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

Geologic units in Lewis county, Idaho

[Additional scientific data in this geographic area]

Quartz diorite, tonalite, granodiorite, orthogneiss, migmatite; Cretaceous to Jurassic quartz dioritic plutons; western Idaho, Blue Mountains island-arc complex (Early Cretaceous to Late Jurassic) at surface, covers 9 % of this area

Lower Cretaceous to Upper Jurassic intrusions in west-central Idaho.

Lithology: quartz diorite; tonalite; granodiorite; orthogneiss; migmatite; gabbro; trondhjemite; aplite

Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers 0.3 % of this area

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

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

Limestone, slate; Upper Triassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex; (Late Triassic) at surface, covers 0.5 % of this area

Upper Triassic shale overlying reefal limestone and dolomite in west-central Idaho.

Lithology: limestone; slate; shale; dolostone (dolomite); phyllite; marble; skarn (tactite); amphibolite schist; greenschist

Basalt lava flows; Middle Miocene flood-basalt flows of subunit 2b; Columbia Plateau (Miocene) at surface, covers 85 % of this area

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

Lithology: basalt; lava flow

Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary) at surface, covers 0.4 % of this area

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

Lithology: alluvium; glacial drift; colluvium

Shale, limestone, and sandstone; Triassic marine to non-marine epicontinental deposits (subunits are TRl and TRu) (Triassic) at surface, covers 0.4 % of this area

Triassic shallow-marine to non-marine sediments of eastern Idaho; subdivisions are (TRu and TRl).

Lithology: shale; limestone; sandstone; chert; conglomerate

Metavolcanic and metasedimentary rocks; Middle to Lower Triassic greenschist-facies metamorphic rocks; western Idaho, Blue Mountains island-arc complex (Middle and Early Triassic) at surface, covers 2 % of this area

Middle and Lower Triassic metabasalt and submarine volcaniclastics of western Idaho

Lithology: mafic metavolcanic rock; metasedimentary rock; quartzite; meta-conglomerate; meta-argillite; marble; keratophyre

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

Lakes and streams

Lithology: water

Basalt lava flows; Early Miocene valley-filling basalt flows of subunit 1b; Columbia Plateau (Miocene) at surface, covers 1 % of this area

Miocene basalt flows of western Idaho; commonly porphyritic and exposed on lower slopes.

Lithology: tholeiite; lava flow