Mud and salt flats
Older alluvial deposits
Lake Bonneville deposits
Alluvium and colluvium
Salt Lake Formation and other Basin & Range valley-filling alluvial, lacustrine, and volcanic materials. Valley fill is more than 8,000 feet thick in places and includes salt masses under the Sevier Desert.
Schist of Stevens Spring, Quartzite of Yost, Schist of Upper Narrows, and Elba Quartzite
Oquirrh Group (10,000+ feet thick) of Cedar Mountains and vicinity, is equivalent, in part to Arcturus Formation and Ely Limestone elsewhere
In Northwestern Utah: Dacitic tuff (8.5 my). In Logan-Huntsville Allochthon: rhyolite.
Gerster Limestone, Plympton Formation and Kaibab Limestone.
Tuffaceous sediments, mudstone, sandstone, conglomerate.
Adamellite intrusion 2.5 b.y. by Rb-Sr
Tuffaceous sediments, mudstone, sandstone, valley fill.
Fish Haven Dolomite, Eureka Quartzite, and Pogonip Group
Pilot Shale, Guilmette Formation, and Simonson and Sevy Dolomites.
Green Creek Complex
Little metamorphosed allochthonous remnants.
Intrusions, chiefly granitic, of various dates.
Schist of Mahogany Peaks, Quartzite of Clarks Basin
Ochre Mountain Limestone (Great Blue equivalent) and Woodman Formation (Deseret Humbug equivalent).
Great Blue, Humbug and Deseret Formations.
Ely Springs Dm, Eureka Qtz, Crystal Peak Dm, Watson Ranch Qzt, and the Pogonip Group (Lehman Formation, Kanosh Shale, Juab, Wah Wah, Fillmore, and House Limestones).
McCoy Creek and Sheeprock Groups (10,000+ feet thick).
Bloomington, Blacksmith, Ute, and Langston Formations.
St. Charles Formation, Worm Creek Quartzite, and Nounan Dolomite.
Manning Canyon Shale.
Geertsen Canyon Quartzite (upper part of the Bingham Group).
Fish Haven Dolomite, Swan Peak Quartzite, and Garden City Limestone.
Mutual Formation, Mineral Fork Tillite, and Big Cottonwood Formation (16,000 feet thick).
Leatham Formation, Beirdneau Sandstone, Hyrum Dolomite, and Water Canyon Formation.
Granitic rocks (140 my) in House Range and near Wendover.
Moenkopi (in Blue Mountain) and Thaynes (north of Confusion Range) Formations.
Alluvial materials, Axtell and Harkers Formations
Browns Hole (570 my), Mutual, Inkom Formations; Caddy Canyon Quartzite, Papoose Creek, Kelley Canyon, Maple Canyon, and Perry Canyon Formations; Diamictite member
Farmington Canyon Complex and Little Willow Schist and Gneiss (2.6 billion years old).
Notch Peak, Orr, Lamb, Weeks, and Wah Wah Summit Formations.
Granitic rock (26 my).
Metaquartzite and schist.
Gravel and subordinate sand and silt deposited at mouths of canyons; largest fans are in Basin and Range Province in east-central and southeastern Idaho. (Quaternary Sediments).
Prospect Mountain Quartzite (3,500 feet thick).
Little metamorphosed allochthonous remnants.
Bloomington Formation, Maxfield Limestone, and Ophir Formations.
Trippe Ls, Marjum/Pierson Cove Fms, Wheeler Shale, Swasey Ls, Whirlwind Fm, Dome Ls, Chisholm Fm, Howell Fm, and Pioche Fm.
Wasatch and Evanston? Formations undivided.
Marine phosphorite, shale, and chert of Phosphoria Formation, fine-grained sandstone and mudrock of Wells, Quadrant, Amsden, and Shedhorn formations, and fine-grained sandstone, carbonaceous mudstone, and limestone of the Snaky Canyon Formation and Sun Valley and Oquirrh groups. Located in south-central and eastern Idaho. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).
