Geologic units in Arizona (state in United States)

Additional scientific data in this geographic area

Quaternary surficial deposits, undivided (Quaternary) at surface, covers 16 % 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)

Permian sedimentary rocks (Permian) at surface, covers 9 % 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)

Pliocene to middle Miocene deposits (Middle Miocene to Pliocene) at surface, covers 9 % 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 Miocene to Oligocene volcanic rocks (Oligocene to Middle Miocene) at surface, covers 8 % 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)

Glen Canyon Group (Early Jurassic) at surface, covers 5 % 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)

Early Pleistocene to latest Pliocene surficial deposits (Late Pliocene to Early Pleistocene) at surface, covers 4 % 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)

Chinle Formation (Late Triassic) at surface, covers 4 % 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)

Holocene to middle Pliocene basaltic rocks (Middle Pliocene to Holocene) at surface, covers 3 % 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)

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)

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)

Early Proterozoic granitic rocks (Early Proterozoic) at surface, covers 3 % 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)

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)

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)

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)

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)

Late to middle Miocene basaltic rocks (Middle to Late Miocene) at surface, covers 2 % 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 2 % 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)

Holocene river alluvium (Holocene) at surface, covers 2 % 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)

San Rafael Group (Middle to Late Jurassic) at surface, covers 1 % 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)

Early Proterozoic metamorphic rocks (Early Proterozoic) at surface, covers 1 % of this area

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

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)

Middle Miocene to Oligocene sedimentary rocks (Oligocene to Middle Miocene) at surface, covers 1.0 % 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)

Shinarump Conglomerate Member, Chinle Formation (Late Triassic) at surface, covers 1.0 % 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 Proterozoic sedimentary rocks (Middle Proterozoic) at surface, covers 0.9 % 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 to Late Jurassic sedimentary rocks with minor volcanic rocks (Late Jurassic to Cretaceous) at surface, covers 0.7 % 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 Proterozoic metasedimentary rocks (Early Proterozoic) at surface, covers 0.7 % 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 Tertiary to Late Cretaceous granitic rocks (Late Cretaceous to Early Tertiary) at surface, covers 0.6 % 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 0.6 % 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 0.6 % 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)

Morrison Formation (Late Jurassic) at surface, covers 0.5 % 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)

Jurassic granitic rocks (Jurassic) at surface, covers 0.5 % 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)

Early Tertiary to Late Cretaceous volcanic rocks (Late Cretaceous to Early Tertiary) at surface, covers 0.4 % 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)

Middle Miocene to Oligocene granitic rocks (Oligocene to Middle Miocene) at surface, covers 0.4 % 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 Pleistocene to late Miocene basin deposits (Late Pliocene to Early Pleistocene) at surface, covers 0.4 % 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)

Middle Proterozoic diabase (Middle Proterozoic) at surface, covers 0.3 % 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)

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)

Middle Miocene to Oligocene volcanic and sedimentary rocks, undivided (Oligocene to Middle Miocene) at surface, covers 0.3 % 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 0.2 % 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)

Jurassic volcanic rocks (Jurassic) at surface, covers 0.2 % 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)

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)

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)

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

Alluvium and colluvium

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).

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

Eolian deposits

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.

Quaternary alluvium and marine deposits (Pleistocene 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.

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

Moenkopi Formation.

Alluvium, undifferentiated (Holocene and Pleistocene) at surface, covers < 0.1 % of this area

Unit is present in all counties. Some counties divided the alluvium into younger and older units, and some did not. For those that did not, or used other generalized terms for Quaternary rocks, the unit Qal has been used for the general undivided alluvium. Additionally, when polygons have been edited and changed to alluvium, Qal was used as the general value; hence it now is present in all counties. Qya-Younger alluvium: Map unit is used in Churchill, Elko, Esmeralda, Eureka, Humboldt, Lander, and Lincoln Counties where geologic information suggests better-defined younger versus older alluvium. It is mostly interchangeable with Qal, except that it implies some specifically younger Quaternary deposits.

