|Name||Nashoba Formation - Boxford Member|
|Geologic age||Ordovician or Proterozoic Z|
Metamorphic > Amphibolite
Metamorphic > Gneiss > Biotite-gneiss
|Comments||Part of Nashoba Zone (Silurian and Older Rocks). Secondary unit description per MA017. Although age on MA State bedrock map is shown as Proterozoic Z or Ordovician (due to uncertainty regarding actual rocks sampled by Olszewski and a strong belief that rocks of Nashoba zone correlated with Ordovician rocks to the west), author now feels that rocks of Nashoba zone (except for Tadmuck Brook Schist) are all Proterozoic, but that they are unlike the Proterozoic rocks of neighboring Milford-Dedham zone. [No formal age change is made in this report.] per MA017.|
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.
Goldsmith, Richard, 1991, Stratigraphy of the Nashoba zone, eastern Massachusetts; An enigmatic terrane, IN Hatch, N.L., Jr., ed., The bedrock geology of Massachusetts: U.S. Geological Survey Professional Paper, 1366-F, 22 p.
|Counties||Essex - Middlesex - Worcester|