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

Geologic units in Custer county, Idaho

[Additional scientific data in this geographic area]

Open Water (Holocene) at surface, covers 0.2 % of this area

Lakes and streams

Lithology: water

Gravel, sand, and silt; Quaternary basin-filling alluvium; Snake River Plain, Basin and Range provinces (Quaternary) at surface, covers 9 % of this area

Quaternary detritus; generally basin-filling deposits of central and southern Idaho.

Lithology: alluvium; alluvial fan; alluvial terrace

Quartzite, argillite, carbonate, meta-conglomerate, siltite, intermediate volcanic rock; Late Proterozoic rifted continental margin; southeastern Idaho (Late Proterozoic) at surface, covers 0.1 % of this area

Younger Precambrian detrital units of central and southeastern Idaho; subdivisions are (Z2s and Z1s).

Lithology: quartzite; argillite; carbonate; conglomerate; siltstone; intermediate volcanic rock

Shale, arenite, siltstone, limestone, and chert; thrust-bounded Devonian to Ordovician deep-marine-basin deposits; central Idaho (Devonian and Silurian) at surface, covers 0.4 % of this area

Devonian and Silurian thrusted, deep-water argillite beds of central Idaho.

Lithology: shale; arenite; siltstone; limestone; chert

Glacial debris; Late Pleistocene glacial till, outwash, and alluvium of continental glaciers; northern Idaho (Late Pleistocene ) at surface, covers 1 % of this area

Pleistocene till, moraines and similar unsorted glacial debris.

Lithology: till; outwash; alluvium

Dolostone, limestone, arenite, and chert: Devonian to Ordovician marine outer continental-shelf deposits; east-central Idaho (Devonian to Ordovician) at surface, covers 0.2 % of this area

Devonian to Ordovician marine calcareous sediments north of the Snake Plain.

Lithology: dolostone (dolomite); limestone; arenite; chert

Shale, conglomerate, sandstone, siltstone, limestone, and chert; Mississippian turbidite flysch from a western source; central Idaho (Mississippian) at surface, covers 3 % of this area

Mississippian thrusted, shallow-to-deep marine detrital units of central Idaho.

Lithology: shale; conglomerate; sandstone; siltstone; limestone; chert

Quartzite, meta-conglomerate, dolostone, argillite; Middle Proterozoic Swauger quartzite; southern Belt province (Middle Proterozoic) at surface, covers 1 % of this area

Intermediate Precambrian sediments, red-tinted quartzite with minor conglomeratic and dolomitic lenses of southern Idaho

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

Conglomerate, sandstone, and siltstone; Eocene to Late Cretaceous alluvial-fan deposits; east-central Idaho, Cordilleran fold-thrust belt, piggyback basins (Eocene to Late Cretaceous ) at surface, covers < 0.1 % of this area

Lower Tertiary to Upper Mesozoic breccia, conglomerate and sandstone; syntectonic in part.

Lithology: conglomerate; arkose; siltstone; limestone

Glacial debris; Late Pleistocene till, outwash, and alluvium of valley glaciers; high mountain valleys (Late Pleistocene ) at surface, covers 2 % of this area

Pleistocene upland valley deposits; commonly derived from alpine glaciation.

Lithology: till; outwash; alluvium

Surficial sediments; Quaternary alluvial, lacustrine, eolian, and glacial-outwash deposits, undivided; Snake River Plain, and Basin-and-Range provinces (Quaternary) at surface, covers < 0.1 % of this area

Quaternary surficial cover; Snake Plain stream, lake, wind and glacial-flood mantle.

Lithology: loess; colluvium

Tuffaceous shale, sandstone, conglomerate, and lignite; Eocene to Pliocene alluvial and lacustrine deposits; central and southern Idaho (Tertiary) at surface, covers 0.5 % of this area

Tertiary continental sediments; predominantly Upper Tertiary in age; subdivisions are:(Tpd, Tmd, and Ted).

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

Dolostone, arenite, conglomerate, and chert; Silurian to Middle Ordovician marine outer continental-shelf deposits; east-central Idaho (Silurian to Middle Ordovician) at surface, covers < 0.1 % of this area

Silurian to Middle Ordovician marine carbonate-to-clastic strata of east-central Idaho.

Lithology: dolostone (dolomite); arenite; conglomerate; chert

Dolostone, limestone, sandstone, shale, and conglomerate; Devonian marine continental-shelf deposits; east-central and southeastern Idaho (Devonian) at surface, covers 0.5 % of this area

Devonian bedded dolomite and limestone interval of eastern and southern Idaho.