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

Kaibab Limestone and Toroweap Formation.

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.

Cutler Group (Pennsylvanian to Early Permian) at surface, covers < 0.1 % of this area

Cutler Group (White Rim Ss, De Chelly Ss, Organ Rock Shale, Cedar Mesa Ss, Halgaito Fm, and Elephant Canyon Fm). Includes Natural Bridges National Monument.

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

Chinle Formation and Shinarump Conglomerate Member.

Proterozoic basement rocks - Gneiss and schist (Early Proterozoic) at surface, covers < 0.1 % of this area

Exposed mostly in Clark and Lincoln Counties, with two small outliers in southern Nye County.

Triassic rocks, undivided (Triassic) at surface, covers < 0.1 % of this area

Continental red beds.

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

Upper Jurassic nonmarine rocks.

Intertongued Mancos Shale and Dakota Sandstone of west-central New Mexico (Cenomanian) at surface, covers < 0.1 % of this area

Includes the Whitewater Arroyo Tongue of Mancos Shale and the Twowells Tongue of the Dakota.

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).

Upper middle Tertiary basaltic andesites and andesites of the Mogollon Group (Lower Miocene and uppermost Oligocene (22-26 Ma)) at surface, covers < 0.1 % of this area

Includes Bearwallow Mountain Andesite and basaltic andesite of Mangas Mountain; also near vent basaltic lavas and shallow intrusions in the Chuska Mountains.

Chinle Group (Upper to middle Triassic) at surface, covers < 0.1 % of this area

Map unit includes Moenkopi Formation (Middle Triassic) at base in many areas; in eastern part of state the following five formations are mapped: TRr, TRb, TRt, TRg, and TRs.

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

Chinle Shale and Shinarump Conglomerate Member.

Younger andesite and intermediate flows and breccias (Miocene) at surface, covers < 0.1 % of this area

Includes some rocks mapped as the Kate Peak and Alta Formations on the Washoe South map; Wahmonie and Salyer Formations on the Nye South map; Gilbert Andesite on the Esmeralda map; pyroxene, hornblende phenoandesite, and phenodacite on the Elko map; and other unnamed units. It corresponds to the unit Ta3 on the 1978 State map. It is present everywhere except Eureka and White Pine Counties.

Crevasse Canyon Formation (Santonian to Coniacian) at surface, covers < 0.1 % of this area

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

Chuska Sandstone (Middle to upper Oligocene) at surface, covers < 0.1 % of this area

Restricted to Chuska Mountains.

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

Entrada and Carmel Formations (Arapien Shale at Marysvale).

Piedmont alluvial deposits (Holocene to lower Pleistocene) at surface, covers < 0.1 % of this area

Includes deposits of higher gradient tributaries bordering major stream valleys, alluvial veneers of the piedmont slope, and alluvial fans. May locally include uppermost Pliocene deposits.

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

May locally include Wingate Sandstone.

Upper Tertiary sedimentary units (Pliocene to upper Oligocene) at surface, covers < 0.1 % of this area

Includes Bidahochi Formation (Pliocene to upper Miocene), Picuris Formation (Miocene to Oligocene), Las Feveras Formation (Pliocene), lower Gila Group units in the southwest, and unnamed Pliocene unit in northwestern Socorro County.

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

Moenkopi Formation.

Zuni and Entrada Sandstones, undivided (Middle Jurassic) at surface, covers < 0.1 % of this area

Zuni and Entrada Sandstones, undivided

Gila Group, Formation, or Conglomerate (Middle Pleistocene to uppermost Oligocene?) at surface, covers < 0.1 % of this area

Includes Mimbres Formation and several informal units in southwestern basins.

Alluvium (Holocene to upper Pleistocene) at surface, covers < 0.1 % of this area

Alluvium

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

Consists of Entrada Sandstone, Todilto and Summerville Formations, Bluff Sandstone, and locally Zuni Sandstone (or only Acoma Tongue of Zuni).

