Geologic units in Oneida county, Idaho

Sedimentary rocks (Permian and Pennsylvanian). (Permian and Pennsylvanian) at surface, covers 32 % of this area

Marine phosphorite, shale, and chert of Phosphoria Formation, fine-grained sandstone and mudrock of Wells, Quadrant, Amsden, and Shedhorn formations, and fine-grained sandstone, carbonaceous mudstone, and limestone of the Snaky Canyon Formation and Sun Valley and Oquirrh groups. Located in south-central and eastern Idaho. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).

Lake Bonneville deposits. (Pleistocene) at surface, covers 31 % of this area

Silt, clay, sand, and gravel deposited in and at margins of former Lake Bonneville (33-11 calibrated ka) and sand and gravel deposited in giant flood bars by outburst floods from the lake (17.4 calibrated ka). The 1,575-m (5,170 ft) Lake Bonneville shoreline was used to determine the maximum extent of the lake deposits. Flood deposits follow Bonneville flood path from near Downey and the Portneuf River westward along the Snake River to Lewiston. They include sand and silt deposited in slack-water areas to 740 m (2,430 ft) elevation in the Boise, Weiser, Payette, and Snake river drainages. (Quaternary Sediments).

Sedimentary rocks associated with Basin and Range extension. (Quaternary, Pliocene, and Miocene) at surface, covers 10 % of this area

Fluvial, fan, and lacustrine deposits and intercalated volcanic rocks of the Basin and Range Province (~16-2 Ma); consolidated to weakly consolidated sandstone, siltstone, arkose, conglomerate, mudstone, tuffaceous sediment, basalt, basaltic tephra, and rhyolite tuff. Includes deposits of Lake Idaho (Idaho Group) in western Snake River Plain and Salt Lake Formation deposited in Basin and Range Province of east-central Idaho. (Quaternary to Eocene Continental Sediments and Sedimentary Rocks).

Alluvial-fan deposits. (Quaternary) at surface, covers 7 % of this area

Gravel and subordinate sand and silt deposited at mouths of canyons; largest fans are in Basin and Range Province in east-central and southeastern Idaho. (Quaternary Sediments).

Loess deposits. (Pleistocene) at surface, covers 5 % of this area

Wind-deposited quartzose and calcareous silt in southeastern Idaho. Only shown where thick enough to mask older units; commonly 7-15 m (23-50 ft) thick. (Quaternary Sediments).

Sedimentary rocks (Ordovician and Cambrian). (Ordovician and Cambrian) at surface, covers 4 % of this area

Marine limestone, dolomite, and subordinate shale and sandstone of Cambrian carbonate bank of southeast Idaho stratigraphically up to St. Charles Formation and Ordovician Garden City Limestone. Includes Bayhorse succession (Cash Creek Quartzite, Garden Creek Phyllite, Bayhorse Dolomite, Ramshorn Slate, and Clayton Mine Quartzite) of Clayton area and Pioneer Mountains; quartzite of Kamiak Butte north of Moscow; and Cambrian Gold Creek quartzite, Rennie Shale, and Lakeview Limestone east of Bayview. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).

Basalt (Pliocene and Miocene). (Pliocene and Miocene) at surface, covers 2 % of this area

Flows and cinder cones of olivine tholeiite basalt, and shallow basalt intrusives (~15-3 Ma); includes basalt in Owyhee County and southwest of Twin Falls, basalt of Weiser (basalt to andesite), basalt of Cuddy Mountain (alkali basalt and picro-basalt) north of Cambridge, basalt in Mount Bennett Hills north of Gooding, andesite at Square Mountain near Magic Reservoir, and Cub River diabase sill east of Preston. Includes gabbro at depth in cross section D-D’-D”. (Quaternary to Eocene Continental Volcanic and Intrusive Rocks).

Sedimentary rocks (Devonian to Ordovician). (Devonian to Ordovician) at surface, covers 2 % of this area

Marine dolostone and limestone and sandstone in east-central and southeastern Idaho (Summerhouse, Kinnikinic, and Swan Peak sandstones, Fish Haven, Laketown, Jefferson, Three Forks, and Darby formations) and deep-water carbonaceous mudrocks of Phi Kappa, Trail Creek, and Milligen formations east of Ketchum. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).

Rhyolite (Pliocene and Miocene). (Pliocene and Miocene) at surface, covers 2 % of this area

Rhyolite tuffs and flows of Heise volcanic field (6.6-4.5 Ma; includes Blacktail Creek, Walcott, Conant Creek, and Kilgore tuffs), and rhyolite domes and flows of Magic Reservoir area (6.6-3 Ma). (Quaternary to Eocene Continental Volcanic and Intrusive Rocks).

Sedimentary rocks (Mississippian). (Mississippian) at surface, covers 2 % of this area

Marine limestone of Mississippian carbonate banks and turbiditic sandstone, mudstone, and conglomerate of Antler flysch trough; includes Madison and Lodgepole formations and Chesterfield Range Group of southeastern Idaho; McGowan Creek Formation, White Knob Limestone, and overlying carbonate bank of Lost River Range; and Copper Basin Group of Pioneer Mountains. Includes poorly dated Salmon River assemblage east of Stanley, consisting of argillite, siltstone, calcareous sandstone, and limestone. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).

Alluvial deposits. (Quaternary) at surface, covers 2 % of this area

Deposits in valleys consisting of gravel, sand, and silt. Includes younger terrace deposits. May contain some glacial deposits and colluvium in uplands. (Quaternary Sediments).

Windermere Supergroup. (Cambrian and Neoproterozoic) at surface, covers 0.9 % of this area

Upper part consists of shallow marine and fluvial quartzose sandstone, and minor siltite, shale, and limestone of the Brigham Group of southeast Idaho, Wilbert Formation of east-central Idaho, and quartzites of unknown affinity west of Borah Peak. More highly metamorphosed equivalents are quartzite, metaconglomerate, metasiltite, calc-silicate marble, and schist of Gospel Peaks successions C and D in central Idaho; mature quartzite, biotite schist, and minor calc-silicate rocks of Syringa metamorphic sequence east of Moscow; and schist and quartzite in the Albion Range (Elba Quartzite, schist of Upper Narrows, quartzite of Yost, schist of Stevens Spring, quartzite of Clarks Basin, schist of Mahogany Peaks, and Harrison Summit Quartzite). Lower part consists of diamictite, immature sandstone, and bimodal volcanic rocks related to continental rifting. Includes Pocatello Formation (700-665 Ma), formation of Leaton Gulch near Challis, Shedroof Conglomerate in extreme northwest Idaho, and metamorphic equivalents (schist, marble, calc-silicate rocks, metaconglomerate, and ~686 Ma metavolcanic rocks) of Gospel Peaks successions A and B in central Idaho. (Paleocene to Neoproterozoic Sedimentary and Igneous Rocks of the Cordilleran System).

Sediments and sedimentary rocks (Pleistocene and Pliocene). (Pleistocene and Pliocene) at surface, covers 0.5 % of this area

Older gravel, sand, and silt deposited in fans, streams, and lakes. Includes older terrace gravels and Tuana Gravel northwest of Twin Falls. (Quaternary to Eocene Continental Sediments and Sedimentary Rocks).

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

Lake Bonneville deposits

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

Older alluvial deposits

Wells Formation (Pennsylvanian to Permian) at surface, covers < 0.1 % of this area

Wells Formation.

Salt Lake Formation? (Middle Miocene to Late Pliocene) at surface, covers < 0.1 % of this area

Tuffaceous sediments, mudstone, sandstone, valley fill.