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Geologic units in Arizona (state in United States)

Additional scientific data in this geographic area

Pliocene to middle Miocene deposits (Middle Miocene to Pliocene) at surface, covers 10 % 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)

Quaternary surficial deposits, undivided (Quaternary) at surface, covers 10 % 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)

Lithology: sand; gravel; mud; silt

Permian sedimentary rocks (Permian) at surface, covers 10 % 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)

Middle Miocene to Oligocene volcanic rocks (Oligocene to Middle Miocene) at surface, covers 7 % of this area

Lava, tuff, fine-grained intrusive rock, and diverse pyroclastic rocks. These compositionally variable volcanic rocks include basalt, andesite, dacite, and rhyolite. Thick felsic volcanic sequences form prominent cliffs and range fronts in the Black (Mohave County), Superstition, Kofa, Eagletail, Galiuro, and Chiricahua Mountains. This unit includes regionally extensive ash-flow tuffs, such as the Peach Springs tuff of northwestern Arizona and the Apache Leap tuff east of Phoenix. Most volcanic rocks are 20-30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona, but this unit includes some late Eocene rocks near the New Mexico border in east-central Arizona. (11-38 Ma)

Early Pleistocene to latest Pliocene surficial deposits (Late Pliocene to Early Pleistocene) at surface, covers 5 % 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)

Lithology: gravel; sand; mud; silt

Holocene to middle Pliocene basaltic rocks (Middle Pliocene to Holocene) at surface, covers 4 % 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)

Early Proterozoic granitic rocks (Early Proterozoic) at surface, covers 4 % 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)

Moenkopi Formation (Early and Middle(?) Triassic) at surface, covers 3 % of this area

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

Late and middle Pleistocene surficial deposits (Middle to Late Pleistocene) at surface, covers 3 % of this area

Unconsolidated to weakly consolidated alluvial fan, terrace, and basin-floor deposits with moderate to strong soil development. Fan and terrace deposits are primarily poorly sorted, moderately bedded gravel and sand, and basin-floor deposits are primarily sand, silt, and clay. (10-750 ka)

Lithology: gravel; sand; mud; silt

Holocene surficial deposits (Holocene) at surface, covers 3 % 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)

Lithology: sand; gravel; mud; silt

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)

Permian to Pennsylvanian sedimentary rocks (Pennsylvanian to Permian) at surface, covers 3 % 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)

Late to middle Miocene basaltic rocks (Middle to Late Miocene) at surface, covers 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)

Sedimentary rocks of the Late Cretaceous Mesaverde Group (Late Cretaceous) at surface, covers 3 % 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)

Middle Proterozoic granitic rocks (Middle Proterozoic) at surface, covers 2 % of this area

Mostly porphyritic biotite granite with large microcline phenocrysts, with local fine-grained border phases and aplite. Associated pegmatite and quartz veins are rare. This unit forms large plutons, including the Oracle Granite, Ruin Granite, granite in the Pinnacle Peak - Carefree area northeast of Phoenix, and several bodies west of Prescott. (1400-1450 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)

Glen Canyon Group (Early Jurassic) at surface, covers 2 % 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 2 % 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)

Early Proterozoic metamorphic rocks (Early Proterozoic) at surface, covers 2 % of this area

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

San Rafael Group (Middle to Late Jurassic) at surface, covers 2 % 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)

Oligocene to Paleocene[?] sedimentary rocks (Paleocene(?) to Oligocene) at surface, covers 1 % 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 1 % 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)

Middle Miocene to Oligocene sedimentary rocks (Oligocene to Middle Miocene) at surface, covers 1 % of this area

Con-glomerate, sandstone, mudstone, limestone, and rock-avalanche breccia (sheet-like deposits of crushed rock) deposited and tilted during widespread normal faulting and basin development. Sediments, mostly conglomerate and sandstone, are commonly medium to dark brown, reddish brown, or brownish gray; younger strata are generally lighter colors. Most deposits are 20 to 30 Ma in southeastern Arizona and 15 to 25 Ma in central and western Arizona. (11-32 Ma)

