Georgia Geology

I can describe Georgia's geology as varied, challenging, and a bit messy. The state comprises three major geologic zones:

Rocks in each zone differ strongly in age and character from those in other zones. Physiographic divisions generally follow geologic zones, although Blue Ridge landforms have greater relief than the rolling Piedmont.

Georgia’s elevations range from zero (sea level) at the coast to 4,784 feet (1,458 meters) at Brasstown Bald in our northeast mountains. In Georgia's relatively mild, wet climate -- subtropical in low-elevation southern counties -- rocks decompose quickly (in the context of geologic time). We have lots of saprolite and vegetation, but in some areas of Georgia the most difficult part of geologic investigation is finding rock!

* Reality Check! *

Geologists: If you find errors of fact or wacky interpretations in this section, please e-mail me.
These pages reflect my understanding, and I am not a professional or trained geologist.


Georgia's Geologic Zones
Ridge and Valley Blue Ridge / Piedmont Coastal Plain
Area of Georgia Northwest corner Northeast and central Southern
Major Cities Rome Atlanta, Athens Columbus, Macon, Augusta, Savannah
Boundaries East: Carters Dam Fault;
South: Emerson Fault		 Northwest: Carters Dam and Emerson Faults;
South: Fall Line		 North: Fall Line;
Southeast: Atlantic coast
Landforms Northeast-trending ridges and valleys; flat-topped mountains in extreme northwest (Cumberland Plateau) Rounded mountains in north; foothills diminishing south to Fall Line; dendritic drainage patterns Low, rolling hills and plains; meandering rivers
Rock Type Sedimentary: sandstone, shale, limestone, dolomite, chert Metamorphic: gneiss, schist, quartzite, meta-everything
Igneous: granite, diabase		 Sedimentary: sandstone, limestone, weakly lithified and loose sediments
Rock Age Cambrian to Pennsylvanian Pre-Cambrian to Triassic / Jurassic Late Cretaceous to Holocene
Major Features Lookout and Sand Mountains; southern extension of the Great Valley; Coosa River Blue Ridge mountains, including Brasstown Bald and Tallulah Falls Dome; Cohutta mountains; Murphy marble belt; Brevard fault zone; upper Chattahoochee River; Pine Mountain; Soapstone Ridge; Stone Mountain Trail Ridge; the Okefenokee Swamp; lower Chattahoochee River; Providence Canyon; Altamaha river system; Carolina bays; limesinks; barrier islands
Probable Origin Relatively shallow marine environment, near shore of proto-North America; deformed in more-or-less parallel wrinkles when proto-Africa collided to assemble Pangea Iapetus (Atlantic ancestor) ocean basin crust and sediment; remnants of island arcs or microcontinents; possible fragments of proto-Africa; multiply deformed and strongly metamorphosed during closure of Iapetus basin Relatively shallow marine environment; deposited on underlying metamorphic rocks since late Cretaceous time, when sea level stood at the Fall Line
Fossils Cambrian to Pennsylvanian marine creatures and terrestrial plants Almost none; a few trilobites in slate Cretaceous to Holocene marine and terrestrial; rare dinosaur fragments

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