Geologic units in North Dakota (state in United States)

Additional scientific data in this geographic area

Pierre Formation (Upper Cretaceous) at surface, covers 24 % of this area

Dark-gray shale; marine offshore sediment; as thick as 700 metres (2,300 feet).

Sentinel Butte Formation (Paleocene) at surface, covers 22 % of this area

Grayish-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 200 metres (600 feet).

Bullion Creek Formation (Paleocene) at surface, covers 12 % of this area

Yellowish-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 200 metres (600 feet).

Fox Hills Formation (Upper Cretaceous) at surface, covers 11 % of this area

Olive-brown sand, shale, and sandstone; marine shoreline and off-shore sediment; as thick as 120 metres (400 feet).

Cannonball Formation (Paleocene) at surface, covers 8 % of this area

Olive-brown sand, shale, and sandstone; marine shoreline and offshore sediment; as thick as 120 metres (400 feet).

Hell Creek Formation (Upper Cretaceous) at surface, covers 5 % of this area

Gray sand, silt, clay, and sandstone; river sediment; as thick as 150 metres (500 feet).

Carlile Formation (Upper Cretaceous) at surface, covers 3 % of this area

Dark-gray shale; marine offshore sediment; as thick as 120 metres (400 feet).

Niobrara Formation (Upper Cretaceous) at surface, covers 2 % of this area

Light-brown to dark-gray calcareous shale; marine offshore sediment; as thick as 75 metres (250 feet).

Belle Fourche-Skull Creek, Undivided (Lower to Upper Cretaceous) at surface, covers 2 % of this area

Belle Fourche Formation (as described in Kb). Mowry Formation: medium- to dark-gray shale; marine offshore sediment; as thick as 55 metres (180 feet). Newcastle Formation: light-gray, fine- to medium-grained sandstone; marine shoreline and offshore sediment; as thick as 45 metres (150 feet). Skull Creek Formation: medium-gray to dark-gray shale; marine offshore sediment; as thick as 40 metres (140 feet).

Greenhorn Formation (Upper Cretaceous) at surface, covers 2 % of this area

Dark-gray calcareous shale; marine offshore sediment; as thick as 45 metres (150 feet).

Mowry-Skull Creek, Undivided (Lower to Upper Cretaceous) at surface, covers 1 % of this area

Mowry, Newcastle, and Skull Creek Formations (as described in Kbs).

Belle Fourche Formation (Upper Cretaceous) at surface, covers 1 % of this area

Medium- to dark-gray, silty to sandy shale; marine offshore sediment; as thick as 105 metres (350 feet).

Slope Formation (Paleocene) at surface, covers 1 % of this area

Grayish-brown and yellowish-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 100 metres (300 feet).

Inyan Kara (Lower Cretaceous) at surface, covers 1 % of this area

Light-gray, fine to coarse sandstone and gray shale; river, lake, and nearshore marine sediment; as thick as 135 metres (450 feet).

Precambrian Rocks (Precambrian) at surface, covers 0.9 % of this area

Greenschists and amphibolites; banded iron formation; stretched pebble conglomerates; metabasalt; serpentinite; felsic tuff; mylonite; intermediate felsic plutonic rocks; migmatite; layered gneiss.

Undifferentiated Jurassic Sediments (Jurassic) at surface, covers 0.8 % of this area

Dark-gray, greenish, and varicolored shale with local limestone (Swift and Rierdon Formation equivalents); mainly nearshore marine sediments; as thick as 180 metres (600 feet).

Golden Valley Formation (Eocene and Paleocene) at surface, covers 0.7 % of this area

Upper member: yellowish-brown micaceous sandstone, sand, silt, and clay; fluvial sediment; as thick as 60 metres (200 feet). Lower member: white or yellow clay, silt, and sand; a weathering zone developed on underlying unit; as thick as 20 metres (65 feet).

