Named for community of Yellow Dirt, Lowell 7.5-min quad, Heard Co., western GA. Includes rocks previously mapped as the informally named Yellow Dirt gneiss of Crawford and Medlin (1974). Consists of fine- to medium-grained, biotite-epidote-muscovite-quartz-plagioclase-microcline gneiss that generally has strong cataclastic textures (blastomylonite and mylonite gneiss). Thickness estimated at 75-240 m (250-800 ft). Bounds Sandy Springs Group for long distances. Because it is fault bounded, its stratigraphic position and age are unknown.

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 therefore changed to Middle Proterozoic(?) to Permian(?).

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