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

Geologic units in Bonner county, Idaho

[Additional scientific data in this geographic area]

Gravel, sand, and silt; glacial outburst flood deposits, outwash, fanglomerate, and alluvium, undivided; Pleistocene (Pleistocene) at surface, covers 20 % 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

Glacial drift, undivided (Pleistocene) at surface, covers < 0.1 % of this area

Glacial and glaciofluvial sand, gravel, and till; includes alpine glacier outwash and till as well as some Recent alluvium.

Lithology: glacial drift; till; outwash; alluvium

Argillite, siltite, and quartzite; Middle Proterozoic Ravalli Group; northern Belt Province (Middle Proterozoic) at surface, covers 3 % of this area

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

Lithology: meta-argillite; siltstone; quartzite

Biotite schist, hornfels, amphibolite, and mylonite; Middle Proterozoic rocks of the Prichard Formation, metamorphosed near the Cretaceous Kaniksu batholith; northern Belt province (Eocene to Middle Proterozoic) at surface, covers 0.9 % of this area

Intermediate Precambrian age metasediments; generally low-to-medium grade; argillite, siltite and minor quartzite of northern Idaho.

Lithology: mica schist; hornfels; amphibolite; mylonite

Gabbro, diorite, quartz diorite, aplite; Late to Middle Proterozoic sills injected into sedimentary strata of the Belt Basin; northern Belt province (Late to Middle Proterozoic) at surface, covers 2 % of this area

Younger Precambrian dioritic and amphibolitic sills of northern Idaho; basaltic or mafic; as gabbro.

Lithology: gabbro; diorite; quartz diorite; aplite

Siltite, argillite, and quartzite; Middle Proterozoic Prichard Formation; northern Belt province (Middle Proterozoic) at surface, covers 15 % of this area

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

Lithology: siltstone; meta-argillite; quartzite

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

Precambrian rocks, undivided (Proterozoic) at surface, covers 0.1 % of this area

Predominantly phyllite with some schist, limestone, dolomite, quartzite, and volcanic rocks; northeastern Pend Oreille County. Mainly quartzite sandstone in upper part, dark-gray argillite with sandstone and limestone in middle part, and sandstone with argillite in lower part; southeastern Pend Oreille County. Banded slate with quartzite and dolomite; southwestern Stevens County. Quartzite, siliceous argillite, and argilliceous quartzite grading into argillite and quartz-mica schists form south ot north; southeastern Stevens County. Quartzite, argillite, quartz-feldspar gneiss, and other metamorphic rocks in northeastern Whitman and southeastern Spokane Counties are partly if not all extenstions of the Belt strata.

Lithology: argillite; siltstone; quartzite; dolostone; phyllite; limestone; gneiss; schist; sandstone

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

Alluvium: mainly valley fill consisting of silt, sand, and gravel; includes some terrace deposits and glacial drift of Pleistocene age in some areas; locally includes hot spring tufa. The older part of the alluvium, where present, is probably of Pliocene age.

Lithology: alluvium; glacial drift; carbonate

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 5 % 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)

Granitoid intrusions, metasedimentary rocks, and migmatite, undivided; Cretaceous intrusions and Proterozoic host rocks, undivided; northern and central Idaho (Cretaceous to Early Proterozoic) at surface, covers 0.9 % of this area

Mixed, highly altered and migmatitic rocks; derived from imbrication and dynamic events

Lithology: granitoid; metasedimentary rock; migmatite

Migmatitic paragneiss, quartzite, orthogneiss, and amphibolite; Early Proterozoic to Late Archean metamorphic rocks; northern Belt province; Settlement antiform in Priest River metamorphic core complex (Early Proterozoic to Late Archean) at surface, covers 1 % of this area

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

Lithology: paragneiss; migmatite; quartzite; orthogneiss

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, 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 0.4 % of this area

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

Lithology: granite; quartz monzodiorite; granodiorite

Basalt lava flows; Middle Miocene flood-basalt flows of subunit 2b; Columbia Plateau (Miocene) at surface, covers < 0.1 % of this area

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

Lithology: basalt; lava flow

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 17 % 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

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

Mostly unconsolidated silt, sand, and gravel valley fill with some clay; includes low-level terrace, marsh, peat, artificial fill, and glacial deposits locally.

Lithology: alluvium; alluvial terrace; peat; glacial drift

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

Mesozoic granitic rocks, undivided (Mostly Cretaceous-Jurassic) at surface, covers 0.2 % of this area

Granite, quartz monzonite, quartz diorite, granodiorite, and trondhjemite. Includes diorite in southeastern Washington; diorite and gabbro near Concunully in Okanogan County; gneiss, schist, and migmatites in areas of Chelan, Colville, and Okanogan batholiths. Includes high-grade metamorphic rocks of Precambrian age in Spokane area.

Lithology: granite; granodiorite; quartz monzonite; tonalite; orthogneiss; trondhjemite; quartz diorite; diorite; gabbro; schist; migmatite; syenite

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

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

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

Mica schist, quartzite, migmatite, amphibolite; Middle to Early Proterozoic metamorphic rocks; northern Belt province, Spokane dome of Priest River metamorphic core complex (Middle Proterozoic to Early Proterozoic) at surface, covers 4 % of this area

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

Lithology: mica schist; quartz-feldspar schist; quartzite; migmatite; amphibolite

Open Water (Holocene) at surface, covers 9 % of this area

Lakes and streams

Lithology: water

Glacial debris; Late Pleistocene glacial till, outwash, and alluvium of continental glaciers; northern Idaho (Late Pleistocene ) at surface, covers 9 % of this area

Pleistocene till, moraines and similar unsorted glacial debris.

Lithology: till; outwash; alluvium

Argillite, siltstone, quartzite, and dolostone; Middle Proterozoic Missoula Group; northern Belt province (Middle Middle Proterozoic) at surface, covers 2 % 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

Limestone, arenite, and shale; Cambrian marine continental-shelf deposits; northern Idaho (Middle Cambrian) at surface, covers 1 % of this area

Middle Cambrian thinly laminated claystone overlying coarse-grained pebbly quartzite of northern Idaho.

Lithology: limestone; arenite; shale