Manhattan Schist (Including Waramaug Formation and Canaan Mountain Schist)

Dark-gray to silvery, rusty-weathering, generally coarse grained, foliated but poorly layered to massive gneiss or schistose gneiss, composed of quartz, oligoclase, microcline, biotite, and muscovite, and generally sillimanite and garnet. Amphibolite layers locally, especially near base where in places separately mapped as unit CAma. Cambrian Manhattan Schist in this report includes four informal members: Warren member, garnetiferous biotite schist member, Shepaug member, and schistose granulite member. The Warren member occurs only in the Above All thrust sheet, the Shepaug member only in the Rabbit Hill thrust sheet. The schist member occurs in both. The granulite member occurs in the Rabbit Hill thrust sheet and the Lake Waramaug thrust sheet. The Warren includes mainly interbedded, dark-gray, muscovite-garnet-chlorite-plagioclase-biotite-quartz schist, amphibolite lenses, siliceous granulite, and finely-layered schistose gneiss. The Shepaug consists of interbedded orthoclase-garnet-plagioclase-biotite-quartz schistose gneiss, rusty-weathering, schistose gneisses and schists with sillimanite rods, and subordinate granulite beds with sillimanite nodules similar to those in the schistose granulite member (Panish, 1992).
State Connecticut
Name Manhattan Schist (Including Waramaug Formation and Canaan Mountain Schist)
Geologic age Cambrian?
Lithologic constituents
Major
Metamorphic > GneissDark-gray to silvery, rusty-weathering, generally coarse grained, foliated but poorly layered to massive gneiss or schistose gneiss, composed of quartz, oligoclase, microcline, biotite, and muscovite, and generally sillimanite and garnet.
Minor
Metamorphic > AmphiboliteAmphibolite layers locally, especially near base where in places separately mapped as unit CAma.
Comments Part of Western Uplands; Proto-North American (Continental) Terrance - Displaced Iapetus Terrane; including Waramaug Formation and Canaan Mountain Schist. Secondary unit description per CT003.
References

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

Panish, P.T., 1992, The Mt. Prospect region of western Connecticut; mafic plutonism in Iapetus-sequence strata and thrust emplacement onto the North American margin, IN Robinson, Peter, and Brady, J.B., eds., Guidebook for field trips in the Connecticut Valley region of Massachusetts and adjacent states; Volume 2: University of Massachusetts, Geology Department Contribution, no. 66, New England Intercollegiate Geological Conference, 84th Annual Meeting, Amherst, MA, October, 9-11, 1992, p. 398-423.

NGMDB product
Counties Fairfield - Litchfield