Carbonate Shelf Sequence - Bioclastic limestone (Pennsylvanian and Upper Mississippian) at surface, covers < 0.1 % of this area

Mostly Lower Pennsylvanian limestone is present in Nye, Elko, Eureka, White Pine, Lincoln, and Clark Counties, and is most commonly referred to as the Ely Limestone. A ledgy gray limestone mapped as the Moleen Formation is included here. It is not mapped separately from unit PIPc in most of White Pine County, southeastern Elko County, southern Lincoln, and western Clark Counties. Throughout most of the area of exposure unit lies conformably or disconformably beneath unit PIPc and depositionally above unit IPMcl. In southern Nye County this unit includes the Tippipah Limestone, and in Clark County it includes the Callville Limestone. In a north-south trending belt starting at the north end of the Pancake Range in Nye County and continuing north up through the Diamond Mountains along the Eureka-White Pine County border, Lower Pennsylvanian limestone is overlain unconformably by clastic rocks of the Siliciclastic overlap assemblage (Pacl, PIPacl). North of the Diamond Mountains, where Lower Pennsylvanian carbonate is not recognized separately, the coeval facies are grouped with unit IPMcl. Unit IPMbc is primarily Pennsylvanian, but in places contains Late Mississippian fossils as well.

Gallup Sandstone (Turonian) at surface, covers < 0.1 % of this area

Generally regressive marine sandstone.

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

Generally poorly age constrained. This unit includes rocks originally mapped as the Pyramid sequence in Washoe County, the Mizpah Trachyte in Nye County, the Malpais Basalt, Rabbit Spring Formation, and Mira Basalt in Esmeralda County, and many other poorly dated unnamed basaltic and andesitic rocks around the State. It corresponds to unit Tba on the 1978 State map.

Callville Limestone (Pennsylvanian) at surface, covers < 0.1 % of this area

Callville Limestone.

Lower-upper middle Tertiary basaltic andesites and andesites of the Mogollon Group (Upper Oligocene (26-29 Ma)) at surface, covers < 0.1 % of this area

Includes La Jara Peak Basaltic Andesite, Uvas Basaltic Andesite, basaltic andesites of Poverty Creek and Twin Peaks, Squirrel Springs Canyon Andesite, Razorback Basalt, Bear Springs Basalt, flows of Gila Flat, Salt Creek Formation, Middle Mountain Formation, and the Alum Mountain Group. Pre-Amalia-Tuff lavas in the Questa caldera are dominantly silicic andesites and dacites; elsewhere silicic lavas are a minor component of Tual.

Alluvial materials, Axtell and Harkers Formations (Pliocene to Quaternary) at surface, covers < 0.1 % of this area

Alluvial materials, Axtell and Harkers Formations

Upper middle Tertiary rhyolitic lavas and local tuffs (Upper Oligocene (24-29 Ma)) at surface, covers < 0.1 % of this area

Includes Taylor Creek Rhyolite, Fanney Rhyolite, rhyolite of Rocky Canyon, rhyolite of Hardy Ridge, and upper rhyolite members of the Luis Lopez and Sawmill Canyon formations.

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.

Middle Tertiary volcaniclastic sedimentary units (Oligocene to upper Eocene) at surface, covers < 0.1 % of this area

Mostly syneruptive volcaniclastic sedimentary aprons. Lower units dominantly derived from volcanic highlands of andesitic to dacitic composition. Locally includes minor lavas and tuffs. Younger units (above and intertongued with Mogollon Group tuffs, Turp) include upper Bell Top Formation, South Crosby Peak Formation, and upper Spears Group units near Quemado. Older units (below and intertongued with Datil Group tuffs, Tlrp) include Palm Park, lower Bell Top, Espinaso and Pueblo Creek Formatios and lower Spears Group formations such as Rincon Windmill, Chavez Canyon, and Dog Springs.

Proterozoic basement rocks - Felsic phaneritic intrusive rocks (Middle Proterozoic) at surface, covers < 0.1 % of this area

This porphyritic rapakivi granite is present only in Clark County where it intrudes Proterozoic gneiss and schist (Xm).

