Geologic units in Grant county, Minnesota

Volcaniclastic rocks of felsic to intermediate composition (Neoarchean) at surface, covers 39 % of this area

Volcaniclastic rocks of felsic to intermediate composition.

Schist and tonalitic to granodioritic paragneiss (Neoarchean) at surface, covers 24 % of this area

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

Schist of sedimentary protolith (Neoarchean) at surface, covers 16 % of this area

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

Undifferentiated (Cenomanian to Campanian) at surface, covers 9 % 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.

Foliated to gneissic tonalite, granodiorite, and diorite (Neoarchean) at surface, covers 7 % 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.

Mafic metavolcanic rocks (Neoarchean) at surface, covers 2 % 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).

Granite to granodiorite (Neoarchean) at surface, covers 2 % of this area

Granite to granodiorite. Variably magnetic.

Dioritic to granodioritic intrusion of uncertain age (Archean or Paleoproterozoic) at surface, covers 1 % of this area

Dioritic to granodioritic intrusion of uncertain age. Moderate gravity and magnetic expression.

Magnetic intrusions, undifferentiated (Archean) at surface, covers 0.5 % of this area

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

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.