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Geologic Unit: Berwick

Berwick Formation of Merrimack Group (ME*,MA*,NH*)


Geologic Province:
New England province*

Areal Extent:

Type Locality:
Named from development at Berwick, York Co., ME (Katz, 1917).
Reference section: in Salmon Falls River between Berwick, ME, and Somersworth, NH (Hussey, 1985).

Unit Name History:
Named Berwick Gneiss (Katz, 1917).
Redescribed as Berwick Formation; Age modified (Freedman, 1950).
Assigned to Merrimack Group; Revised to include Gove Member in NH; Age modified (Billings, 1955).
Age modified (Billings, 1956).
Included in Merrimack Group in ME; Age modified (Hussey, 1968).
Extended into MA; Included in Merrimack Group; Age modified (Goldsmith and others, 1982).
MA State Geol. Map usage (Zen and others, 1983).
Reference section (Hussey, 1985).
Not used in ME (Thomson and Guidotti, 1989).
NH State Geol. Map usage; Age modified; Isotopic dating (Lyons and others, 1997).

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