Odenville Formation

Last updated
Odenville Limestone
Stratigraphic range: Ordovician
Type Formation
Underliespost-Knox formations
OverliesNewala Limestone
Thickness0-366 feet
Location
Region Alabama
Country United States
Type section
Named for Odenville, Alabama
Named byCharles Butts

The Odenville Limestone is a geologic formation in Alabama. It preserves fossils dating from the early Ordovician Period.

As first described by geologist Charles Butts in a 1926 report on Alabama’s geology, the Odenville consisted of “impure argillaceous and siliceous dark fine-grained cherty limestone,” about fifty feet in thickness. [1]

Butts’ original type exposure could not be located by subsequent mappers, so the Odenville nomenclature was dropped and the formation was considered a locally-occurring facies of the underlying Newala Limestone. [2]

Keith Roberson in 1988, [3] and Ed Osborne in 1992, [4] demonstrated the Odenville is indeed a distinctive, mappable lithologic unit, and the term was restored to the Ordovician nomenclature used by the Geological Survey of Alabama in the Appalachian fold-and-thrust belt. [5]

As defined today, the Odenville Limestone is described as a dark gray, primarily dolomitic, stylonodular limestone [6] whose fossil assemblage includes brachiopods and sponges. It is the uppermost member of the Knox Group, a related suite of carbonate rocks deposited at the end of the Cambrian and beginning of the Ordovician. [7]

The Odenville Limestone occupies a narrow outcrop belt within the Cahaba Valley. Its extent along strike reaches from the overlap of Coastal Plain sediments in northwestern Chilton County [8] to a point just northeast of its type locality, where it appears to pinch out in central St. Clair County. [9] The formation does not crop out among Ordovician units exposed in the Coosa Deformed Belt. [10] The Odenville may be present among Knox Group units in the Coosa Valley, but lack of exposures and intense weathering have precluded definitive identification of the Odenville in Knox-underlain areas between Pell City and Talladega. [11]

See also

References

  1. ↑ "Geology of Alabama" (PDF). Geological Survey of Alabama. p. 99. Retrieved November 13, 2022.
  2. ↑ Osborne, W. Edward; Irvin, G. Daniel (2002). Geology of the Odenville 7.5-Minute Quadrangle, St. Clair County, Alabama. Geological Survey of Alabama.
  3. ↑ Roberson, Keith (1988). The post–Knox unconformity and its relationship to bounding stratigraphy, Alabama Appalachians. Master's thesis, University of Alabama.
  4. ↑ Osborne, W. Edward (1992). Bedrock geology of the Cahaba Valley area between Helena and Lake Purdy, Shelby and Jefferson Counties, Alabama. Geological Survey of Alabama.
  5. ↑ "National Geologic Map Database - Geolex". U.S. Geological Survey. Retrieved November 13, 2022.
  6. ↑ Osborne, W. Edward; Irvin, G. Daniel (2002). "Cross Section A-A' and Explanation for the Geologic Map of the Odenville 7.5-Minute Quadrangle, St. Clair County, Alabama" (PDF). Geological Survey of Alabama. Retrieved November 13, 2022.
  7. ↑ Lacefield, Jim (2013). Lost Worlds in Alabama Rocks (second ed.). Alabama Museum of Natural History. pp. 94–95.
  8. ↑ Osborne, W. Edward; Irvin, G. Daniel (2002). "Geologic Map of the Montevallo 7.5-Minute Quadrangle, Chilton and Shelby counties, Alabama" (PDF). Geological Survey of Alabama. Retrieved August 9, 2024.
  9. ↑ Osborne, W. Edward; Garry, W. Brent; Thomas, William A. (2019). "Geologic Map and Cross Sections of the Ashville 7.5-Minute Quadrangle, St. Clair and Blount counties, Alabama" (PDF). Geological Survey of Alabama. Retrieved August 9, 2024.
  10. ↑ Thomas, William A.; Drahovzal, James A.; Ward, Willard E. (2013). "Geologic Map and Cross Sections of the Pell City 7.5-Minute Quadrangle, St. Clair and Talladega counties, Alabama" (PDF). Geological Survey of Alabama. Retrieved August 9, 2024.
  11. ↑ Irvin, G.D.; Thomas, W.A.; Osborne, W.E.; Drahovzal, J.D.; Ward, W.E. (2005). Geology of the Vincent 7.5-Minute Quadrangle, Shelby, St. Clair and Talldega counties, Alabama. Geological Survey of Alabama.


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