|Geologic age||Lower Jurassic|
Sedimentary > Clastic > Conglomerate
Sedimentary > Clastic > Sandstone > Arkose
|Comments||Part of Mesozoic Basins (Jurassic and Triassic Rocks); Sedimentary and Volcanic Rocks of Hartford Basin. Secondary unit description per MA003 as reported in USGS Geologic Names lexicon (Rf. MA024): Used as Portland Formation of Early Jurassic age. Consists of reddish-brown to pale-red arkose and siltstone, and gray sandstone, gray siltstone, and black shale; interpreted as lake beds. Reddish-brown to pale-red conglomerate and arkose mapped separately as an informal member. Assigned to Newark Supergroup. Upper part may be Middle Jurassic according to Cornet (1977) (Robinson and Luttrell, 1985).|
Zen, E-An (ed.), Goldsmith, R. (comp.), Ratcliffe, N.M. (comp.), Robinson, P. (comp.), Stanley, R.S. (comp.), Hatch, N.L., Jr., Shride, A.F., Weed, E.G.A., and Wones, D.R., 1983, Bedrock Geologic Map of Massachusetts: U.S. Geological Survey, Reston, VA, scale 1: 250,000.
Robinson, Peter and Luttrell, G.W., 1985, Revision of some stratigraphic names in central Massachusetts, IN Stratigraphic notes, 1984: U.S. Geological Survey Bulletin, 1605-A, p. A71-A78.
USGS Geologic Names lexicon found at: http://ngmdb.usgs.gov/Geolex/
|Counties||Hampden - Hampshire|