Island Mill Formation named as part of cover sequence in parautochthonous assemblage. Named for Island Mill, a peninsula into Allatoona Reservoir, Allatoona Dam 7.5-min quad, Bartow Co., northwestern GA. Type section is designated as outcrops along shore of Allatoona Reservoir from tip of Island Mill peninsula for 600 m northward along both sides of peninsula. Characteristic outcrops may also be seen on next peninsula to the east, north of George Washington Carver State Park in Allatoona Dam quad. Consists of interlayered dark-gray to nearly black graphitic metapelites (phyllite/schist) and tan to cream-colored nongraphitic metapelites. Maximum mapped outcrop width is approx 1.3 km (about 4000 ft), but isoclinal folds are present so stratigraphic thickness is unknown. Overlain by Bill Arp Formation; underlain by undivided Chilhowee Group. Stratigraphic position is probably between Nantahala and Bill Arp Formations. Basal unit along Emerson fault near Emerson, GA, in Rockmart South 7.5-min quad. Age is Late Proterozoic to Middle Ordovician. Report includes geologic map and correlation chart.

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