Salina Group (Peru)

The Salina Group or Salina Formation is a Late Silurian age unit of sedimentary rock found in North Eastern and Midwestern North America. Named for its Halite beds, the term Salina Group first know usage was by James D. Dana in 1863.

The Salina is an extensive formation, covering many states and a province of Canada. It ranges from West Virginia, up through Ohio, Pennsylvania to Michigan and New York. The Salina is also found in the Canadian Province of Ontario. (see Figure 1)

The thickness of the Salina varies greatly with in the two basins. In Michigan it ranges from 84' thick in the southwestern corner of the state to an estimated 5,000' think in Gladwin County.

The Salina is of economic importance, for salt mining, oil reservoir, gypsum mining and possible natural gas storage. Research has also been done on the viability of storing radioactive waste in the salt beds of the Salina.

Description

The Salina Formation is composed chiefly of dolomite and shale, interbedded with anhydrite, gypsum, and salt.

Stratigraphy

Stratigraphically, the Salina is placed in the Late Silurian age and is the lower member of the Cayugan Series. It overlies predominantly the Lockport, in parts central to northeast Pennsylvania it overlies the Bloomsburg. The Salina underlies the Helderberg Group

Being a thick formation the Salina has sub units 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 of Anhydrite. In an extensive study in the State of Michigan each unit was mapped.

Unit H is also known as the Bertie Formation. In the Michigan Basin the Bertie is pinched out and the Bass Islands Formation makes up the upper most Salina.

Unit G is the Camillus it consists of dolomite and anhydrite.

Unit F is the youngest and largest salt in the group, also known as the Syracuse 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 E consist of shale, but can include dolomitic shale and dolomite. Anhydrite may also be present with in this unit. Also part of the Syracuse.

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

Unit C marks the top of the Vernon Formation It is a shaly dolomite, however it can range from pure shale to pure dolomite beds with in the unit. Anhydrite can be prevalent with in this unit as well.

Unit B is another salt unit and marks the Middle Vernon. The percentage of salt can be from 90% to 100%. Thin dolomite beds run through this unit.

Unit A consist of dolomite and shaly dolomite and it the bottom of the Vernon. Where the formation thickens there may also be one or two large salt beds with in the unit. Anhydrite can be found throughout this unit.

Due to unit A having two salt or anhydrite beds many divide it into the A1 and A2, with A1 being the basal unit.

Economic Resources

Salt

Mines for extracting salt as well as brine wells can be found in Western New York and North East Ohio. In Michigan Detroit is host to salt mining operations as well.

Salt production in Ohio predates settlement by Europeans. Native Americans collected and processed brine from springs in several locations all over Ohio. Salt could also be collected at so called "salt licks" where brine would seep out of the ground and deposit it's minerals on the ground. Licking County was Named for the abundant salt licks found in the area. Mahoning County's name is derived from a Native American term "ma-hon-ink" meaning "at the lick".
Throughout the early 1800s Ohio's salt demand exceeded its production from brine wells and licks. Oil and gas exploration starting lead to the discovery of salt in the 1860s. It was not until 1886 when the Cleveland Rolling Mill was drilling its second natural gas well and hit brine. The salt was at a depth of approximately 1,900'. After a series of discoveries of salt around the same depth it was concluded that there must be a large regional salt deposit. By the 1890s several brine wells were drilled and producing in Cleveland. In total during this period there were five salt producing companies operating in North East Ohio. Clarence Foster examined drilling records from Standard Oil along Lake Erie. Along with Sterling Morton built a Salt mine at a depth of 1800' in the 1890s. This was located on Cleveland's East side.

Gypsum

In 1827, Gypsum was first identified in Michigan, near Grand Rapids. An Odawa man discovered it in a rock outcrop along Plaster Creek where it enters Grand River. In 1838 Michigan's first state geologist, Douglass Houghton arrived to select a site for salt mining. He reported an abundance of gypsum in the area. Daniel Ball and business partner Warren Granger constructed a mill to process gypsum in 1841.

In 1838, Douglass Houghton and Bela Hubbard discovered an outcrop of gypsum at the mouth of the Au Gres River located Saginaw Bay. The first mill was operational in 1862 in Alabaster, Michigan.

Oil and Gas

The Salina serves as an oil reservoir formation along the Findlay Arch from South Western Michigan down in to North West Ohio. Salt in not present along the Arch System.

References

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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