USGS Visual Identifier
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Geologic Unit: Walloomsac

Walloomsac Formation (CT*,MA*,NY*,VT*)
Walloomsac Schist (CT*)
Walloomsac Slate (NY*)

Ordovician, Middle*

Geologic Province:
New England province*

Areal Extent:

Type Locality:
Exposures in Walloomsac River Valley, west and northwest of Bennington, VT, in both Bennington Co., VT, and Rensselaer Co., NY (Prindle and Knopf, 1932).

Unit Name History:
Named Walloomsac slate (Prindle and Knopf, 1932).
Age modified (Osberg, 1952).
Redescribed as Walloomsac Formation; Extended into CT (Zen, 1966).
Age modified; Biostratigraphic dating (Ratcliffe, 1974).
Age modified (Harwood, 1979).
MA State Geol. Map usage (Zen and others, 1983).
Revised (Baskerville, 1992).
Age modified; Biostratigraphic dating (Ratcliffe and others, 1993).

Note: If you need more information, please contact Nancy Stamm (
Asterisks (*) indicate usage by the U.S. Geological Survey. Other usages by state geological surveys.

"No current usage" implies that a name has been abandoned or that it has fallen into disuse. Former usage and, if known, replacement name given in parentheses ().

Slashes (/) indicate unit name usage violates the 1983 North American Stratigraphic Code. This violation may be explained within brackets ([ ]).

U.S. Department of the Interior, U.S. Geological Survey, Reston, VA, USA
Database project personnel
Last modified: 15-Jan-2013