Geology of the Navajo Nation
The Navajo Nation lies entirely on the Colorado Plateau, and is made up of an array of geologic features including gentle uplifts, monoclines, broad basins, diatremes, and laccolith ranges (Baars, 1995 ).
The geologic setting of Navajo Country is made up of the Chuska Mountains and Defiance Uplift that separate the San Juan Basin and the Black Mesa-Holbrook Basin. The San Juan Basin is bounded on the east by monoclines and underlying basement faults of the Chama and Nacimiento-San Pedro Mountains, on the south by the Zuni Uplift, on the west by the Defiance Uplift, and to the north by the Hogback monocline and La Plata Mountains. West of the Defiance Uplift is the Black Mesa-Holbrook Basin complex, bounded on the south by the faulted escarpment of the Mogollon Rim, to the west by the Echo Cliffs and East Kaibab monoclines and to the north by the Comp Ridge monocline of the Monument Upwarp (Baars, 1995 ).
The geologic history of Navajo Country goes back more than 1.8 billion years. Precambrian basement rock is made up of mostly metamorphic rock with some igneous rock and underlies younger unmetamorphosed sedimentary rock. Paleozoic rocks are composed of thick layers of limestone, sandstone, siltstone, and shale that accumulated in shallow continental tropical seas. Mesozoic rocks were formed mostly by terrestrial deposits and are mainly sandstones with some shale (Geology of the Colorado Plateau (more info) ). Cenozoic rocks include igneous intrusions, diatremes and terrace gravels (Baars, 1995 ).
To further investigate the geology of the Navajo Nation, follow the links below.
Geology of the Colorado Plateau
Online resources containing information about the geology of the Colorado Plateau.
- Geology of the Colorado Plateau (more info) This National Park Service report provides a thorough discussion of the geology of the Colorado Plateau, and is complete with maps, stratigraphic columns and structural cross sections. Specifically, the report describes the plateau physiography, exposed stratigraphic units, structural evolution and adjacent volcanic centers. Precambrian through Tertiary rock units are briefly discussed.
- Definition of Colorado Plateau (more info) This site is a brief summary of the Colorado Plateau Province with information about the geology of the area. Also covered in this site are the protected lands on the Colorado Plateau Province, with links to the National Parks, National Monuments, and Wilderness areas of this area. Links within the text lead to definitions of geological terms, and a search box allows users to search within the site.
- Colorado Plateau Region (more info) This web site briefly describes the geology of the Colorado Plateau. Topics include metamorphic, igneous, and sedimentary rocks, and Miocene uplift and erosion. Also included are imbedded links that lead to a glossary of terms.
- Geologic Provinces of the United States: Colorado Plateau Province (more info) This site covers information pertaining to the Colorado Plateau physiographic province. Topics include building the basement, lithic layer cake, and rising crust and downcutting streams. Links within the text lead to a glossary of terms, a geologic time scale and a list of National Parks exhibiting Colorado Plateau geology. A map is included that allows the user to click on and view information on other geologic provinces. Links are also provided that allow users to view maps and illustrations.
- Geology of the Colorado Plateau (more info) This web page provides a general description of the geology of the Colorado Plateau. Topics include information about the various geologic environments and processes active during the Precambrian and the Paleozoic, Mesozoic and Cenozoic Eras.
- MAP LINKS - Colorado Plateau, Misc. (more info) This site provides links to a variety of maps in the area of the Colorado Plateau, where the Navajo Nation lies. Maps provided include a Colorado Plateau Map with Subdivisions, Shaded Relief Maps of the Colorado Plateau, Colorado Plateau Aquifers, Distribution of Eolian Sand on the Colorado Plateau, and Federally Owned Coal and Federal Lands in the Colorado Plateau Region. Also included on this site are links to maps of Arizona, Colorado, New Mexico, Utah and Wyoming.
Geologic and Topographic Maps
Resources containing geologic and topographic maps on the Navajo Nation.
Suggestions for Future Reading about the Geology of the Colorado Plateau
Resources about the geology of the Colorado Plateau.
- Navajo Country. Baars, 1995 This book provides a geologic and natural history of the Four Corners region of the American Southwest. The Four Corners area includes Arizona, Colorado, New Mexico, and Utah. (citation and description)
- A Navajo-English Thesaurus of Geological Terms. [Blackhorse, Semken and Charley, 2003] This is a bilingual Navajo-English thesaurus of selected common geological and related terms designed for the use of geoscientists and geoscience educators who work on or near the Navajo Nation, or who have an interest in Navajo ethnogeology. (citation and description)
- 40Ar/39Ar Age Determinations for the Carrizo Mountains Laccolith, Navajo Nation, Arizona. [Semken and McIntosh, 1997] This article from the New Mexico Geological Society Guidebook contains information about Late Cretaceous (73.8-70.65 Ma) ages for hornblende separates from the Carrizo Mountains laccolith. Three specimens of diorite porphyry were examined using the 40Ar/39Ar step-heating method and no evidence of excess 40Ar or contamination by older xenocrysts was found. This has called into question some previously published K-Ar ages from the Four Corners area. This article thus confirms that the Carrizo Mountains intrusive center is an Arizona extension of the Laramide-age Colorado mineral belt. (citation and description)
- Ch'ooshgai doo Tsezhiin 'ii' ahi: The Chuska Mountains, Defiance Plateau, and Navajo Volcanic Field. [Semken, 2002] This is the guidebook from the Fourteenth Annual Western Slope Field Geologic Conference. The guidebook covers the geology of the Chuska Mountains region of the central Colorado Plateau, which crosses several major monoclines from the San Juan Basin on the east to the Deviance Plateau on the west. The book focuses on the stratigraphy exposed by the Laramide uplift and subsequent erosion, and on the mid-Tertiary Navajo Volcanic Field. Also examined is the unusual igneous petrology of several Navajo Volcanic Field centers, as well as their diverse structures and volcanic features. (citation and description)
- Black Rocks Protruding Up: The Navajo Volcanic Field. [Semken, 2003] This article in Geology of the Zuni Plateau provides information about the mid-Tertiary age volcanoes, dikes and sills of the Navajo volcanic field on the Colorado Plateau. (citation and description)
- Ti' Dine bitse' dadiniil': Field Guide to a Geologic Excursion in the Northeastern Navajo Nation. [Semken, Slate and Crank, 1992] This guidebook was used for the Western Slope Field Geologic Conference in 1992. The road log covers a portion of the Navajo Nation from Shiprock, New Mexico to Chinle, Arizona. The guidebook includes information about the local geology, stratigraphic correlation charts for the San Juan Basin and southern Utah, and a supplemental road log for the Hasbidito Creek dikes in Arizona. (citation and description)
- The Shiprock Uranium-mill Tailings Remedial Action (UMTRA) Site. [Tsosie, Semken and Harrison, 1997] This article in the New Mexico Geological Society Guidebook discusses a uranium mill tailings site in Shiprock, New Mexico and its effect on the local environment. The site, located on a high terrace adjacent to the San Juan River, has been the focus of a Department of Energy remediation program. This article provides information about the floodplain and its stratigraphy, hydrology, conductivity and the relationships between hydrology and conductivity. (citation and description)