Salina Group
Stratigraphic range:Homerian-Přídolí ~430–420 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Halite (Salina Group, Silurian; Detroit Salt Company mine, Detroit, Michigan, USA)
Type	Geological group
Unit of	Cayugan Series
Sub-units	Appalachian Basin & Michigan Basin Bertie Formation Camillus Formation Syracuse Formation Vernon Formation Illinois Basin Wabash Formation Liston Creek Member Kenneth Limestone Member Kokomo Limestone Member Misslssinewa Shale Formation Pleant Mills Limestone Limberlost Member
Underlies	Helderberg Group
Overlies	Lockport Group &Bloomsburg Formation
Lithology
Primary	Dolomite &Shale
Other	Anhydrite,Limestone,Gypsum &Halite
Location
Region	Appalachian Basin &Michigan Basin of easternNorth America
Country	United States of America andCanada
Type section
Named for	Salt found within the formation
Named by	James Dwight Dana

TheSalina Group orSalina Formation is aLate Silurian-age,Stratigraphic unit ofsedimentary rock that is found in Northeastern and MidwesternNorth America. Named for itsHalite beds, the phrase "Salina Group" was first used as a descriptive term by James D. Dana in 1863.^[1]

The Salina is an extensive formation. It ranges fromWest Virginia up throughPennsylvania intoOhio and thenMichigan in the United States, and from Pennsylvania intoNew York. It is also found in theCanadian province ofOntario. (See Figure 1.)

The thickness of the Salina Group varies greatly within the two basins, ranging from 84 feet in the southwestern corner of Michigan to an estimated 5,000 feet in that state'sGladwin County.^[3]

This formation is of economic importance forsaltmining,oil reservoir creation,^[4]gypsum mining,^[5] and potentialnatural gas storage.^[6] Research has also been done on the viability of storingradioactive waste in the salt beds of the Salina.^[7]

The Salina Formation is composed chiefly ofdolomite andshale, interbedded withanhydrite,gypsum, andsalt.^[8]

Stratigraphically, the Salina is placed in theLate Silurian age and is the lower member of the CayuganSeries. It overlies predominantly theLockport; in parts central to northeast Pennsylvania it overlies theBloomsburg Formation. It also underlies theHelderberg Group.^[9]

Being a thick formation, the Salina has subunits, as well as letter designations for the different formations. The letters originate at the base (oldest) with the A unit to the stratigraphic top H unit (youngest) made up ofAnhydrite.^[10]

During an extensive study in the state ofMichigan, each unit was mapped. Unit A consists of dolomite and shaly dolomite, and is the bottom of the Vernon. Where the formation thickens, there may also be one or two large salt beds within the unit. Anhydrite can be found throughout this unit.^[3] Due to unit A having two salt or anhydrite beds, it is often divided into the A1 and A2, with A1 being the basal unit.^[11]

Unit B is another salt unit and marks the Middle Vernon. The percentage of salt can range from 90% to 100%. Thin dolomite beds run through this unit. In comparison, Unit C marks the top of theVernon Formation. It is a shaly dolomite; however, it can range from pure shale to pure dolomite beds within the unit. Anhydrite can be prevalent within this unit as well.

Unit D, the bottom of the Syracuse formation, is almost pure salt. Some dolomite may also occur within this unit. It is the thinnest unit of the Salina, and is not always present.

Unit E consists of shale, but can include dolomitic shale and dolomite. Anhydrite may also be present within this unit and is also part of the Syracuse.

Unit F is the youngest and largest salt in the group, also known as theSyracuse Formation. Where thicker, the F has beds of salt separated by rock grading from shale to dolomite, often with anhydrite present especially in the shale.

Unit G is theCamillus, which consists of dolomite and anhydrite while unit H is known as theBertie Formation. In the Michigan Basin, the Bertie is pinched out; theBass Islands Formation makes up the upper most Salina.

Wabash Formation made up of the Liston Creek Member, Kenneth Limestone Member, Kokomo Limestone Member and the Mississinewa Shale member.

ThePleasant Mills Formation is made up of the Louisville Equivalent Member and Waldon Equivalent Member and Limberlost Dolomite Member. The Pleasant Mills Formation is equivalent to the entire "A Unit" in the Appalachian Basin.^[12]

Salt mines and brine wells are located in Western New York, Northeast Ohio and Detroit, Michigan with Ohio's salt production predating European settlement of the area as Native Americans collected and processed brine from springs in several locations, including "salt licks" where minerals were deposited by brine seeping out of the ground. Licking County was named for this natural phenomenon.^[13] Mahoning County's name is derived from a Native American term "ma-hon-ink" meaning "at the lick."^[14]

Throughout the early 1800s, Ohio's salt demand exceeded its production from brine wells and licks. Oil and gas exploration facilitated the discovery of salt during the 1860s; however, it was not until 1886 when theCleveland Rolling Mill was drilling its second natural gas well that it hit brine. The salt was located at a depth of approximately 1,900 feet.^[14]

By the 1890s, brine wells were drilled and operating in Cleveland. During this period, five salt-producing companies operated in Northeast Ohio.Sterling Morton built a salt mine at a depth of 1800 feet on Cleveland's east side and Clarence Foster examined drilling records fromStandard Oil alongLake Erie.^[14]

In 1827, Gypsum was first identified in Michigan, near Grand Rapids. AnOdawa man discovered it in a rock outcrop alongPlaster Creek where it entersGrand River.^[15]

In 1838, Michigan's first stategeologist,Douglass Houghton, arrived to select a site for salt mining and reported an abundance of gypsum in the area. That same year, he andBela Hubbard discovered an outcrop of gypsum at the mouth of theAu Gres River inSaginaw Bay.^[15] In 1841, Daniel Ball and business partner Warren Granger built a mill to process gypsum in 1841; a mill built by Houghton and Hubbard inAlabaster, Michigan became operational in 1862.^[15]

The Salina serves as an oil reservoir formation along the Findlay Arch from Southwestern Michigan down into Northwest Ohio. Salt is not present along the Arch System.

Medusaegraptusgraminiformis (Ruedemann 1925)

Orbiculoidea bertiensis (Ruedemann)

Lingula semina (Ruedemann)

Cyathophyllum hydraulicum (Simpson)

Eurypterus remipes (DeKay, 1825)

Archaeophonus eurypteroides (Kjellesvig-Waering 1966)

Proscorpius osborni (Whitfield 1885)

Paracarcinosoma scorpionis (Grote & Pitt)

Eurypterus lacustris (Harlan, 1834)

Erettopterus waylandsmithi (Kjellesvig-Waering & Caster 1955)

Waeringopterus cumberlandicus (Leutze, 1961)

Waeringopterus apfeli (Leutze, 1961)

Dolichopterus herkimerensis (Caster and Kjellesvig-Waering 1956)

Leperditia scalaris (Jones 1856)

Megalomus canadensis (Hall, 1852)

• Silurian United States
• Silurian Ohio
• Silurian New York
• Silurian West Virginia
• Silurian Canada
• Silurian Ontario
• Silurian geology of Pennsylvania
• Silurian geology of New York (state)
• Silurian Michigan
• Geologic groups of the United States
• Geologic groups of Ontario

• Articles with short description
• Short description matches Wikidata