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

Geologic units in Crook county, Wyoming

Cloverly and Morrison Formations (N,S) or Cloverly Formation, Inyan Kara Group, and Morrison Formation (Phanerozoic | Mesozoic | Jurassic-Late Cretaceous-Early) at surface, covers 22 % 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

Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Blue-gray to dark-gray, fissile to blocky shale with persistent beds of bentonite, black organic shale, or light-brown chalky shale. Contains minor sandstone, conglomerate, and abundant carbonate and ferruginous concretions. Thickness 1,000-2,700 ft (305-823 m).

Lithology: shale; clay or mud; sandstone; conglomerate

Granitic rocks (Archean) at surface, covers < 0.1 % of this area

GRANITIC ROCKS OF 2,600-Ma AGE GROUP. Teton Range--Mount Owen Quartz Monzonite. Age 2,500+/- Ma; may be of Early Proterozoic age. Gros Ventre and Washakie Ranges--Granitic rocks. Yellowstone National Park, Owl Creek, Granite, and Seminoe Mountains, Rawlins uplift, and Medicine Bow Mountains--Granite. Wind River Range--Granodiorite to porphyritic and equigranular granite. Sierra Madre--Granite and granodiorite. Laramie Mountains--Granite, amphibolite, and minor amounts of metasedimentary rocks. Hartville uplift--Granite and quartz monzonite. Black Hills uplift--Granite and minor amounts of metasedimentary rocks.

Lithology: granitoid

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 0.2 % 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

Upper Miocene Rocks (Phanerozoic | Cenozoic | Tertiary | Miocene-Late) at surface, covers 0.4 % of this area

UPPER MIOCENE ROCKS--Southwest Wyoming: South end of Wind River Range--Siliceous, arkosic, and locally radioactive sandstone, claystone, and conglomerate. Fission-track age about 27 Ma. Recent work suggests that part of these deposits may be of Eocene age. Pliocene and Miocene (as originally defined 2) South Pass Formation. Saratoga Valley--White to greenish-gray tuffaceous sandstone, siltstone, and claystone; locally conglomeratic. North Park Formation; Central Wyoming: Arkosic sandstone, conglomerate, and siltstone; some light-colored tuffaceous radioactive claystone and white cherty limestone. North of Sweetwater River in Granite Mountains--Light-colored tuffaceous radioactive claystone, siltstone, sandstone, and arkose. Moonstone Formation; East Wyoming: Light-colored tuffaceous claystone, sandstone, and conglomerate. Ogallala Formation in Denver Basin.

Lithology: sandstone; claystone; conglomerate; siltstone; limestone

Minnekahta Limestone and Opeche Shale (Phanerozoic | Paleozoic | Permian) at surface, covers < 0.1 % of this area

Minnekahta Limestone-Purple to gray, finely crystalline, thin- to medium-bedded limestone with varying amounts of red shale. Thickness 30-50 ft (9-15 m). Opeche Shale- Red siltstone, argillaceous sandstone and shale interbedded with caliche layers. Thickness 85-130 ft (26-40 m).

Lithology: siltstone; sandstone; shale; limestone

Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 6 % of this area

PIERRE SHALE (AGE 72 TO 78 Ma)--Dark-gray concretionary marine shale; contains several bentonite beds.

Lithology: shale; mixed clastic/volcanic

Lower Miocene and Upper Oligocene rocks, or Rocks equivalent to Upper and Lower Miocene AND White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene-Late Miocene-Early(?) Miocene-Middle(?) Miocene-Late) at surface, covers 0.2 % of this area

LOWER MIOCENE AND UPPER OLIGOCENE ROCKS--Light-colored soft porous sandstone and underlying white tuffaceous claystone and siltstone. Arikaree Formation in Denver Basin; ROCKS EQUIVALENT TO UPPER AND LOWER MIOCENE ROCKS AND WHITE RIVER FORMATION--Light-colored sandstone, white tuffaceous blocky claystone, and siltstone. Black Hills.

