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.
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 shale; includes the Wonewoc Sandstone, Eau Claire Formation, and Mt. Simon Sandstone.
Interlayered volcanic, volcaniclastic, sedimentary, and hypabyssal intrusive rocks. Includes parts of the Mille Lacs Group, North and South Range Groups, and Glen Township Formation.
Mylonitic, gneissic, and schistose rocks of plutonic and volcanic protolith.
Granitic rocks, undifferentiated. Largely inferred from geophysical maps.
Granitoid intrusions, variably magnetic. Includes the Ann Lake granite (~1,784 Ma) and Glendorado pluton (~1,788 Ma).
Tonalite to leucodiorite (~1,792, 1,793, 1,800 Ma).
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).
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.