The Nonesuch Shale is a Proterozoic geologic formation that outcrops in

Michigan Michigan () is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, upper Midwestern United States. With a population of nearly 10.12 million and an area of nearly , Michigan is the List of U.S. states and ...

and

Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake M ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

, but has been found by drill holes to extend in the subsurface as far southwest as

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to th ...

. The Nonesuch is a

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

sequence of shale, siltstone, and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

, 150 to 210 m thick, that conformably overlies the

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. All ...

Copper Harbor Conglomerate and is conformably overlain by the fluvial Freda Sandstone. Together, the Copper Harbor, Nonesuch, and Freda make up the Oronto Group. The Nonesuch is Middle Proterozoic, with an estimated age of approximately 1.1 billion years. It was deposited in the Midcontinent Rift. The Nonesuch beds contain common organic carbon and

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

Natural resources

The Nonesuch Formation has been a major source of

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

, and is considered a prospective source of

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

Copper

Copper was discovered in the Nonesuch in the 1800s, but early mining efforts, such as those at the

Nonesuch Mine __NOTOC__ The Nonesuch Mine is an abandoned copper mine and small ghost town in the southeast corner of the Porcupine Mountains State Park in Carp Lake Township, Ontonagon County, near Silver City, Michigan, United States. The area was given it ...

Ontonagon County, Michigan Ontonagon County ( ) is a county in the Upper Peninsula of the U.S. state of Michigan. As of the 2020 Census, the population was 5,816, making it Michigan's third-least populous county. The county seat is Ontonagon. The county was set off i ...

, failed because of the difficulty of recovering the fine grains of

native copper Native copper is an uncombined form of copper that occurs as a natural mineral. Copper is one of the few metallic elements to occur in native form, although it most commonly occurs in oxidized states and mixed with other elements. Native coppe ...

. The

Copper Range Company The Copper Range Company was a major copper-mining company in the Copper Country of Michigan, United States. It began as the Copper Range Company in the late 19th century as a holding company specializing in shares in the copper mines south of Hou ...

opened the White Pine mine in

, in 1955. The principal ore minerals were

chalcocite Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system. ...

and

. The underground mine produced copper from the Nonesuch Shale until it closed in 1995.

Petroleum

The Nonesuch Shale has sufficient organic carbon content (greater than 0.5%) to be considered a potential sourcebed for petroleum. Oil identified as Precambrian has been found seeping into the White Pine copper mine in Michigan.J.A. Seglund, “Midcontinent Rift continues to show promise as petroleum prospect,” ''Oil and Gas Journal'', 15 May 1989, p.55-58. Exploration wells have been drilled to Nonesuch-equivalent sediments in the rift basins in Michigan,

, and

, but no commercial petroleum deposits have been discovered.

References

External links

Iowa Geological Survey: ''Exploring the Midcontinent Rift''
PDF file, retrieved 27 December 2008. {{Stratigraphic column of Michigan Proterozoic North America Shale formations of the United States Geologic formations of Michigan Geologic formations of Wisconsin Geography of Ontonagon County, Michigan

Natural resources

Copper

Petroleum

See also

References

External links