| Eau Claire Formation | |
| Type: | Formation |
| Age: | Cambrian |
| Period: | Cambrian |
| Prilithology: | Sandstone |
| Otherlithology: | Siltstone, shale, dolomite |
| Namedfor: | Outcrops along the Eau Claire River, Eau Claire County, Wisconsin[1] |
| Namedby: | E. O. Ulrich |
| Region: | Indiana, Illinois, Wisconsin, Michigan, Minnesota, western Ohio, and western Kentucky. Equivalent to the Bonneterre Formation in Missouri |
| Country: | United States |
| Unitof: | Munising Group |
| Underlies: | Davis Formation, Galesville Sandstone, Kerbel Formation, Knox Dolomite, and Potosi Dolomite |
| Overlies: | Mount Simon Sandstone |
| Thickness: | 400 to 1000 feet in Indiana |
The Eau Claire Formation is a geologic formation in the north central United States. It preserves trilobite fossils from the Cambrian Period.[1]