The Black River Group is a

geologic group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into superg ...

that covers three sedimentary basins in the Eastern and Midwestern

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

. These include the

Appalachian Basin The geology of the Appalachians dates back more than 1.2 billion years to the Mesoproterozoic era when two continental cratons collided to form the supercontinent Rodinia, 500 million years prior to the development of the range during the form ...

Illinois Basin The Illinois Basin is a Paleozoic depositional and structural basin in the United States, centered in and underlying most of the state of Illinois, and extending into southwestern Indiana and western Kentucky. The basin is elongate, extending a ...

and the

Michigan Basin The Michigan Basin is a geologic basin centered on the Lower Peninsula of the U.S. state of Michigan. The feature is represented by a nearly circular pattern of geologic sedimentary strata in the area with a nearly uniform structural dip towar ...

. It dates back to the Late

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

. It is roughly equivalent to the Platteville Group in

Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...

. In Kentucky and Tennessee it is also known as the High Bridge Group. In areas where this Geologic Unit thins it is also called the Black River Formation (undifferentiated). One example of this is over the

Cincinnati Arch The Cincinnati Arch is a broad structural Tectonic uplift, uplift between the Illinois Basin to the west, the Michigan Basin to the northwest, and the Appalachian Basin and Black Warrior Basin to the east and southeast. It existed as a positive t ...

and Findley Arch. Large parts of the Black River have been dolomized (where the parent limestone CaCO₃ has been turned into dolomite CaMg(CO₃)_2.) This happed when there was interaction of hot saline brine and the limestone. This created hydrothermal dolomites that in some areas serve as

petroleum Petroleum, also known as crude oil or simply oil, is a naturally occurring, yellowish-black liquid chemical mixture found in geological formations, consisting mainly of hydrocarbons. The term ''petroleum'' refers both to naturally occurring un ...

reservoirs.

Description

The Black River Group is characterized by

carbonates A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group . ...

, primarily

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

. Some dolostones can be found in localized areas. Due to fracturing and porosity naturally occurring with in the formation it servers as a gas reservoir throughout its reach. It also serves as an oil reservoir in Michigan and North West Ohio.

Stratigraphy

The Black River Group is predominantly composed of carbonates. In addition clay minerals maybe found in differing amounts. Locally sand and silt maybe found in thin horizons especially in the eastern reaches of the unit. In addition there are K-bentonite beds. These were formed as a result of

volcanic eruptions A volcanic eruption occurs when material is expelled from a volcanic vent or fissure. Several types of volcanic eruptions have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior h ...

depositing layers of

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

. The Black River Group was deposited during a time when large parts of North America were a passive cratonic margin. North America at the time was near the equator and was a tropical environment. Large parts of what is now North America were covered by the

Iapetus Ocean The Iapetus Ocean (; ) existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). It was in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalon ...

. The Black River Group was formed during a time of transition time where

Laurentia Laurentia or the North American craton is a large continental craton that forms the Geology of North America, ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of ...

was subject to the beginnings of the

Taconic Orogeny The Taconic orogeny was a mountain building period that ended 440 million years ago (Ma) and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the east coast of the ...

. During the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

the Iapetus began to slowly close. As Laurentia moved towards an

island arc Island arcs are long archipelago, chains of active volcanoes with intense earthquake, seismic activity found along convergent boundary, convergent plate tectonics, tectonic plate boundaries. Most island arcs originate on oceanic crust and have re ...

that it would eventually collide with the crust folded downward. As this happened the carbonate deposition of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

gradually gave way to clastic deposits of a deep marine environment. As a result, there are more siliceous deposits to the east. The Taconic Orogeny occurred to the east and this formed a basin, but further west the crust buckled up into an arch. The result was the

. This arch was eroded back to late Ordovician aged rock. This split the basin of the Iapetus Ocean into three separate basins.

Subunits

Black River Formation

The Black River Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

and

Michigan Michigan ( ) is a peninsular U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest, Upper Midwestern United States. It shares water and land boundaries with Minnesota to the northwest, Wisconsin to the west, ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

New York State

Amsterdam Limestone

The Amsterdam Limestone is a

New York New York most commonly refers to: * New York (state), a state in the northeastern United States * New York City, the most populous city in the United States, located in the state of New York New York may also refer to: Places United Kingdom * ...

. It dates back to the

. It is a unit of the Black River Group in Eastern New York.

= Fossils

= '' Cartersoceras noveboracense''

Waterton Limestone

The Waterton Limestone is a geologic formation in New York. It dates back to the Ordovician period. It is a unit of the Black River Group in Eastern New York.

Lowville Formation

The Lowville Formation is a geologic formation in New York and

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 ...

. It preserves fossils dating back to the Ordovician period.

Energy production

The Black River Group acts as a reservoir for

natural gas Natural gas (also fossil gas, methane gas, and gas) is a naturally occurring compound of gaseous hydrocarbons, primarily methane (95%), small amounts of higher alkanes, and traces of carbon dioxide and nitrogen, hydrogen sulfide and helium ...

and

. The reservoirs are associated with dolostones and. Gas and oil fields can be found in New York, Pennsylvania, Ohio, Indiana, Kentucky, Michigan, and Tennessee.

References

{{Stratigraphic column of West Virginia Ordovician Indiana Ordovician Michigan Ordovician Ohio Ordovician West Virginia Dolomite groups Mudstone groups Limestone groups of the United States