Oldman Formation
{{Short description|Geologic formation in Canada}}
{{Infobox rockunit
| name = Oldman Formation
| image =
| caption =
| type = Geological formation
| age = Campanian, {{Fossil range|77.5|76.5}}
| period = Campanian
| prilithology = Sandstone
| otherlithology = Mudstone and bentonite
| namedfor = Oldman River
| namedby = Russell, L.S. and Landes, R.W.
| year_ts = 1940Russell, L.S. and Landes, R.W., 1940. Geology of the southern Alberta Plains; Geological Survey of Canada, Memoir 221.
| region = Western Canada Sedimentary Basin
| country = {{flag|Canada}}
| coordinates = {{Coord|49|37|41|N|112|53|23|W|name=Oldman Formation|display=inline,title}}
| unitof = Belly River Group
| subunits =
| underlies = Dinosaur Park Formation
| overlies = Foremost Formation
| thickness = up to {{convert|328|ft|m|-1}}{{Cite web|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:011229|archive-url=https://archive.today/20130222074639/http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:011229|url-status=dead|archive-date=2013-02-22|title=Oldman Formation|author=Lexicon of Canadian Geological Units|access-date=2009-02-06}}
| extent =
| area =
| map = {{Location map+ | Canada#Alberta
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | Canada#Alberta
| lat_deg = 49.6
| lon_deg = -112.9
| mark = Lightgreen pog.svg
| marksize = 10
}}
}}
| map_caption =
}}
The Oldman Formation is a stratigraphic unit of Late Cretaceous (Campanian stage) age that underlies much of southern Alberta, Canada. It consists primarily of sandstones that were deposited in fluvial channel and floodplain environments. It was named for exposures along the Oldman River between its confluence with the St. Mary River and the city of Lethbridge, and it is known primarily for its dinosaur remains and other fossils.Eberth, D.A. and Hamblin A.P. 1993. Tectonic, stratigraphic, and sedimentologic significance of a regional discontinuity in the upper Judith River Group (Belly River wedge) of southern Alberta, Saskatchewan, and northern Montana. Canadian Journal of Earth Sciences 30: 174-200.
Lithology
The Oldman Formation is composed primarily of light-colored, fine-grained sandstones. They are upward-fining, lenticular to sheet-like bodies that are yellowish, steep-faced and blocky in outcrop. The formation also includes lesser amounts of siltstone and mudstone.Eberth, D.A. 2005. The geology. In: Currie, P.J., and Koppelhus, E.B. (eds), Dinosaur Provincial Park: A Spectacular Ancient Ecosystem Revealed. Indiana University Press: Bloomington and Indianapolis, p. 54-82. {{ISBN|0-253-34595-2}}.
Depositional environments
File:Daspletosaurus hunting.jpg
The sediments of the Oldman Formation were deposited in fluvial channels (the sandstones) and a variety of channel margin, overbank and floodplain environments (the siltstones and mudstones). The formation is about {{convert|40|m|ft|-1}} thick at Dinosaur Provincial Park in southeastern Alberta. It thickens toward the southwest, and northwestern Montana appears to have been the primary source of the sediments.
Relationship to other units
The Oldman Formation is a member of the Belly River Group (also known as the Judith River Group). It conformably overlies the Foremost Formation, and is separated from the overlying Dinosaur Park Formation by a regional disconformity. The sediments of the Oldman are superficially similar to those of the Dinosaur Park, which was included in the Oldman Formation prior to the recognition of the disconformity. The two formations can also be distinguished by petrographic and sedimentologic differences.
Age
The Oldman Formation was deposited during the middle Campanian, between about 77.5 and 76.5 million years ago.{{cite journal|last=Arbour, V.M.|author-link=Victoria Arbour|author2=Burns, M. E.|author3=Sissons, R. L.|year=2009|title=A redescription of the ankylosaurid dinosaur Dyoplosaurus acutosquameus Parks, 1924 (Ornithischia: Ankylosauria) and a revision of the genus|journal=Journal of Vertebrate Paleontology|volume=29|issue=4|pages=1117–1135|doi=10.1671/039.029.0405|bibcode=2009JVPal..29.1117A }} It lies fully within magnetic polarity Chron 33n.Lerbekmo, J.F. 1989. The position of the 33-33r (Campanian) polarity chron boundary in southeastern Alberta. Bulletin of Canadian Petroleum Geology 37: 43-47.
Fossil content
List of dinosaurs found in the formation:Weishampel, D.B., Barrett, P.M., Coria, R.A., Le Loueff, J., Xu X., Zhao X., Sahni, A., Gomani, E.M.P., & Noto, C.N. 2004. Dinosaur distribution. In: Weishampel, D.B., Dodson, P., & Osmólska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 517-606.
{{paleobiota-key-compact}}
= Theropods =
= Ornithischians =
See also
- List of fossil sites (with link directory)
- List of dinosaur-bearing rock formations
References
{{Reflist}}
= Bibliography =
- D.A. Eberth. 1996. Origin and significance of mud-filled incised valleys (Upper Cretaceous) in southern Alberta, Canada. Sedimentology 43:459–477
- Ryan, M. J., and Russell, A. P., 2001. Dinosaurs of Alberta (exclusive of Aves): In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 279–297
{{Western Canadian Sedimentary Basin| South AB=yes}}
Category:Upper Cretaceous Series of North America
Category:Sandstone formations of Canada