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Geologic units in Sheridan county, Wyoming

[Additional scientific data in this geographic area]

Plutonic rocks (Archean) at surface, covers 10 % of this area
PLUTONIC ROCKS. Wind River Range--Largely granite gneiss; contains diorite and quartz diorite facies. Bighorn Mountains--Quartz diorite to quartz monzonite. Age 2,900+ Ma.
Lithology: granitoid
White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers < 0.1 % of this area
WHITE RIVER FORMATION (AGE 31 TO 35 Ma)--White to pale-pink blocky tuffaceous claystone and lenticular arkosic conglomerate.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; mixed clastic/volcanic
Wasatch Formation (E) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.3 % of this area
WASATCH FORMATION Moncrief Member--Conglomerate of Precambrian clasts, interbedded with drab sandstone and claystone.
Lithology: conglomerate
Wasatch Formation (E) (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.4 % of this area
WASATCH FORMATION Kingsbury Conglomerate Member--Conglomerate of Paleozoic clasts, interbedded with drab sandstone and variegated claystone.
Lithology: conglomerate; medium-grained mixed clastic; fine-grained mixed clastic
Wasatch Formation (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 38 % of this area
WASATCH FORMATION -- in Thrust belt: Main body--Variegated red to gray, brown, and gray mudstone and sandstone; conglomeratic lenses; in southwest Wyoming--Drab to variegated claystone and siltstone, carbonaceous shale and coal, buff sandstone, arkose, and conglomerate. In northwestern part of Green River Basin is thick arkosic light-yellowish-tan sandstone intertonguing with pale-green to gray claystone and shale; in east Wyoming--Drab sandstone and drab to variegated claystone; numerous coal beds in lower part.
Lithology: mudstone; sandstone; conglomerate; coal
Chugwater and Goose Egg Formations (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers 0.5 % of this area
CHUGWATER AND GOOSE EGG FORMATIONS (north Wyoming). CHUGWATER FORMATION--Red siltstone and shale. Alcova Limestone Member in upper middle part in north Wyoming. Thin gypsum partings near base in north and northeast Wyoming. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone; CHUGWATER FORMATION OR GROUP (south Wyoming)--Red shale and siltstone containing thin gypsum partings near base. Group includes Popo Agie Formation (red shale and red, yellow, and purple siltstone; lenses of lime-pellet conglomerate), Crow Mountain Sandstone (red and gray, thick bedded), Alcova Limestone, and Red Peak Formation (red siltstone and shale). Chugwater Formation includes as members all the units listed above. Includes overlying Jelm Formation in Shirley and Seminoe Mountains and at northern end of Laramie Basin. JELM FORMATION--Red sandstone. GOOSE EGG FORMATION--Red sandstone and siltstone, white gypsum, halite, and purple to white dolomite and limestone.
Lithology: siltstone; sandstone; shale; conglomerate; evaporite; dolostone (dolomite); limestone
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 4 % of this area
FORT UNION FORMATION northwest, southwest, and central Wyoming--Brown to gray sandstone, gray to black shale, and thin coal beds; east Wyoming--Light-colored massive sandstone, drab shale, and thick coal beds.
Lithology: sandstone; shale; coal
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 9 % of this area
FORT UNION FORMATION Tongue River Member--Thick beds of yellow sandstone interbedded with gray and black shale and many coal beds.
Lithology: sandstone; shale; coal
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 0.5 % of this area
FORT UNION FORMATION Tullock Member--Soft gray sandstone, gray and brown carbonaceous shale, and thin coal beds.
Lithology: sandstone; shale; coal
Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 2 % of this area
FORT UNION FORMATION Lebo Member--Dark-gray clay shale and concretionary sandstone.
Lithology: shale; sandstone
Undivided surficial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.8 % of this area
UNDIVIDED SURFICIAL DEPOSITS--Mostly alluvium, colluvium, and glacial and landslide deposits. Primarily in Yellowstone area and Bighorn Mountains.
