| Trenton Group | |
|---|---|
| Stratigraphic range: Middle-Upper Ordovician ~ | |
 Trenton Formation in Canada | |
| Type | Formation |
| Sub-units |
|
| 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 |
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]
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.
The Glens FallsLimestone 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]
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]
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]
