| Bass Islands Formation | |
| Type: | Formation |
| Age: | Silurian |
| Period: | Silurian |
| Region: | Michigan |
| Country: | United States |
| Subunits: | St. Ignace Dolomite, Put-in-Bay Dolomite, Tymochtee Dolomite |
| Underlies: | Amherstburg Formation, Columbus Limestone, and Helderberg Group |
| Overlies: | Salina Formation |
The Bass Islands Formation is a geologic formation in Michigan. It preserves fossils dating back to the Silurian period.