Lower middle Tertiary rhyolitic lavas and local tuffs (Lower Oligocene to upper Eocene (31-36 Ma)) at surface, covers < 0.1 % of this area

Includes Mimbres Peak Formation, rhyolite of Cedar Hills, and other units in the Bootheal region.

Rio Salado Tongue of the Mancos Shale (Turonian) at surface, covers < 0.1 % of this area

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.

Carbonate Shelf Sequence - Limestone (Mississippian) at surface, covers < 0.1 % of this area

This unit is present in southern Nye, Lincoln, and Clark Counties. Unit includes the Monte Cristo Limestone, and Lower Mississippian rocks referred to as the Joana, Mercury, Bristol Pass, and Rogers Spring Limestones. It generally lies depositionally above Devonian carbonate rocks and beneath Pennsylvanian carbonate and clastic rocks. In the Meadow Valley Mountains in southern Lincoln County it is also shown sitting on a thin horizon of Pilot Shale and overlain by a thin Mississippian clastic unit assigned to unit IPMcl.

Younger tuffaceous sedimentary rocks (Pliocene and Miocene) at surface, covers < 0.1 % of this area

Tuffaceous and other young Tertiary sedimentary rocks. Most of these rocks are sedimentary with a strong volcanic component - a few are tuffaceous with a strong sedimentary component. This unit includes rocks originally mapped as the High Rock sequence in Washoe County; the Horse Camp Formation in northern Nye County; the Esmeralda Formation in Mineral and Esmeralda Counties; older lake beds in Lincoln County; the Belted Range Tuff; the Indian Trail Formation (now abandoned); Timber Mountain, Paintbrush, and Crater Flat Tuffs; Wahmonie and Salyer Formations in southern Nye County; the Siebert Tuff in Esmeralda County; the Muddy Creek Formation in Clark County; and the Thousand Creek and Virgin Valley “beds” in Humboldt County; and other unnamed units. It corresponds to units Ts3 and Tts from the 1978 State map. It is present in all counties.

Carbonate Shelf Sequence - Cherty limestone, dolomite, shale, and sandstone (Middle to Lower Permian) at surface, covers < 0.1 % of this area

These Permian rocks include cherty limestone, dolomite, shale, sandstone, bioclastic limestone, and phosphatic limestone exposed in Elko, White Pine, Lincoln, and Clark counties. This unit includes rocks mapped as the Phosphoria Formation; the Gerster Limestone, Plympton Formation, Kaibab Limestone, and Grandeur Formation of the Park City Group; the Park City Group undivided; the Toroweap Formation; and the Coconino Sandstone. Unit Pc is disconformably overlain by Triassic unit TRmt in scattered places in eastern and southern Nevada. It depositionally overlies unit Psc. It matches closely with unit Pc of Stewart and Carlson (1978).

Upper middle Tertiary rhyolitic pyroclastic rocks of the Mogollon Group, ash-flow tuffs (Upper Oligocene (24-30 Ma)) at surface, covers < 0.1 % of this area

Regional ash-flow tuffs include the La Jencia, Vick's Peak, Lemitar, South Canyon, Bloodgood Canyon, Shelley Peak, Davis Canyon, Park, Rhyolite Canyon, Apache Springs, and Amalia Tuffs; the tuffs of Horseshoe Canyon, Diamond Creek, Garcia Camp, Caronita Canyon, Turkey Springs, and Little Mineral Creek; and the Jordan Canyon Formation. Includes some locally erupted lavas and tuffs within thick intra-caldera units; includes minor volcaniclastic sedimentary units between thin outflow sheets.

Basaltic to andesitic lava flows (Neogene) at surface, covers < 0.1 % of this area

Includes minor vent deposits. Flows are commonly interbedded in the Santa Fe and Gila Groups.

Silicic to intermediate volcanic rocks (Neogene, mostly Miocene) at surface, covers < 0.1 % of this area

Rhyolite and dacite flows with associated minor tuffs. Commonly interbedded with Santa Fe or Gila Group sedimentary units. Dacitic lavas in northern Jemez Mountains are Pliocene.

