Geologic Unit: Ayer
Ayer Granite (CT*,MA*)
Ayer Granodiorite (NH*,MA)
Type area: from Hampstead, NH, through Ayer, north-central MA (Emerson, 1917).
Unit Name History:
Named Ayer Granite (Emerson, 1917).
Revised to Ayer Granodiorite (Jahns, 1942; Billings, 1955).
Age modified; Isotopic dating (Goldsmith and others, 1982).
MA State Geol. Map usage (Zen and others, 1983).
Overview; Isotopic dating (Wones and Goldsmith, 1991).
NH State Geol. Map usage; Age modified; Isotopic dating (Lyons and others, 1997).
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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