Fluvial and lacustrine deposits associated with Columbia River Basalt Group and equivalent basalts (17-8 Ma); consolidated to weakly consolidated sandstone, siltstone, arkose, conglomerate, claystone, and tuffaceous sediment; subordinate intercalated basalt and rhyolitic tuff. Includes Payette and Sucker Creek formations in southwestern Idaho, sediments associated with basalt of Weiser in western Idaho, and Latah Formation in northern Idaho. Includes sedimentary rocks of uncertain origin in southwest corner of Idaho. (Quaternary to Eocene Continental Sediments and Sedimentary Rocks).
Upper part consists of shallow marine and fluvial quartzose sandstone, and minor siltite, shale, and limestone of the Brigham Group of southeast Idaho, Wilbert Formation of east-central Idaho, and quartzites of unknown affinity west of Borah Peak. More highly metamorphosed equivalents are quartzite, metaconglomerate, metasiltite, calc-silicate marble, and schist of Gospel Peaks successions C and D in central Idaho; mature quartzite, biotite schist, and minor calc-silicate rocks of Syringa metamorphic sequence east of Moscow; and schist and quartzite in the Albion Range (Elba Quartzite, schist of Upper Narrows, quartzite of Yost, schist of Stevens Spring, quartzite of Clarks Basin, schist of Mahogany Peaks, and Harrison Summit Quartzite). Lower part consists of diamictite, immature sandstone, and bimodal volcanic rocks related to continental rifting. Includes Pocatello Formation (700-665 Ma), formation of Leaton Gulch near Challis, Shedroof Conglomerate in extreme northwest Idaho, and metamorphic equivalents (schist, marble, calc-silicate rocks, metaconglomerate, and ~686 Ma metavolcanic rocks) of Gospel Peaks successions A and B in central Idaho. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).
Silt, clay, sand, and gravel deposited in and at margins of former Lake Bonneville (33-11 calibrated ka) and sand and gravel deposited in giant flood bars by outburst floods from the lake (17.4 calibrated ka). The 1,575-m (5,170 ft) Lake Bonneville shoreline was used to determine the maximum extent of the lake deposits. Flood deposits follow Bonneville flood path from near Downey and the Portneuf River westward along the Snake River to Lewiston. They include sand and silt deposited in slack-water areas to 740 m (2,430 ft) elevation in the Boise, Weiser, Payette, and Snake river drainages. (Quaternary Sediments).
Pend Oreille granodiorite gneiss near Priest River (~2650 Ma); schist, gneiss, and subordinate quartzite along North Fork Clearwater River; Kelly Creek granite gneiss northeast of Pierce (~2670 Ma); orthogneiss in Pioneer Mountains (~2600 Ma and 695 Ma); granite gneiss, granite, schist, and amphibolite of Green Creek complex in Albion Mountains (~2600 Ma); granite gneiss in Beaverhead Mountains east of Leadore (~2450 Ma); and marble, quartzite, schist, and amphibolite of uncertain age near Henrys Lake. (Mesoproterozoic to Archean Basement Rocks).
Marine limestone, dolomite, and subordinate shale and sandstone of Cambrian carbonate bank of southeast Idaho stratigraphically up to St. Charles Formation and Ordovician Garden City Limestone. Includes Bayhorse succession (Cash Creek Quartzite, Garden Creek Phyllite, Bayhorse Dolomite, Ramshorn Slate, and Clayton Mine Quartzite) of Clayton area and Pioneer Mountains; quartzite of Kamiak Butte north of Moscow; and Cambrian Gold Creek quartzite, Rennie Shale, and Lakeview Limestone east of Bayview. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).
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.
Biotite, muscovite-biotite, and muscovite granite of the Almo pluton (29 Ma) at City of Rocks National Reserve and Castle Rocks State Park southeast of Oakley. (Quaternary to Eocene Continental Volcanic and Intrusive Rocks).
