| Belly River Formation | |
| Type: | Group |
| Period: | Late Cretaceous |
| Prilithology: | Sandstone, Shale |
| Otherlithology: | Conglomerate, Coal, Bentonite |
| Namedfor: | Belly River |
| Namedby: | George Mercer Dawson, 1883 |
| Country: |  Canada |
| Coordinates: | 49.6316°N -112.8754°W |
| Underlies: | Bearpaw Formation |
| Overlies: | Wapiabi Formation |
| Thickness: | up to 1300m (4,300feet) |
The Belly River Group is a stratigraphical unit of Late Cretaceous age in the Western Canadian Sedimentary Basin.
It takes the name from the Belly River, a tributary of the Oldman River in southern Alberta, and was first described in outcrop on the banks of the Oldman River (at the time considered part of the Belly River) and Bow River by George Mercer Dawson in 1883.[1]
The Belly River Group is composed of very fine grained sandstone with coarse grained beds and minor bentonite, coal, green shale, and concretionary beds.[2]
Gas is produced from the Belly River Group in the Deep Basin, in west-central Alberta and in the Canadian Rockies foothills.
Dinosaur remains are among the fossils that have been recovered from the formation.[3]
The Belly River Group reaches a maximum thickness of 1300m (4,300feet) in its western reaches, and thins out eastward to about 350m (1,150feet) in the Canadian Plains. It is found throughout southern Alberta, and as far east as eastern Saskatchewan. From south to north, it is present from the United States border to the Wapiti River region, south of the Peace River Country.[2]
The Belly River Group is conformably overlain by the Bearpaw Formation and gradually overlies the Wapiabi Formation, the Colorado Group shale or the Lea Park Formation shale.[2]
It is equivalent to the Milk River Formation and Pakowki Formation. The Belly River has group status in the Canadian Rockies foothills and is replaced by the Oldman Formation (Judith River Formation in Montana) and Foremost Formation in southern Alberta.