Fitchburg Complex (MADfgd;0)

State	Massachusetts
Name	Fitchburg Complex
Geologic age	Lower Devonian or younger
Original map label	Dfgd
Comments	Part of Merrimack Belt (Silurian, Devonian and Pennsylvanian Rocks) Secondary unit description per MA007 as reported in USGS Geologic Names lexicon (re.f MA024): Fitchburg Complex mapped as three small stocks intruding Worcester Formation east of Wekepeke fault and west of Clinton. Also intrudes Paxton and Littleton Formations. U-Pb zircon age of 390 +/-15 Ma and Rb-Sr whole-rock age of 402 +/-11 Ma were both reported by Zartman and Naylor (1984) (Wones and Goldsmith, 1991).
Primary rock type	granitic gneiss
Secondary rock type	mica schist
Other rock types	phyllite
Lithologic constituents	Major Metamorphic > Gneissstrongly foliated biotite granodiorite to tonalite gneiss Incidental Metamorphic > Metasedimentary > Metaclastic > Phylliteintrudes and contains inclusions of Dl (Littleton Formation) Metamorphic > Schistintrudes and contains inclusions of Dl (Littleton Formation)
Map references	Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.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. 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. [http://pubs.er.usgs.gov/publication/pp1366EJ] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Middlesex - Worcester