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Mineral Resources > Online Spatial Data > Geology > by state > Idaho Geology

Geologic units in Shoshone county, Idaho

[Additional scientific data in this geographic area]

High-grade metasedimentary biotite schist, biotite gneiss, and calc-silicate gneiss; Middle Proterozoic northern Belt province near Idaho batholith (Middle Proterozoic) at surface, covers 1 % of this area

Precambrian high-grade metamorphic rock; kyanite-sillimanite calc-silcate bearing schist and gneiss; scapolite common

Lithology: mica schist; paragneiss; calc-silicate rock

Basalt lava flows; Middle Miocene flood-basalt flows of subunit 2b; Columbia Plateau (Miocene) at surface, covers 0.5 % of this area

Miocene basalt flows of western Idaho; commonly finely crystalline and exposed on upper slopes.

Lithology: basalt; lava flow

Monzogranite, granodiorite, syenite, monzodiorite, monzonite, and diorite; Eocene phaneritic to porphyro-aphanitic intrusions (subunits are Teif and Teii); northern Idaho to central Idaho (Eocene) at surface, covers 2 % of this area

Eocene intrusions including large granitic plutons and dike swarms of central Idaho

Lithology: granite; quartz monzodiorite; granodiorite

Syenite, monzonite, quartz syenite; Late to Early Cretaceous syenitic intrusions; northern Idaho (Cretaceous) at surface, covers 0.2 % of this area

Cretaceous syenitic to monzonitic intrusions

Lithology: syenite; monzonite; quartz syenite; alkali syenite

Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers 1 % of this area

Quaternary alluvium; may contain some glacial deposits and colluvium in uplands

Lithology: alluvium; alluvial terrace; floodplain; alluvial fan; colluvium

Prichard formation (Proterozoic | Mesoproterozoic) at surface, covers < 0.1 % of this area

Prichard formation: dark-gray, generally argillaceous rocks, locally sandy or quartzitic; locally metamorphosed to schist.

Lithology: meta-argillite; quartzite; carbonate; chert

Diabase, metagabbro, and diorite and related rocks (Proterozoic) at surface, covers < 0.1 % of this area

Diabase, metagabbro, and diorite and related rocks: dark gray fine to medium grained, mostly in dikes and sills; dominantly mafic but contain alkalai feldspar and micropegmatite in some areas.

Lithology: diorite; gabbro

Basalt flows and incidental andesite, and latite flows; Miocene mafic to intermediate volcanics; subunits are Tmib, Tm1b, Tm2b, Tm3b; Columbia Plateau, Owyhee Plateau (Miocene) at surface, covers 0.2 % of this area

Miocene plateau basalt flows of western Idaho; subdivisions are (Tm3b, Tm2b, Tm1b).

Lithology: basalt; latite; lava flow

Intrusive rocks: mostly Late Cretaceous granodioritic to granitic plutons of the Idaho batholithic assemblage, but including some Eocene intrusions; northern Idaho and Atlanta batholith (Cretaceous to Eocene) at surface, covers < 0.1 % of this area

Cretaceous plutons; probably includes unmapped older and younger crystalline bodies.

Lithology: granodiorite; peraluminous granite; quartz monzonite; quartz diorite; tonalite; trondhjemite; pegmatite; alkali-granite (alaskite)

Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary) at surface, covers 3 % of this area

Quaternary colluvium, fanglomerate, and talus plus some glacial debris in upland valleys.

Lithology: alluvium; glacial drift; colluvium

Ravalli group (Proterozoic | Mesoproterozoic) at surface, covers < 0.1 % of this area

Ravalli group: a diverse assemblage with numerous subdivisions, only a few of which have been recognized over large enough areas to be distinguished here. Near Idaho the rocks are light colored and siliceous, ranging from pure white quartzite to siliceous shale, mostly in subdued tones of gray, green, purple, and red. Near Missoula the rocks are dark-gray quartzite and quartzitic argillite. In and near Glacier National Park the Grinnell, Appekunny, and Altyn formations are distinguished.

