Portland Formation

Reddish-brown to pale red conglomerate and arkose.
State Massachusetts
Name Portland Formation
Geologic age Lower Jurassic
Lithologic constituents
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).
NGMDB product
Counties Hampden - Hampshire