Ellis Group

The Ellis Group is a stratigraphical unit of Bajocian-Oxfordian age in Alberta, Saskatchewan, Montana and Wyoming in the Western Canadian Sedimentary Basin. It takes the name from Fort Ellis, Montana, and was first described in outcrop in the Rocky Creek Canyon by A.C. Peale in 1893.

Lithology
The Ellis Group is composed of shale and sandstones deposited in a marine and transitional environment.

Hydrocarbon production
Oil is produced from the Sawtooth Formation in southeastern Alberta.

Distribution
The Ellis Group laterally occurs in the subsurface in southern Alberta and northern and central Montana. It is typically 80 m, but thickens on either side of the Sweetgrass Arch and reaches up to 150 m in southeastern Alberta.

Subdivisions
The Ellis Group includes the following formations, from top to bottom:

Relationship to other units
The Ellis Group is unconformably overlain by the shales and sandstones of the Mannville Group and rests on the carbonates of the Rundle Group. It grades westwards to the shales of the Fernie Group, and eastwards to the shale, sandstones and limestones of the Vanguard and Shaunavon Formations.