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.

100 m.y. to 8,000 – Late Cretaceous to Holocene – Coastal Plain 2 100 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

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 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 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 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.

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

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

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..

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.

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.

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

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.

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.)

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.

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

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

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

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

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

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

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