Lithology: alluvium; colluvium; glacial drift; landslide
Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers < 0.1 % of this area
GRAVEL, PEDIMENT, AND FAN DEPOSITS--Mostly locally derived clasts. Includes some glacial deposits along east flank of Wind River Range. Locally includes some Tertiary gravels.
Lithology: unconsolidated deposit
Landslide deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 2 % of this area
LANDSLIDE DEPOSITS--Locally includes intermixed landslide and glacial deposits, talus, and rock-glacier deposits.
Lithology: landslide; glacial drift
Glacial deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.4 % of this area
GLACIAL DEPOSITS--Till and outwash of sand, gravel, and boulders.
Lithology: glacial drift
Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 3 % of this area
ALLUVIUM AND COLLUVIUM--Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.
Lithology: alluvium; colluvium
Tensleep Sandstone and Amsden Formation (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late Pennsylvanian(?) Permian) at surface, covers 2 % of this area
TENSLEEP SANDSTONE AND AMSDEN FORMATION. North Wyoming: TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. Permian fossils have been found in the topmost beds of the Tensleep at some localities in Washakie Range, Owl Creek Mountains, and southern Bighorn Mountains. AMSDEN FORMATION--Red and green shale and dolomite; at base is brown sandstone. South Wyoming: TENSLEEP SANDSTONE AND AMSDEN FORMATION. TENSLEEP SANDSTONE--White to gray sandstone containing thin limestone and dolomite beds. AMSDEN FORMATION--Red and green shale and dolomite; at base is persistent red to brown sandstone.
Lithology: sandstone; carbonate; shale
Bighorn Dolomite, Gallatin Limestone, and Gros Ventre Formation (TB), Bighorn Dolomite, Snowy Range Formation, Pilgrim Limestone, Park Shale, Meagher Limestone, Wolsey Shale, and Flathead Sandstone (Y), Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone (N), or Whitewood Dolomite, and WInnipeg and Deadwood Formations (NE) (Phanerozoic | Paleozoic | Cambrian-Middle Cambrian-Furongian(?) Ordovician-Early(?) Ordovician-Middle(?) Ordovician-Late) at surface, covers 2 % of this area
BIGHORN DOLOMITE, GALLATIN LIMESTONE, and GROS VENTRE FORMATION. BIGHORN DOLOMITE (Thrust Belt)--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Gray and tan limestone. GROS VENTRE FORMATION--Greenish-gray micaceous shale. BIGHORN DOLOMITE, SNOWY RANGE FORMATION, PILGRIM LIMESTONE, PARK SHALE, MEAGHER LIMESTONE, WOLSEY SHALE, AND FLATHEAD SANDSTONE (Yellowstone). BIGHORN DOLOMITE--Light-gray massive siliceous dolomite. SNOWY RANGE FORMATION (Gallatin Group)--Medium-gray limestone and underlying greenish-gray shale. PILGRIM LIMESTONE (Gallatin Group)--Blue-gray and yellow mottled hard limestone. PARK SHALE--Green micaceous soft shale. Upper part may be Late Cambrian. MEAGHER LIMESTONE--Blue-gray and yellow mottled hard limestone. WOLSEY SHALE--Green micaceous soft shale. FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. BIGHORN DOLOMITE, GALLATIN LIMESTONE, GROS VENTRE FORMATION, AND FLATHEAD SANDSTONE (north Wyoming). BIGHORN DOLOMITE--Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone. GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. WHITEWOOD DOLOMITE, AND WINNIPEG AND DEADWOOD FORMATIONS (northeast Wyoming). WHITEWOOD DOLOMITE--Buff massive fossiliferous dolomite. WINNIPEG FORMATION--Pink to yellow siltstone and shale. DEADWOOD FORMATION--Red and brown quartzitic sandstone.
