The Straits Schist (Goshen Formation of Massachusetts)

Silvery to gray, non-rusty, coarse- to very coarse grained, generally poorly layered schist, composed of quartz, muscovite, biotite, oligoclase, garnet, and commonly with staurolite and kyanite or sillimanite; graphitic almost throughout. Distinctive sequence of metamorphic strata overlying the Collinsville Formation in the Bristol quad., is here correlated with the Straits Schist of Fritts (1963) in the Southington quad. Consists mainly of rusty-weathering, medium- to coarse-grained, commonly crenulated, garnet-bearing, graphitic, muscovite-rich, plagioclase-quartz schist with graded bedding. Unit is called The Straits Schist following the original usage of Rodgers and others (1959). In the southern part of the Bristol quad., unit includes the Southington Mountain Member (here reduced in rank) in its upper part. Age of The Straits is inferred to be Silurian or Devonian. Unit is tentatively correlated with the Goshen Formation based on lithologic similarities and a possible unconformity at the base (Simpson, 1990).
State Connecticut
Name The Straits Schist (Goshen Formation of Massachusetts)
Geologic age Devonian or Silurian or both
Lithologic constituents
Major
Metamorphic > SchistSilvery to gray, non-rusty, coarse- to very coarse grained, generally poorly layered schist, composed of quartz, muscovite, biotite, oligoclase, garnet, and commonly with staurolite and kyanite or sillimanite; graphitic almost throughout
Comments Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Hartland Belt Secondary unit description per CT008.
References

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

Simpson, H.E., 1990, Bedrock geology of the Bristol quadrangle, Hartford, Litchfield, and New Haven Counties, Connecticut: U.S. Geological Survey Bulletin, 1573, 13 p.

https://pubs.er.usgs.gov/publication/b1573

NGMDB product
Counties Fairfield - Hartford - Litchfield - New Haven