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

Geologic units in Jefferson county, Idaho

Gravel, sand, and clay; Quaternary-Tertiary colluvium and fanglomerate; western Idaho (Pleistocene and Pliocene) at surface, covers < 0.1 % of this area

Pleistocene and Pliocene fanglomerate, colluvium, and poorly sorted gravel deposits.

Lithology: alluvial fan; colluvium; residuum; gravel; clay or mud; sand; silt

Sand; Holocene dunes; Snake River Plain (Holocene) at surface, covers 6 % of this area

Recent active sand dunes and eolian deposits.

Lithology: dune sand; eolian

Rhyolite ignimbrites; Early Pleistocene felsic volcanics; Yellowstone Plateau (Early Pleistocene) at surface, covers < 0.1 % of this area

Lower Pleistocene silicic volcanic units of the Island Park-Yellowstone area.

Lithology: rhyolite; ignimbrite

Gravel, sand, and silt; glacial outburst flood deposits, outwash, fanglomerate, and alluvium, undivided; Pleistocene (Pleistocene) at surface, covers 12 % 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

Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers 9 % of this area

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

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

Basalt, gravel, and pumice; Late Pleistocene basaltic volcanics and interlayered sedimetnsof subunit 3b; Snake River Plain (Late Pleistocene) at surface, covers 23 % of this area

Upper Pleistocene Snake Plain basaltic lava flows, unit 3.

Lithology: tholeiite; lava flow; gravel; pumice

Basalt and gravel; Late Pleistocene basalt flows and interlayered gravel of subunit 2b; Snake River Plain (Late Pleistocene) at surface, covers 18 % of this area

Upper Pleistocene Snake Plain basaltic lava flows, unit 2.

Lithology: tholeiite; lava flow; gravel

Basalt, clay, and gravel; Late Pleistocene basalt flows with interlayered alluvial and lacustrine sediments; Snake River Plain and vicinity (subunits are Qpu1b, Qpu2b, Qpu3b, and Qpu4b) (Late Pleistocene) at surface, covers 6 % of this area

Upper Pleistocene Snake Plain lava flows; local stratigraphic position shown by (Qpu4b, Qpu3b, Qpu2b, Qpu1b).

Lithology: tholeiite; lava flow; clay or mud; gravel

Basalt flows, pumice, and tuff; Early Pleistocene to Pliocene basaltic volcanics; Snake River Plain (Early Pleistocene) at surface, covers 7 % of this area

Lower Pleistocene to Pliocene basalts with associated tuffs and volcanic detritus.

Lithology: tholeiite; lava flow; pumice; tuff

Basalt flows, pyroclastic debris, clastic sediments, and diatomite; Pliocene basaltic volcanics and clastic sediments; Snake River Plain and vicinity (Pliocene) at surface, covers < 0.1 % of this area

Pliocene olivine basalt flows and associated tuff and detritus of southern Idaho.

Lithology: basalt; lava flow; tuff; mixed clastic/volcanic

Surficial sediments; Quaternary alluvial, lacustrine, eolian, and glacial-outwash deposits, undivided; Snake River Plain, and Basin-and-Range provinces (Quaternary) at surface, covers 17 % of this area

Quaternary surficial cover; Snake Plain stream, lake, wind and glacial-flood mantle.

Lithology: loess; colluvium

Open Water (Holocene) at surface, covers 0.5 % of this area

Lakes and streams

Lithology: water

Rhyolite ot trachyte ignimbrites and flows; Pliocene felsic volcanics; eastern Snake River Plain and vicinity (Pliocene) at surface, covers 0.5 % of this area

Pliocene silicic welded tuff, ash, and flow rock; most common in southwestern Idaho.

Lithology: rhyolite; trachyte; ignimbrite; lava flow; tuff; volcanic breccia (agglomerate)

Gravel, sand, and silt; Quaternary basin-filling alluvium; Snake River Plain, Basin and Range provinces (Quaternary) at surface, covers 0.2 % of this area

Quaternary detritus; generally basin-filling deposits of central and southern Idaho.

Lithology: alluvium; alluvial fan; alluvial terrace