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Glastonbury Gneiss

Glastonbury Gneiss - Gray, medium- to coarse-grained, massive to well-foliated granitoid gneiss composed of oligoclase, quartz, microcline, and biotite (as patches), also epidote and hornblende in many areas, commonly associated with layers of amphibolite; elsewhere minor muscovite and garnet.
StateConnecticut
NameGlastonbury Gneiss
Geologic ageMiddle? Ordovician
Original map labelOgl
CommentsPart of Eastern Uplands; Iapetus (Oceanic) Terrane - Bronson Hill Anticlinorium
Primary rock typegranitic gneiss
Secondary rock typeamphibolite
Other rock types
Lithologic constituents
Major
Metamorphic > GneissGray, medium- to coarse-grained, massive to well-foliated granitoid gneiss composed of oligoclase, quartz, microcline, and biotite (as patches), also epidote and hornblende in many areas, commonly associated with layers of amphibolite; elsewhere minor muscovite and garnet.
Minor
Metamorphic > Amphibolitecommonly associated with layers of amphibolite
Map references
Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, data format: shapefile, file name: bedrock, downloaded from: http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000 on 9/18/2003, scale 1:50,000.
Unit references
Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 125,000.
Geographic coverageHartford - Middlesex - Tolland

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