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Mineral Resources > Online Spatial Data > Geology > by state > Minnesota Geology

Geologic units in Pine county, Minnesota

Denham Formation (Early Proterozoic) at surface, covers 0.3 % of this area

Denham Formation - Quartz arenite and siltstone, oxide iron-formation, marble, mafic hypabyssal intrusions and fragmental volcanic rocks metamorphosed to the staurolite grade of the amphibolite facies

Lithology: sandstone; siltstone; iron formation; marble; metavolcanic rock

Chengwatana Volcanic Group (Middle Proterozoic) at surface, covers 0.5 % of this area

Chengwatana Volcanic Group - Gray basalt flows, interflow breccia, tuff, and minor sedimentary rocks

Lithology: basalt

Copper Harbor Conglomerate (Middle Proterozoic) at surface, covers 0.1 % of this area

Copper Harbor Conglomerate - Red lithic conglomerate and sandstone; mafic to felsic volcanic flows similar to those of the unnamed formation (unit Yu) are interlayered with the sedimentary rocks.

Lithology: conglomerate; sandstone; basalt

Fond du Lac Formation (Middle Proterozoic) at surface, covers 5 % of this area

Fond du Lac Formation - Red to dark-brown shale, feldspathic sandstone, and arkose of fluvial origin. Includes the Oldenberg Point Member, a pronounced basal unit of quartz-pebble conglomerate in the Duluth area.

Lithology: shale; sandstone; arkose; conglomerate

Hinckley Sandstone (Middle Proterozoic) at surface, covers 34 % of this area

Hinckley Sandstone - Buff to tan quartz arenite of lacustrine and eolian origin.

Lithology: arenite

Migmatitic gneiss, amphibolite, and granite (Middle to Early Archean) at surface, covers 2 % of this area

Migmatitic gneiss, amphibolite, and granite - Montevideo and Morton Gneisses (3600-3000 m.y.) in the Minnesota River Valley, southwestern Minnesota; McGrath Gneiss (2750 m.y.) east of Mille Lacs Lake; components of Hillman Migmatite southwest of Mille Lacs Lake; and Sartell Gneiss in Stearns County. Inferred to include various younger rocks, including granitoid intrusions in the Hillman Migmatite and pillowed basalt in poorly exposed areas of southwestern Minnesota.

Lithology: gneiss; amphibolite; granite; basalt

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metagraywacke, metasiltstone, and a variety of schistose rocks metamorphosed to the amphibolite facies (Early Proterozoic) at surface, covers 3 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metagraywacke, metasiltstone, and a variety of schistose rocks metamorphosed to the amphibolite facies

Lithology: metasedimentary rock; schist

Upper Cambrian, undivided (Late Cambrian) at surface, covers 9 % of this area

Upper Cambrian, undivided - Jordan Sandstone; dolomite, glauconite, and silty glauconite rocks of the St. Lawerence and Franconia Formation; Ironton and Galesville Sandstones; sandy and shaly rocks of the Eau Claire Formation; and the Mt. Simon Sandstone.

Lithology: dolostone (dolomite); sandstone; shale

Cambrian, undivided (Cambrian) at surface, covers < 0.1 % of this area

Cambrian, undivided - Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations

Lithology: sandstone; dolostone (dolomite); shale

Chengwatana Volcanic Group (Middle Proterozoic) at surface, covers 47 % of this area

Chengwatana Volcanic Group - Basalt and related volcanogenic and interflow sedimentary rocks in east-central Minnesota

Lithology: basalt; rhyolite; clastic