Lithology: meta-argillite; quartzite

Quartzite, mica schist, and calc-silicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic) at surface, covers 0.2 % of this area

Precambrian, high-grade metamorphic rock; metasediments; kyanite-sillimanite schist, and micaceous quartzite

Lithology: quartzite; mica schist; calc-silicate rock

Siltite, argillite, and quartzite; Middle Proterozoic Prichard Formation; northern Belt province (Middle Proterozoic) at surface, covers 5 % of this area

Intermediate Precambrian sediments, gray interlaminated siltite and argillite with minor quartzite of northern Idaho.

Lithology: siltstone; meta-argillite; quartzite

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

Glacial drift: morainal and outwash plain deposits of mountain glaciers; mainly ill-sorted and poorly rounded boulders, cobbles, pebbles, and sand; may include alluvium in places

Lithology: glacial drift; alluvium

Argillite, siltite, and quartzite; Middle Proterozoic Ravalli Group; northern Belt Province (Middle Proterozoic) at surface, covers 10 % of this area

Intermediate Precambrian sediments, multicolored siltite and argillite overlying quartzite and siltite of northern Idaho.

Lithology: meta-argillite; siltstone; quartzite

Anorthosite (folded sill-like intrusive or metasomatic bodies); Middle Proterozoic; northern Idaho, Boehls Butte metamorphic core complex (Middle Proterozoic) at surface, covers 1 % of this area

Highly metamorphosed, probably Precambrian, intrusive rock; anorthosite common

Lithology: anorthosite

Mica schist, quartzite, and calc-silcicate rock; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Proterozoic) at surface, covers 2 % of this area

Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite calc-silicate schist and gneiss, scapolite common

Lithology: mica schist; quartzite; calc-silicate rock

Schist, phyllite, quartzite, and calc-silicate rock; Middle Proterozoic metasedimentary rocks of Wallace Formation; northern Belt province (Middle Proterozoic) at surface, covers 16 % of this area

Intermediate Precambrian age metasediments; generally low-to-medium grade; carbonate bearing argillite and siltite of northern Idaho.

Lithology: mica schist; phyllite; quartzite; calc-silicate rock

Garnet-sillimanite-biotite schist; Middle Proterozoic Prichard Formation, northern Belt province (Early Middle Proterozoic) at surface, covers 10 % of this area

Precambrian high-grade metamorphic rock; metasediment; kyanite-sillimanite-garnet-mica coarse-grained schist and gneiss; minor quartzite

Lithology: schist; gneiss; quartzite

Quartzite and muscovite schist; Middle Protrerozoic metasedimentary rocks of the Ravalli Group; northern Belt province (Middle Proterozoic) at surface, covers 4 % of this area

Intermediate Precambrian age metasediments; dominantly quartzite with minor micaceous layers and mica schists of northern Idaho.

Lithology: quartzite; mica schist

Basalt, andesite, diorite, lamprophyre intrusions; Tertiary to Cretaceous, undivided; northern Idaho, central Idaho (Cretaceous or Eocene) at surface, covers < 0.1 % of this area

Eocene intrusions including large granitic plutons and dike swarms of central Idaho

Lithology: gabbro; diabase; diorite; lamprophyre

Argillite, siltstone, quartzite, and dolostone; Middle Proterozoic Missoula Group; northern Belt province (Middle Middle Proterozoic) at surface, covers 12 % of this area

Intermediate Precambrian sediments, light-colored siltite overlying multicolored fine-grained detrital beds of northern Idaho.