Lithology: fine-grained mixed clastic; mixed clastic/volcanic

Greenhorn Formation and Belle Fourche and Mowry Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 11 % of this area

GREENHORN FORMATION AND BELLE FOURCHE AND MOWRY (Kmr) SHALE. GREENHORN FORMATION--Light-colored limestone, marl, and limy sandstone interbedded with gray concretionary shale. BELLE FOURCHE SHALE--Black soft bentonitic concretionary shale. MOWRY SHALE (AGE 94 TO 98 Ma)--Silvery-gray hard siliceous shale containing abundant fish scales and bentonite beds.

Lithology: mixed clastic/carbonate; fine-grained mixed clastic; mixed clastic/volcanic

Pierre shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Pierre shale: dark-gray clay shale with calcareous and ferruginous concretions and sandy members.

Lithology: shale; sandstone; bentonite

Intrusive and extrusive igneous rocks (Phanerozoic | Cenozoic | Tertiary | Eocene) at surface, covers 0.9 % of this area

INTRUSIVE AND EXTRUSIVE IGNEOUS ROCKS (CHIEFLY EOCENE; AGE OF INTRUSIVES ABOUT 53 TO 55 Ma)--Incorporates masses of Mississippian through Cambrian formations. Confined to Black Hills.

Lithology: plutonic rock (phaneritic); volcanic rock (aphanitic)

Pahasapa and Englewood Limestones (Phanerozoic | Paleozoic | Devonian-Late Carboniferous Mississippian-Early) at surface, covers 0.4 % of this area

PAHASAPA AND ENGLEWOOD LIMESTONES. PAHASAPA LIMESTONE--Gray massive dolomitic limestone. ENGLEWOOD LIMESTONE--Pink slabby dolomitic limestone.

Lithology: limestone

Minnekahta Limestone and Opeche Shale (Phanerozoic | Paleozoic | Permian) at surface, covers 3 % of this area

MINNEKAHTA LIMESTONE AND OPECHE SHALE. MINNEKAHTA LIMESTONE--Gray slabby hard limestone. Locally is a member of the Goose Egg Formation. OPECHE SHALE--Red soft sandy shale. Locally is a member of the Goose Egg Formation.

Lithology: limestone; shale

Madison Group (Phanerozoic | Paleozoic | Devonian Carboniferous Mississippian) at surface, covers < 0.1 % of this area

Includes: Pahasapa Limestone (Mississippian)-White, light-gray to tan, fine- to medium-crystalline limestone and dolomite containing brown to gray chert. Solution features including collapse breccia, sinkholes, and caves are prevalent. Thickness 300-630 ft (91-192 m). Englewood Formation (Mississippian to Dovonian)- Pink, lavender to light-gray, thin- to medium-bedded, finely crystalline, argillaceous, dolomitic limestone. Thickness 30-63 ft (9-19 m).

Lithology: limestone; dolostone (dolomite); chert

Niobrara formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Niobrara formation: chiefly calcareous shale with limestone concretions; many thin bentonite beds locally.

Lithology: shale; bentonite

Madison Limestone, Darby Formation, Bighorn Dolomite, Gallatin Limestone, Gros Ventre Formation, and Flathead Sandstone (N), Madison Limestone and Cambrian rocks (S), Minnekahta Limestone, Opeche Shale, Minnelusa Formation, Pahasapa and Englewood Limestones, Whitewood Dolomite, Winnipeg and Deadwood Formations (NE), or Paleozoic, undifferentiated (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous(?) Permian) at surface, covers 0.2 % of this area