Ludlow Formation (Paleocene) at surface, covers 0.5 % of this area

Grayish-brown and yellowish-brown silt, sand, clay, sandstone, and lignite; river, lake, and swamp sediment; as thick as 100 metres (300 feet).

Red River Formation (Ordovician) at surface, covers 0.2 % of this area

Yellowish- to brownish-gray limestone and dolomite; offshore marine sediment; as thick as 215 metres (700 feet).

Winnipeg Group (Ordovician) at surface, covers 0.1 % of this area

Light-gray to greenish-gray shale and light-gray sandstone; marine nearshore and offshore sediment; as thick as 125 metres (400 feet).

White River Group (Oligocene) at surface, covers < 0.1 % of this area

Brule Formation: pinkish siltstone, clay and sand; river and lake sediment; as thick as 50 metres (150 feet). Chadron Formation: light-colored sand with quartzite and porphyry pebbles, overlain by dark clay; river and lake sediment; as thick as 30 metres (100 feet).

Piper Formation Equivalent (Jurassic) at surface, covers < 0.1 % of this area

White to buff, brown, or gray limestone, gypsum, and anhydrite; offshore marine sediments; as thick as 190 metres (625 feet).

Upper Ordovician (Upper Ordovician) at surface, covers < 0.1 % of this area

Limestone, shaley limestone, and dolostone; includes the Maquoketa Formation, and the Stewartville, Prosser, and Cummingsville Formations of the Galena Group. Also includes limestone and dolostone of the Red River Formation, and sandstone and shale of the Winnipeg Formation in northwest Minnesota.

Upper and Middle Tertiary Rock, Undivided (Oligocene, Miocene, or Pliocene) at surface, covers < 0.1 % of this area

Butte caprock consisting of fluvial or lacustrine sandstone or limestone of Oligocene, Miocene, or Pliocene age; may include the White River Group in some areas or the Killdeer Formation (informal unit) on the Killdeer Mountains; as thick as 120 metres (400 feet).

Pierre Shale (Upper Cretaceous) 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, and light-brown chalky shale. Contains minor sandstone, conglomerate, and abundant carbonate and ferruginous concretions. Thickness up to 1,000 ft (305 m).

Ludlow Formation (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).

Mafic metavolcanic rocks (Neoarchean) at surface, covers < 0.1 % of this area

Mafic metavolcanic rocks. Includes minor volcaniclastic and hypabyssal intrusive rocks metamorphosed to lower greenschist to lower amphibolite facies; includes the Ely Greenstone (~2,722 Ma).

Hell Creek Formation (Late Cretaceous) at surface, covers < 0.1 % 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).

Undifferentiated (Cenomanian to Campanian) at surface, covers < 0.1 % of this area

Conglomerate, sandstone, mudstone, shale, marlstone, siltstone, and minor lignite, deposited in marine and non-marine settings; likely Cenomanian to Campanian age. Unit outline is the product of contouring the stratigraphic top and base, from which an isopach grid was created. Because the distribution is patchy, unit boundaries were drawn from the gridded data to represent locations where more than 25 feet (8 meters) of thickness occurs. As a result, many areas outside of the unit boundaries may be overlain by thin Cretaceous strata and the unit is depicted without a contact line.

Tongue River Formation (Paleocene) at surface, covers < 0.1 % of this area

White, gray, and tan, massive, cross-bedded sandstone with interbedded gray, brown, and green claystone, bentonitic claystone, clayely siltstone, carbonate concretions, and lignite. Thickness up to 285 ft (87 m).

Cannonball Formation (Paleocene) at surface, covers < 0.1 % of this area

Gray and tan siltstone, sandy to silty claystone, and fine-grained, calcareous clayely to silty sandstone, and abundant, round to lenticular carbonate concretions. Thickness up to 180 ft (55 m).

Granitic intrusion (Neoarchean) at surface, covers < 0.1 % of this area

Granitic intrusion. Includes the Sacred Heart (~2592, 2,603 Ma) and Ortonville granites, the Shannon Lake Granite (~2,674), and other intrusions having low gravity and magnetic signatures.

