GEOLEX database Geologic Unit: Ayer Usage: Ayer Granite (CT*,MA*) Ayer Granodiorite (NH*,MA) Age: Silurian, Early* Geologic Province: New England province* Areal Extent: CT* MA* NH* Type Locality: 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). Note: If you need more information, please contact Nancy Stamm (nstamm@usgs.gov). 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 URL http://ngmdb.usgs.gov/ngmdb/ngm_catalog.ora.html Database project personnel Last modified: 7-Jan-2007