Alluvium

Mostly unconsolidated silt, sand, and gravel valley fill with some clay; includes low-level terrace, marsh, peat, artificial fill, and glacial deposits locally.
State Washington
Name Alluvium
Geologic age Holocene
Lithologic constituents
Major
Unconsolidated > Fine-detrital > Silt (Alluvial)
Unconsolidated > Coarse-detrital > Sand (Alluvial)
Minor
Unconsolidated > Coarse-detrital > Gravel (Alluvial, Glacial)
Incidental
Unconsolidated > Peat (Bed)
Unconsolidated > Fine-detrital > Clay (Alluvial)
References

Huntting, M.T., Bennett, W.A.G., Livingston, V.E.Jr., and Moen, W.S., 1961, Geologic Map of Washington: Washington Division of Mines and Geology, scale 1:500,000.

NGMDB product
Counties Adams - Asotin - Benton - Chelan - Clallam - Clark - Columbia - Cowlitz - Douglas - Ferry - Franklin - Garfield - Grant - Grays Harbor - Jefferson - King - Kittitas - Klickitat - Lewis - Mason - Okanogan - Pacific - Pend Oreille - Pierce - Skagit - Skamania - Snohomish - Spokane - Stevens - Thurston - Wahkiakum - Walla Walla - Whatcom - Whitman - Yakima