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

Geologic units in Crow Wing county, Minnesota

Late-tectonic intrusions of the Penokean orogen (Early Proterozoic) at surface, covers 0.2 % of this area

Late-tectonic intrusions of the Penokean orogen - Includes the St. Cloud and Rockville Granites and Reformatory granodiorite of east-central Minnesota, the Section 28 granite, the Cedar Mountain Complex, and other unnamed intrusions exposed along the Minnesota River Valley in southwestern Minnesota

Lithology: granite; granodiorite

North Range Group; Rabbit Lake Formation (Early Proterozoic) at surface, covers 1 % of this area

North Range Group; Rabbit Lake Formation - Mudstone, graywacke, iron-rich strata, and associated mafic metavolcanic rocks metamorphosed to the greenschist facies. Includes thin beds of carbonate-silicate iron-formation

Lithology: mudstone; graywacke; metavolcanic rock; iron formation

Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks (Early Proterozoic) at surface, covers 9 % of this area

Animikie Group; Shale, siltstone, feldspathic graywacke, and associated volcaniclastic rocks - Includes the Rove Formation in Cook County, the Virginia Formation in St. Louis, Itasca, and Lake Counties, and the Thomson Formation in Carlton County

Lithology: shale; siltstone; graywacke; mixed clastic/volcanic

Fond du Lac Formation (Middle Proterozoic) at surface, covers < 0.1 % 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

Felsic to intermediate volcanic and volcaniclastic rocks, mica schist, phyllite, and granitoid rocks (Late Archean) at surface, covers 22 % of this area

Felsic to intermediate volcanic and volcaniclastic rocks, mica schist, phyllite, and granitoid rocks - Variably and cataclastically deformed. Unit forms aeromagnetic "quiet zone" and probably contains some rocks of Paleoproterozoic age.

Lithology: felsic volcanic rock; intermediate volcanic rock; schist; phyllite; granitoid

Syntectonic to pretectonic granitoid rocks (Late Archean) at surface, covers 0.9 % of this area

Syntectonic to pretectonic granitoid rocks - Granite and granodiorite of the Vermilion Granitic Complex, the Giants Range and Bemidji batholiths, as well as smaller intrusions of tonalite and monzonite of the Algoman orogen in northern Minnesota. Also includes the Odessa, Sacred Heart, and Fort Ridgely Granites exposed along the Minnesota River Valley in southwestern Minnesota.

Lithology: granite; granodiorite; tonalite; monzonite

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, slate, and silicate iron-formation metamorphosed to the lower greenschist facies and related conditions (Early Proterozoic) at surface, covers 9 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, slate, and silicate iron-formation metamorphosed to the lower greenschist facies and related conditions - Includes substantial quantities of mafic to intermediate igneous rocks

Lithology: schist; slate; iron formation

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartz arenite, siltstone, and chert-rich dolostone of the Trout Lake Formation in Crow Wing County (Early Proterozoic) at surface, covers 5 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartz arenite, siltstone, and chert-rich dolostone of the Trout Lake Formation in Crow Wing County

Lithology: arenite; siltstone; dolostone (dolomite)

Animikie Group; Iron-formation - Iron-formation (Early Proterozoic) at surface, covers 0.3 % of this area

Animikie Group; Iron-formation - Includes the Gunflint Iron Formation in Cook County and the Biwabik Iron Formation and subjacent units of arenite and conglomerate assigned to the Pokegama Quartzite in Itasca, St. Louis, and Lake Counties. Also includes thin lenses of iron-formation (Remer Member) in the Virginia Formation in Itasca County.

Lithology: iron formation; arenite; conglomerate

North Range Group; Trommald Formation (Early Proterozoic) at surface, covers 0.9 % of this area

North Range Group; Trommald Formation - Carbonate-silicate iron-formation overlain by hematite iron-formation and associated manganese oxide deposits. Also contains substantial quantities of volcanic and hypabyssal rocks of generally mafic composition. Metamorphosed to greenschist facies.

Lithology: iron formation; metavolcanic rock

Mille Lacs Group and related rocks of the Penokean fold-and-thrust bets; Graphitic schist, phyllite and slate interbedded on a fine scale (Early Proterozoic) at surface, covers 6 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Graphitic schist, phyllite and slate interbedded on a fine scale

Lithology: schist; phyllite; slate

Pokegama Quartzite (Early Proterozoic) at surface, covers 6 % of this area

Pokegama Quartzite - Quartz arenite, siltstone, and shale. Shown only in Crow Wing County.

Lithology: arenite; siltstone; shale

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 0.3 % 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

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies (Early Proterozoic) at surface, covers 7 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Metabasalt, metadiabase, and metasedimentary rocks metamorphosed to lower amphibolite facies - Includes fragmental volcanic rocks, mafic hypabyssal intrusions, graphitic argillite, and oxide iron-formation

Lithology: metavolcanic rock; diabase; metasedimentary rock; argillite; iron formation

Migmatitic gneiss, amphibolite, and granite (Middle to Early Archean) at surface, covers 8 % 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

Coleraine Formation (Cretaceous) at surface, covers 0.8 % of this area

Coleraine Formation - Jasper-pebble conglomerate, sandstone, and shale of diverse origin on the Mesabi range of northern Minnesota, and unnamed sandstone and shale of nonmarine to marine origin in east-central Minnesota

Lithology: conglomerate; sandstone; shale

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartzite at Dam Lake (Early Proterozoic) at surface, covers 3 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Quartzite at Dam Lake - Quartz arenite and sericitic quartz schist; includes a substantial component of mafic volcanic rock fragments

Lithology: arenite; schist; volcanic rock

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Slate, argillite, and metasiltstone metamorphosed to the lower greenschist facies (Early Proterozoic) at surface, covers 11 % of this area

Mille Lacs Group and related rocks of the Penokean fold-and-thrust belt; Slate, argillite, and metasiltstone metamorphosed to the lower greenschist facies - Includes lesser amounts of mafic hypabyssal intrusions, and fragmental mafic volcanic rocks

Lithology: slate; argillite; metsedimentary rock; metavolcanic rock

North Range Group; Mahnomen Formation (Early Proterozoic) at surface, covers 10 % of this area

North Range Group; Mahnomen Formation - Claystone, shale, siltstone, and graywacke metamorphosed to the greenschist facies

Lithology: claystone; shale; siltstone; graywacke