Rocks mapped as the Shelton facies of the Trap Falls Formation by Crowley (1968) are here named the Shelton Member of the Trap Falls in the Hartland belt of the Connecticut Valley synclinorium. It consists of white, light-gray, or buff, fine- to medium-grained, foliated granitic gneiss composed of sodic plagioclase, quartz, microcline, muscovite, and garnet in tiny grains, interlayered with mica schist, biotite, gneiss, and calc-silicate rock. It is thought to be the metavolcanic equivalent of granitic gneiss which has been termed Ansonia, Mine Hill, "Tyler Lake," and "Siscowit" gneiss. Age is Early or Middle Ordovician.

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

Shelton Member of Trap Falls Formation (Rodgers, 1985) is here referred to as Shelton muscovite granite. On the basis of field and laboratory studies, Ansonia, Beardsley, Pumpkin Ground, and Shelton gneisses, previously considered stratigraphic units, are reinterpreted as plutonic. Shelton is a foliated, medium-grained, garnet-bearing muscovite leucogranite with a conspicuous white color and abundant garnets. Age of crystallization determined from U-Pb garnet analysis is 380+/-3 Ma (Middle Devonian). Southeast margin of the Shelton is in contact with the Trap Falls Formation.

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