Lithology: limestone; dolostone (dolomite); shale; sandstone
Bighorn Dolomite (Phanerozoic | Paleozoic | Ordovician-Middle Ordovician-Late) at surface, covers 2 % of this area
BIGHORN DOLOMITE--Light-gray massive siliceous dolomite in northern Yellowstone area. Gray massive cliff-forming siliceous dolomite and locally dolomitic limestone in Thrust belt and northern Wyoming.
Lithology: dolostone (dolomite)
Madison Group and Darby Formation (TB, N) or Madison Group and Three Forks and Jefferson Formations (Y) (Phanerozoic | Paleozoic | Devonian-Late Carboniferous Mississippian-Early(?) Mississippian-Middle(?) Mississippian-Late) at surface, covers 6 % of this area
MADISON GROUP AND DARBY FORMATION (Thrust Belt, north Wyoming). MADISON GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). DARBY FORMATION--Yellow and greenish-gray shale and dolomitic siltstone underlain by fetid brown dolomite and limestone. MADISON GROUP AND THREE FORKS AND JEFFERSON FORMATIONS (Yellowstone). MADISON GROUP--Group includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). THREE FORKS FORMATION--Pink, yellow, and green dolomitic siltstone and shale. JEFFERSON FORMATION--Massive siliceous dolomite.
Lithology: limestone; dolostone (dolomite); mudstone
Mesaverde Formation (N) or Mesaverde Group (S) (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.3 % of this area
MESAVERDE FORMATION (north Wyoming)--Light-colored massive to thin-bedded sandstone, gray sandy shale, and coal beds. In Jackson Hole locally contains gold-bearing quartzite conglomerate. North of North Fork Powder River east of the Bighorn Mountains, consists solely of the Parkman Sandstone Member; MESAVERDE GROUP (SOUTH WYOMING). Includes Almond Formation, Ericson Sandstone, Rock Springs and Blair Formations in Rock Springs uplift; Almond Formation (white and brown soft sandstone, gray sandy shale, coal and carbonaceous shale), Pine Ridge Sandstone (light-gray sandstone and thin coal beds), and Allen Ridge (gray sandstone, shale, and thin coal beds) and Haystack Mountains (gray marine sandstone and shale) Formations in Rawlins uplift; Pine Ridge Sandstone (light-gray sandstone and thin coal beds) and Rock River Formation (soft sandstone and sandy shale) in Laramie Basin.
Lithology: sandstone; shale; coal; conglomerate
Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 0.2 % of this area
MOWRY (Kmr) AND THERMOPOLIS SHALES. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.
Lithology: shale; sandstone; mixed clastic/volcanic
Lance Formation, Fox Hills Sandstone, Meeteetse Formation, Bearpaw and Lewis Shales (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.3 % of this area
LANCE FORMATION (Kl north), FOX HILLS SANDSTONE (Kfh), MEETEETSE FORMATION (Km), AND BEARPAW AND LEWIS (Kle) SHALES--In the Bighorn Basin consists of Lance, Meeteetse and, in the southeastern part, tongue of Lewis Shale; in the northern part of the Wind River Basin, of Lance, Meeteetse, and Lewis, and, in the southeastern part of the basin, of Lance and Lewis; on the west side of the Powder River Basin north of T. 45 N., of Lance, Fox Hills, and Bearpaw, and, to the south, of Lance, Fox Hills, and Lewis. LANCE FORMATION--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses. FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils. MEETEETSE FORMATION (AGE ABOUT 73 Ma)--Chalky-white to gray sandstone, yellow, green, and dark-gray bentonitic claystone, white tuff, and thin coal beds. BEARPAW SHALE--Dark-greenish-gray shale containing thin gray sandstone partings. LEWIS SHALE (AGE ABOUT 68 Ma)--Gray marine shale containing many gray and brown lenticular concretion-rich sandstone beds.
Lithology: medium-grained mixed clastic; fine-grained mixed clastic; mixed clastic/volcanic; coal
Lance Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.5 % of this area
LANCE FORMATION north Wyoming--Thick-bedded buff sandstone and drab to green shale; thin conglomerate lenses; south and northeast Wyoming--Brown and gray sandstone and shale; thin coal and carbonaceous shale beds.
