Geodiversity Atlas—Southern Colorado Plateau Network Index

Photo looking across a muddy river to layered rock cliffs
Grand Canyon National Park, Arizona. View from the Tonto Trail looking northeast toward Shinumo Creek, type locality of the Shinumo Sandstone, just southwest of river mile 109.2. Rocks of the Unkar Group overlie the Vishnu Schist.

Photograph ES180 from Billingsley et al. (2019).

Geology and Stratigraphy of the Southern Colorado Plateau Network Parks

The Southern Colorado Plateau Inventory and Monitoring Network is composed of 19 national park units in Arizona, Colorado, New Mexico, and Utah. Park units of the Southern Colorado Plateau Network include Aztec Ruins National Monument, Bandelier National Monument, Canyon De Chelly National Monument, Chaco Culture National Historical Park, El Malpais National Monument, El Morro National Monument, Glen Canyon National Recreation Area, Grand Canyon National Park, Hubbell Trading Post National Historic Site, Mesa Verde National Park, Navajo National Monument, Petrified Forest National Park, Petroglyph National Monument, Rainbow Bridge National Monument, Salinas Pueblo Missions National Monument, Sunset Crater Volcano National Monument, Valles Caldera National Preserve, Walnut Canyon National Monument, Wupatki National Monument, and Yucca House National Monument. Parks that comprise the Southern Colorado Plateau Network protect a combined 1,269,514 hectares (3,137,038 acres) of land and vary in size from 13 hectares (34 acres) in Yucca House, to 507,523 hectares (1,254,117 acres) in Glen Canyon.

The Colorado Plateau is characterized as a high-standing crustal block of relatively undeformed strata that exhibit broad flexures, monoclines (step-like folds), normal faults, igneous laccoliths (dome-like intrusions), and volcanoes. The province is surrounded by the Rocky Mountains and Uinta Mountains to the north and northeast, the Rio Grande Rift Valley to the east, and the Mogollon Rim to the south. The western boundary of the Colorado Plateau represents a transition zone where geologic features are transitional between typical Colorado Plateau and the Basin and Range. Many of the parks in the Southern Colorado Plateau Network represent iconic geologic landscapes consisting of sparely vegetated plateaus, mesas, deep canyons, and badlands that encompass the area drained by the Colorado River and its tributaries. Parks of the Southern Colorado Plateau Network occupy four of the six sections of the Colorado Plateau as defined by Rigby (1977):

  1. Grand Canyon section, the highest structural part of the Colorado Plateau—Grand Canyon, Sunset Crater Volcano, Walnut Canyon, and Wupatki;
  2. Canyonlands section, a region of deeply incised canyons, large monoclines, and laccolithic mountains—Glen Canyon, Mesa Verde, Rainbow Bridge, and Yucca House;
  3. Navajo section, an area of scarped plateaus that is less dissected than the Canyonlands section— Aztec Ruins, Canyon De Chelly, Chaco Culture, Hubbell Trading Post, Navajo National Monument, and Petrified Forest; and the
  4. Datil section, which is largely volcanic in origin—El Malpais and El Morro.

Only Bandelier, Petroglyph, Salinas Pueblo Missions, and Valles Caldera are located outside the Colorado Plateau physiographic province in and near the Rio Grande Rift, an area characterized by east–west crustal extension. Dynamic crustal extensional processes associated with the Rio Grande Rift resulted in thick packages of sedimentary deposits (Santa Fe Group), but also thinned and weakened the crust, producing fault-bounded basins and numerous volcanic fields throughout New Mexico and Colorado (Keller and Baldridge 1999; KellerLynn 2017).

A Brief Geologic History—Southern Colorado Plateau Network

A few examples of events and Network resources in each geologic time period are highlighted below, from youngest to oldest.

Cenozoic bedrock and surficial deposits are found in most parks of the Southern Colorado Plateau Network and include igneous rocks associated with the Rio Grande Rift, Albuquerque volcanic field, San Francisco volcanic field, and Valles–Toledo caldera complex (a caldera is a basin formed when a magma chamber is emptied by eruption and the overlying rock collapses into it).

