Geologic units in Grand Forks county, North Dakota

Additional scientific data in this geographic area

Inyan Kara (Lower Cretaceous) at surface, covers 18 % 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).

Belle Fourche Formation (Upper Cretaceous) at surface, covers 16 % of this area

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

Mowry-Skull Creek, Undivided (Lower to Upper Cretaceous) at surface, covers 14 % of this area

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

Carlile Formation (Upper Cretaceous) at surface, covers 12 % of this area

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

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

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

Greenhorn Formation (Upper Cretaceous) at surface, covers 9 % of this area

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

Winnipeg Group (Ordovician) at surface, covers 7 % 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).

Niobrara Formation (Upper Cretaceous) at surface, covers 6 % of this area

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

Precambrian Rocks (Precambrian) at surface, covers 4 % of this area

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

Red River Formation (Ordovician) at surface, covers 3 % of this area

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

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.

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.

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.

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

Granite to granodiorite. Variably magnetic.

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).