Holocene river alluvium (Holocene) at surface, covers 1 % of this area

Unconsolidated to weakly consolidated sand and gravel in river channels and sand, silt, and clay on floodplains. Also includes young terrace deposits fringing floodplains. (0-10 ka)

Lithology: sand; gravel; mud; silt

Middle Proterozoic sedimentary rocks (Middle Proterozoic) at surface, covers 1 % 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)

Cretaceous sedimentary rocks (Cretaceous) at surface, covers 1.0 % 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)

Early Proterozoic metasedimentary rocks (Early Proterozoic) at surface, covers 0.9 % 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)

Cretaceous to Late Jurassic sedimentary rocks with minor volcanic rocks (Late Jurassic to Cretaceous) at surface, covers 0.9 % of this area

Sandstone and conglomerate, rarely forms prominent outcrops; massive conglomerate is typical near base of unit and locally in upper part. These deposits are nonmarine except in southeastern Arizona, where prominent gray marine limestone (Mural Limestone) forms the middle of the Bisbee Group. Sandstones are typically medium-bedded, drab brown, lithic-feldspathic arenites. Includes Bisbee Group (largely Early Cretaceous) and related rocks, Temporal, Bathtub, and Sand Wells formations, rocks of Gu Achi, McCoy Mountains Formation, and Upper Cretaceous Fort Crittenden Formation and equivalent rocks. (80-160 Ma)

Early Tertiary to Late Cretaceous granitic rocks (Late Cretaceous to Early Tertiary) at surface, covers 0.8 % of this area

Porphyritic to equigranular granite to diorite emplaced during the Laramide orogeny. Larger plutons are characteristically medium-grained, biotite +/- hornblende granodiorite to granite. Smaller, shallow-level intrusions are typically porphyritic. Most of the large copper deposits in Arizona are associated with porphyritic granitic rocks of this unit, and are thus named 'porphyry copper deposits'. (50-82 Ma)

Early Tertiary to Late Cretaceous muscovite-bearing granitic rocks (Late Cretaceous to Early Tertiary) at surface, covers 0.8 % of this area

Light-colored peraluminous muscovite granite with or without garnet; commonly forms sills and is associated with abundant pegmatite dikes and sills. This unit includes granites in the Harcuvar and Harquahala Mountains of western Arizona and in the Santa Catalina, Rincon, Tortolita, Picacho, and Coyote Mountains of south-central Arizona. These granites typically represent the youngest phase of voluminous magmatism during the Laramide orogeny in Arizona. This unit also includes several muscovite-bearing granites in southern Arizona that are associated with calc-alkaline granites of unit TKg, and a batholith in the Cabeza Prieta area of southwestern Arizona. (50-80 Ma)

Early Proterozoic metavolcanic rocks (Early Proterozoic) at surface, covers 0.8 % 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)

Jurassic granitic rocks (Jurassic) at surface, covers 0.7 % of this area

Granite to diorite, locally foliated and locally alkalic; includes Triassic(?) granitoids in the Trigo Mountains. This unit includes two dominant assemblages of igneous rocks. The Kitt Peak-Trigo Peaks superunit includes, from oldest to youngest: dark, foliated or gneissic diorite, medium-grained equigranular to porphyritic granodiorite, and small, irregular intrusions of light-colored, fine-grained granite. The Ko Vaya superunit, limited to south-central Arizona, includes texturally heterogeneous K-feldspar-rich granitic rocks. (150-180 Ma)

Middle Miocene to Oligocene granitic rocks (Oligocene to Middle Miocene) at surface, covers 0.5 % of this area

Granite to diorite representing solidified magma chambers that were the likely source of overlying and nearby volcanic rocks of map unit Tv. The granitic rocks are typically equigranular and fine- to medium-grained. (14-26 Ma)

