Usage of Waterford Group follows Goldsmith (1980; 1985). Described as a sequence of metavolcanic and metaplutonic plagioclase gneisses and amphibolites that unconformably overlies the Plainfield Formation in the Hope Valley terrane. (Hope Valley and Esmond-Dedham terranes compose the Avalon superterrane of this report.) Thickness of Waterford is variable; ranges to 3,100 m. Group subdivided (ascending) into Mamacoke Formation with its upper Cohanzie Member (first used?), New London Gneiss, and Rope Ferry Gneiss. New London consists of a layered facies and a massive facies. Layered facies described as alternating layers of light-colored biotite-quartz-plagioclase gneiss and amphibolite. Massive facies described as a granodiorite gneiss with a uniform texture, grain size, and color. Contains shiny black biotite plates and distinctive magnetite grains.

Source: GNU records (USGS DDS-6; Reston GNULEX).