Lithology: dolostone (dolomite); limestone; sandstone; shale; conglomerate

Argillite, quartzite, and calc-silicate rock; Middle Proterozoic Yellowjacket Formation; southern Belt province (Middle Proterozoic) at surface, covers < 0.1 % of this area

Intermediate Precambrian sediments, dark-colored, feldspathic quartzite with minor limestone beds of southern Idaho.

Lithology: meta-argillite; quartzite; calc-silicate rock

Limestone and sandstone; Early Jurassic Cordilleran retroarc-foreland-basin deposits; southeastern Idaho (Early Jurassic) at surface, covers < 0.1 % of this area

Lower Jurassic shallow-marine to non-marine sediments; shaley, sandy limestone overlaying red, crossbedded sandstone of eastern Idaho.

Lithology: limestone; sandstone

Dolostone, quartzite, shale, and limestone; Upper to Middle Ordovician marine continental-shelf deposits; east central Idaho (Late and Middle Ordovician) at surface, covers 0.9 % of this area

Upper and Middle Ordovician dolomite and quartzite unconformably overlying (Ol).

Lithology: dolostone (dolomite); arenite; shale; limestone

Quartz monzodiorite, monzogranite, granodiorite, monzonite, diorite; Eocene phaneritic to porphyro-aphanitic intrusions of the quartz monzodiorite suite; Challis magmatic belt (Eocene) at surface, covers 0.3 % of this area

Eocene intrusions of intermediate (mafic to felsic) composition

Lithology: quartz monzodiorite; monzogranite; granodiorite; quartz monzonite; quartz diorite

Dolostone, shale, arenite, siltstone, limestone, conglomerate, and chert; Ordovician and Cambrian marine outer continental-shelf deposits; central Idaho (Ordovician and Cambrian) at surface, covers 1 % of this area

Ordovician and Cambrian thrusted dolomite, siltstone, and quartzite of central Idaho.

Lithology: dolostone (dolomite); shale; arenite; siltstone; limestone; conglomerate; chert

Dolostone, limestone, siltstone, arenite, and chert; Devonian and Silurian marine upper continental-slope deposits; east-central and central Idaho; (Devonian and Silurian) at surface, covers 2 % of this area

Devonian and Silurian shallow-water marine carbonate units of east-central Idaho.

Lithology: dolostone (dolomite); limestone; siltstone; arenite; chert

Gabbroic intrusions; probably Cretaceous; mostly satellitic to the Idaho batholith (Cretaceous ) at surface, covers < 0.1 % of this area

Cretaceous plutons; basaltic or mafic; as gabbro; probably includes unmapped older and younger crystalline bodies.

Lithology: gabbro

Quartzite, marble, Calc-silicate rock, schist, and meta-conglomerate; Ordovician to Middle Proterozoic metasedimentary rocks; central Idaho, Pioneer Mountains metamorphic core complex (Ordovician to Middle Proterozoic) at surface, covers < 0.1 % of this area

Ordovician to Middle Proterozoic metasedimentary rocks, undivided

Lithology: quartzite; marble; calc-silicate rock; pelitic schist; meta-conglomerate

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 14 % 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)

Mica schist, quartzite, gneiss, and amphibolite; Late to Early Proterozoic high-grade metasedimentary rocks (subunits are ZXmhs, ZXmhq, and ZXmhc); trans-Idaho metamorphic province (Proterozoic) at surface, covers 0.3 % of this area

Precambrian high-grade metamorphic rock; metasediment

Lithology: mica schist; quartzite; calc-silicate rock; paragneiss; amphiibolite

Arenite, shale, dolostone, siltstone, conglomerate, chert, and limestone; Lower Ordovician marine outer continental-shelf deposits; central Idaho (Early Ordovician) at surface, covers 0.6 % of this area

Lower Ordovician dolomite, nodular cherty limestone, and intraformational conglomerate.

Lithology: arenite; shale; dolostone (dolomite); siltstone; conglomerate; chert; limestone

Chert, shale, phosphorite, and carbonates; Permian restricted marine epicontinental-basin deposits; southeastern Idaho (Permian) at surface, covers < 0.1 % of this area

Permian phosphatic sandstone, mudstone and chert of east-central Idaho.

Lithology: chert; shale; phosphorite; dolostone (dolomite); arenite; limestone

Felsic gneiss, mafic gneiss, orthogneiss, and calc-silicate rock; Early Proterozoic metamorphic rocks; central Idaho; Pioneer Mountains metamorphic core complex (Early Proterozoic) at surface, covers 0.2 % of this area

Precambrian, high-grade metamorphic rock; metasediment subdivisions are (PC3, PC2, PC1).