MADISON LIMESTONE, DARBY FORMATION, BIGHORN DOLOMITE, GALLATIN LIMESTONE, GROS VENTRE FORMATION, AND FLATHEAD SANDSTONE (north Wyoming). MADISON LIMESTONE OR 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. 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. MADISON LIMESTONE AND CAMBRIAN ROCKS (south Wyoming). MADISON LIMESTONE--Includes Mission Canyon Limestone (blue-gray massive limestone and dolomite), underlain by Lodgepole Limestone (gray cherty limestone and dolomite). CAMBRIAN ROCKS--On south flank of Granite Mountains, blue-gray and yellow mottled hard dense limestone interbedded with soft green micaceous shale; dull-red quartzitic sandstone at bae. On and south of Rawlins uplift, glauconitic quartzitic sandstone. MINNEKAHTA LIMESTONE, OPECHE SHALE, MINNELUSA FORMATION, PAHASAPA AND ENGLEWOOD LIMESTONES, WHITEWOOD DOLOMITE, AND WINNIPEG AND DEADWOOD FORMATIONS--Various combinations (northeast Wyoming). MINNEKAHTA LIMESTONE--Gray slabby hard limestone. Locally is a member of the Goose Egg Formation. OPECHE SHALE--Red soft sandy shale. Locally is a member of the Goose Egg Formation. MINNELUSA FORMATION--Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum. PAHASAPA LIMESTONE--Gray massive dolomititc limestone. ENGLEWOOD LIMESTONE--Pink slabby dolomitic limestone. WHITEWOOD DOLOMITE--Buff massive fossiliferous dolomite. WINNIPEG FORMATION--Pink to yellow siltstone and shale. DEADWOOD FORMATION--Red and brown quartzitic sandstone. PALEOZOIC ROCKS, undifferentiated (Thrust Belt).

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

Sundance and Gypsum Spring Formations (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers 12 % 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

White River Formation (Phanerozoic | Cenozoic | Tertiary | Oligocene (31-35 Ma)) at surface, covers 0.2 % 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

Lance Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 6 % 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

Metabasalt (Archean(?) Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Dark-green amphibolite and amphibolite schist. Thickness of individual flows 50-200 ft (15-61 m).

Lithology: amphibolite; schist

Newcastle Sandstone and Skull Creek Shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers 9 % of this area

NEWCASTLE SANDSTONE AND SKULL CREEK SHALE. NEWCASTLE SANDSTONE--Gray sandstone and sandy shale containing some bentonite and coal. SKULL CREEK SHALE--Black soft fissile shale.

Lithology: sandstone; shale; bentonite; coal

Belle Fourche shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Belle Fourche shale: dark blue-gray siliceous shale with many calcareous and ferruginous concretions and intercalated thin layers of bentonite.

Lithology: shale; bentonite; sandstone

Metagraywacke (Archean(?) Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Gray, siliceous mica schist and impure quartzite. Thickness undetermined.

Lithology: schist; quartzite

Whitewood Limestone, Winnipeg Formation, and Deadwood Formation (Phanerozoic | Paleozoic | Cambrian Ordovician) at surface, covers < 0.1 % of this area

Whitewood Limestone (Ordovician)- Mottled, tan, gray to lavender, fine- to medium-crystalline, sparsely fossiliferous limestone and dolomite. Thickness up to 70 ft (21 m). Winnipeg Formation (Ordovician)- Grat and light-green, fissile shale, and tan, calcareous siltstone, sandy shale, and limestone lenses. Thickness up to 110 ft (34 m). Deadwood Formation (Ordovician to Cambrian)- Variegated, yellow to red, brown, gray, and green, glauconitic, conglomerate, sandstone, shale, dolomitic limestone, and dolomite. Thickness 4-400 ft (1-122 m).

Lithology: conglomerate; shale; limestone; dolostone (dolomite); siltstone

Alluvium and Colluvium (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 8 % of this area

ALLUVIUM AND COLLUVIUM--Clay, silt, sand, and gravel in flood plains, fans, terraces, and slopes.

Lithology: alluvium; colluvium

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.7 % of this area

FOX HILLS SANDSTONE--Light-colored sandstone and gray sandy shale containing marine fossils.

