State | Connecticut |
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Name | Brookfield Gneiss |
Geologic age | Middle? Ordovician |
Lithologic constituents |
Major
Metamorphic > Metaigneous > OrthogneissGneiss (dioritic and granodioritic) - Dark and light, commonly speckled or banded, medium- to coarse-grained, massive to poorly foliated gneiss, composed of plagioclase, biotite, and hornblende, generally with quartz and K-feldspar, the latter commonly as megacrysts 1 to 3 cm across (also plagioclase megacrysts in darker rocks).
Incidental
Metamorphic > Amphibolite
Metamorphic > Schist > Amphibole-schisthornblende schist
|
Comments | Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Newtown Gneiss of Crowley, 1968 (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. |
NGMDB product | |
Counties | Fairfield - Litchfield - New Haven |