Partridge Formation (includes Brimfield Schist of Emerson, 1917) (MAOpsa;0)

State	Massachusetts
Name	Partridge Formation (includes Brimfield Schist of Emerson, 1917)
Geologic age	Middle Ordovician
Lithologic constituents	Major Metamorphic > Amphibolite Metamorphic > Schist > Mica-schistsulfidic mica schist
Comments	Part of Bronson Hill Zone (Ordovician and Older Rocks). U-Pb zircon ages suggest that the Ammonoosuc Volcanics and tuffs of the Partridge Formation were erupted between 453 to 449 Ma, meaning they are of late Middle Ordovician and earliest Late Ordovician age. The stratigraphic relationships of these two units is very complex with current thought being that the Partridge lies between the lower and upper members of the Ammonoosuc Volcanics (Tucker and Robinson, 1990) per MA015.
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., and Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000. https://pubs.er.usgs.gov/publication/70046713 Tucker, R.D. and Robinson, Peter, 1990, Age and setting of the Bronson Hill magmatic arc; a re-evaluation based on U-Pb zircon ages in southern New England: Geological Society of America Bulletin, v. 102, no. 10, p. 1404-1419.
NGMDB product	NGMDB product page for 16357
Counties	Franklin - Hampden - Hampshire - Worcester

State

Massachusetts

Name

Partridge Formation (includes Brimfield Schist of Emerson, 1917)

Geologic age

Middle Ordovician

Lithologic constituents

Major

Metamorphic > Amphibolite

Metamorphic > Schist > Mica-schistsulfidic mica schist

Comments

Part of Bronson Hill Zone (Ordovician and Older Rocks). U-Pb zircon ages suggest that the Ammonoosuc Volcanics and tuffs of the Partridge Formation were erupted between 453 to 449 Ma, meaning they are of late Middle Ordovician and earliest Late Ordovician age. The stratigraphic relationships of these two units is very complex with current thought being that the Partridge lies between the lower and upper members of the Ammonoosuc Volcanics (Tucker and Robinson, 1990) per MA015.

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., and Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.

https://pubs.er.usgs.gov/publication/70046713

Tucker, R.D. and Robinson, Peter, 1990, Age and setting of the Bronson Hill magmatic arc; a re-evaluation based on U-Pb zircon ages in southern New England: Geological Society of America Bulletin, v. 102, no. 10, p. 1404-1419.

NGMDB product

NGMDB product page for 16357

Counties

Franklin - Hampden - Hampshire - Worcester