Rierdon Formation
| Ellis Group Stratigraphic range: Bajocian-Oxfordian |
|
|---|---|
| Type | Geological formation |
| Sub-units |
Swift Formation Rierdon Formation Sawtooth Formation |
| Underlies | Mannville Group |
| Overlies | Rundle Group, Shaunavon Formation |
| Thickness | up to 150 metres (490 ft) |
| Lithology | |
| Primary | Shale, sandstones |
| Other | Siltstone, limestone |
| Location | |
| Region | WCSB |
| Country |
 Canada
|
| Type section | |
| Named for | Fort Ellis |
| Named by | A.C. Peale, 1893 |
The Ellis Group is a stratigraphical unit of Bajocian-Oxfordian age 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 .C. Peale in 1893.
The Ellis Group is composed of shale and sandstones deposited in marine and transitional environment.
Oil is produced from the Sawtooth Formation in south-eastern Alberta.
The Ellis Group Lateral occurs in the sub-surface in southern Alberta and northern and central Montana. It is typically 80 metres (260 ft), but thickens on either side of the Sweetgrass Arch and reaches up to 150 metres (490 ft) in south-eastern Alberta.
The Ellis Group includes the following formations, from top to bottom:
The Ellis Group is unconformably overlain by the shale and sandstone of the Mannville Group and rests on the carbonates of the Rundle Group. It grades westwards to the Fernie Group shale, and eastwards to shale, sandstones and limestone of the Vanguard Formation and Shaunavon Formation.
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