Named for exposures on southeast side of Long Island Creek, near and along Roswell Rd, Sandy Springs 7.5-min quad, northwestern GA. Consists of dark-gray, epidote-biotite-plagioclase gneiss, weathering to yellow saprolite. Good exposures seen in cuts for driveways at new IBM facility on US Hwy 41, just southeast of Chattahoochee River in Northwest Atlanta 7.5-min quad. Thickness is unknown. Gneiss is in fault contact with adjacent rocks. Forms a mappable boundary with Sandy Springs Group. Age is unknown but is probably late Precambrian and (or) early Paleozoic [age is stated on p. 43 in another part of volume].

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

Yellow Dirt Gneiss is revised as an informal facies of Long Island Creek Gneiss. Sinha and Higgins (1987, Geological Society of America, Abstracts with Programs, v. 19, no. 7, p. 847) reported an age of 460 Ma for Yellow Dirt rocks. Authors now consider that age to be preliminary because it was determined partly on small intrusive granitic plutons of Yellow Dirt and partly on mylonitized Yellow Dirt, and because the date has not yet been supported by U-Pb ages from zircons. Age of Long Island Creek Gneiss and its Yellow Dirt facies is changed to Middle Proterozoic(?) to Permian(?).

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