Erving Formation (MADeg;0)

State	Massachusetts
Name	Erving Formation
Geologic age	Lower Devonian
Original map label	Deg
Comments	Part of Connecticut Valley Belt (Silurian and Devonian Rocks) Secondary unit description per MA006. as reported in USGS Geologic Names lexicon (ref. MA024): Erving Formation in its type area consists of gray, well-bedded fine-grained, quartz-plagioclase-biotite granulite with very thin to thick beds of muscovite-biotite schist. Second most abundant rock type is hornblende-andesine-epidote-sphene amphibolite; occurs west of Pelham dome, as well as in areas around Quabbin Hill, Wilbraham, Whately, and Leeds. Pink coticule granulite occurs within main granulite bodies, usually within 1 to 2 m of contact with amphibolite; common in type area, as well as near Leverett and near Quabbin Hill on shores of Quabbin Reservoir. Near base of formation in Wilbraham area, includes a unit of interlayered amphibolite and gray to rusty schist. In most areas, Erving is highest exposed unit, except in Wilbraham and Whately areas where it is overlain by Waits River and Gile Mountain Formations, respectively. Thicknesses vary from 200 to 900 m. Age is Devonian in this report (Hatch and others, 1988).
Primary rock type	granulite
Secondary rock type	schist
Other rock types
Lithologic constituents	Major Metamorphic > Granulite Minor Metamorphic > Schist > Mica-schist
Map references	Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon at Boston College in 1998.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. Hatch, N.L., Jr., Robinson, Peter and Stanley, R.S., 1988, Stratigraphy of the Connecticut Valley belt, Chapter B, IN Hatch, N.L., Jr., ed., Bedrock geology of Massachusetts: U.S. Geological Survey Professional Paper, 1366-A-D, p. B1-B34. [http://pubs.er.usgs.gov/publication/pp1366AD] USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/]
Geographic coverage	Franklin - Hampden - Hampshire