Mineral Resources On-Line Spatial Data
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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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.