Geologic units in Coconino county, Arizona

Additional scientific data in this geographic area

Permian sedimentary rocks (Permian) at surface, covers 37 % of this area

Gray to tan, cherty limestone of Kaibab and Toroweap Formations, and underlying white to tan, fine-grained Coconino Sandstone. Limestone was deposited in a shallow sea, and sandstone was deposited in near-shore dunes and beach settings. (270-280 Ma)

Glen Canyon Group (Early Jurassic) at surface, covers 14 % of this area

Conspicuous red, cross-bedded Wingate Sandstone and the conspicuously cross-bedded, eolian, red to buff Navajo Sandstone form prominent cliffs in northern Arizona. These two sandstone units are separated by variably colored siltstone, silty sandstone, and sandstone of the Kayenta and Moenave Formations. (180-210 Ma)

Pliocene to late Miocene basaltic rocks (Late Miocene to Pliocene) at surface, covers 8 % of this area

Mostly dark, inconspicuously flat, low-lying or mesa-forming basalt deposited as lava flows. Rocks included in this unit are located almost entirely in the large volcanic fields south and west of Flagstaff, in smaller fields in northwesternmost Arizona, and in the Hopi Buttes volcanic field on the Navajo and Hopi Indian Reservations north of Holbrook. Original volcanic landforms have been obscured by erosion. (4-8 Ma)

Holocene to middle Pliocene basaltic rocks (Middle Pliocene to Holocene) at surface, covers 8 % of this area

Mostly dark-colored basaltic lava and cinders young enough that some original volcanic landforms are still apparent. Includes a small amount of andesite, dacite, and rhyolite. Rocks of this map unit are largely restricted to six areas widely distributed in Arizona: San Francisco and Uinkaret volcanic fields in northern Arizona (0-4 Ma); Springerville (0-4 Ma) and San Carlos (0-2 Ma) volcanic fields in east-central Arizona; and San Bernardino (0-1 Ma) and Sentinel (1-4 Ma) volcanic fields in southern Arizona. Rocks of this unit are also present in the extreme southwestern part of Arizona where they were erupted at the edge of the Pinacate volcanic field (0-2 Ma) in northwestern Sonora. (0-4 Ma)

Moenkopi Formation (Early and Middle(?) Triassic) at surface, covers 5 % of this area

Dark red sandstone and mudstone; includes gypsum beds in northwestern Arizona; deposited on a low-relief coastal plain. (230-245 Ma)

Permian to Pennsylvanian sedimentary rocks (Pennsylvanian to Permian) at surface, covers 5 % of this area

Interbedded sandstone, shale, and limestone usually characterized by ledgy outcrops. Orange to reddish sandstone forms cliffs near Sedona. This unit includes Supai Group and Hermit Shale in northern Arizona and Naco Group in southern Arizona. It was deposited in coastal-plain to shallow-marine settings during time of variable and changing sea level. Rocks of this map unit in southern Arizona may be in part equivalent to Permian rocks of map unit P in central and northern Arizona. (280-310 Ma)

Quaternary surficial deposits, undivided (Quaternary) at surface, covers 5 % of this area

Unconsolidated to strongly consolidated alluvial and eolian deposits. This unit includes: coarse, poorly sorted alluvial fan and terrace deposits on middle and upper piedmonts and along large drainages; sand, silt and clay on alluvial plains and playas; and wind-blown sand deposits. (0-2 Ma)

San Rafael Group (Middle to Late Jurassic) at surface, covers 4 % of this area

Commonly cross-bedded, ledge-forming sandstone and slope-forming siltstone. Rock typically has a striped red and white aspect. The Carmel Formation and Entrada Sandstone are prominent members of this group. (Late to Middle Jurassic, about 160-180 Ma)

Chinle Formation (Late Triassic) at surface, covers 3 % of this area

Colorful mudstone, such as in the Painted Desert, and less abundant lenses of sandstone and conglomerate, deposited by a large river system. This unit typically is eroded into badlands topography and contains clays that are prone to shrinking and swelling. (210-230 Ma)

Mississippian, Devonian, and Cambrian sedimentary rocks (Cambrian, Devonian, and Mississippian) at surface, covers 2 % of this area

Brown to dark gray sandstone grades upward into green and gray shale, overlain by light to medium gray or tan limestone and dolostone. This unit includes the Tapeats Sandstone, Bright Angel Shale, Muav Limestone, Temple Butte Formation and Redwall Limestone in northern Arizona, and the Bolsa Quartzite, Abrigo Formation, Martin Formation, and Escabrosa Limestone in southern Arizona. These rocks record intermittent sea-level rise and inundation in early Paleozoic time. (330-540 Ma)

