Cooleyville Granitic Gneiss (MADpgg;0)

State	Massachusetts
Name	Cooleyville Granitic Gneiss
Geologic age	Devonian
Original map label	Dpgg
Comments	Part of Connecticut Valley Belt (Silurian and Devonian Rocks); Prescott Complex. Secondary unit description per MA003 as reported in USGS Geologic Names lexicon (ref. MA024): Assigned to implicitly reinstated and revised Prescott Complex. Applied to extensive exposures of fine- to coarse-grained gneissic biotite tonalite, granodiorite, and granite that surround hornblende gabbro of Prescott Complex on Prescott Peninsula of Quabbin Reservoir. Unit is named for village of Cooleyville, western edge of Town of New Salem, Franklin Co., MA. Typical exposures occur in hills 0.8 to 3.2 km northeast, east, and southeast of Cooleyville. Intrudes Lower Devonian Littleton Formation and contains extensive inclusions of hornblende gabbro of Prescott Complex. Foliation and lineation are congruent and are identical to those found in adjacent gneiss domes that formed during Acadian Orogeny. Preliminary Rb-Sr whole-rock isochron (Naylor, 1970), based in part on deformed aplite dikes within the Cooleyville, suggests a minimum age of 385 m.y. (Devonian) (Robinson and Luttrell, 1985).
Primary rock type	tonalite
Secondary rock type	granite
Other rock types	gabbro
Lithologic constituents	Major Igneous > Plutonic > Granitic > GraniteBiotite tonalite to granite in composition, strongly foliated and lineated. Igneous > Plutonic > Granitic > TonaliteBiotite tonalite to granite in composition, strongly foliated and lineated. Minor Igneous > Plutonic > Gabbroic > Gabbrocontains inclusions of Dpgb (hornblende gabbro)
Map references	Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.
Unit references	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., Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000. Robinson, Peter and Luttrell, G.W., 1985, Revision of some stratigraphic names in central Massachusetts, IN Stratigraphic notes, 1984: U.S. Geological Survey Bulletin, 1605-A, p. A71-A78. [http://pubs.er.usgs.gov/publication/b1605A] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Franklin