Foliated to gneissic tonalite and granodiorite.
Granitic orthogneiss and migmatite. Geophysical map patterns imply this unit intruded other gneisses.
Granitoid gneiss with dioritic to amphibolitic enclaves. Produces moderately high and varied gravity and magnetic signatures.
Amphibolitic to dioritic gneiss.
Schist and tonalitic to granodioritic paragneiss. Typically adjacent to large batholithic complexes.
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.
Gabbro, pyroxenite, diorite, and lamprophyre. Includes the Watab quartz diorite (~1,780 Ma), St. Wendell quartz gabbro, and an unnamed diorite (~1,786 Ma).
Granitoid intrusion. Constrained solely by low gravity and magnetic signatures.
Interlayered volcanic, volcaniclastic, sedimentary, and hypabyssal intrusive rocks. Includes parts of the Mille Lacs Group, North and South Range Groups, and Glen Township Formation.
Leucogranite. Occurs along the Yellow Medicine Shear Zone and elsewhere, primarily in batholithic settings.
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.
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).
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.