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

Geologic units in Twin Falls county, Idaho

Basalt and gravel; Late Pleistocene basalt flows and interlayered gravel of subunit 2b; Snake River Plain (Late Pleistocene) at surface, covers < 0.1 % of this area

Upper Pleistocene Snake Plain basaltic lava flows, unit 2.

Lithology: tholeiite; lava flow; gravel

Limestone, sandstone, dolostone, and chert; Permian to Pennsylvanian marine epicontinental-basin deposits; southeastern Idaho; (Early Permian to Early Pennsylvanian) at surface, covers 0.5 % of this area

Lower Permian to Lower Pennsylvanian chert, limestone, and sandstone of southern Idaho; subdivisions are (Ps, and PNs).

Lithology: limestone; sandstone; dolostone (dolomite); chert; siltstone; shale

Welded and nonwelded silicic ash-flow tuffs (Middle Miocene to Late Miocene) at surface, covers < 0.1 % of this area

WELDED AND NONWELDED SILICIC ASH-FLOW TUFFS-Locally includes thin units of air-fall tuff and sedimentary rock

Lithology: rhyolite

Gravel, sand, and silt; Quaternary basin-filling alluvium; Snake River Plain, Basin and Range provinces (Quaternary) at surface, covers 0.9 % of this area

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

Lithology: alluvium; alluvial fan; alluvial terrace

Basalt and silt; Late Pleistocene basalt flows and interlayered lacustrine silt beds of subunit 1b; Snake River Plain (Late Pleistocene) at surface, covers < 0.1 % of this area

Upper Pleistocene Snake Plain basaltic lava flows, unit 1.

Lithology: tholeiite; lava flow; silt

Glacial debris; Late Pleistocene glacial till, outwash, and alluvium of continental glaciers; northern Idaho (Late Pleistocene ) at surface, covers < 0.1 % of this area

Pleistocene till, moraines and similar unsorted glacial debris.

Lithology: till; outwash; alluvium

Rhyolite, quartz latite, and latite ignimbrites and flows; Miocene felsic volcanics; Owyhee Plateau; (Miocene) at surface, covers 36 % of this area

Miocene silicic flows, tuffs; most common in southwestern Idaho.

Lithology: rhyolite; latite; quartz latite; ignimbrite; lava flow

Open Water (Holocene) at surface, covers 0.4 % of this area

Lakes and streams

Lithology: water

Basalt flows, pumice, and tuff; Early Pleistocene to Pliocene basaltic volcanics; Snake River Plain (Early Pleistocene) at surface, covers 21 % 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 31 % of this area

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

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

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 < 0.1 % 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

Limestone, arenite, dolostone, chert, siltstone, shale; Upper Paleozoic marine continental-shelf deposits; southeastern Idaho (Late Paleozoic) at surface, covers < 0.1 % of this area

Upper Paleozoic marine sediments in southern Idaho.

Lithology: limestone; arenite; dolostone (dolomite); chert; siltstone; shale

Gravel, sand, and silt; glacial outburst flood deposits, outwash, fanglomerate, and alluvium, undivided; Pleistocene (Pleistocene) at surface, covers 0.7 % 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, silt, clay; Late Pleistocene glacio-alluvial and lacustrine deposits; Basin and Range, and Snake River Plain (Late Pleistocene) at surface, covers 0.2 % of this area

Upper Pleistocene deposits; outwash, fanglomerate, flood and terrace gravels.

Lithology: outwash; alluvium; lake or marine deposit (non-glacial); gravel; sand; silt; clay or mud

Gravel; Early Pleistocene alluvium; western Snake River Plain (Pleistocene) at surface, covers 3 % of this area

Lower Pleistocene deposits; outwash, fanglomerate, flood and terrace gravels.

Lithology: alluvium; gravel; sand; silt; clay or mud

Clastic debris; Quaternary colluvium, fanglomerate, talus, and glacial deposits; upland-valley margins (Quaternary) at surface, covers < 0.1 % of this area

Quaternary colluvium, fanglomerate, and talus plus some glacial debris in upland valleys.

Lithology: alluvium; glacial drift; colluvium

Silt, clay, sand, and gravel; Quaternary-Tertiary alluvial and lacustrine deposits; western Snake River Plain (Early Pleistocene and Late Pliocene) at surface, covers 3 % of this area

Pleistocene and Pliocene stream and lake deposits.

Lithology: lake or marine deposit (non-glacial); alluvium; silt; clay; sand; gravel

Rhyolitic flows and shallow intrusive rocks (Middle Miocene to Late Miocene) at surface, covers < 0.1 % of this area

RHYOLITIC FLOWS AND SHALLOW INTRUSIVE ROCKS

Lithology: rhyolite; dacite; trachyte

Alluvial deposits (Quaternary) at surface, covers < 0.1 % of this area

ALLUVIAL DEPOSITS-Locally includes beach and sand dune deposits

Lithology: alluvium; mass wasting; dune sand; lake or marine deposit (non-glacial)

Silt, clay, and diatomite; Middle Pleistocene lacustrine sediments of lava-dammed lakes; western Snake River Plain (Middle Pleistocene) at surface, covers 0.3 % of this area

Middle Pleistocene lava-dammed Snake Plain lake beds of silt, clay and diatomite.

Lithology: lake or marine deposit (non-glacial); alluvium; silt; clay or mud; diatomite; sand; gravel

Basalt flows (Late Miocene to Middle Miocene) at surface, covers < 0.1 % of this area

BASALT FLOWS

Lithology: basalt

Gravel, sand, and silt; Quaternary; alluvium (Quaternary) at surface, covers 3 % of this area

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

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