Trenton Group

In Black River Valley: Cobourg Formation-Hillier shale and limestone Member, Hallowell limestone Member; Denley, Sugar River, Kings Falls, and Rockland Limestones. In Champlain Valley: Glens Falls Formation-Montreal shale and limestone Member, Larrabee limestone Member.
State New York
Name Trenton Group
Geologic age Middle Ordovician
Lithologic constituents
Sedimentary > Carbonate > Limestone
Sedimentary > Clastic > Mudstone > Shale
Comments part of Lorraine, Trenton, and Black River Groups up to 1600 ft. (490 m). Secondary unit description from USGS Lexicon website (ref. NY046) and reference NY036: Revised stratigraphic correlations based on reinterpretation of graptolites and K-bentonites in the area suggest that the lower part of the Utica Shale is the lateral equivalent of a large part of the lower Trenton Group and is older than the Denley Limestone, with which it has been previously equated. Authors state that it is not yet clear exactly how much of the lower Trenton Group is equivalent to the lower part of the Utica Shale, which is named the Flat Creek Member in this report. The member lies between the Glens Falls Limestone of the Trenton below and the Dolgeville Formation above in the central Mohawk Valley. Diagram shows the Flat Creek interfingering with the Sugar River Limestone of the Trenton Group near East Canada Creek. The Indian Castle Member (a new name proposed for that upper part of the Utica overlying the Dolgeville Formation) interfingers with the Rust Member of the Denley Limestone between Wolf Hollow Creek and Trenton Falls. The Utica youngs westward and near Trenton Falls oversteps the Steuben and Denley Limestones at the top of the Trenton Group. In the study area, the Trenton ranges in age from Rocklandian to Edenian, while the base of the Utica is Kirkfieldian in the central region and the top reaches the Maysvillian in the western region (Goldman and others, 1994).

Fisher, D.W., Isachsen, Y.W., and Rickard, L.V., 1970, Geologic Map of New York State, consisting of 5 sheets: Niagara, Finger Lakes, Hudson-Mohawk, Adirondack, and Lower Hudson, New York State Museum and Science Service, Map and Chart Series No. 15, scale 1:250,000.

Goldman, Daniel, Mitchell, C.E., Bergstrom, S.M., Delano, J.W. and Tice, Steven, 1994, K-bentonites and graptolite biostratigraphy in the Middle Ordovician of New York State and Quebec; a new chronostratigraphic model: Palaios, v. 9, no. 2, p. 124-143.

USGS Geologic Names lexicon found at:

NGMDB product
Counties Clinton - Herkimer - Jefferson - Lewis - Oneida