| 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 |
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.
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]
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