The Gunflint Range is an

iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the f ...

deposit in northern

Minnesota Minnesota ( ) is a U.S. state, state in the Upper Midwestern region of the United States. It is bordered by the Canadian provinces of Manitoba and Ontario to the north and east and by the U.S. states of Wisconsin to the east, Iowa to the so ...

in the United States and

Northwestern Ontario Northwestern Ontario is a secondary region of Northern Ontario in the Canadian province of Ontario which lies north and west of Lake Superior and west of Hudson Bay and James Bay. It includes most of subarctic Ontario. Its western boundary is the ...

, Canada. The range extends from the extreme northern portion of

Cook County, Minnesota Cook County is the easternmost County (United States), county in the U.S. state of Minnesota. As of the 2020 United States census, 2020 census, the population was 5,600, making it Minnesota's seventh-least populous county. Its county seat is G ...

into the

Thunder Bay District Thunder Bay District is a district#Ontario, district and Census divisions of Canada, census division in Northwestern Ontario in the Canadian province of Ontario. The County seat, district seat is Thunder Bay. Most of the district (93.5%) is uni ...

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

. The Gunflint Iron Formation is a continuation of the

Mesabi Range The Mesabi Iron Range is a mining district and mountain range in northeastern Minnesota following an elongate trend containing large deposits of iron ore. It is the largest of four major iron ranges in the region collectively known as the Iro ...

to the southwest. The two have been separated by the intrusion of the

Duluth Gabbro The Duluth Complex, the related Beaver Bay Complex, and the associated North Shore Volcanic Group are rock formations which comprise much of the Basement (geology), basement bedrock of the Geology of Minnesota#Northeastern Minnesota: ancient bedroc ...

complex. The iron deposit is a

banded iron formation Banded iron formations (BIFs; also called banded ironstone formations) are distinctive units of sedimentary rock consisting of alternating layers of iron oxides and iron-poor chert. They can be up to several hundred meters in thickness and e ...

of the Early

Proterozoic The Proterozoic ( ) is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, and is the longest eon of Earth's geologic time scale. It is preceded by the Archean and followed by the Phanerozo ...

Animikie Group The Animikie Group is a geologic group composed of sedimentary and metasedimentary rock, having been originally deposited between 2,500 and 1,800 million years ago during the Paleoproterozoic era, within the Animikie Basin. This group of formati ...

. The Gunflint Iron Formation is overlain by " brecciated and complexly deformed iron formations", which in turn is overlain by ejecta from the " Sudbury meteorite impact event." This Sudbury Impact Layer is overlain by the Rove Formation.

Stromatolite Stromatolites ( ) or stromatoliths () are layered Sedimentary rock, sedimentary formation of rocks, formations (microbialite) that are created mainly by Photosynthesis, photosynthetic microorganisms such as cyanobacteria, sulfate-reducing micr ...

structures are evident within the Gunflint Iron Formation.Geology of the Gunflint Iron Formation and the Sudbury Impact Layer, Northeastern Minnesota
/ref> The

chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...

s of the Gunflint (the Gunflint Chert) are noted for containing

Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...

microfossil A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

References

{{coord, 48.184, N, 89.835, W, display=title Geology of Minnesota Geology of Ontario Iron ore deposits

See also

References