| Cummingsville Formation | |
|---|---|
| Stratigraphic range: Ordovician | |
 Cummingsville Formation in Decorah, Iowa. The Cummingsville is the brown upper unit; the Decorah Shale is below. | |
| Type | Formation |
| Overlies | Decorah Shale |
| Location | |
| Country | United States |
| Extent | Iowa and Minnesota |
The Cummingsville Formation is a geologic formation in Iowa and Minnesota. It preserves fossils dating back to the Ordovician period.