# Kaibab Formation Canonical page: https://lithomap.app/resources/geologic-formations/united-states/kaibab-formation Last reviewed: September 17, 2026 Page purpose: Comprehensive United States geologic formation reference for human readers, search systems, and language models. Major region: Colorado Plateau / Rockies Regional setting: Colorado Plateau and eastern Basin and Range Age: Early Permian Age detail: Leonardian regional stage; approximately 270 million years old Depositional setting: Shallow tropical sea, shoreline flats, and evaporitic environments Rock types: Limestone, Dolostone, Sandstone, Gypsum, Chert States in recognized usage: Arizona, Nevada, Utah ## Summary The Kaibab forms much of the resistant rim of the Grand Canyon and records a shallow Permian sea whose limestones, dolostones, sandstones, chert, and gypsum capture repeated marine advances and retreats. ## Distribution The formation is widespread across northern Arizona and extends into southern Utah and southeastern Nevada. At the Grand Canyon it caps large portions of the plateau, while farther east and west its composition and subdivisions change. Modern usage favors “Kaibab Formation” because the unit is not limestone everywhere. West of a broad north–south boundary in Arizona it is commonly divided into the Fossil Mountain and Harrisburg Members; eastern equivalents can be more sandy and remain undivided. ## Geological history Warm, shallow marine water covered the region during part of Permian time. Carbonate mud, shells, and skeletal debris became limestone and dolostone, while silica formed nodules and beds of chert. Shoreline sand and restricted, evaporating water produced sandstone and gypsum-bearing intervals. The formation captures more than one environment and more than one shoreline position. The fossiliferous, cliff-forming Fossil Mountain Member differs from the more varied Harrisburg Member, which includes carbonate, sandstone, red beds, chert, and gypsum. ## Fossil record Common fossils include brachiopods, bryozoans, sponges, crinoid fragments, mollusks, echinoids, cephalopods, and other marine invertebrates. Fossil Mountain Member exposures are especially well known for marine fossils. Most fossils are hard parts or impressions of seafloor organisms. Preservation and abundance vary with rock type; gypsum-rich or sandy beds generally tell a different environmental story than fossiliferous limestone. ## Minerals and geological resources Calcite and dolomite dominate the carbonate rocks. Chert consists of microcrystalline quartz, and gypsum is conspicuous in some upper or western intervals. Quartz is also common in sandstone, with clay minerals and iron oxides in finer or red beds. Chert nodules weather out of limestone and may resemble collectible silica material, but removal may be prohibited. Mineral presence is a description of the rock—not permission to collect within a park, monument, tribal land, or other restricted area. ## Field context - Kaibab limestone and chert can make rough, sharp terrain with hidden solution cavities. - Collecting is prohibited in Grand Canyon National Park and other National Park Service units. - The rim-forming unit may be thin, faulted, or removed by erosion away from familiar viewpoints. ## Connected field guides - Chert (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/chert - Gypsum (mineral; Named rock type and mineral context) — https://lithomap.app/resources/mineral-identification/gypsum - Limestone (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/limestone - Sandstone (rock; Named rock type and mineral context) — https://lithomap.app/resources/rock-identification/sandstone - Dolostone (rock; Named rock type) — https://lithomap.app/resources/rock-identification/dolostone - Calcite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/calcite Mapped location and formation context support an identification but cannot establish one. Compare several physical properties and use laboratory analysis when the material remains ambiguous. ## Connected state geology guides - Utah geology — https://lithomap.app/resources/geology/united-states/utah - Arizona geology — https://lithomap.app/resources/geology/united-states/arizona ## Authoritative sources - Geolex Kaibab references — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/UnitRefs/KaibabRefs_9032.html - Geolex Fossil Mountain references — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/UnitRefs/FossilMountainRefs_8178.html ## Formation photograph - Image: https://lithomap.app/_delivery/formations/kaibab-formation.webp - Description: Layered Kaibab Limestone and associated strata at Walnut Canyon National Monument, Arizona - Creator: Jlahorn - License: CC BY-SA 3.0 — https://creativecommons.org/licenses/by-sa/3.0/ - Source record: https://commons.wikimedia.org/wiki/File:Walnut_canyon_strata.jpg Formation-level information does not prove that a fossil or mineral occurs at a specific coordinate. It also does not establish ownership, access, collecting permission, present conditions, or specimen identity.