Mapped units in Aztec Ruins include the Paleocene Nacimiento Formation and Pleistocene Naha and Tsegi Alluviums. The Naha Alluvium is also mapped in Chaco Culture. Several Cenozoic-age units are found in Bandelier and adjacent Valles Caldera, including the Eocene Galisteo Formation; Miocene Chamita, Tesuque, and Paliza Canyon Formations; Miocene–Pliocene Cochiti Formation; Pliocene Tschicoma Formation; and Pleistocene Tewa Group (Bandelier Tuff, Cerro Toledo Formation, Valles Rhyolite). Cenozoic volcanic rocks, basalt flows, and dikes are located in both El Malpais, El Morro, Salinas Pueblo Missions, and Wupatki. A number of volcanic units are distributed throughout Grand Canyon and record Miocene, Pliocene, and Pleistocene-age volcanism. The Miocene Bidahochi Formation is found in Petrified Forest. Several Cenozoic-age deposits are mapped in Petroglyph and include the Pliocene–Pleistocene Ceja Formation and Pleistocene Lomatas Negras Formation, Los Duranes Formation, and volcanic rocks associated with the Albuquerque volcanic field. The volcanic landscape of Sunset Crater Volcano consists entirely of Pleistocene-age volcanic rock lava flows, volcanic ash, and cinder deposits of the San Francisco volcanic field.

Geologically young surficial deposits of Pleistocene-Holocene-age are mapped in nearly every park of the Southern Colorado Plateau Network, and predominantly consist of alluvium, colluvium, alluvial fan deposits, eolian sands, terrace gravels, landslide deposits, and slump deposits.
Mesozoic rocks are mapped in 13 of the 19 park units of the Southern Colorado Plateau Network. Exposure in Glen Canyon may represent the best overall Mesozoic stratigraphic section in the National Park Service, providing exceptional documentation of ancient ecosystems and paleoclimates from about 252 million to 66 million years ago. Mapped units in Glen Canyon include the Triassic Moenkopi Formation and Chinle Formation; Triassic–Jurassic Glen Canyon Group (Wingate Sandstone, Moenave Formation, Kayenta Formation and Navajo Sandstone); Jurassic San Rafael Group (Entrada Sandstone, Page Sandstone, Carmel Formation, Romana Sandstone, and Summerville Formation) and Morrison Formation; and Cretaceous Naturita Formation [formerly Dakota Formation], Tropic Shale, and Straight Cliffs Formation.

Several units are found is multiple parks, such as the Triassic Moenkopi Formation (Glen Canyon, Grand Canyon, and Wupatki) and Chinle Formation (Canyon De Chelly, Glen Canyon, Grand Canyon, Hubbell Trading Post, and Petrified Forest); Triassic–Jurassic Glen Canyon Group (Glen Canyon, Grand Canyon, Navajo National Monument, and Rainbow Bridge); Jurassic Zuni Sandstone (El Malpais and El Morro); and Cretaceous Naturita Formation (El Malpais, El Morro), Mesaverde Group (Chaco Culture, Mesa Verde), and Mancos Shale (El Malpais, Mesa Verde, Yucca House). Other mapped Mesozoic rocks within the park units of Southern Colorado Plateau Network include the Jurassic Wanakah Formation (El Malpais) and Cretaceous Pictured Cliffs Sandstone and Lewis Shale (Chaco Culture), Tres Hermanos Sandstone (El Malpais), and Point Lookout Sandstone (Mesa Verde).
Thick sequences of Paleozoic sedimentary rocks are mapped in several of the park units of the Southern Colorado Plateau Network. The extensive and world-renowned Paleozoic strata exposed in Grand Canyon include the Cambrian Tonto Group (Sixtymile Formation, Tapeats Sandstone, Bright Angel Formation, and Muav Formation), Mississippian Redwall Limestone, Surprise Canyon Formation, Pennsylvanian–Permian Supai Group and related units (Watahomigi Formation, Manakacha Formation, Wescogame Formation, Pakoon Limestone, and Esplanade Sandstone), and the Permian Hermit Formation. The Permian Coconino Sandstone is exposed in Grand Canyon and Walnut Canyon. The Permian Toroweap Formation is mapped in Grand Canyon, Walnut Canyon, and Wupatki. The Permian Kaibab Formation is found in Glen Canyon, Grand Canyon, Walnut Canyon, and Wupatki.

