|Name||Unit c [of Stockbridge Marble]|
|Geologic age||Upper Cambrian|
Metamorphic > Metasedimentary > Metacarbonate > MarbleGray, generally massive dolomite marble, commonly contains quartz grains.
Sedimentary > Clastic > Sandstonelocally beds of sandstone; may be calcitic near top
|Comments||Part of Western Uplands; Proto-North American (Continental) Terrane - Carbonate Shelf Secondary unit description from USGS Geologic Names lexicon (ref. CT017): Revised as Stockbridge Formation, a heterogeneous rock group that may be mapped as seven lithostratigraphic units A through G (ascending). Highest bed as mapped by Dale (1923) is interbedded with overlying schist and is reassigned to Walloomsac Formation. Units A, B, and C are mostly dolostone and include important beds of arkose and phyllite. Units D and F are heterogeneous rocks consisting of silty limestone, dolostone, calcite marble, phyllite, and calcareous sandstone. Sandstone shows cross-stratification that allows determination of the top of bedding. Units E and G are massive, white to gray calcite marble that include interbedded pale, massive, fine-grained dolostone. Because of this heterogeneity, the name is revised to Stockbridge Formation. Excellent exposures may be seen at Vossburg Hill and on hillside south of South Egremont village in Egremont quad, MA and NY. Yields no fossils but overlies Cheshire Quartzite of Early Cambrian age and underlies Middle Ordovician Walloomsac Formation; therefore, the Stockbridge spans the age between Early Cambrian and Early or Middle Ordovician.|
Rodgers, John, compiler, 1985, Bedrock Geological Map of Connecticut: Connecticut Geological and Natural History Survey, Hartford, Connecticut, 2 sheets, scale 1:125,000.
USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/