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

Nugget Sandstone.

Lower middle Tertiary andesitic to dacitic lavas and pyroclastic flow breccias (Upper to middle Eocene (33-43 Ma)) at surface, covers < 0.1 % of this area

Includes Rubio Peak Formation, Orejon Andesite, andesite of Dry Leggett Canyon, andesite of Telephone Canyon, and other units in southwestern, central, and northern New Mexico. Locally includes minor mafic lavas. Ancient landslide blocks of Mader Limestone, as much as one mile long, occur within Rubio Peak lavas in the central Black Range, west of Winston.

Basaltic to andesitic lava flows (Upper Pleistocene to lower Pliocene) at surface, covers < 0.1 % of this area

Includes minor vent deposits.

Lower middle Tertiary rhyolitic to dacitic pyroclastic rocks of the Datil Group, ash-flow tuffs (Lower Oligocene to upper Eocene (31-36 Ma)) at surface, covers < 0.1 % of this area

Regional ash-flow tuffs include Hell's Mesa, Kneeling Nun, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump, Oak Creek, Bluff Creek, Gillespie, Box Canyon, Cooney and Chiquito Peak Tuffs; the tuffs of Steins Mountain, Black Bill Canyon, Woodhaul Canyon, and Farr Ranch; tuffs of the Organ cauldron; and lower tuffs in the Bell Top Formation. Includes some locally erupted lavas and tuffs within thick intra-caldera units; includes minor volcaniclastic sedimentary units and lavas between thin outflow sheets.

Coconino Sandstone, Supai Group, and Pakoon Formation (Early Permian) at surface, covers < 0.1 % of this area

Coconino Sandstone, Supai Group, and Pakoon Formation.

Dakota Sandstone (Cenomanian) at surface, covers < 0.1 % of this area

Includes Oak Canyon, Cubero, and Paguate Tongues; includes Clay Mesa Tongue of Mancos Shale.

Felsic phaneritic intrusive rocks (Miocene to Eocene) at surface, covers < 0.1 % of this area

Tertiary felsic intrusive rocks are widely scattered in every county across the State. They are generally described as granitic rocks, granodiorite, monzonite, quartz monzonite, alaskitic granite, quartz diorite, dacite, and rhyodacite in the places where they are shown separately on county maps.

Carbonate Shelf Sequence - Dolomite, limestone, and shale (Cambrian) at surface, covers < 0.1 % of this area

Occurs in southern and eastern Nevada. The Bonanza King and Carrara Formations are the primary formations in southern Nye County; the Dunderberg Shale in northern Nye and Lincoln Counties; the Hamburg Dolomite in Eureka County; the Nopah Formation in southern Nye and Esmeralda Counties; the Patterson Pass and Pioche Shales, the Chisholm and Highland Peak Formations, and the Lyndon Limestone in Lincoln County; the Pole Canyon Limestone and the Lincoln Peak and Windfall Formations in northern Nye County; and undifferentiated limestone and dolomite in Lincoln, Clark, White Pine, Eureka, northern Nye, and Elko Counties. This unit is conformably overlain by the Ordovician shelf rocks (OCc), and is depositional on the underlying Proterozoic-Cambrian quartzite of CZq.

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.

Carbonate Shelf Sequence - Limestone and minor dolomite (Upper and Middle Devonian) at surface, covers < 0.1 % of this area

Includes generally cliff-forming, thin- to thick-bedded limestone. These rocks are mainly shallow water subtidal, intertidal, and supratidal deposits formed on a broad inner carbonate shelf (Stewart, 1980). The Devils Gate Limestone and Guilmette Formation in northern Nevada are the principal units, and the Sultan Limestone is included from the southern part of the State. Unit is overlain (usually disconformably) by the Pilot Shale of unit MDcl except in southernmost Nevada where it is overlain by Mississippian carbonate (Mc). It depositionally overlies Middle and Lower Devonian unit Dcd. In a few places, such as southern Nevada and parts of Eureka County, regional mapping did not distinguish the Upper and Middle Devonian section from the Lower Devonian section, and all of the Devonian is included in unit Dc. Rocks mapped as the Simonson Dolomite would fit into this depositional sequence (sequences 9 and 10 of Cook and Corboy, 2004), but they are not differentiated from the underlying dolomites in White Pine or Elko Counties, so they are all included in unit Dcd here, not unit Dc. This unit crops out in Clark, Elko, Eureka, Lander, Lincoln, Nye, and White Pine Counties.

