Hebron Gneiss (CTSOh;0)

State	Connecticut
Name	Hebron Gneiss
Geologic age	Silurian and Ordovician
Lithologic constituents	Major 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 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
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.
References	Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000. 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. https://pubs.er.usgs.gov/publication/b1796
NGMDB product	NGMDB product page for 54245
Counties	Hartford - Middlesex - New London - Tolland - Windham

State

Name

Hebron Gneiss

Geologic age

Silurian and Ordovician

Lithologic constituents

Major

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

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

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.

References

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

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.

https://pubs.er.usgs.gov/publication/b1796

NGMDB product

NGMDB product page for 54245

Counties

Hartford - Middlesex - New London - Tolland - Windham