Trenton Limestone Group

{{Infobox rockunit

| name = Trenton Group

| image = MPEP407-09.jpg

| caption = Trenton Formation in Canada

| type = Formation

| age = Middle-Upper Ordovician
~{{Fossil range|470|443.8}}

| period = Ordovician

| prilithology = Limestone

| otherlithology =Chert

| namedfor =Trenton Falls New York

| namedby =Lardner Vanuxem in 1838

| region = Indiana, Michigan, Ohio, Pennsylvania, Virginia, West Virginia[http://hdl.handle.net/10919/19078 Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau]

| country = United States, Canada

| coordinates =

| unitof =

| subunits = *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

| thickness =

| extent = Appalachia, Midwestern and Southeastern United States

| area =

| map =

| map_caption =

}}

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.{{cite web |title=Trenton Limestone |url=https://igws.indiana.edu/compendium/trenton-limestone |website=Indiana Geological and Water Survey |publisher=Indiana University |access-date=6 July 2020}}{{cite web |last1=Orton |first1=Edward |title=THE TRENTON LIMESTONE AS A SOURCE OF PETROLEUM AND INFLAMMABLE GAS IN OHIO AND INDIANA, in Eighth Annual report of the United States Geological Survey to the Secretary of the Interior, 1886-1887: Part 2 |url=https://pubs.er.usgs.gov/publication/ar8_2 |publisher=USGS |access-date=6 July 2020 |pages=547–556 |date=1889}}

Stratigraphy

In the Illinois Basin, Michigan Basin and Cincinnati Arch the Trenton Limestone is classified as a Geological formation rather than a group.{{Cite web |title=Trenton Limestone |url=https://legacy.igws.indiana.edu/IGNIS/GeoNamesDetails.cfm?ID=4488A3C4-35E2-46DA-ACA7-394CF05B5193 |access-date=2025-06-30 |website=legacy.igws.indiana.edu |language=en}}

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.{{Cite web |title=Geolex — GlensFalls publications |url=https://ngmdb.usgs.gov/Geolex/UnitRefs/GlensFallsRefs_1820.html |url-status=live |archive-url= |archive-date= |access-date=2025-07-03 |website=ngmdb.usgs.gov}} 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 VermontDavid A. MacLean FACIES RELATIONSHIPS WITHIN THE GLENS FALLS LIMESTONE OF VERMONT AND NEW YORK

= 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.{{Cite web |last=CORNELL |first=SEAN |date=30 June 2025 |title=CLASSIC LOCALITIES OF THE BLACK RIVER AND TRENTON GROUPS (UPPER ORDOVICIAN) IN THE BLACK RIVER VALLEY: REVISITED THROUGH TRADITIONAL AND SEQUENCE STRATIGRAPHY |url=https://ottohmuller.com/nysga2ge/Files/2005/NYSGA%202005%20A4%20and%20B1%20-%20Classic%20Localities%20Of%20The%20Black%20River%20And%20Trenton%20Groups%20(Upper%20Ordovician)%20In%20The%20Black%20River%20Valley%20-%20Revisited%20Through%20Traditional%20And%20Sequence%20Stratigraphy.pdf |url-status=live |access-date=30 June 2025}} {{Cite web |last=SELLECK |first=BRUCE W. |date=30 June 2025 |title=BLACK RIVER AND TRENTON GROUPS, NORTHWESTERN NEW YORK STATE |url=https://www.nysga-online.org/wp-content/uploads/2019/06/NYSGA-2014-B1-Black-River-and-Trenton-Groups-Northwestern-New-York-State.pdf |access-date=30 June 2025 |website=New York Geological Survey}}{{Cite web |title=Napanee Limestone - Route 12 D - NYSDEC |url=https://dec.ny.gov/regulatory/permits-licenses/seqr/critical-environmental-areas/unique-geological-features/napanee-limestone-route-12d |access-date=2025-06-30 |website=dec.ny.gov |language=en}}

= 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. Located at the base of the Selby the Hounsfield Metabentonite Bed, part of the Deicke and Millbrig bentonite layers.