Oligocene to Paleocene[?] sedimentary rocks (Paleocene(?) to Oligocene) at surface, covers 2 % of this area

Light colored, weakly to moderately consolidated conglomerate and sandstone deposited largely or entirely before mid-Tertiary volcanism and extensional faulting. Most sediment was deposited by early Cenozoic streams that flowed northeastward onto the Colorado Plateau from areas to the southwest that are now lower in elevation than the Plateau. Sediments of this map unit, other than the Chuska Sandstone in northeasternmost Arizona, are commonly referred to as "rim gravels" because they now rest on or near the Mogollon Rim, which is the southwestern edge of the Colorado Plateau. (30-65 Ma)

Shinarump Conglomerate Member, Chinle Formation (Late Triassic) at surface, covers 2 % of this area

Basal conglomerate and pebbly sandstone of the Chinle Formation is relatively resistant to erosion and forms extensive benches in some parts of the Colorado Plateau. (210-230 Ma)

Cretaceous sedimentary rocks (Cretaceous) at surface, covers 1 % of this area

Tan sandstone (Dakota Sandstone) overlain by gray shale (Mancos Shale); deposited in beach, river delta, and shallow sea settings. The Mancos Shale is overlain by the Mesaverde Group (map unit Kmv). This unit includes related sandstone and shale exposed near Show Low, Morenci (Pinkard Formation), and around Deer Creek south of Globe. (about 88-97 Ma)

Holocene to middle Pliocene volcanic rocks (Middle Pliocene to Holocene) at surface, covers 0.9 % of this area

Rhyolite to andesite deposited as a sequence of lava flows and associated rocks; generally light to medium gray, tan, or reddish brown. These rocks are part of the San Francisco volcanic field. (0-4 Ma)

Holocene surficial deposits (Holocene) at surface, covers 0.8 % of this area

Unconsolidated deposits associated with modern fluvial systems. This unit consists primarily of fine-grained, well-sorted sediment on alluvial plains, but also includes gravelly channel, terrace, and alluvial fan deposits on middle and upper piedmonts. (0-10 ka)

Sedimentary rocks of the Late Cretaceous Mesaverde Group (Late Cretaceous) at surface, covers 0.8 % of this area

Gray to buff sandstone with interbedded shale and coal. These rocks, which are similar to slightly younger rocks that form Mesa Verde in southwestern Colorado, were deposited on the margin of a shallow sea. Rocks of this map unit host the only large coal deposits in Arizona. (84-88 Ma)

Early Pleistocene to latest Pliocene surficial deposits (Late Pliocene to Early Pleistocene) at surface, covers 0.6 % of this area

Coarse relict alluvial fan deposits that form rounded ridges or flat, isolated surfaces that are moderately to deeply incised by streams. These deposits are generally topographically high and have undergone substantial erosion. Deposits are moderately to strongly consolidated, and commonly contain coarser grained sediment than younger deposits in the same area. (0.75-3 Ma)

Pliocene to middle Miocene deposits (Middle Miocene to Pliocene) at surface, covers 0.4 % of this area

Moderately to strongly consolidated conglomerate and sandstone deposited in basins during and after late Tertiary faulting. Includes lesser amounts of mudstone, siltstone, limestone, and gypsum. These deposits are generally light gray or tan. They commonly form high rounded hills and ridges in modern basins, and locally form prominent bluffs. Deposits of this unit are widely exposed in the dissected basins of southeastern and central Arizona. (2-16 Ma)

Middle Proterozoic sedimentary rocks (Middle Proterozoic) at surface, covers 0.3 % of this area

Red-brown shale and sandstone, buff to orange quartzite, limestone, basalt, black shale, and sparse conglomerate. This unit includes the Grand Canyon Supergroup, Apache Group, and Troy Quartzite. These rocks were deposited in shallow marine, coastal nonmarine, and fluvial settings. (700-1300)

Late to middle Miocene basaltic rocks (Middle to Late Miocene) at surface, covers 0.3 % of this area

Mostly dark, mesa-forming basalt deposited as lava flows. Rocks of this unit are widely exposed south of Camp Verde (Hickey Formation basalts), in the Mohon Mountains north of Bagdad, "The Mesa" east of Parker, and at other scattered locations in western Arizona. Rocks of this unit were not tilted by middle-Tertiary normal faulting except in a narrow belt from north of Phoenix to the northwest corner of the state. (8-16 Ma)

