USGS Home
Contact USGS
Search USGS

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

Geologic units in Columbia county, Washington

[Additional scientific data in this geographic area]

Quaternary nonmarine deposits (Pleistocene) at surface, covers 39 % of this area

Periglacial eolian deposits. Buff to light-brown, massive, homogenous, unconsolidated loessial silt; some water-laid material locally. Probably early Pleistocene.

Lithology: loess; glaciolacustrine

Younger glacial drift (Pleistocene) at surface, covers 0.7 % of this area

Advance and recessional outwash, stratified drift, and associated deposits. Primarily silt, sand, and gravel with some clay. Includes alluvium locally and scabland deposits of eastern Washington.

Lithology: outwash; stratified drift; alluvium

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

Pliocene-Pleistocene volcanic rocks (Mostly Pleistocene) at surface, covers < 0.1 % of this area

Light-gray andesite, andesite porphyry, and open-textured basalt flows with minor associated mudflows and breccia. Includes restricted areas of valley flow basalt in Snake River Canyon in southeastern Washington and in Spokane area.

Lithology: andesite; basalt

Miocene volcanic rocks (Middle Miocene) at surface, covers 57 % of this area

Dark-gray to black, dense aphanitic basalt flows; commonly columnar jointed, less commonly irregularly and platy jointed; some flows vesicular, grading to scoriaceous; includes minor pillow lava, palagonite beds, and interbedded soil profiles and sedimentary beds; contains diatomite beds locally. Maximum thickness in south-central Washington may be in excess of 10,000 feet; much thinner in western Washington, where flows are mostly associated with marine sedimentary rocks. Includes acidic and intermediate volcanic rocks in northern Cascade Mountains.

Lithology: tholeiite; andesite; dacite; rhyolite; sandstone; siltstone; conglomerate

Carboniferous-Permian sedimentary and volcanic rocks (Devonian to Permian; some Jurassic) at surface, covers 0.2 % of this area

Sedimentary and volcanic rocks, undivided. Cherty and slaty argillite, siltstone, graywacke, chert, greenstone, tuff, andesite, and spilitic volcanics.

Lithology: graywacke; siltstone; greenstone; phyllite; chert; argillite; arkose; shale; andesite; spilite; limestone; marble; quartzite; slate; conglomerate

Alluvium (Holocene) at surface, covers 3 % 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

Mesozoic granitic rocks, undivided (Mostly Cretaceous-Jurassic) at surface, covers < 0.1 % 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