Mamacoke Formation (CTZwm;0)

Mamacoke Formation

Interlayered (but layers locally indistinct) light- to dark-gray, medium-grained gneiss, composed of plagioclase, quartz, and biotite; sillimanite, garnet, hornblende, or microcline in certain layers; in upper part locally contains quartz-sillimanite nodules or thin layers of quartzite, amphibolite, or calc-silicate rock.

State	Connecticut
Name	Mamacoke Formation
Geologic age	Proterozoic Z?
Lithologic constituents	Major Metamorphic > GneissInterlayered (but layers locally indistinct) light- to dark-gray, medium-grained gneiss, composed of plagioclase, quartz, and biotite; sillimanite, garnet, hornblende, or microcline in certain layers. Incidental Metamorphic > Metasedimentary > Metaclastic > Quartzitein upper part locally contains quartz-sillimanite nodules or thin layers of quartzite Metamorphic > Metasedimentary > Calc-silicate-rockcalc-silicate rock in upper part Metamorphic > Amphibolitein upper part
Comments	Part of Eastern Uplands; Avalonian (Continental) Terrane; Avalonian Anticlinorium
References	Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.
NGMDB product	NGMDB product page for 54245
Counties	Middlesex - New London

Mamacoke Formation

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