Pliocene to middle Miocene volcanic rocks (Middle Miocene to Pliocene) at surface, covers 0.2 % of this area

Rhyolite to andesite deposited as lava flows and related rocks associated with basaltic rocks of map units Tby and Tb. (2-12 Ma)

Morrison Formation (Late Jurassic) at surface, covers < 0.1 % of this area

Commonly cliff-forming, cross-bedded sandstone lenses alternating with slope-forming siltstone, mudstone and shale. Colors are highly variable, and include greenish gray, reddish brown, pink, white, and purple. Sands were deposited by braided streams with finer sediment representing overbank or lacustrine deposits. (145-160 Ma)

Early Proterozoic granitic rocks (Early Proterozoic) at surface, covers < 0.1 % of this area

Wide variety of granitic rocks, including granite, granodiorite, tonalite, quartz diorite, diorite, and gabbro. These rocks commonly are characterized by steep, northeast-striking foliation. (1600-1800 Ma)

Early Proterozoic metasedimentary rocks (Early Proterozoic) at surface, covers < 0.1 % of this area

Metasedimentary rocks, mostly derived from sandstone and shale, with minor conglomerate and carbonate rock. Includes quartz-rich, mostly nonvolcanic Pinal Schist in southeastern Arizona and variably volcanic-lithic sedimentary rocks in the Yavapai and Tonto Basin supergroups in central Arizona. (1600-1800 Ma)

Early Proterozoic metavolcanic rocks (Early Proterozoic) at surface, covers < 0.1 % of this area

Weakly to strongly metamorphosed volcanic rocks. Protoliths include basalt, andesite, dacite, and rhyolite deposited as lava or tuff, related sedimentary rock, and shallow intrusive rock. These rocks, widely exposed in several belts in central Arizona, include metavolcanic rocks in the Yavapai and Tonto Basin supergroups. (1650 to 1800 Ma)

Early Proterozoic metamorphic rocks (Early Proterozoic) at surface, covers < 0.1 % of this area

Undivided metasedimentary, metavolcanic, and gneissic rocks. (1600-1800 Ma)

Eolian deposits (Quaternary) at surface, covers < 0.1 % of this area

Eolian deposits

Paleozoic sedimentary rocks (Paleozoic) at surface, covers < 0.1 % of this area

Undivided Paleozoic limestone, dolostone, quartzite, shale, and related sedimentary rocks. (248-544 Ma)

Alluvium and colluvium (Quaternary) at surface, covers < 0.1 % of this area

Alluvium and colluvium

Glen Canyon Group (Early Jurassic) at surface, covers < 0.1 % of this area

Glen Canyon Group (Navajo Ss, Kayenta Fm, and Wingate Ss). Includes Rainbow Bridge.

Bluff Ss, Summerville Fm, Curtis Fm, Entrada Ss, and Carmel Formation (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

Bluff Ss, Summerville Fm, Curtis Fm, Entrada Ss, and Carmel Formation. Includes Arches National Park.

Navajo Sandstone, Kayenta and Moenave Formations (Early to Middle Jurassic) at surface, covers < 0.1 % of this area

Navajo Sandstone, Kayenta and Moenave Formations. Includes Zion National Park (Navajo Ss).

Kaibab Limestone and Toroweap Formation (Early Permian) at surface, covers < 0.1 % of this area

Kaibab Limestone and Toroweap Formation.

Morrison Formation (Brushy Basin and Salt Wash Members) (Late Jurassic) at surface, covers < 0.1 % of this area

Morrison Formation (Brushy Basin and Salt Wash Members).

Moenkopi Formation (Early Triassic) at surface, covers < 0.1 % of this area

Moenkopi Formation.

Entrada and Carmel Formations (Middle Jurassic) at surface, covers < 0.1 % of this area

Entrada and Carmel Formations (Arapien Shale at Marysvale).

Chinle Formation and Shinarump Conglomerate Member (Late Triassic) at surface, covers < 0.1 % of this area

Chinle Formation and Shinarump Conglomerate Member.

Nugget Sandstone (Early Jurassic) at surface, covers < 0.1 % of this area

Nugget Sandstone.

Chinle Shale and Shinarump Conglomerate Member (Late Triassic) at surface, covers < 0.1 % of this area

Chinle Shale and Shinarump Conglomerate Member.