Granitoid intrusion (Neoarchean) at surface, covers < 0.1 % of this area

Granitoid intrusion. Constrained solely by low gravity and magnetic signatures.

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

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

Tongue River Member of Fort Union Formation (Tertiary) at surface, covers < 0.1 % of this area

Yellowish orange sandstone, sandy and silty carbonaceous shale, and coal. Alluvial plain. Thickness as much as 300 m (984 ft).

Gabbro, peridotite, pyroxenite, lamprophyre, and metamorphic equivalents (Neoarchean) at surface, covers < 0.1 % of this area

Gabbro, peridotite, pyroxenite, lamprophyre, and metamorphic equivalents. Includes the Oaks intrusion (~2,671 Ma) in the Wabigoon subprovince, and a ~2,639 Ma lamprophyre in the western Wawa subprovince; locally defined by variably high gravity and magnetic signatures.

Granodiorite to hornblende diorite, locally magmatically foliated (Neoarchean) at surface, covers < 0.1 % of this area

Granodiorite to hornblende diorite, locally magmatically foliated. Includes the Britt Granodiorite (~2,685 Ma) and other intrusions having moderate gravity and magnetic signatures.

Sentinel Butte Member of Fort Union Formation (Tertiary) at surface, covers < 0.1 % of this area

Dark gray shale with interbedded lignite and gray sandstone. Nonmarine. Thickness 200 m (656 ft).

Granite to granodiorite (Neoarchean) at surface, covers < 0.1 % of this area

Granite to granodiorite. Variably magnetic.

Niobrara Formation (Upper Cretaceous) at surface, covers < 0.1 % 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 up to 150 ft (46 m).

Fox Hills Sandstone (Upper Cretaceous) at surface, covers < 0.1 % of this area

Bluish-green to green, white to dark-gray, and yellow to tan, carbonaceous and iron-stained, cross-bedded, very fine- to coarse-grained, glauconitic sandstone and siltstone. Interbedded with gray and green to brown shale and siltyshale. Thickness up to 200 ft (61 m).

Terrace Deposits (Quaternary) at surface, covers < 0.1 % 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).

Hallock Red Beds (Jurassic) at surface, covers < 0.1 % of this area

Shale, limestone, dolomite, siltstone, and sandstone.

Volcaniclastic rocks of felsic to intermediate composition (Neoarchean) at surface, covers < 0.1 % of this area

Volcaniclastic rocks of felsic to intermediate composition.

Biotite schist of graywacke protolith, and schist-rich migmatite (Neoarchean) at surface, covers < 0.1 % of this area

Biotite schist of graywacke protolith, and schist-rich migmatite.

Foliated to gneissic tonalite, granodiorite, and diorite (Neoarchean) at surface, covers < 0.1 % of this area

Foliated to gneissic tonalite, granodiorite, and diorite. Includes the Lookout Mountain tonalite (~2,718 Ma) of the Giants Range batholith and other intrusions within batholithic complexes defined by a low-to-moderate gravity signature with magnetic foliation apparent from aeromagnetic maps.

Schist of sedimentary protolith (Neoarchean) at surface, covers < 0.1 % of this area

Schist of sedimentary protolith. Metamorphosed to upper greenschist to amphibolite facies.

Carlile Shale (Upper Cretaceous) at surface, covers < 0.1 % of this area

Dark-gray to black, silty to sandy shale with several zones of septarian, fossiliferous, carbonate concretions. Contains up to three sandstone units in the upper portion of the formation and sandy calcareous marl at the base. Thickness up to 330 ft (100 m).

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

Gravel, sand, silt, and clay deposits of stream and river channels, and floodplains.

Ludlow Member of Fort Union Formation (Tertiary) at surface, covers < 0.1 % of this area

Gray and brown shale, siltstone, silty or bentonitic claystone, sandstone, and coal. Alluvial plain with marine-influenced tongues. Thickness as much as 230 m (755 ft).