Willow Creek Formation
| Willow Creek Formation Stratigraphic range: Late Cretaceous to Paleocene |
|
|---|---|
| Type | Geological formation |
| Underlies | Porcupine Hills Formation |
| Overlies | St. Mary River Formation |
| Lithology | |
| Primary | Shale, Sandstone |
| Location | |
| Coordinates | 49°46′19″N 113°22′09″W / 49.77208°N 113.36920°WCoordinates: 49°46′19″N 113°22′09″W / 49.77208°N 113.36920°W |
| Region |
 Alberta
|
| Country |
 Canada
|
| Type section | |
| Named for | Willow Creek |
| Named by | G.M. Dawson, 1883 |
The Willow Creek Formation is a stratigraphic unit of Late Cretaceous to Early Paleocene age in the Western Canada Sedimentary Basin of southwestern Alberta. It was first described by George Mercer Dawson in 1883 along the Willow Creek, a tributary of the Oldman River. Williams and Dyer defined the type section in 1930 at the mouth of Willow Creek, east of Fort Macleod.
The formation straddles the Cretaceous-Paleogene (K-Pg) boundary, which divides it into an upper, Early Paleocene member and a lower, Late Cretaceous member. Dinosaur remains are among the fossils that have been recovered from the Late Cretaceous portion.
The Willow Creek Formation is composed of non-marine varicolored shales, red beds and sandstones. The shales and red beds include calcite nodules and caliche deposits. The sandstones are soft, light grey, massively bedded and cross-bedded, with harder conglomeratic sandstones toward the base of the formation.
The sediments were eroded from the Canadian Cordillera, and were transported eastward by river systems and deposited in fluvial channel and floodplain environments. The caliche and red beds reflect deposition under arid to semi-arid climate conditions. This contrasts with the equivalent Scollard Formation north of the Bow River, which includes coal deposits indicative of a more humid environment.
The Willow Creek Formation is present in southwestern Alberta, south of the Bow River, and extends a short distance into northern Montana. It thins eastward from the foothills of the Canadian Rockies to its limit east of Vulcan, Alberta. Thicknesses exceeding 1000 meters have been reported.
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