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Mineral Resources > Online Spatial Data > Geology > by state > South Dakota Geology

Geologic units in Meade county, South Dakota

[Additional scientific data in this geographic area]

Pahasapa Limestone, Englewood Formation, Whitewood Limestone, Winnipeg Formation, and Deadwood Formation (Phanerozoic | Paleozoic | Cambrian Ordovician(?) Silurian(?) Devonian(?) Carboniferous Mississippian) at surface, covers 0.4 % of this area

Note: see individual descriptions

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

Whitewood Limestone, Winnipeg Formation, and Deadwood Formation (Phanerozoic | Paleozoic | Cambrian Ordovician) at surface, covers 0.2 % 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

Belle Fourche Shale, Mowry Shale, Newcastle Sandstone,and Skull Creek Shale (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers < 0.1 % of this area

Note: see individual unit descriptions

Lithology: shale; siltstone; claystone; sandstone; limestone; clay or mud

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

White River Group (Phanerozoic | Cenozoic | Tertiary | Eocene Oligocene) at surface, covers 0.4 % of this area

Includes: Brule Formation (Oligocene)- White, pink, light-green, and light-brown, massive to thin-bedded, bentonitic claystone, tuffaceous siltstone, and well-bedded, calcareous, tuffaceous quartz sandstone. Thickness up to 150 ft (46 m). Chadron Formation (Eocene)- Upper beds are gray, light-brown to maroon bentonite, claystone, siltstone tuffaceous fine-grained sandstone, and local, silicified carbonate lenses. Basal portion consists of poorly cemented, white, coarse-grained arkose and conglomerate. Thickness up to 160 ft (49 m). Chamberlain Pass Formation (Eocene)- Pale olive to pale red, mottled mudstone containing white, cross-bedded channel sandstone with basal conglomerate. Thickness up to 32 ft (10 m). Slim Buttes Formation (Eocene)- White, grayish- to yellowish-orange,pale-red to pink siltstone, clayey siltstone, bentonitic claystone,medium- to fine-grained sandstone, and conglomerate. Thickness up to 48 ft (15 m).

Lithology: claystone; siltstone; clay or mud; sandstone; mudstone; conglomerate

Carlile Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 1 % of this area

Dark-gray to black, silty to sandy shale with several zones of septarian, fossiliferous, carbonate concertions. Contains up to three sandstone beds near the middle of the formation and sandy calcareous marl at the base. Thickness 345-620 ft (105-189 m).

Lithology: shale; sandstone; limestone

Alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 11 % of this area

Clay to boulder-size clasts with locally abundant organic material. Thickness up to 75 ft (23m).

Lithology: clay or mud; silt; sand; gravel

Minnelusa Formation (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian Permian) at surface, covers 0.6 % 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

Metaconglomerate and Metaquartzite (Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Light-gray to gray, conglomeratic and feldspathic schist, biotite schist, taconite, and phyllite. Individual conglomerate and fanglomerate tongues from 100-500 ft (30-152 m) thick. Total thickness over 10,000 ft (3,048 m).

Lithology: schist; iron formation; phyllite

Belle Fourche Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.9 % of this area

Dark-gray to black bentonitic shale containing minor limestone lenses, bentonite layers, fossiliferous calcarenite, and large, ferruginous, carbonate concretions. Thickness 150-350 ft (46-107 m).

Lithology: shale; limestone; clay or mud

Ludlow Formation (Phanerozoic | Cenozoic | Tertiary | Paleocene ) at surface, covers < 0.1 % of this area

White, tan, yellow, and gray, cross-bedded, fine- to medium-grained,silty sandstone interbedded with locally bentonitic, gray siltstone, claystone, and sandy to silty claystone. Characterized by uranium-bearing lignite beds and "clinker" beds fromed by burning coalseams. Thickness up to 420 ft (128 m).

Lithology: sandstone; siltstone; claystone

Inyan Kara Group (Phanerozoic | Mesozoic | Cretaceous-Early ) at surface, covers 1 % of this area

Includes: Fall River Formation- Variegated brown, red, gray to purple, calcareous, well-sorted, fine-grained sandstone, siltstone, and shale containing mica flakes. Thickness 100-200 ft (30-61 m). Lakota Formation- Yellow, brown, red-brown, gray to black silty shale, pebble conglomerate, and massive to thin-bedded, cross-bedded sandstone. Locally interbedded with fresh-water limestone and bituminous coal beds. Thickness 35-500 ft (11-152 m).

Lithology: shale; sandstone; conglomerate; siltstone; limestone; coal

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

Landslide, slump, and collapsed material composed of chaotically mixed boulders and finer grained rock debris. Thickness up to 180 ft (55m).

Lithology: sand; gravel

Terrace Deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 16 % of this area

Clay to boulder-size clasts deposited as pediments, paleochannels, and terrace fills of former flood plains. Thickness up to 75 ft (23m).

Lithology: clay or mud; silt; sand; gravel

Older Metasedimentary Rocks (Archean ) at surface, covers < 0.1 % of this area

Gray phyillite, mica schist, and biotite-plagioclase schist. Total thickness unknown; approximately 500 ft (152 m) exposed.

Lithology: phyllite; schist

Minnekahta Limestone and Opeche Shale (Phanerozoic | Paleozoic | Permian) at surface, covers 0.3 % 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

Greenhorn Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.4 % of this area

Gray shale, mudstone, marl, calcarenite, and shaley limestone grading upward into light-gray to tan, alternating marl and thin-bedded, fossiliferous limestone. Thickness 225-315 ft (69-96 m).