Other Paleozoic-age units include the Pennsylvanian Hermosa Group (Glen Canyon), Pennsylvanian– Permian Supai Formation (Canyon De Chelly), Permian San Andres Limestone (El Malpais and Salinas Pueblo Missions), Abo Formation (El Malpais and Salinas Pueblo Missions), Cutler Group (Canyon De Chelly and Glen Canyon), Glorieta Sandstone (El Malpais), Yeso Formation (El Malpais), and Arroyo de Alamillo Formation (Salinas Pueblo Missions).
Precambrian-age rocks are mapped in the Upper, Middle, and Lower Granite Gorges of Grand Canyon and include the oldest exposures in the Southern Colorado Plateau Network (Seaman et al. 2021). These ancient exposures include the Paleoproterozoic Elves Chasm pluton (1.84 billion years old); Granite Gorge Metamorphic Suite (1.751–1.750 billion years old) that includes the Vishnu, Brama, and Rama schists; granodioritic intrusive rocks of the Zoroaster Plutonic Complex (1.740–1.713 billion years old); granitic intrusive rocks (Phantom granite) and pegmatite dikes (Cremation pegmatite) between 1.698–1.662 billion years old; and the Quartermaster granite in western Grand Canyon (1.375 billion years old) (Karlstrom et al. 2021). The Grand Canyon Supergroup is localized to Grand Canyon and includes the Mesoproterozoic Unkar Group (Bass Formation, Hakatai Shale, Shinumo Sandstone, Dox Formation, and Cardenas Basalt), and Neoproterozoic Chuar Group (Nankoweap Formation, Galeros Formation, and Kwagunt Formation). Other Precambrian exposures are mapped in El Malpais, consisting of Mesoproterozoic metamorphic and igneous rocks about 1.4 billion years old.

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    Type Sections—Southern Colorado Plateau Network

    small image of a report cover with a tiny photo of red rock cliffs

    The geologic history above is excerpted from a report titled, "National Park Service geologic type section inventory: Southern Colorado Plateau Inventory & Monitoring Network". Type sections are essential reference locations for the geoscientists who study geologic history and paleontology. A summary of the type sections in each park can be found at the links below.

    • Aztec Ruins National Monument, New Mexico (no designated stratotypes identified)

    • Bandelier National Monument, New Mexico [Site Under Development]

    • Canyon De Chelly National Monument, Arizona [Site Under Development]

    • Chaco Culture National Historical Park, New Mexico (no designated stratotypes identified)

    • El Malpais National Monument, New Mexico (no designated stratotypes identified)

    • El Morro National Monument, New Mexico (no designated stratotypes identified)

    • Glen Canyon National Recreation Area, Arizona and Utah [Site Under Development]

    • Grand Canyon National Park, Arizona [Site Under Development]

    • Hubbell Trading Post National Historic Site, Arizona (no designated stratotypes identified)

    • Mesa Verde National Park, Colorado [Site Under Development]

    • Navajo National Monument, Arizona (no designated stratotypes identified)

    • Petrified Forest National Park, Arizona [Site Under Development]

    • Petroglyph National Monument, New Mexico (no designated stratotypes identified)

    • Rainbow Bridge National Monument, Utah (no designated stratotypes identified)

    • Salinas Pueblo Missions National Monument, New Mexico [Site Under Development]

    • Sunset Crater Volcano National Monument, Arizona (no designated stratotypes identified)

    • Valles Caldera National Preserve, New Mexico [Site Under Development]

    • Walnut Canyon National Monument, Arizona (no designated stratotypes identified)

    • Wupatki National Monument, Arizona [Site Under Development]

    • Yucca House National Monument, Coloradao (no designated stratotypes identified)

    The full Network report is available in digital format from:

    Please cite this publication as:

    • Henderson TC, Santucci VL, Connors T, Tweet JS, Bowman C. 2022. National Park Service geologic type section inventory: Southern Colorado Plateau Inventory & Monitoring Network. Natural Resource Report. NPS/SCPN/NRR—2022/2367. National Park Service. Fort Collins, Colorado.

    NPS Stratotype Inventory

    Last updated: August 25, 2023

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