Lithology: meta-argillite; siltstone; quartzite; dolostone (dolomite); limestone

Open Water (Holocene) at surface, covers < 0.1 % of this area

Lakes and streams

Lithology: water

Garnet-mica schist, gneiss, and quartzite; Proterozoic high-grade metasedimentary rocks; trans-Idaho metamorphic province (Late to Early Proterozoic) at surface, covers < 0.1 % of this area

Precambrian high-grade metamorphic rock; metasediment; Kyanite-sillimanite-garnet-mica schist and gneiss; minor quartzite

Lithology: mica schist; paragneiss; quartzite; orthogneiss

Amphibolite after gabbro, diabase, and diorite; Middle Proterozoic sill-like intrusions; southern and northern Belt provinces (Middle Proterozoic) at surface, covers < 0.1 % of this area

Younger or Intermediate Precambrian age intrusive rock undifferentiated; Intrusive rock of eastern Idaho; appears older than Cretaceous, possibly Precambrian; Highly metamorphosed rock of central Idaho; age and origin of rock questionable.

Lithology: amphibolite; gabbro; diabase; diorite

Sandstone, conglomerate, siltstone, tuff, claystone, limestone, and diatomite; Pliocene tuffaceous alluvial and lacustrine deposits; Snake River Plain and vicinity, southeastern Idaho (Pliocene ) at surface, covers 0.2 % of this area

Pliocene stream and lake deposits; may be due to volcanic and block-faulting events.

Lithology: sandstone; conglomerate; siltstone; tuff; claystone; shale; limestone

Siltite, argillite, dolostone, and quartzite; Middle Proterozoic Wallace Formation; northern Belt province (Early Middle Proterozoic) at surface, covers 29 % of this area

Intermediate Precambrian sediments, dark-colored calcareous and dolomitic argillite and siltite of northern Idaho.

Lithology: siltstone; meta-argillite; dolostone (dolomite); quartzite

Metamorphosed granodiorite, quartz monzonitek tonalite, quartz diorite; mostly Cretaceous orthogneiss and migmatite; northern and Atlanta batholith; margins of Bitterroot and Atlanta batholiths (Cretaceous) at surface, covers 0.2 % of this area

Metamorphosed granitic intrusive rock; associated with pluton margins and stress areas.

Lithology: granodiorite; quartz monzonite; tonalite; quartz diorite; orthogneiss; migmatite

Missoula group (Proterozoic | Mesoproterozoic) at surface, covers < 0.1 % of this area

Missoula group: chiefly red, maroon, or purple argillite; sandy or quartzitic argillite, and generally impure quartzite and limestone. The larger limestone masses are similar to the Siyeh limestone of the Piegan group. The Missoula group includes numerous named formations, most of which cannot be traced with confidence far from their type localities. Among these are the Marsh shale in the Helena region, the Striped Peak and Libby formations in northwestern Montana, five near Missoula, and others in and south of Glacier National Park.

Lithology: quartzite; meta-argillite; carbonate; meta-conglomerate

Gabbro, diorite, amphibolite, lamprophyre; Tertiary to Late Proterozoic, undivided; northern Idaho (Tertiary to Late Proterozoic) at surface, covers 0.5 % of this area

Younger Precambrian dioritic and amphibolitic sills of northern Idaho.

Lithology: gabbro; diorite; amphibolite; lamprophyre

Peraluminous monzogranite, granodiorite, pegmatite, aplite, and migmatite; mostly Cretaceous intrusions of the Kaniksu batholithic assemblage, but with minor Eocene intrusions, undivided; northern Idaho (Cretaceous to Eocene) at surface, covers < 0.1 % of this area

Cretaceous plutons; felsic; as granite or quartz monzonite; probably includes unmapped older and younger crystalline bodies.

Lithology: peraluminous granite; granodiorite; granitoid; pegmatite; aplite; migmatite; orthogneiss

Wallace formation (Proterozoic | Mesoproterozoic) at surface, covers 0.1 % of this area

Wallace formation: A heterogeneous unit that includes dark-gray argillite, arenaceous and argillaceous limestone, in part dolomitic, and gray limy quartzite, with shale and sandstone in large areas. The argillaceous and sandy or quartzitic rocks are commonly slightly calcareous. The dominantly carbonate-rich rocks contain "molar tooth" or segregation structures. Commonly characterized by thin laminae. Locally red rocks near the top may represent a transition into the Missoula group.

Lithology: meta-argillite; carbonate; quartzite