Georgia Geology Notes 4 Provinces

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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.
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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
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• 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
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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
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• 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
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Georgia Geology Notes
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Interbedded shales and limestones, Ordovician
Lexington Ls., Kentucky. Similar rock types are
present in Valley and Ridge Province of NW Ga.
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• 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.
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Piedmont Blue Ridge
Deformed gneiss on Ronald Reagan Parkway
Etowah River tunnel
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Triassic/Jurassic diabase (basalt) dike Vulcan
quarry, Beaver Ruin Rd./I-85
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• 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..

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• 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.

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• 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.

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

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Review
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• 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.)

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Groundwater Resources
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• 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.

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Geology and Ecology
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• 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

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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
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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
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Present-day Appalachian (Cumberland) Plateau
(left side) Valley Ridge Province folded,
thrust-faulted Paleozoic Era sedimentary rocks.
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Compression during Continental Collisions
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Change from passive margin to clastic wedge is
recorded in Taylor Ridge roadcut on I-75 N _at_
Ringgold, GA.
Photo by P. Bouker
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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
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Valley Ridge
Fall Line
Coastal Plain
Atlantic Ocean
Blue Ridge Piedmont Igneous Metamorphics