1. Georgia Geology Notes – 4 Provinces
Blue Ridge
Valley & Ridge*
Piedmont
Fall Line
Coastal Plain
*Some authors include part of the Appalachian Plateau with the Valley & Ridge Province, while others combine the Blue Ridge & Piedmont.

2. 100 m.y. to 8,000 – Late Cretaceous to Holocene – Coastal Plain2
100 m.y. to 8,000 – Late Cretaceous to Holocene – Coastal Plain
220 m.y. to 190 m.y. – Diabase Dikes
545 m.y. to 286 m.y. – Cambrian – Pennsylvanian Periods (Valley & Ridge)
1.1 b.y. to 360? m.y. – Precambrian – Devonian? (Blue Ridge & Piedmont)
Geologic Time Scale

3. Valley & Ridge Province – (incl. Appalachian Plateau) 3
Valley & Ridge Province – (incl. Appalachian Plateau)
Cambrian – Pennsylvanian folded & faulted sedimentary rocks (544 to 286 m.y.)
Fracture and karst aquifers
Bounded by Cartersville and Great Smoky Mt. faults
Alternating anticlines & synclines, thrust faults
Cambrian – Ordovician sediments deposited on passive margin. Limestones, shales, sandstones.
Ordovician – Pennsylvanian – mostly clastics derived from rising highlands. Sandstones, shales, coal (Pennsylvanian Period)
Adapted from Ga. Geologic Survey state geologic map, 1977

4. 4
Four Major Events in Appalachian History –
Late Precambrian – Iapetus Ocean rifting
Late Ordovician Period – Taconic Orogeny
Late Devonian Period – Acadian Orogeny
Pennsylvanian Period – Alleghenian Orogeny
Taconic Orogeny –collision of Island Arc & Laurentia continent uplifted mountain range “Taconic Highlands”. Erosion of highlands produced a series of northwestward prograding “clastic wedges” (river deltas). Later orogenies rejunvenated uplands.
Shallow marine conditions
Foreland Basin
Taconic Highlands

5. 5
Interbedded shales and limestones, Ordovician Lexington Ls., Kentucky. Similar rock types are present in Valley and Ridge Province of NW Ga. , suggest passive margin deposition with a distant clastic source.

6. 6
Blue Ridge Province –
Precambrian – Devonian(?) igneous and metamorphic rocks – includes phyllites, schists, gneisses, metabasalts, other metavolcanics, marble, quartzite
Fracture aquifers, except for a few karst aquifers – Murphy Syncline
Highest topography in Georgia – 28 peaks > 4,000 ft.
Combined Blue Ridge & Piedmont geologic map
Piedmont Province – similar to Blue Ridge, except topography is lower and there are more igneous rocks – Pennsylvanian-aged granites & Triassic/Jurassic-aged diabase dikes.

7. Piedmont & Blue Ridge features7
Piedmont & Blue Ridge features
Deformed gneiss on Ronald Reagan Parkway
Etowah River cave

8. Triassic/Jurassic diabase (basalt) dike – Vulcan quarry, Beaver Ruin Rd./I-85

9. Appalachian Mountains – a quick summary
Late Precambrian (600 m.y.) – Rifting of super- continent, opening of Iapetus Ocean.
Late Ordovician (450 my.) – Island arc collision with North America – Taconic Orogen y
Clastic wedges accumulate NW of Taconic
Highlands.
Late Devonian (410 to 380 m.y.) – Collision of Baltica and North America – Acadian Orogeny
Late Pennsylvanian (320 m.y.) – Collision of N.A. with Africa, final deformation & uplift. Stone Mt. and other granites emplaced – 300 m.y..

10. Fall Line Cities – Columbus, Macon, Augusta 10
Fall Line – separates crystalline rocks of Piedmont from present extent of softer sediments of Coastal Plain.
Fall Line Cities – Columbus, Macon, Augusta
Marked by waterfalls and rapids.
Piedmont may have been partially covered by Eocene and Oligocene transgressions (sea level rises). Shoreline may have been low ridge of Brevard Fault Zone. Evidence eroded away.

