Trenton Limestone Group

Trenton Group
Stratigraphic range: Middle-Upper Ordovician ~470–443.8 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Trenton Formation in Canada
Type	Formation
Sub-units	Hillier Limestone, Dolgeville Limestone Steuben Limestone Denley Limestone Sugar River Limestone Glens Falls Limestone Kings Falls Limestone Napanee Limestone Selby Limestone
Underlies	Medina Group
Overlies	Black River & Plattin Formation
Lithology
Primary	Limestone
Other	Chert
Location
Region	Indiana, Michigan, Ohio, Pennsylvania, Virginia, West Virginia[1]
Country	United States, Canada
Extent	Appalachia, Midwestern and Southeastern United States
Type section
Named for	Trenton Falls New York
Named by	Lardner Vanuxem in 1838

Description

The Trenton Group is a Geologic Group in Kentucky, Michigan, Ohio, New York, Indiana, Pennsylvania, and West Virginia. It is also present in Ontario. It dates back to the Ordovician period. It is primarily composed of limestone. It has served as a gas field in several states.^[2][3]

Stratigraphy

In the Illinois Basin, Michigan Basin and Cincinnati Arch the Trenton Limestone is classified as a Geological formation rather than a group.^[4]

In the Appalachian Basin the Trenton is broken down into formations and members.

Glens Falls Limestone

The Glens Falls Limestone contains thin fossiliferous beds. The inclusion of ripple marks indicates this formation was deposited in a shallow marine environment.^[5] The Glens Falls contains two members, the upper member is the Shoreham and the lower Larrabee Member. The upper member contains more clay and silica where the lower member contains more carbonate material. Both are named for separate quarries located in Vermont^[6]

Napanee Limestone

The Napanee is a thin bedded deep water limestone. The formation is composed of thin interbedded wackestone and shale. This formation can be organic rich in parts and sub surface is dark grey to blackish, while at surface it will weather to a tan or buff color. Fossils can be abundant including bryozoans, brachiopods, crinoids, trilobites, and other molluscs. Dalmanella rogata is rather common.^{[7] [8][9]}

Selby Limestone

The Selby is primarily composed of a nodular dark grey packstone and grainstone with bioclast inclusions. Fossils found within the Selby include orthocones, various types of brachiopods, and a small amount of crinoids.^[7] Located at the base of the Selby the Hounsfield Metabentonite Bed, part of the Deicke and Millbrig bentonite layers.^[8]

See also

• Trenton Gas Field
• Indiana gas boom
• Petroleum industry in Ohio