Basaltic to andesitic lava flows (Middle to lower Pleistocene) at surface, covers < 0.1 % of this area

Includes vent deposits.

Basaltic to andesitic lava flows (Miocene) at surface, covers < 0.1 % of this area

Includes minor vent deposits. Flows are commonly interbedded in the Santa Fe and Gila Groups.

Mancos Shale, lower part (Turonian and Cenomanian) at surface, covers < 0.1 % of this area

Mancos Shale, lower part

Older Quaternary alluvium and marine deposits (Pleistocene) at surface, covers < 0.1 % of this area

Older alluvium, lake, playa, and terrace deposits.

Mancos Shale (Cenomanian to Campanian) at surface, covers < 0.1 % of this area

Divided into Upper and Lower parts by Gallup Sandstone.

Fence Lake Formation (Miocene) at surface, covers < 0.1 % of this area

Conglomerate and conglomeratic sandstone, coarse fluvial volcaniclastic sediments, minor eolian facies, and pedogenic carbonates of the southern Colorado Plateau region.

Tertiary intrusive rocks of intermediate to silicic composition (Pliocene to Eocene) at surface, covers < 0.1 % of this area

Includes monzonitic to granitic plutons, stocks, laccoliths, and porphyritic dikes in deeply eroded magmatic centers; and andesitic, dacitic, or rhyolitic plugs and dikes near cauldrons or stratovolcanoes. In the Latir field, fine-grained rhyolitic dikes commonly cut coarse-grained granitic plutons. Includes alkaline laccoliths, plugs, and dikes in Colfax County. North-trending dikes near Capitan include some mafic diabase dikes.

Paleogene sedimentary units (Paleogene) at surface, covers < 0.1 % of this area

Includes Baca, Galisteo, El Rito, Blanco Basin, Hart Mine, Love Ranch, Lobo, Sanders Canyon, Skunk Ranch, Timberlake, and Cub Mountain Formations.

Crossbedded quartzite, siltstone, and phyllite (Lower Cambrian and latest Proterozoic) at surface, covers < 0.1 % of this area

These lowermost Cambrian to Precambrian strata are scattered over much of central and eastern Nevada and form the base of the Phanerozoic part of the continental margin stratigraphic section. They include the Campito, Deep Spring, Harkless, and Poleta Formations, and the Reed Dolomite in Esmeralda County; the Gold Hill Formation in northern Nye County; unnamed quartzite and shale in White Pine County; the Osgood Mountain quartzite in Humboldt County; the Prospect Mountain Quartzite in northern Nye, Lincoln, Eureka, and Elko Counties; unnamed quartzite and shale in Lander and Clark counties; and the Stirling Quartzite, Wood Canyon Formation, and Zabriskie Quartzite in southern Nye County. In a number of places, these rocks are depositional on Late Proterozoic unit Zqs. In southernmost Clark County, CZq is lying unconformably directly on Early Proterozoic gneiss (Xm). In the east-central part of Nevada, CZq is overlain depositionally by Cambrian carbonate (Cc) of the Carbonate shelf sequence. In the Nolan belt, these rocks are depositionally overlain by unit Ctd. In the Osgood Mountains in Humboldt County, Permian and Pennsylvanian rocks of the Siliciclastic overlap assemblage (PIPacl, Pacl) rest unconformably directly on the Osgood Mountain Quartzite.

Landslide deposits and colluvium (Holocene to Pleistocene) at surface, covers < 0.1 % of this area

Landslide deposits on western flanks of Socorro Mountains not shown for clarity.