Lithology: sandstone; shale

Spearfish Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic-Early(?) Triassic-Middle(?) Triassic-Late) at surface, covers 6 % of this area

SPEARFISH FORMATION--Red shale, red siltstone, and white gypsum beds; gypsum beds especially abundant near base.

Lithology: mudstone; evaporite

Trachytic Intrusive Rocks (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers < 0.1 % of this area

Tan to reddish-brown, iron-stained stocks, laccoliths, sills, and dikes of trachyte, quartz trachyte, and alkalic rhyolite. Contains phenocrysts of sanidine, orrthoclase, anorthoclase, aegirine-augite and biotite in a finely crystalline orthoclase-quartz biotite groundmass.

Lithology: trachyte; trachyte; rhyolite

Mowry shale (Phanerozoic | Mesozoic | Cretaceous-Early) at surface, covers < 0.1 % of this area

Mowry shale: chiefly light-gray silicified shale and claystone with minor amounts of sandy shale and sandstone; contains some thick beds of bentonite.

Lithology: fine-grained mixed clastic; bentonite

Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Alluvium: mainly valley fill consisting of silt, sand, and gravel; includes some terrace deposits and glacial drift of Pleistocene age in some areas; locally includes hot spring tufa. The older part of the alluvium, where present, is probably of Pliocene age.

Lithology: alluvium; glacial drift; carbonate

Metasedimentary and metavolcanic rocks (Proterozoic | Paleoproterozoic ) at surface, covers < 0.1 % of this area

METASEDIMENTARY AND METAVOLCANIC ROCKS. Sierra Madre--Granite gneiss, felsic gneiss, amphibolite, and metavolcanic rocks. Medicine Bow Mountains--Granite gneiss, felsic gneiss, amphibolite, and hornblende gneiss. Laramie Mountains--Pelitic schist, marble, granite gneiss, layered amphibolite, and felsic gneiss. Black Hills--Pelitic schist; includes minor amounts of granite and amphibolite.

Lithology: metasedimentary rock; metavolcanic rock

Landslide deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.6 % of this area

LANDSLIDE DEPOSITS--Locally includes intermixed landslide and glacial deposits, talus, and rock-glacier deposits.

Lithology: landslide; glacial drift

Gravel, pediment, and fan deposits (Phanerozoic | Cenozoic | Quaternary | Pleistocene Holocene) at surface, covers 0.6 % 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

Niobrara Formation and Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 3 % of this area

NIOBRARA FORMATION (Kn) AND CARLILE SHALE (Kcl). NIOBRARA FORMATION (AGE ABOUT 83 Ma)--Light-colored limestone and gray to yellow speckled limy shale. CARLILE SHALE--Dark-gray sandy shale; Sage Breaks Member at top; Turner Sandy Member in middle.

Lithology: shale; fine-grained mixed clastic; limestone

Minnelusa Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Early Pennsylvanian-Middle(?) Pennsylvanian-Late(?) Permian) at surface, covers 5 % of this area

MINNELUSA FORMATION--Buff and red limy sandstone; some thin limestone beds, solution breccias, and gypsum.

Lithology: sandstone; limestone; evaporite

Fort Union Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers 4 % of this area

FORT UNION FORMATION Tullock Member--Soft gray sandstone, gray and brown carbonaceous shale, and thin coal beds.

Lithology: sandstone; shale; coal

Greenhorn formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Greenhorn formation: mainly light-gray marl and calcareous shale.

Lithology: mudstone; limestone; bentonite

Carlile shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers < 0.1 % of this area

Carlile shale: dark-gray shale with calcareous and ferruginous concretions; middle part commonly sandy

Lithology: shale

Minnelusa Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers < 0.1 % of this area

Variegated, yellow to red, gray to brown, pink to purple, and black, interbedded sandstone, siltstone, shale, limestone, dolomite, calcarenite, chert and brecciated beds. Thickness 394-1,175 ft (120-358 m).

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