Lithology: felsic gneiss; mafic gneiss; orthogneiss; calc-silicate rock

Black argillite, quartzite, siltite, marble, chert, and syngenetic silver-lead-zinc deposits; Devonian euxinic marine-basin deposits; central Idaho (Devonian) at surface, covers < 0.1 % of this area

Devonian thrusted, deep-water siliceous argillite and quartzite of central Idaho.

Lithology: meta-argillite; quartzite; marble; calc-silicate rock; siltstone; chert

Limestone, shale, siltstone, chert, and conglomerate; Mississippian western turbiditic flysch to eastern shallow-water carbonates; east-central Idaho (Mississippian) at surface, covers 7 % of this area

Mississippian shallow-water carbonate-to-clastic sequence of east-central Idaho.

Lithology: limestone; shale; siltstone; sandstone; chert; conglomerate

Trachyandesite, latite, trachybasalt flows, dikes, and volcaniclastic debris; Eocene intermediate volcanics; central Idaho, southern Challis volcanic field (Eocene) at surface, covers 24 % of this area

Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.

Lithology: trachyandesite; latite; trachybasalt; dacite; trachyte; lava flow; volcanic breccia (agglomerate)

Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers 4 % of this area

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

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

Monzogranite, syenogranite, and syenite; Eocene phaneritic to porphro-aphanitic intrusions of the pink monzogranite suite; Challis magmatic belt (Eocene) at surface, covers 3 % of this area

Eocene intrusions of predominantly felsic (pink granite) composition

Lithology: granite; quartz syenite

Dacite to rhyolite (or rhodacite) ignimbrites; Eocene rhyodacitic cauldron complex; east-central Idaho, central Challis volcanic field (Eocene) at surface, covers 16 % of this area

Eocene mixed silicic and basaltic volcanic ejecta, flows and reworked debris.

Lithology: rhyodacite; ignimbrite; lava flow; rhyolite; quartz latite; dacite; andesite; basalt; volcanic breccia (agglomerate); mixed clastic/volcanic

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 1 % of this area

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

Lithology: granite; quartz monzodiorite; granodiorite

Gravel, sand, and silt; glacial outburst flood deposits, outwash, fanglomerate, and alluvium, undivided; Pleistocene (Pleistocene) at surface, covers 0.9 % of this area

Pleistocene outwash, fanglomerate, flood and terrace gravels; sudivisions are: (Qpug, Qpmg, and Qplg).

Lithology: stratified glacial sediment; alluvium; outwash; alluvial fan; alluvial terrace

Limestone, dolostone, sandstone, siltstone, and chert; Lower Permian to Lower Pennsylvanian marine continental-shelf deposits; east-central Idaho (Early Permian to Early Pennsylvanian) at surface, covers 0.2 % of this area

Lower Permian to Lower Pennsylvanian (Carboniferous) shallow-water detritus.

Lithology: limestone; dolostone (dolomite); arenite; siltstone; chert

Quartzite, siltstone, conglomerate, and metavolcanic rocks; Late and Middle Proterozoic, undivided; Atlanta batholith roof pendants (Late and Middle Proterozoic, undivided) at surface, covers < 0.1 % of this area

Precambrian, high-grade metamorphic rock

Lithology: quartzite; meta-argillite; metaconglomerate; schist; calc-silicate rock; marble; amphibolite; mafic metavolcanic rock; felsic metavolcanic rock

Arenite, dolostone, limestone, siltstone, and shale; Cambrian marine outer continental-shelf deposits; central Idaho (Cambrian) at surface, covers < 0.1 % of this area

Cambrian thrusted quartzite, fine-grained detritus, and dolomite of central Idaho.

Lithology: arenite; dolostone (dolomite); limestone; siltstone; shale

Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary) at surface, covers 4 % of this area

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

Lithology: alluvium; glacial drift; colluvium

Quartzite, siltite, argillite, and mica schist; Middle Proterozoic Lemhi Group; southern Belt province (Middle Proterozoic) at surface, covers < 0.1 % of this area

Intermediate Precambrian sediments, feldspathic quartzite and siltstone of southern Idaho.

Lithology: quartzite; siltstone; meta-argillite; exhalite; mica schist; lamprophyre

Sandstone, limestone, siltstone, shale, and conglomerate; Lower Permian to Middle Pennsylvanian deltaic turbidites; central Idaho; (Early Permian) at surface, covers 2 % of this area

Lower Permian to Middle Pennsylvanian thrusted, marine detritus of central Idaho.

Lithology: sandstone; limestone; siltstone; conglomerate; shale