Marine dolostone and limestone and sandstone in east-central and southeastern Idaho (Summerhouse, Kinnikinic, and Swan Peak sandstones, Fish Haven, Laketown, Jefferson, Three Forks, and Darby formations) and deep-water carbonaceous mudrocks of Phi Kappa, Trail Creek, and Milligen formations east of Ketchum. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).
Isom Fm (tuff), Needles Range Fm (ash-flow tuff), Escalante Desert Fm (ash-flow tuff), Sawtooth Peak Fm (ash-flow tuff), and Tunnel Springs Tuff.
Rhyolitic flows, domes, plugs, breccias, quartz latite, rhyodacite, quartz porphyry dikes, and other shallow intrusive rocks. This unit includes rocks mapped as the Cañon Rhyolite on the Washoe North map, the Jarbidge Rhyolite and phenorhyolitic and phenodacitic flows and domes on the Elko County map, and other unnamed units. It has a distribution similar to Tt3, with exposures in the northern and southern parts of the State, but only crops out in a few places in the central region. It corresponds to unit Tr3 on the 1978 State map, and also includes a few rocks mapped as Trt on the 1978 State map. This unit is exposed in every county except White Pine.
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.
This largely siliciclastic unit of siltstone, sandstone, limestone, and dolomite crops out in Elko, White Pine, Lincoln, and Clark Counties. It includes rocks originally mapped as the Arcturus Formation, Rib Hill Sandstone, undivided Kaibab Limestone, Toroweap Formation, and Coconino Sandstone in Clark County; and the Pequop Formation and red beds in Lincoln County. Unit Psc represents a strong influx of clastic material over the carbonate shelf during the Early Permian, presumably derived primarily from the craton to the east. It is depositionally overlain by unit Pc and lies conformably above unit PIPc. At its western and northern edges it can be difficult to distinguish from Permian clastic rocks of the Siliciclastic overlap assemblage (units Pacl and PIPacl). It follows closely with unit Psc of Stewart and Carlson (1978).
Deposits in valleys consisting of gravel, sand, and silt. Includes younger terrace deposits. May contain some glacial deposits and colluvium in uplands. (Quaternary Sediments).
Marine limestone of Mississippian carbonate banks and turbiditic sandstone, mudstone, and conglomerate of Antler flysch trough; includes Madison and Lodgepole formations and Chesterfield Range Group of southeastern Idaho; McGowan Creek Formation, White Knob Limestone, and overlying carbonate bank of Lost River Range; and Copper Basin Group of Pioneer Mountains. Includes poorly dated Salmon River assemblage east of Stanley, consisting of argillite, siltstone, calcareous sandstone, and limestone. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).
Basalt flows, plugs and dikes, some olivine basalt, and andesite and latitic rocks. This unit corresponds with unit Tb on the 1978 State map. It is present on the Washoe North, Washoe South, Lincoln, Clark, Elko, Eureka, Humboldt, Nye South, and Lander County maps.
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).
Includes the Sheep Pass Formation and equivalents in northern Nye, Lincoln, Elko, Eureka, Lander, and White Pine Counties. In most places the Sheep Pass Formation is Paleocene or Eocene (Fouch, Hanley, and Forester, 1979), although rocks from the Carlin-Piñon Range area that contain Late Cretaceous fossils have been included in the Sheep Pass Formation (Smith and Ketner, 1976, 1978). It corresponds to unit Ts1 on the 1978 State map.
Fluvial, fan, and lacustrine deposits and intercalated volcanic rocks of the Basin and Range Province (~16-2 Ma); consolidated to weakly consolidated sandstone, siltstone, arkose, conglomerate, mudstone, tuffaceous sediment, basalt, basaltic tephra, and rhyolite tuff. Includes deposits of Lake Idaho (Idaho Group) in western Snake River Plain and Salt Lake Formation deposited in Basin and Range Province of east-central Idaho. (Quaternary to Eocene Continental Sediments and Sedimentary Rocks).