Early Tertiary to Late Cretaceous volcanic rocks (Late Cretaceous to Early Tertiary) at surface, covers 0.5 % of this area

Rhyolite to andesite and closely associated sedimentary and near-surface intrusive rocks; commonly dark gray to dark greenish gray or greenish brown. In the ranges west of Tucson, this unit includes thick welded ash-flow tuffs. Volcanic rocks of this unit are inferred to be derived from vents and volcanoes above magma chambers that solidified to form the granitic rocks of map unit TKg. These rocks are restricted to southeastern Arizona except for a small outcrop near Bagdad. (50-82 Ma)

Early Pleistocene to late Miocene basin deposits (Late Pliocene to Early Pleistocene) at surface, covers 0.5 % of this area

Poorly sorted, variably consolidated gravel and sand that range widely in age. These sediments are generally light gray or tan. This unit is generally mapped in areas of deep late Cenozoic stream incision and landscape degradation where thin Quaternary deposits (map units Qy, Qm, Qo) discontinuously blanket older deposits (map units Tsy or Tsm) and the two cannot be differentiated at the scale of this map. (0.75-10 Ma)

Lithology: gravel; sand; mud; silt

Morrison Formation (Late Jurassic) at surface, covers 0.4 % 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)

Middle Proterozoic diabase (Middle Proterozoic) at surface, covers 0.4 % of this area

Dark gray to black sills (intrusions mostly parallel to bedding) in strata of the Apache Group and irregular to sheet-like intrusions in other rocks. Present in east-central and southeastern Arizona. Some sills are more than 100 m thick. Exposures are extensive north of Globe. (1050-1150 Ma)

Middle Miocene to Oligocene volcanic and sedimentary rocks, undivided (Oligocene to Middle Miocene) at surface, covers 0.4 % of this area

Sequences of diverse volcanic rocks with abundant interbedded sedimentary rocks. (11-32 Ma)

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

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

Jurassic sedimentary and volcanic rocks (Jurassic) at surface, covers 0.3 % of this area

Sandstone and conglomerate derived from volcanic rocks with associated intermediate-composition lava flows, breccias, and tuffs. In southern Arizona this unit includes rocks of the Artesa sequence, Pitoikam Formation, Mulberry Wash volcanics, Rudolfo Red Beds, Recreation Red Beds, and Gardner Canyon Formation. In western Arizona it includes the Harquar Formation, rocks of Slumgullion, and related(?) unnamed units in the Kofa and Middle Mountains. This unit is characterized by maroon, brown, and purplish-gray volcanic-lithic sandstone and siltstone, with subordinate to abundant conglomerate, quartz-rich sandstone and sparse limestone. (150-170 Ma)

Pliocene to middle Miocene volcanic rocks (Middle Miocene to Pliocene) at surface, covers 0.3 % 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)

Jurassic volcanic rocks (Jurassic) at surface, covers 0.3 % of this area

Massive quartz-feldspar porphyry, generally interpreted as thick, welded rhyolitic tuffs, with locally abundant lava, and sandstone and conglomerate derived from volcanic rocks. Rare eolian quartzite units are interbedded in southern Arizona. Includes Ali Molina Formation, Mount Wrightson Formation, part of the Canelo Hills Volcanics, Cobre Ridge tuff, Black Rock volcanics, Planet Volcanics, and equivalent rocks. (160-200 Ma)

Tertiary to Early Proterozoic gneissic rocks (Early Proterozoic to Tertiary) at surface, covers 0.3 % of this area

Gneissic rocks with complex histories, typically with well developed, light-colored granitoid layers and dark-colored biotite- and amphibole-rich layers. Protoliths are of Tertiary to Proterozoic age. This unit includes variably mylonitic gneisses in metamorphic core complexes that have been exhumed from middle crustal levels by large-displacement middle Tertiary normal faults, and gneiss exposed at scattered locations near the Colorado River in southwestern Arizona. These rocks are interpreted to record Proterozoic, Mesozoic, and Tertiary metamorphism and deformation. (15-1800 Ma)

