralization, and terrestrial and marine sedimentary strata. Beginning approximately 90 million years ago, west–east compression resulting from the collision of tectonic plates formed extensive north–south trending mountain ranges extending from Arizona to Canada. Further geologic complexity was introduced when the crust began pulling apart about 15 to 10 million years ago. Regionally extensive faulting displaced the crust during the development of modern basin-and-range topography in southeastern Arizona.
Rock units in Coronado National Memorial record episodes from the tectonic and depositional history of the last 300 million years. Oceans once covered this semi-arid environment, and after their disappearance, southeastern Arizona became a region of catastrophic volcanic activity. Today, four major biological provinces intersect in the memorial. Although these treasures escaped notice by Coronado's expedition in 1540, today’s memorial preserves this geologic richness and biological diversity for the enjoyment of all.
Also see, Coronado—Geologic History
Paleontological Resources
The Paleozoic limestones in the Huachuca Mountains, and throughout Arizona, preserve fossils of a variety of marine invertebrates. However, contact metamorphism from igneous intrusions, volcanic activity, deformation from faulting, and recrystallization of limestone to dolomite in the region destroyed many fossils (Charles Ferguson, Arizona Geological Survey, and Floyd Gray, Geologist, U.S. Geological Survey, personal communication, April 2006).
All NPS fossil resources are protected under the Paleontological Resources Preservation Act of 2009 (Public Law 111-11, Title VI, Subtitle D; 16 U.S.C. §§ 470aaa - 470aaa-11).
Cave and Karst
During the Quaternary (2.6 million years ago to present), groundwater percolating through cracks in the limestone dissolved calcite and eventually formed caves. There are nine known solution caves including the largest and most famous, Coronado Cave, located 1.2 km (0.75 mi) north of the memorial’s visitor center. Historical graffiti in the caves date back to 1892.
Also see, Coronado—Coronado Cave Geology
All NPS cave resources are protected under the the Federal Cave Resources Protection Act of 1988 (FCRPA)(16 U.S.C. § 4301 et seq.).
Abandoned Mineral Lands
Coronado National Memorial’s inventory of abandoned mineral lands includes 62 mine shafts, adits, and test pits (National Park Service 2007b). The State of Texas Mine within the memorial and the Morgan Mine, located just north of the park in South Fork Canyon, are two of the largest abandoned mines in the area. Because they pose a safety hazard to visitors, most mines in the memorial are marked with warning signs and are off-limits to the public.
NPS AML sites can be important cultural resources and habitat, but many pose risks to park visitors and wildlife, and degrade water quality, park landscapes, and physical and biological resources. Be safe near AML sites—Stay Out and Stay Alive!
Regional Geology
Coronado National Memorial is a part of the Basin and Range Physiographic Province and shares its geologic history and some characteristic geologic formations with a region that extends well beyond park boundaries.
The Geologic Resources Inventory produces digital geologic maps and reports for more than 270 natural resource parks. The products listed below are currently available for this park, check back often for updates as many maps, reports, and posters are still in progress.
- Scoping summaries are records of scoping meetings where NPS staff and local geologists determined the park’s geologic mapping plan and what content should be included in the report.
- Digital geologic maps include files for viewing in GIS software, a guide to using the data, and a document with ancillary map information. Newer products also include data viewable in Google Earth and online map services.
- Reports use the maps to discuss the park’s setting and significance, notable geologic features and processes, geologic resource management issues, and geologic history.
- Posters are a static view of the GIS data in PDF format. Newer posters include aerial imagery or shaded relief and other park information. They are also included with the reports.
- Projects list basic information about the program and all products available for a park.
Source: Data Store Saved Search 2794. To search for additional information, visit the Data Store.
A NPS Soil Resources Inventory project has been completed for Coronado National Memorial and can be found on the NPS Data Store.
Source: Data Store Saved Search 2840. To search for additional information, visit the Data Store.
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National Park Service Geodiversity Atlas
The servicewide Geodiversity Atlas provides information on geoheritage and geodiversity resources and values within the National Park System. This information supports science-based geoconservation and interpretation in the NPS, as well as STEM education in schools, museums, and field camps. The NPS Geologic Resources Division and many parks work with National and International geoconservation communities to ensure that NPS abiotic resources are managed using the highest standards and best practices available.