Plainfield Formation (CTZp;0)

Plainfield Formation

Interlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite, light- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline), medium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet, dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside), amphibolite, diopsite-bearing quartzite, and calc-silicate rock. In places contains quartz-sillimanite nodules.

State	Connecticut
Name	Plainfield Formation
Geologic age	Proterozoic Z?
Lithologic constituents	Major Metamorphic > Metasedimentary > Metaclastic > QuartziteInterlayered light-gray, thin-bedded quartzite, in places with feldspar, mica, graphite, or pyrite; diopsite-bearing quartzite Minor Metamorphic > Schistmedium- to dark-gray schist composed of quartz, oligoclase, biotite, sillimanite, and garnet Metamorphic > Gneisslight- to medium-gray gneiss composed of quartz, oligoclase, and biotite (rarely microcline); dark-gray or green gneiss composed of plagioclase, quartz, biotite, and hornblende (commonly with diopside) Incidental Metamorphic > Metasedimentary > Calc-silicate-rock Metamorphic > Amphibolite
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	New London - Windham

Plainfield Formation

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