Proterozoic granitic rocks (Proterozoic) at surface, covers 0.2 % of this area

Undivided Early and Middle Proterozoic granitic rocks (units Xg and Yg). (1400-1800 Ma)

Holocene to middle Pliocene volcanic rocks (Middle Pliocene to Holocene) at surface, covers 0.2 % 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)

Middle Miocene to Oligocene shallow intrusions (Oligocene to Middle Miocene) at surface, covers 0.1 % of this area

Generally very fine-grained, porphyritic rhyolite to dacite in small, irregular-shaped bodies formed as subvolcanic intrusions in volcanic fields of southern and western Arizona, or in concentrated zones of dikes in the Mohave and Black Mountains of northwestern Arizona. The unit consists of mafic tuff, breccia and shallow intrusions at Buell Park in northeastern Arizona. (14-35 Ma)

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

Brown to maroon, resistant quartzite and minor conglomerate of the Mazatzal Group, exposed primarily in the Payson area. (1650? -1700 Ma)

Jurassic and Triassic sedimentary and volcanic rocks (Triassic and Jurassic) at surface, covers < 0.1 % of this area

Undivided massive quartz-feldspar porphyry of the Jurassic Planet Volcanics, quartz-rich metasandstone of the Jurassic Vampire Formation, and quartzite, phyllite, and fine grained, variably calcareous metasiltstone of the Triassic Buckskin Formation; exposed primarily in the Buckskin and Rawhide Mountains of western Arizona. This unit also includes sandstone and conglomerate beneath Jurassic volcanic rocks in the central Dome Rock Mountains. (160-240 Ma)

Jurassic to Cambrian metamorphosed sedimentary rocks (Cambrian to Jurassic) at surface, covers < 0.1 % of this area

Highly faulted and folded rocks of units Jv, J_, and Pz, deformed and metamorphosed in Jurassic, Cretaceous and Tertiary time. This unit is restricted to west-central Arizona. (160-540 Ma)

Orocopia Schist (Late Cretaceous to Early Tertiary) at surface, covers < 0.1 % of this area

Mostly gray, fine-grained quartz-feldspar-mica schist, with sparse metabasalt and metachert. The unit is exposed in tectonic windows in the southwestern corner of Arizona. It is interpreted as metamorphosed marine sandstone that was tectonically emplaced beneath southwestern Arizona during early Tertiary subduction of Pacific Ocean sea floor. (65-165 Ma)

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

Lithology: alluvium; colluvium

Triassic and Jurassic sedimentary rocks in southeastern Utah (Early Jurassic) at surface, covers < 0.1 % of this area

Triassic (1) sedimentary rocks in Salt southwestern Utah (Early Triassic) at surface, covers < 0.1 % of this area

Permian (2) sedimentary rocks in southwestern Utah (Early Permian) at surface, covers < 0.1 % of this area

Lithology: limestone; evaporite; chert

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

Lithology: eolian

Jurassic (1) sedimentary rocks in southeastern Utah (Middle to Late Jurassic) at surface, covers < 0.1 % of this area

Triassic (2) sedimentary rocks in southwestern Utah (Late Triassic) at surface, covers < 0.1 % of this area

continental red beds (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Triassic rocks, undivided; continental red beds

Triassic and Jurassic sedimentary rocks in southwestern Utah (Early to Middle Jurassic) at surface, covers < 0.1 % of this area

Jurassic (2) sedimentary rocks in southeastern Utah (Late Jurassic) at surface, covers < 0.1 % of this area

intertongued Dakota-Mancos sequence (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Intertongued Dakota-Mancos sequence of west-central New Mexico; includes the Whitewater Arroyo Tongue of Mancos Shale and the Twowells Tongue of the Dakota

