Preston Gabbro plus Quinebaug Formation (CTOp+Oq;0)

Preston Gabbro plus Quinebaug Formation

Preston Gabbro - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene, or olivine or both. Quinebaug Formation - Medium- to dark-gray, commonly greenish, medium-grained, well-layered gneiss, composed of hornblende, andesine, biotite, and epidote, commonly with quartz or garnet, interlayered with amphibolite.

State	Connecticut
Name	Preston Gabbro plus Quinebaug Formation
Geologic age	Middle Ordovician or older
Lithologic constituents	Major Metamorphic > GneissMedium- to dark-gray, commonly greenish, medium-grained, well-layered gneiss, composed of hornblende, andesine, biotite, and epidote, commonly with quartz or garnet. Igneous > Plutonic > Gabbroic > GabbroPreston Gabbro - Dark, medium- to coarse-grained, mainly massive gabbro, composed of labradorite, augite, and opaques, generally with hornblende, locally hypersthene, or olivine or both. Minor Metamorphic > AmphiboliteQuinebaug Formation - interlayered with amphibolite.
Comments	Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Units are described seperately on printed map; combined in digital map.
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

Preston Gabbro plus Quinebaug Formation

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