Winona Formation
The Winona Formation (also called the Winona Sand or the Winona Greensand[1]) is a sand geologic formation in Mississippi. It preserves fossils dating back to the Paleogene period.
| Winona Formation Stratigraphic range: Paleogene | |
|---|---|
| Type | Formation |
| Unit of | Claiborne Group |
| Underlies | Sparta Formation |
| Overlies | Tallahatta Formation |
| Lithology | |
| Primary | sand glauconite |
| Other | ironstone |
| Location | |
| Region |  Mississippi |
| Country |  United States |
| Type section | |
| Named for | Winona, Mississippi |
Description
The Winona Formation was originally described as a member of the Tallahatta Formation or as a member of the Lisbon Formation, both of which are members of the Claiborne Group.[1][2] It was upgraded to formation status and is considered a separate formation from both by the Mississippi Dept. of Environmental Quality Office of Geology.[2] The Winona formation is a medium to fine grain poorly sorted sand that contains silt, clay, and fossils. It has a high glauconite content, up to 50% in some areas.[2] Fossils, molds, and casts are commonly found in lithified beds,[2] and the fossil assemblage includes bivalves, gastropods, echinoids, shark teeth, crabs, foraminifera, and ostracods.[1] The depositional environment for this formation is considered a shallow-water, near shore marine shelf facies as part of a marine transgression series.[1][2]
References
- Thomas, Emil P. "The Claiborne" (PDF). Mississippi State Geological Survey Bulletin. 48: 28–33. Retrieved 28 June 2018.
- Merrill, Robert K.; Sims, James J.; Gann, Delbert E.; Liles, Kenneth J. (1985). "Newton County geology and mineral resources" (PDF). Mississippi Bureau of Geology Bulletin. 126: 33–34. Retrieved 28 June 2018.
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Retrieved 22 June 2014.