11. Coastal Plain Province –
Late Cretaceous to Holocene (Recent) deposits at shoreline. Age – 70 m.y. - >10,000 yr.
Layered sediments, sands, clays, limestones.
Late Cretaceous sediments – mostly deltaic, including Providence Sand.
Paleocene – Oligocene sediments – mostly marine.
Miocene – Holocene – mostly continental deltaic, fluvial and alluvial sediments, except near coast.
Aquifers – uniform sediments, a few karst wells.

12. Residuum of Paleocene Clayton Fm
Residuum of Paleocene Clayton Fm. over deltaic Cretaceous Providence Sand

13. Resources
Valley & Ridge Province
Oil & Natural gas (other states), Coal, Limestone, Barite.
Blue Ridge Province
Marble, minerals in pegmatites, Gold, Sulfide minerals (including Copper), Talc, Corundum.
Piedmont Province
Granite, minor Gold, Copper, Feldspar, minerals in pegmatites, minor Marble.
Coastal Plain
Limestone, Kaolin, Bauxite, Sand.

14. Georgia Geology Notes - Review
Valley and Ridge Province
Hard, compacted Paleozoic sedimentary rocks, folded and faulted during uplift of Appalachian Mts.
Blue Ridge Province
Hard, Precambrian to Paleozoic metamorphic rocks, folded, faulted, and metamorphosed during uplift of Appalachian Mts.
Piedmont Province
Hard, Precambrian to Paleozoic metamorphic and igneous rocks, similar to Blue Ridge Province.
Coastal Plain Province
Soft, uncompacted Late Cretaceous through Cenozoic sediments, layers inclined gently toward Atlantic Ocean and Gulf of Mexico (SW Ga.)

15. Georgia Geology Notes - Groundwater Resources
Valley & Ridge Province –
Fracture zones, karst features (caverns, enlarged fractures)
Blue Ridge Province –
Fracture zones, karst features (in Marble)
Piedmont Province –
Fracture zones
Coastal Plain Province –
More uniform aquifers (softer sand, limestone, karst features – Regional Floridan aquifer – Georgia and Florida.

16. Georgia Geology Notes - Geology and Ecology
Geologic structures affect topography and stream channel distribution
Rock types influence soil type
Soil type influences nature of rainfall infiltration
Soil type and topography influence vegetation types
Hardness of rock influences type of porosity and permeability and aquifer types
Topography influences climate and microclimate
Rock type influences chemistry and pathways of ground water

17. Early Paleozoic Era Continental Shelf, preserved as Early Cambrian – Middle Ordovician (545 to 430 m.y.) sedimentary rocks – Valley & Ridge Province
Rifted continental margin – approx. 1.1 b.y.
Iapetus Ocean opening until Early Ordovician Period

18. Initial collision of N. America (Laurentia) & Island Arc System (Taconic Orogeny) downwarped continental margin – created Foreland Basin & Taconic Highlands.
Inland Sea to Northwest (mostly limestones)
Taconic Highlands
Foreland Basin

19. Present-day Appalachian (Cumberland) Plateau (left side) & Valley & Ridge Province – folded, thrust-faulted Paleozoic Era sedimentary rocks.
Compression during Continental Collisions

20. Change from passive margin to clastic wedge is recorded in Taylor Ridge roadcut on I-75 Ringgold, GA.
Photo by P. Bouker

21. Rifted continental margin – eroded Appalachian Mts.
Late Mesozoic/Early Cenozoic Era Continental Shelf, preserved as Late Cretaceous – Recent sediments – Coastal Plain Province
Continental Shelf deposits
Rifted continental margin – eroded Appalachian Mts.
Atlantic Ocean opening began during Late Triassic Period

22. Coastal Plain Atlantic Ocean
Valley & Ridge
Fall Line
Coastal Plain
Atlantic Ocean
Blue Ridge & Piedmont Igneous & Metamorphics