Brimfield Schist (Includes Hamilton Resevoir Formation) (CTObr;0)

State	Connecticut
Name	Brimfield Schist (Includes Hamilton Resevoir Formation)
Geologic age	Upper? and Middle Ordovician
Lithologic constituents	Major Metamorphic > GneissGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across; minor layers and lenses of hornblende- and pyroxene-bearing gneiss. Metamorphic > SchistGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across. Minor Metamorphic > Amphibolite Metamorphic > Metasedimentary > Calc-silicate-rock
Comments	Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Brimfield Schist and equivalent formations (includes Tatnic Hill Formation) (Upper? and Middle Ordovician). The age of the Brimfield Group in this area is Cambrian(?) based on the intrusion of 440 my Hedgehog Hill gneiss in the top of the Hamilton Reservoir Formation in the upper part of the Brimfield, although the top of the Brimfield may be Ordovician or older Paleozoic (Pease, 1989) per CT013.
References	Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000. Pease, M.H., Jr., 1989, Correlation of the Oakdale Formation and Paxton Group of central Massachusetts with strata in northeastern Connecticut: U.S. Geological Survey Bulletin, 1796, 26 p. https://pubs.er.usgs.gov/publication/b1796
NGMDB product	NGMDB product page for 54245
Counties	Hartford - Middlesex - New London - Tolland - Windham

State

Name

Brimfield Schist (Includes Hamilton Resevoir Formation)

Geologic age

Upper? and Middle Ordovician

Lithologic constituents

Major

Metamorphic > GneissGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across; minor layers and lenses of hornblende- and pyroxene-bearing gneiss.

Metamorphic > SchistGray, rusty-weathering, medium- to coarse-grained, interlayered schist and gneiss, composed of oligoclase, quartz, K-feldspar, and biotite, and commonly garnet, sillimanite, graphite, and pyrrhotite. K-feldspar partly as augen 1 to 3 cm across.

Minor

Metamorphic > Amphibolite

Metamorphic > Metasedimentary > Calc-silicate-rock

Comments

Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Brimfield Schist and equivalent formations (includes Tatnic Hill Formation) (Upper? and Middle Ordovician). The age of the Brimfield Group in this area is Cambrian(?) based on the intrusion of 440 my Hedgehog Hill gneiss in the top of the Hamilton Reservoir Formation in the upper part of the Brimfield, although the top of the Brimfield may be Ordovician or older Paleozoic (Pease, 1989) per CT013.

References

Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.

Pease, M.H., Jr., 1989, Correlation of the Oakdale Formation and Paxton Group of central Massachusetts with strata in northeastern Connecticut: U.S. Geological Survey Bulletin, 1796, 26 p.

https://pubs.er.usgs.gov/publication/b1796

NGMDB product

NGMDB product page for 54245

Counties

Hartford - Middlesex - New London - Tolland - Windham