Geology of Georgia

1
Geology of Georgia

• Paleozoic Deposits of the
• Late Ordovician, Silurian and Early Devonian
  Periods
• by
• Kimberly Sams
• May 1, 2006

2
GeologicTime Scale
Source Geologic Time Scale, Geological Society
of America, 1999, from Boggs, 2006.
3
Periods in this Chapter

• From oldest to youngest
• Late Ordovician
• Ordovician 490 and 443 million years ago
• Silurian
• 443 and 417 million years ago
• Early Devonian
• Devonian 417 and 354 million years ago

4
Geographic Region

• Ridge and Valley (Great Valley) and Plateau
• Northwest Georgia
• Blue Ridge
• Northeast Georgia

Source Carl Vinson Institute of Government, The
University of Georgia, 1999.
5
Geologic Mapof Georgia
Source Geologic Map of Georgia, Georgia
Geological Survey, 1976, from Cochran, 2006.
6
Geologic Mapof Georgia
Source Geologic Map of Georgia (12,000,000),
Lawton, 1977, Georgia Geological Survey, from
Cochran, 2006.
7
Geologic Map of theEastern United States
Source Physiographic Provinces of the United
States, U.S. Department of the Interior, U.S.
Geological Survey, 2000.
8
Principal Rocks
Source Dr. John Anderson, Georgia State
University
9
Upper Ordovician

• Two levels of the stratigraphic column
• Trenton Limestone
• Evidence that Trenton Limestone was once referred
  to as the Inman Formation
• Overlies the Lowville-Moccasin limestone of the
  Middle Ordovician
• Maysville Limestone
• Evidence that Maysville Limestone was once
  referred to as the Leipers Formation
• Overlies Trenton Limestone

10
Upper Ordovician

• Trenton Limestone
• Possibly also referred to as the Inman Formation
• Limestone
• Gray-red or green-gray
• Calcisiltites and shales
• Laminated to thinly bedded, finely cross-bedded
• Globular bryozoans, brachiopods, carbonized
  pelecypods

11
Upper Ordovician

• Maysville Limestone
• Possibly also referred to as the Leipers
  Formation
• Limestone
• Medium-gray
• Argillaceous clcilutite or calcisiltite
• Thick bedded
• Burrowing organisms, large brachiopods

12
Silurian

• Two levels of the stratigraphic column
• Sequatchie Formation
• Red Mountain Formation
• Primarily iron-rich sandstone, siltstone and shale

13
Silurian

• Sequatchie Formation
• Similar to the Murfreesboro limestone
• found in the valleys of the West Chickamauga
  Creek
• Divided into three members
• Ringgold (lower)
• Shellmound (middle)
• Mannie (upper)

14
Silurian

• Sequatchie Formation (continued)
• Ringgold Member
• Siltstones, sandstones and shales
• Red, green and gray
• No fossils
• member resembles those deposited in a clastic
  tidal flat (Chowns and OConnor, 1992)
• Mud cracks, ripple marks, birdseye structures

15
Silurian

• Sequatchie Formation (continued)
• Shellmound Member
• Siltstones
• Calcarenites and calcareous
• Bioturbated siltstones (most recognizable
  feature)
• Brachiopods, bivalves, bryozoans

16
Silurian

• Sequatchie Formation (continued)
• Mannie Member
• Shale rich in phosphate, limestones, bioturbated
  sandy mudstones, muddy sandstones siltstones,
  bioclastic wackestones
• Gastropods, bivalves, bryozoans

17
Silurian

• Red Mountain Formation
• Once called the Rockwood Formation?
• Comparisons of a historical geological formation
  table for Georgia
• Otto Veatch, 1909
• the Rockwood Formation forms the uppermost
  division of the Silurian system.

18
Silurian

• Red Mountain Formation (continued)
• Deposition
• Taconic and Acadian orogenies in the Appalachian
  Mountain Basin
• cephalopods in broken ore samples
• 5-15 mm long and 2-3 mm in diameter

19
Silurian

• Red Mountain Formation (continued)
• Lower Member
• Interbedded shales and sandstones
• Gray-red
• Parallel laminations, shallowing upwards,
  cross-bedded sandstones that coarsens upward with
  sole marks
• More fossiliferous than other Red Mountain Members

20
Silurian

• Red Mountain Formation (continued)
• Middle Member
• Shale, ironstone, some interbedded sandstone and
  shale
• Gray

21
Silurian

• Red Mountain Formation (continued)
• Upper Member
• Alternating beds of sandstone and shale
• Fossiliferous limestone and ironstone seams

22
Lower Devonian

• Devonian deposits
• Sandstone, shale, chert
• One level of the stratigraphic column
• Chattanooga Shale
• Armuchee Chert/Frog Mountain Chert (lower)

23
Lower Devonian

• Armuchee Chert (Frog Mountain Chert)
• Light gray with lenses of medium to coarse
  grained sandstone and shale
• Deposited in thin layers
• Shallow marine shelf environment
• Accumulations of sponges due to spiculitic
  appearance of the chert