Crevasse Canyon Formation (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Crevasse Canyon Formation; coal-bearing units are Dilco and Gibson Coal Members; other members are Bartlett Barren, Dalton Sandstone, and Borrego Pass Sandstone (or Lentil)

Chinle Group (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Chinle Group; Upper Triassic; includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped:

Triassic (2) sedimentary rocks in southeastern Utah (Late Triassic) at surface, covers < 0.1 % of this area

upper Tertiary sedimentary units (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Upper Tertiary sedimentary units; includes Bidahochi Formation, the Picuris Formation, and Las Feveras Formation, and locally fanglomerates; Pliocene to upper Miocene

Rock Point Formation of Chinle Group (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area

Rock Point Formation of Chinle Group; Upper Triassic. May locally include Lukachukai Member of Wingate Sandstone

Lithology: sandstone; siltstone

Quaternary alluvium and marine deposits (Pliocene to Holocene) at surface, covers < 0.1 % of this area

Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast.

piedmont alluvial deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Piedmont alluvial deposits: upper and middle Quaternary; includes deposits of higher gradient tributaries bordering major stream valleys, alluvial veneers of the piedmont slope, and alluvial fans

Lithology: alluvium

San Rafael Group (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

San Rafael Group; consists of Entrada Sandstone, Todilto and Summerville Formations, Bluff Sandstone, and locally Zuni Sandstone (or only Acoma Tongue of Zuni)

Pennsylvanian and Permian sedimentary rocks in southwestern Utah (Pennsylvanian) at surface, covers < 0.1 % of this area

Gallup Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Gallup Sandstone; generally regressive marine sandstone; Turonian

Lithology: sandstone

Andesite and related rocks of intermediate composition (Late Miocene to Middle Miocene) at surface, covers < 0.1 % of this area

ANDESITE AND RELATED ROCKS OF INTERMEDIATE COMPOSITION-Flows and breccias

andesites and basaltic andesites (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Upper Oligocene andesites and basaltic andesites (26-29 Ma); includes La Jara Peak Basaltic Andesite, Uvas Basalt, the basaltic andesite of Poverty Creek, and Squirrel Springs Andesite, the Razorback, Bear Springs Canyon, Salt Creek, Gila Flat, and Middle Mountain Formations, and the Alum Mountain Group; locally includes more silicic flows

Pliocene and Quaternary alluvial material (Pliocene to Quaternary) at surface, covers < 0.1 % of this area

Lithology: alluvium

basaltic andesites (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Miocene and uppermost Oligocene basaltic andesites (22-26 Ma). Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain

silicic flows and massess and associated pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Upper Oligocene silicic (or felsic) flows and masses and associated pyroclastic rocks; includes Taylor Creek, Fanney, and Rocky Canyon Rhyolites

Morrison Formation (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Morrison Formation; Upper Jurassic nonmarine rocks present only in northern one-third of state

alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Alluvium; upper and middle Quaternary

Lithology: alluvium

Dolomite, limestone, and minor amounts of sandstone and quartzite (Devonian) at surface, covers < 0.1 % of this area

DOLOMITE, LIMESTONE, AND MINOR AMOUNTS OF SANDSTONE AND QUARTZITE-Includes units such as Sevy and Simonson Dolomites, Guilmette and Nevada Formations, and Devils Gate Limestone.

Limestone and sparse dolomite, siltstone, and sandstone (Mississippian to Early Permian) at surface, covers < 0.1 % of this area

LIMESTONE AND SPARSE DOLOMITE, SILTSTONE, AND SANDSTONE-Includes units such as undivided Riepe Spring Limestone of Steele (1960) and Ely Limestone or their equivalent in Elko, White Pine, and northern Lincoln Counties and most of the Bird Spring Formation and Callville Limestone in Clark and southern Lincoln Counties. Includes some stratigraphically higher Permian rocks in Leppy Peak, easternmost Elko County.

basalt and andesite flows, Neogene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Basalt and andesite flows; Neogene. Includes flows interbedded with Santa Fe and Gila Groups

