| Interlake Formation (Group) | |
| Type: | Geological formation |
| Prilithology: | dolomite |
| Namedfor: | Interlake Region, Manitoba |
| Namedby: | A.D. Baillie, 1951 |
| Region: | WCSB Williston Basin |
| Country: |  Canada United States |
| Coordinates: | 51.4535°N -98.7603°W |
| Underlies: | Ashern Formation |
| Overlies: | Stonewall Formation |
| Thickness: | up to 335m (1,099feet) |
The Interlake Formation is a stratigraphical unit of Silurian age in the Western Canadian Sedimentary Basin.
It takes the name from the Interlake Region in Manitoba, and was first described in outcrop by A.D. Baillie in 1951.[1]
The Interlake Formation is composed of very finely crystalline dolomite.[2] Oolitic, stromatolitic and biohermal interbeds also occur.
The Interlake Formation is present throughout the Williston Basin.[2] It reaches a maximum thickness of 335m (1,099feet) in the subsurface of North Dakota, and is typically up to 110m (360feet) thick in outcrop in its type locality.
The Interlake Formation is overlain with an angular unconformably by the Ashern Formation and sharply overlays the Stonewall Formation.[2]
In the sub-surface it is given group status and contains, in different regions, the following subdivisions: