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[1]

The Willow Creek Formation is a stratigraphic unit of Late Cretaceous to Early Paleocene age in the Western Canada Sedimentary Basin of southwestern Alberta.[2] 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.[3]

The formation straddles the Cretaceous-Paleogene (K-Pg) boundary, which divides it into an upper, Early Paleocene member and a lower, Late Cretaceous member.[4] Dinosaur remains are among the fossils that have been recovered from the Late Cretaceous portion.[5]

Lithology

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.[6]

Depositional environment

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.

Distribution

The Willow Creek Formation is present in southwestern Alberta, south of the Bow River, and extends a short distance into northern Montana.[7] It thins eastward from the foothills of the Canadian Rockies to its limit east of Vulcan, Alberta. Thicknesses exceeding 1000 meters have been reported.[6]

Relationship to other units

The Willow Creek Formation is overlain by the Porcupine Hills Formation, and underlain by the St. Mary River Formation.[4] It grades into the equivalent Scollard Formation south of the Bow River at about 50° 30’N latitude, and into the Coalspur Formation in the southern foothills.[7] The lower, Late Cretaceous member is correlated with the Frenchman Formation of Saskatchewan, and the upper, Early Paleocene member is correlated with the lower portion of the Ravenscrag Formation.[4]

Vertebrate paleofauna

See also

References

  1. ↑ Dawson, G.M., 1883. Preliminary report on the geology of the Bow and Belly River region, Northwest Territory, with special reference to the coal deposits. Geological Survey of Canada, Report of Progress for 1880-81-82, Part B.
  2. ↑ Lexicon of Canadian Geologic Units. "Willow Creek Formation". Retrieved 2010-01-01.
  3. ↑ Williams, M.Y. and Dyer, W.S., 1930. Geology of southern Alberta and southwestern Saskatchewan; Geological Survey of Canada, Memoir 163.
  4. ↑ 4.0 4.1 4.2 Mossop, G.D. and Shetsen, I., (compilers), Canadian Society of Petroleum Geologists (1994). "The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 24: Upper Cretaceous and Tertiary strata of the Western Canada Sedimentary Basin". Retrieved 2013-08-01.
  5. ↑ Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.
  6. ↑ 6.0 6.1 Glass, D.J., editor, 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada. Canadian Society of Petroleum Geologists, Calgary, Alberta,1423 p. on CD-ROM, ISBN 0-920230-23-7.
  7. ↑ 7.0 7.1 Prior, G. J., Hathaway, B., Glombick, P.M., Pana, D.I., Banks, C.J., Hay, D.C., Schneider, C.L., Grobe, M., Elgr, R., and Weiss, J.A. (2013). "Bedrock Geology of Alberta. Alberta Geological Survey, Map 600". Retrieved 2013-08-13.