Geologic units in Traill county, North Dakota

Additional scientific data in this geographic area

Belle Fourche Formation (Upper Cretaceous) at surface, covers 42 % 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 27 % of this area

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

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).

Precambrian Rocks (Precambrian) at surface, covers 7 % of this area

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

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

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

Belle Fourche-Skull Creek, Undivided (Lower to Upper Cretaceous) at surface, covers 0.4 % 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).

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.

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).

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.

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

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

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

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

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.

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.