Geology of Georgia (U.S. state)

[3] The Appalachian foreland of Georgia, which lies in the northwest corner of the state, is separated from metamorphic rocks of the western Blue Ridge by the Talladega-Cartersville-Great Smoky fault.

Each of these rock units were deposited on the passive margin of North America after it rifted away from the supercontinent of Rodinia during the Neoproterozoic, but prior to the earliest phases of Appalachian mountain building in the Paleozoic.

By the Early Ordovician Period (485 - 470 million years ago), a subduction zone had developed offshore of the North American continent (Laurentia) in the adjacent Iapetus Ocean.

[5] Rocks of the western Blue Ridge are interpreted to be metamorphosed equivalents of stratigraphy in the Appalachian foreland, all of which formed along the Paleozoic margin of ancient North America.

The Piedmont is home to prominent features like Stone Mountain[5] and the Brevard fault zone, which runs parallel to the Chattahoochee River and bisects cities like Suwanee, Atlanta, Buford, and Duluth.

The geological Piedmont includes metamorphic rocks of the Dadeville Complex, an Ordovican arc terrane that lay seaward of the North American continental margin and a fringing back-arc basin.

Rocks of the Carolina terrane collided with ancient North American during the final stages of Appalachian mountain building, but remained sutured to the continent following the Mesozoic breakup of Pangea and the separation of Africa and South America during formation of the Atlantic Ocean.

The Coastal Plain in Georgia is part of a geologic and physiographic region that extends from New Jersey to Texas and consists of sedimentary rocks deposited in the Late Cretaceous to Holocene periods.

[8] It is divided from the Piedmont by the Fall Line, which passes through Georgia from Augusta in the east, then southwestward to Macon, then to Columbus and finally westward to Montgomery, Alabama.

[9] Rocks in the exposed Coastal Plain region of Georgia range from the Late Cretaceous Tuscaloosa Formation to modern Holocene sediments actively forming along the Atlantic coast.

In the subsurface, Triassic basalts of the South Georgia Rift lie beneath younger sedimentary deposits in extensive, regional grabens.