|Geologic age||Proterozoic Z|
Igneous > Plutonic > Granitic > GraniteLight grayish-pink to greenish-gray, equigranular to slightly porphyritic, variably altered, granite south and west of Boston.
Igneous > Plutonic > Syenitic > Quartz-monzoniteBarefoot Hills Quartz Monzonite of Lyons (1969) and Lyons and Wolfe (1971).
Igneous > Plutonic > DioriticIncludes dioritic rock near Scituate and Cohasset.
|Comments||Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA018. Proterozoic Z age of Dedham is based on the following isotopic dates: . 1. 630 +/-15 Ma by U/Pb methods on zircon (Zartman and Naylor, 1984) from Dedham Granite. 2. 595 +/-17 Ma by Rb/Sr whole rock methods (Kovach and others, 1977) from Dedham Granite north of Boston. 3. 640 +/-14 Ma by K/Ar methods on hornblende (Zartman and Naylor, 1984) per MA007.|
Zen, E-An (ed.), Goldsmith, R. (comp.), Ratcliffe, N.M. (comp.), Robinson, P. (comp.), Stanley, R.S. (comp.), Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., and Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.
Wones, D.R. and Goldsmith, Richard, 1991, Intrusive rocks of eastern Massachusetts, Chapter I, IN Hatch, N.L., Jr., ed., The bedrock geology of Massachusetts: U.S. Geological Survey Professional Paper, 1366-E-J, p. I1-I61.
Hepburn, J.C., Hon, Rudolph, Dunning, G.R., Bailey, R.H. and Galli, Kenneth, 1993, The Avalon and Nashoba terranes (eastern margin of the Appalachian Orogen in southeastern New England), IN Cheney, J.T., and Hepburn, J.C., eds., Field trip guidebook for the northeastern United States; 1993 Boston GSA; Volume 2: University of Massachusetts, Geology Department Contribution, no. 67, Joint annual meeting of Geological Society of America, Annual Meeting, and New England Intercollegiate Geological Conference, 85th Annual Meeting, Boston, MA, October 25-28, 1993, p. X1-X31.
|Counties||Bristol - Middlesex - Norfolk - Plymouth - Suffolk|