Lithology: basalt; andesite

Jurassic (1) sedimentary rocks in southeastern Utah (Middle Jurassic) at surface, covers < 0.1 % of this area

Rio Salado Tongue of Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Rio Salado Tongue of the Mancos Shale. Overlies Twowells Tongue of Dakota Sandstone; mapped only where Tres Hermanos Formation or the Atarque Sandstone is present; mapped as Kdr in parts of Socorro County; Turonian

Lithology: shale; limestone

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

ALLUVIAL DEPOSITS-Locally includes beach and sand dune deposits

Precambrian igneous and metamorphic rock complex (Early Proterozoic to Miocene) at surface, covers < 0.1 % of this area

Complex of Precambrian igneous and metamorphic rocks. Mostly gneiss and schist intruded by igneous rocks; may be Mesozoic in part.

silicic flows, domes, and associated pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Oligocene silicic (or felsic) flows, domes, and associated pyroclastic rocks and intrusions; includes Mimbres Peak Formation

intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Tertiary intrusive rocks; undifferentiated

silicic to intermediate volcanic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Silicic to intermediate volcanic rocks; mainly quartz latite and rhyolite Neogene; may locally include flows interbedded with Santa Fe Group

sedimentary and vocaniclastic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Mostly Oligocene and upper Eocene sedimentary and volcaniclastic sedimentary rocks with local andesitic to intermediate volcanics; includes Espinaso, Spears, Bell Top, and Palm Park Formations

Tuffaceous sedimentary rocks (Late Eocene to Late Miocene) at surface, covers < 0.1 % of this area

TUFFACEOUS SEDIMENTARY ROCKS-Locally includes minor amounts of tuff

Triassic (1) sedimentary rocks in Salt southeastern Utah (Early Triassic) at surface, covers < 0.1 % of this area

Intrusive rocks (Late Cretaceous to Middle Miocene) at surface, covers < 0.1 % of this area

INTRUSIVE ROCKS-Aphanitic, porphyritic, and coarsely granular rocks ranging in composition from diorite to granite. Clark County

Permian (1) sedimentary rocks in southwestern Utah (Early Permian) at surface, covers < 0.1 % of this area

Zuni and Entrada Sandstones (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area

Zuni and Entrada Sandstones, undivided

Gila Group (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers < 0.1 % of this area

Gila Group. Includes Mimbres Formation and several informal units in southwestern basins; Middle Pleistocene to uppermost Oligocene

Horse Spring Formation (Late Oligocene to Middle Miocene) at surface, covers < 0.1 % of this area

HORSE SPRING FORMATION-Tuffaceous sedimentary rocks, southern Nevada

basalt or basaltic andesite (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Basalt or basaltic andesite; middle and lower Pleistocene

Limestone and dolomite, locally thick sequences of shale and siltstone (Late Cambrian to Middle Cambrian) at surface, covers < 0.1 % of this area

LIMESTONE AND DOLOMITE, LOCALLY THICK SEQUENCES OF SHALE AND SILTSTONE-Includes units such as Pioche Shale, Eldorado Dolomite, Geddes Limestone, Secret Canyon Shale, Hamburg Dolomite, Dunderberg Shale, and Windfall Formation of northern Nevada and Carrara, Bonanza King, and Nopah Formations of southern Nevada.

Andesite and basalt flows (Early Miocene to Early Pliocene) at surface, covers < 0.1 % of this area

ANDESITE AND BASALT FLOWS-Mostly in about 17 to about 6 m.y. age range. In Humboldt County, locally includes rocks as old as 21 m.y. May include rocks younger than 6 m.y. in places

