Geologic units in Roseau county, Minnesota

Foliated to gneissic tonalite, granodiorite, and diorite (Neoarchean) at surface, covers 18 % 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.

Granitic to granodioritic orthogneiss (Neoarchean) at surface, covers 15 % of this area

Granitic to granodioritic orthogneiss. Includes the McGrath Gneiss (~2,752 ± 15, 2,557 Ma) and unnamed units.

Schist of sedimentary protolith (Neoarchean) at surface, covers 15 % of this area

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

Volcaniclastic rocks of felsic to intermediate composition (Neoarchean) at surface, covers 13 % of this area

Volcaniclastic rocks of felsic to intermediate composition.

Undifferentiated (Cenomanian to Campanian) at surface, covers 8 % 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.

Schist and tonalitic to granodioritic paragneiss (Neoarchean) at surface, covers 7 % of this area

Schist and tonalitic to granodioritic paragneiss. Typically adjacent to large batholithic complexes.

Granitic intrusion (Neoarchean) at surface, covers 6 % 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.

Mafic metavolcanic rocks (Neoarchean) at surface, covers 6 % 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).

Granodiorite to hornblende diorite, locally magmatically foliated (Neoarchean) at surface, covers 6 % 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.

Gabbro, peridotite, pyroxenite, lamprophyre, and metamorphic equivalents (Neoarchean) at surface, covers 3 % 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.

Magnetic intrusions, undifferentiated (Archean) at surface, covers 2 % of this area

Magnetic intrusions, undifferentiated. Typically too small to ascertain gravity expression.

Granitoid intrusion (Neoarchean) at surface, covers 1 % of this area

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

Granite to granodiorite (Neoarchean) at surface, covers 0.6 % of this area

Granite to granodiorite. Variably magnetic.