Lithology: sandstone; shale; conglomerate; coal
Cloverly, Morrison, Sundance, and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late(?) Cretaceous-Early) at surface, covers 0.2 % of this area
CLOVERLY, MORRISON, AND SUNDANCE (Js), AND GYPSUM SPRING FORMATIONS. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N.
Lithology: fine-grained mixed clastic; medium-grained mixed clastic; carbonate; mixed clastic/volcanic; conglomerate; dolostone (dolomite); evaporite
Cloverly and Morrison Formations (N,S) or Cloverly Formation, Inyan Kara Group, and Morrison Formation (Phanerozoic | Mesozoic | Jurassic-Late Cretaceous-Early) at surface, covers 0.3 % of this area
CLOVERLY FORMATION and MORRISON FORMATION. CLOVERLY FORMATION--Rusty sandstone at top, underlain by brightly variegated bentonitic claystone; chert-pebble conglomerate locally at base. MORRISON FORMATION--Dully variegated claystone, nodular limestone, and gray silty sandstone. In southern Yellowstone and Jackson Hole areas the presence of Morrison is questionable; CLOVERLY FORMATION (Hartville uplift) or INYAN KARA GROUP (Black Hills) and MORRISON FORMATION. CLOVERLY FORMATION--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. INYAN KARA GROUP--Rusty to light-gray sandstone containing lenticular chert-pebble conglomerate interbedded with variegated bentonitic claystone. Includes Fall River and Lakota Formations. MORRISON FORMATION, in northeast Wyoming, dully variegated siliceous claystone, nodular white limestone, and gray silty sandstone.
Lithology: sandstone; claystone; conglomerate; limestone
Frontier Formation and Mowry and Thermopolis Shales (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers 0.6 % of this area
FRONTIER FORMATION (Kf) AND MOWRY (Kmr) AND THERMOPOLIS SHALES. FRONTIER FORMATION--Gray sandstone and sandy shale. In Northern Yellowstone area, Yellowish- to medium-gray sandstone; tuffaceous and carbonaceous in lower part. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds. THERMOPOLIS SHALE--Black soft fissile shale; Muddy Sandstone Member at top.
Lithology: sandstone; shale; mixed clastic/volcanic
Fox Hills Sandstone and Bearpaw Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.4 % of this area
FOX HILLS SANDSTONE AND BEARPAW SHALE. FOX HILLS SANDSTONE (Kfh)--Light-colored sandstone and gray sandy shale containing marine fossils. BEARPAW SHALE--Dark-greenish-gray shale containing thin gray sandstone partings.
Lithology: sandstone; shale
Frontier Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area
FRONTIER FORMATION in thrust belt--White to brown sandstone and dark-gray shale; oyster coquina in upper part; coal and lignite in lower part; in north and south Wyoming--Gray sandstone and sandy shale.
Lithology: sandstone; shale; coal
Cody Shale (Phanerozoic | Mesozoic | Cretaceous-Late (78-83 Ma)) at surface, covers 2 % of this area
CODY SHALE (AGE 78 TO 83 Ma) northern Yellowstone area--Gray to brown shale and siltstone; north and south Wyoming--Dull-gray shale, gray siltstone, and fine-grained gray sandstone.
Lithology: shale; siltstone; sandstone
Sundance and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers 0.4 % of this area
SUNDANCE (Js) AND GYPSUM SPRING FORMATIONS. SUNDANCE FORMATION--Greenish-gray glauconitic sandstone and shale, underlain by red and gray nonglauconitic sandstone and shale. GYPSUM SPRING FORMATION--Interbedded red shale, dolomite, and gypsum. In north Wyoming wedges out south in T. 39 N.