Lithology: shale; mudstone; limestone

Hell Creek Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 9 % of this area

Tan to brown, light- to dark-gray, "somber beds" of shale. Interbedded with brown to red carbonaceous shale, gray and brown bentonitic silty shale, and gray, brown and yellow siltstone, sandstone, and claystone-pebble conglomerate. Thickness 260-600 ft (79-183 m).

Lithology: shale; siltstone; sandstone; conglomerate

Morrison Formation, Unkpapa Sandstone, Sundance Formation, and Gypsum Spring Formation (Phanerozoic | Mesozoic | Jurassic-Middle Jurassic-Late) at surface, covers 0.4 % of this area

Morrison Formation (Late Jurassic)- Light-gray to green and variegatedred, brown, yellow, or lavender, silceous claystone, shale, and siltstone containing interbedded sandstone and fresh-water limestone lenses. Thickness up to 150 ft (46 m). Unkpapa Sandstone (Late Jurassic)- White, massive to thin-bedded, fine-grained, argillaceous sandstone. May be variegated to banded red, yellow, brown, or lavender. Thickness up to 267 ft (81 m). Sundance Formation (Late to Middle Jurassic)- Greenish-gray, yellow, tan, red to orange, and white, variegated, interbedded, fine- to coarse-grained sandstone, siltstone, clay, and limestone. Thickness 250-350 ft (76-107 m). Gypsum Springs Formation (Middle Jusassic)- Massive white gypsum and minor maroon siltstone and shale. Thickness up to 40 ft (12 m).

Lithology: sandstone; siltstone; claystone; clay or mud; shale; limestone; evaporite

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

Light-tan to light-gray stocks and small laccoliths of rhyolite. Contains phenocrysts of oligoclase, quartz, and biotite in a finely crystalline orthoclase or sanidine-quartz groundmass.

Lithology: rhyolite

Pierre Shale (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 33 % 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

Spearfish Formation (Phanerozoic | Paleozoic Mesozoic | Permian Triassic) at surface, covers 0.3 % of this area

Red sandy shale, siltstone, sandstone, and minor limestone. Interbedded with abundant gypsum. Thickness 328-559 ft (100-170 m).

Lithology: shale; siltstone; sandstone; evaporite; limestone

Latitic Intrusive Rocks (Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene) at surface, covers 0.4 % of this area

Dark-gray to greenish-gray laccoliths and sills of latite, latitic andesite, and quartz latite. Contains phenocrysts of andesine, oligoclase, biotite, hornblend, and sphene in a finely crystalline andesine-biotite-quartz groundmass.

Lithology: latite; andesite

Niobrara Formation (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 0.6 % of this area

White to dark gray argillaceous chalk, marl, and shale. Weathers yellow to orange. Contains thin, laterally continuous bentonite beds, chalky carbonaceous shale, minor sand, and small concretions. Thickness 160-225 ft (49-69 m).

Lithology: limestone; limestone; shale; clay or mud; sand

Madison Group (Phanerozoic | Paleozoic | Devonian Carboniferous Mississippian) at surface, covers 0.7 % 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

Greenhorn Formation, Belle Fourche Shale, Mowry Shale, Newcastle Sandstone, Skull Creek Shale, Inyan Kara Group, Morrison Formation, Unkpapa Sandstone, Sundance Formation, Spearfish Formation, Minnekahta Limestone, Opeche Shale, Minnelusa Formation, and Pahasapa Limestone (Phanerozoic | Paleozoic Mesozoic | Carboniferous Mississippian Permian(?) Triassic(?) Jurassic(?) Cretaceous-Early(?) Cretaceous-Middle(?) Cretaceous-Late) at surface, covers < 0.1 % of this area

Note: see individual unit descriptions

Lithology: sandstone; siltstone; shale; claystone; mudstone; limestone; conglomerate

Fox Hills Sandstone (Phanerozoic | Mesozoic | Cretaceous-Late) at surface, covers 22 % of this area

Bluish-green to green, white to dark-gray, yellow to tan, carbonaceous and iron-stained, cross-bedded, very fine- to coarse-grained, glaconitic sandstone and siltstone. Interbedded with gray and green to brown shale and silty shale. Thickness 25-400 ft (8-122 m).

Lithology: sandstone; siltstone; shale

Mowry Shale, Newcastle Sandstone, and Skull Creek Shale (Phanerozoic | Mesozoic | Cretaceous-Early ) at surface, covers 0.6 % of this area

Mowry Shale- Black to gray, siliceous, fissile shale and siltstone containing bentonite layers, and sparse sandstone dikes and sills. Thickness 125-250 ft (38-76 m). Newcastle Sandstone- Gray, light-brown to yellow, discontinuously distributed siltstone, claystone, sandy shale, and fine-grained sandstone. Thickness up to 290 ft (88 m). Skull Creek Shale- Dark-gray to blueish-gray shale containing ferruginous, and carbonate concretions. Thickness 150-275 ft (46-84 m).

Lithology: shale; siltstone; sandstone; claystone

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

Clay to boulder-size clasts forming rubble residuum and talus. Thickness up to 30 ft (9m).

Lithology: clay or mud; silt; sand; gravel