Odenville Formation
| Odenville Limestone | |
|---|---|
| Stratigraphic range: Ordovician | |
| Type | Formation |
| Underlies | post-Knox formations |
| Overlies | Newala Limestone |
| Thickness | 0-366 feet |
| Location | |
| Region |  Alabama |
| Country |  United States |
| Type section | |
| Named for | Odenville, Alabama |
| Named by | Charles 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
[edit]
References
[edit]- ^ "Geology of Alabama" (PDF). Geological Survey of Alabama. p. 99. Retrieved November 13, 2022.
- ^ Osborne, W. Edward; Irvin, G. Daniel (2002). Geology of the Odenville 7.5-Minute Quadrangle, St. Clair County, Alabama. Geological Survey of Alabama.
- ^ Roberson, Keith (1988). The post–Knox unconformity and its relationship to bounding stratigraphy, Alabama Appalachians. Master's thesis, University of Alabama.
- ^ 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.
- ^ "National Geologic Map Database - Geolex". U.S. Geological Survey. Retrieved November 13, 2022.
- ^ 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.
- ^ Lacefield, Jim (2013). Lost Worlds in Alabama Rocks (second edition). Alabama Museum of Natural History. pp. 94–95.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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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