24
Devonian

• Chattanooga Shale
• Fissile Shale
• Black to gray
• Deposited in layers up to 10 meters thick
• May be radioactive (Furcron, 1950)
• Few fossils
• Organic matter and pyrite in samples
• Deposited in stagnant, oxygen-deficient sea water

25
Next

• Susan Manfred will discuss the Mississippian

26
References Cited

• Anderson, John, 2006, Communication to Paleozoic
  Team.
• Bishop, A. C., Woolley, A. R., Hamilton, W. R.,
  2005, Guide to Minerals, Rocks Fossils Firefly
  Books (U.S.), Inc., p. 248-250.
• Boggs, Sam, 2006, Principles of Sedimentology and
  Stratigraphy, Pearson Education, Inc., Pearson
  Printice Hall, p. 517.
• Butts, C., 1948, Geology and Mineral Resources of
  the Paleozoic Area in Northwest Georgia, The
  Geological Survey, Bulletin Number 54, Georgia
  State Division of Conservation, Department of
  Mines, Mining and Geology, 1-20.
• Carl Vinson Institute of Government, 1999,
  Physiographic Provinces of Georgia, The
  University of Georgia, Retrieved April 19, 2006,
  from GeorgiaInfo http//www.cviog.uga.edu/Projec
  ts/gainfo/photogallery/physiomap.htm.
• Chowns, T. M., 1972, Molasse Sedimentation in the
  Silurian Rocks of Northwest Georgia, 7th Annual
  Field Trip, Georgia Geological Society
  Guidebooks, Guidebook 11, p. 13-22.
• Chowns, T. M., 1999, Sequence Stratigraphy
  Illustrations from the Silurian Red Mountain
  Formation of the Southern Appalachians, 34th
  Annual Field Trip, Georgia Geological Society
  Guidebooks, v. 19, p. 1-25.
• Chowns, T. M., OConnor, B. J., 1992,
  Cambro-Ordovician Strata in Northwest Georgia and
  Southeast Tennessee, The Knox Group and the
  Sequatchie Formation, 27th Annual Field Trip,
  Georgia Geological Society, Georgia Geological
  Society Guidebooks, v. 12, p. 1-20.
• Coenraads, Robert R, 2005, Rocks and Fossils A
  Visual Guide, Firefly Books Ltd., p. 74-78.
• Furcron, A. S., 1950, Geological Provinces of
  Georgia and Their Principal Mineral Resources, in
  Short Contributions to the Geology, Geography and
  Archaeology of Georgia, The Geological Survey,
  Bulletin Number 56, Georgia State Division of
  Conservation, Department of Mines, Mining and
  Geology, p. 17-20.
• Georgia Conservancy, The, 1999, Sherpa Guides,
  The Armuchee Ridges, ISBN1-56352-461-9,
  Retrieved April 10, 2006, from Sperpa Guides
  http//sherpaguides.com/georgia/mountains/cumberla
  nd_plateau/armuchee_ridges.html.
• Georgia Geological Survey, 1976, Geologic Map of
  Georgia from Chuck Cochran, http//home.att.net/c
  ochran3/rocks01/ggmndx01.htm.
• Georgia Humanities Council, 2006, The New Georgia
  Encyclopedia, Geologic History of Georgia
  Overview, Retrieved April 27, 2006, from
  http//www.georgiaencyclopedia.org/nge/ArticlePrin
  table.jsp?idh-3510.
• Hileman, Greg E., Lee, Roger W., 1993,
  Geochemistry of and Radioactivity in Ground Water
  of the Highland Rim and Central Basin Aquifer
  Systems, Hickman and Maury Counties, Tennessee,
  Investigations Report 92-4092, U.S. Geological
  Survey, Tennessee Department of Environment and
  Conservation, p. 11.
• Kansas Geological Survey, 1943, Forest City
  Basin, Retrieved April 27, 2006, from
  http//www.kgs.ku.edu/Publications/Bulletins/51/03
  _strat4.html.
• Lawton, David E., 1977, Geologic Map of Georgia
  (12,000,000), Georgia Geological Survey,
  Retrieved April 8, 2006, from http//home.att.net/
  cochrans/gmaprv01.htm.
• Milici, Robert C., Wedow, Jr., Helmuth, 1977,
  Upper Ordovician and Silurian Stratigraphy in
  Sequatchie Valley and Parts of the Adjacent
  Valley and Ridge, Tennessee, Geological Survey
  Professional Paper 996, U.S. Deaprtment of the
  Interior, Tennessee Division of Geology, p. 1-8.
• Nunan, W. E., 1972, Sedimentary Environment of
  the Armuchee Chert, Northwest Georgia, 7th Annual
  Field Trip, Georgia Geological Society
  Guidebooks, Guidebook 11, p. 57-65.
• Peyton, Garland, 1950, The Industrial Minerals of
  Georgia, in Short Contributions to the Geology,
  Geography and Archaeology of Georgia, The
  Geological Survey, Bulletin Number 56, Georgia
  State Division of Conservation, Department of
  Mines, Mining and Geology, p. 3-5.