Lithology: basalt; andesite; shoshonite

silicic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Oligocene silicic pyroclastic rocks (ash-flow tuffs); includes Hell's Mesa, Kneeling Nun, lower part of Bell Top Formation, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump and Tadpole Ridge Tuffs, the tuffs of the Organ cauldron, Treasure Mountain Tuff (now known as Chiquito Peak Tuff), Bluff Creek Tuff, Oak Creek Tuff, tuff of Steins Mountain, tuff of Black Bill Canyon, tuff of Farr Ranch, Woodhaul Canyon, Gillespie and Box Canyon Tuffs, Cooney Tuff, and other volcanic and interbedded fluvial and pumiceous units; (31-36.5 Ma)

Dakota Sandstone (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Dakota Sandstone; includes Oak Canyon, Cubero, and Paguate Tongues plus Clay Mesa Tongue of Mancos Shale; Cenomanian

Siltstone, sandstone, limestone, and dolomite (commonly silty or sandy) and gypsum (Early Permian) at surface, covers < 0.1 % of this area

SILTSTONE, SANDSTONE, LIMESTONE, AND DOLOMITE (COMMONLY SILTY OR SANDY), AND GYPSUM (Lower Permian)-Includes units such as Rib Hill Sandstone and Pequop Formation of Steele (1959) in Elko County, Rib Hill Sandstone and Arcturus Formation in White Pine County, Queantoweap Sandstone of NcNair (1951), Hermit Shale, and Coconino Sandstone in Clark and southern Lincoln Counties.

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

AZTEC SANDSTONE (Triassic? And Jurassic)-Friable fine- to medium-grained sandstone with conspicuous large-scale cross strata; considered eolian. Age based on correlation with Navajo Sandstone

Lithology: sandstone

andesite and basaltic andesite flows and associated volcaniclastic units (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Tertiary, (Lower Oligocene and Eocene) andesite and basaltic andesite flows, and associated volcaniclastic units. Includes Rubio Peak Formation, and andesite of Dry Leggett Canyon

Mancos Shale, lower part (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Mancos Shale, Lower part

basalt and andesite flows, Miocene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Basalt and andesite flows; Miocene

Lithology: basalt; andesite

Permian (1) sedimentary rocks in southeastern Utah (Pennsylvanian to Early Permian) at surface, covers < 0.1 % of this area

rhyolitic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Upper Oligocene rhyolitic pyroclastic rocks (ash-flow tuffs); includes Davis Canyon Tuff, South Crosby Peak Formation, La Jencia, Vick's Peak, Lemitar, South Canyon, Bloodgood Canyon, Shelley Peak Tuffs, tuff of Horseshoe Canyon, Park Tuff, Rhyolite Canyon Tuff, Apache Springs Tuff, Diamond Creek, Jordan Canyon, Garcia Camp Tuffs, the Turkey Springs Tuff, the tuff of Little Mineral Creek, the Amalia Tuff, and others. Some contain volcaniclastic and reworked volcaniclastic rocks, and eolian sandstone; (24-29 Ma)

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

Mancos Shale; divided into Upper and Lower parts by Gallup Sandstone

Tertiary nonmarine rocks, undivided (Paleocene to Pliocene) at surface, covers < 0.1 % of this area

Undivided Tertiary sandstone, shale, conglomerate, breccia, and ancient lake deposits.

Cherty limestone and sparse dolomite, shale, and sandstone (Permian) at surface, covers < 0.1 % of this area

CHERTY LIMESTONE AND SPARSE DOLOMITE, SHALE, AND SANDSTONE (Lower and Upper Permian)-Includes units such as Park City Group and equivalent rocks in northern Nevada and Toroweap Formation and Kaibab Limestone in southern Nevada

sedimentary units, Palogene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Paleogene sedimentary units; includes Baca, Galisteo, El Rito, Blanco Basin, Love Ranch, Lobo, Sanders Canyon, Skunk Ranch, Timberlake, and Cub Mountain Formations

landslide deposits and colluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Landslide deposits and colluvium

Lithology: landslide; colluvium

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

METAMORPHIC ROCKS-Gneiss and schist and lesser amounts of gneissic granite, pyroxenite, hornblendite, migmatite, pegmatite, and marble.