Lithology: sandstone; shale; dolostone (dolomite); evaporite
Gallatin Limestone, Gros Ventre Formation and equivalents, and Flathead Sandstone (N) or Cambrian Rocks (S) (Phanerozoic | Paleozoic | Cambrian-Middle Cambrian-Furongian) at surface, covers 1 % of this area
GALLATIN LIMESTONE, GROS VENTRE FORMATION and equivalents, and FLATHEAD SANDSTONE (north Wyoming). GALLATIN LIMESTONE--Blue-gray and yellow mottled hard dense limestone. GROS VENTRE FORMATION--Soft green micaceous shale (Upper and Middle Cambrian Park Shale Member), underlain by blue-gray and yellow mottled hard dense limestone (Middle Cambrian Death Canyon Limestone Member), and soft green micaceous shale (Middle Cambrian Wolsey Shale Member). FLATHEAD SANDSTONE--Dull-red quartzitic sandstone. CAMBRIAN ROCKS (south Wyoming). South flank of Granite Mountains--Blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at base. On and south of Rawlins uplift--Glauconitic quartzitic sandstone.
Lithology: limestone; sandstone; shale
Wasatch formation (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.2 % of this area
Wasatch formation: Light-colored massive sandstone; drab-colored shale and coal in southeastern Montana; and variegated, dominantly red beds of clay and sandstone in north-central Montana.
Lithology: sandstone; shale; coal; claystone
Triassic, undifferentiated (Phanerozoic | Mesozoic | Triassic) at surface, covers < 0.1 % of this area
Triassic, undifferentiated: conglomerate, sandstone, shale, and impure limestone belonging to the Dinwoody and Thaynes formations and other units of Triassic age, and the Chugwater of Triassic and Permian age.
Lithology: fine-grained mixed clastic; limestone; medium-grained mixed clastic
Pennsylvanian, undifferentiated (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian) at surface, covers < 0.1 % of this area
Pennsylvanian, undifferentiated: in western Montana is mainly the Quadrant quartzite but includes limestone and other rocks of Pennsylvanian age so far as present data permit. Farther east other formations of Pennsylvanian or possible Pennsylvanian age are included.
Lithology: sandstone; mudstone; carbonate; conglomerate; chert
Thermopolis shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area
Thermopolis shale: dark-gray shale with some sandstone. The subsurface consists of Muddy sandstone member or Newcastle sandstone member at top, Skull Creek shale member in middle, and Fall River sandstone or First Cat Creek sand of drillers at base.
Lithology: mudstone; sandstone; bentonite
Kootenai formation and associated rocks (Phanerozoic | Mesozoic | Jurassic Cretaceous-Early) at surface, covers < 0.1 % of this area
Kootenai formation and associated rocks: conglomerate, sandstone, shale, and mudstone; purplish and green beds are common; mainly the Kootenai; in southern Montana includes strata that have been mapped as Cloverly formation. Includes Second Cat Creek and Third Cat Creek sands of drillers in central part of State; Sunburst sand of drillers in north-central part; and Cut Bank sand of drillers in western part. As here mapped, may locally include thin units of Jurassic age.
Lithology: medium-grained mixed clastic; mudstone; limestone
Jurassic, undifferentiated (Phanerozoic | Mesozoic | Jurassic) at surface, covers < 0.1 % of this area
Jurassic, undifferentiated: calcareous shale and sandstone; includes the Morrison formation, the Ellis group, Sundance formation, and other rocks of Jurassic age.
Lithology: fine-grained mixed clastic; limestone; evaporite
Cambrian, undifferentiated (Phanerozoic | Paleozoic | Cambrian) at surface, covers < 0.1 % of this area
Cambrian, undifferentiated: comprises Deadwood formation, in south-central Montana, and Red Lion formation, Dry Creek shale, Hasmark formation, Pilgrim limestone, Silver Hill formation, Park shale, Meagher limestone, Wolsey shale, Flathead quartzite, and other units. In a few places quartzite of Cambrian age may be mapped with the Belt series or quartzite of Belt age with the Cambrian rocks.
Lithology: carbonate; mudstone; sandstone; conglomerate

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