Milk River Formation
The Milk River Formation is a sandstone-dominated stratigraphic unit of the Western Canada Sedimentary Basin in southern Alberta, Canada. It was deposited in near-shore to coastal environments during Late Cretaceous (late Santonian to early Campanian) time. Based on uranium-lead dating, palynology and stratigraphic relationships, deposition occurred between ~84.1 and 83.6 Ma.
| Milk River Formation | |
|---|---|
| Stratigraphic range: Santonian-Campanian ~ | |
Outcrops along the Milk River | |
| Type | Geological formation |
| Unit of | Montana Group |
| Sub-units | Deadhorse Coulee Member Virgelle Member Telegraph Creek Member |
| Underlies | Pakowki Formation |
| Overlies | Colorado Group |
| Thickness | up to 113 metres (370 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Siltstone, shale, coal |
| Location | |
| Region | Alberta |
| Country | Canada |
| Type section | |
| Named for | Milk River |
| Named by | D.B. Dowling, 1916 |
The sandstones of the Virgelle Member in the centre of the formation are well-exposed at Writing-on-Stone Provincial Park in southwestern Alberta, where they bear petroglyphs carved into them by First Nations people.
The formation is fossiliferous and has yielded an extensive vertebrate fauna (see Tables below), as well as fossil ammonites. In some areas it hosts shallow natural gas reservoirs.