Paleontology and geology
In the Devonian, a broad and relatively deep marine environment spread into the northern part of Georgia. Reducing circulation caused oxygen-poor conditions and the deposition of muds rich in organic material. Not much marine life was able to live in these bottom waters, although some burrows indicate sporadic colonization of the sea floor. The Appalachians were undergoing a second episode of mountain building (the Acadian Orogeny), which was caused by the closing of the Iapetus Ocean. In the north-central part of Georgia, large bodies of igneous material solidified below the surface as a result of this orogeny. The most famous of these structures is Stone Mountain, a large granitic intrusion now exposed near Atlanta. This map indicates the presence of Devonian rocks in northwestern Georgia; however, no Devonian fossils are known from the state.