Geologic units in Wright county, Minnesota

Claystone, siltstone, and sandstone (Albian) at surface, covers 28 % of this area

Claystone, siltstone, and sandstone. Albian age is tentatively inferred from a single analysis of pollen.

Upper Cambrian (Upper Cambrian) at surface, covers 19 % of this area

Sandstone, siltstone, shale, and dolostone; includes the Jordan Sandstone and St. Lawrence Formation, and the Mazomanie, Lone Rock, and Davis Formations of the Tunnel City Group.

Middle and Upper Cambrian (Middle and Upper Cambrian) at surface, covers 18 % of this area

Sandstone, siltstone, and shale; includes the Wonewoc Sandstone, Eau Claire Formation, and Mt. Simon Sandstone.

Granitic rocks, undifferentiated (Paleoproterozoic) at surface, covers 8 % of this area

Granitic rocks, undifferentiated. Largely inferred from geophysical maps.

Undifferentiated (Cenomanian to Campanian) at surface, covers 7 % 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.

Granite (Paleoproterozoic) at surface, covers 6 % of this area

Granite, reddish, variably porphyritic, massive; includes the St. Cloud Red (~1,779 Ma), Foley (~1,774, 1,779 Ma), Pierz (~1,779 Ma), and Pease granites, and Richmond charnockitic granite (~1,772 Ma). An unnamed granite in south-central Minnesota is slightly older at ~1,792 Ma.

Granitic to granodioritic orthogneiss (Neoarchean) at surface, covers 5 % of this area

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

Gray granodiorite to granite intrusions (Paleoproterozoic) at surface, covers 5 % of this area

Gray granodiorite to granite intrusions. Includes the Reformatory (~1,783 Ma), Freedhem (~1,775, 1,776 Ma), Isle (~1,779 Ma), and Warman (~1,787 Ma) intrusions.

Sandstone, siltstone, and local conglomerate (Mesoproterozoic) at surface, covers 3 % of this area

Sandstone, siltstone, and local conglomerate. Includes the Hinckley Sandstone and Fond du Lac (youngest detrital zircons ~1,000 Ma) and Solar Church Formations; deposition in eolian, fluvial, and lacustrine environments.

Interlayered volcanic, volcaniclastic, sedimentary, and hypabyssal intrusive rocks (Paleoproterozoic) at surface, covers 1 % of this area

Interlayered volcanic, volcaniclastic, sedimentary, and hypabyssal intrusive rocks. Includes parts of the Mille Lacs Group, North and South Range Groups, and Glen Township Formation.

Dioritic to granodioritic intrusion of uncertain age (Archean or Paleoproterozoic) at surface, covers 0.1 % of this area

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

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.

Mafic intrusions including pyroxenite, peridotite, gabbro, and lamprophyre (Paleoproterozoic) at surface, covers < 0.1 % of this area

Mafic intrusions including pyroxenite, peridotite, gabbro, and lamprophyre. Defined largely by magnetic signature. One intrusion in Morrison County is ~1,791 Ma, and lithologically similar intrusions cut the Foley Granite (~1,774 Ma).