|Geologic age||Lower Cambrian and Proterozoic Z|
Metamorphic > Metasedimentary > Metaclastic > Phyllitealbite-spotted phyllite
Metamorphic > Metasedimentary > Metaclastic > Metasandstone > Metagraywackeinterbedded blue-quartz metagraywacke
Sedimentary > Carbonate > Dolostone
Sedimentary > Clastic > Conglomerateblue-quartz conglomerate
Metamorphic > Metasedimentary > Metaclastic > Quartzite
|Comments||Part of Taconic-Berkshire Zone (Ordovician and Older Rocks); in the Taconic Allochthon. Secondary unit description from USGS Geologic Names lexicon (ref MA024): Used as Greylock Schist of Proterozoic Z and Early Cambrian age. Divided into two informal unit. Lowermost unit consists of light-green to gray, white albite-spotted phyllite and interbedded blue-quartz metagraywacke, salmon-pink dolostone, and blue-quartz conglomerate; contains minor interbeds of black and white albite-spotted phyllite resembling part of Hoosac Formation. Uppermost part consists of soft, lustrous green phyllite with minor beds of green quartzite and well-laminated, gray, dolomitic phyllite; resembles parts of Hoosac or Nassau Formations.|
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.