Walloomsac Formation

Slate, phyllite, schist, metagraywacke.
State New York
Name Walloomsac Formation
Geologic age Middle Ordovician
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > Phyllite
Metamorphic > Metasedimentary > Metaclastic > Slate
Metamorphic > Schist
Minor
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywacke
Comments part of Lorraine, Trenton, and Black River Groups up to 4500 ft. (1400 m).
References

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.

NGMDB product
Counties Columbia - Dutchess - Rensselaer