Hebron Gneiss (CTSOh;0)

State	Connecticut
Name	Hebron Gneiss
Geologic age	Silurian and Ordovician
Original map label	SOh
Comments	Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Hebron Gneiss and equivalent formations (including equivalents of Paxton and Oakdale Formations of Massachusetts) (including Bigelow Brook and Southbridge Formations) (Silurian and Ordovician). The Hebron Formation is here restricted to rocks in the area south and west of the Willimantic dome, south of the Wangumbaug Lake fault, and west of a fault in the Fitchville quad delineated by the Lebanon Gabbro. It includes the type area of the Hebron. Other rocks formerly mapped as Hebron are here assigned to the Oakdale, Dudley, and Southbridge Formations. It is separated from all other stratigraphic units by fault or intrusive contacts across which no stratigraphy can be correlated. Age is Late Proterozoic(?) based on correlation with part of the Paxton Group (Pease, 1989) per CT013.
Primary rock type	schist
Secondary rock type	calc-silicate rock
Other rock types	mica schist
Lithologic constituents	Major Metamorphic > Metasedimentary > Calc-silicate-rockgreenish-gray, fine- to medium-grained calc-silicate rock, composed of labradorite, quartz, biotite, actinolite, hornblende, and diopside, and locally scapolite Metamorphic > SchistInterlayered dark-gray, medium- to coarse-grained schist, composed of andesine, quartz, biotite, and local K-feldspar; local lenses of graphitic two-mica schist
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. [http://magic.lib.uconn.edu/connecticut_data.html#environmental] [http://magic.lib.uconn.edu/cgi-bin/MAGIC_DBsearch2.pl?Geography=37800&Loc=0000]
Unit references	Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 125,000. Pease, M.H., Jr., 1989, Correlation of the Oakdale Formation and Paxton Group of central Massachusetts with strata in northeastern Connecticut: U.S. Geological Survey Bulletin, 1796, 26 p. [http://pubs.er.usgs.gov/publication/b1796]
Geographic coverage	Hartford - Middlesex - New London - Tolland - Windham