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. .
Depositional environments
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 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. In Central Montana, The Oldman Formation is equivalent to the upper part of the Mclelland Ferry Member, as well as the Woodhawk and Coal Ridge Members of the Judith River Formation. It is also believed to be equivalent to parts of the Two Medicine Formation in Western Montana.
Age The Oldman Formation was deposited during the middle Campanian, between about 77.5 and 76.5 million years ago. 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.
Theropods Theropods of the Oldman Formation Genus Species Stratigraphic position Material Notes Images Daspletosaurus D. torosus Lower Several specimens with a complete skeleton A tyrannosaurid D. wilsoniUpperTwo skulls with associated postcraniaA tyrannosaurine tyrannosaurid Dromaeosaurus Indeterminate Teeth A dromaeosaurid cf. Hesperonychus Indeterminate Foot claw A dromaeosaurid or an avialan Paronychodon Indeterminate Teeth A troodontid Prismatoolithus P. levis Partial clutch containing 12 eggs Richardoestesia R. isosceles Misreported Indeterminate Teeth A dromaeosaurid Saurornitholestes S. langstoni Partial remains A dromaeosaurid Troodon Dubious Teeth, eggs, embryos A dubious taxon of troodontid, most specimens formerly considered Troodon have been reassigned to other genera such as Stenonychosaurus. Struthiomimus S. altus Several specimens, including a nearly complete skeleton An ornithomimid Tromerosaurus T. solumons Upper A partial skull and skeleton An albertosaurine tyrannosaurid; two referred specimens derive from the lower strata of the overlying Dinosaur Park Formation.
Ornithischians Ceratopsians Ceratopsians of the Oldman Formation Genus Species Stratigraphic position Material Notes Images Albertaceratops A. nesmoi Lower Single skull A ceratopsid Anchiceratops Indeterminate A ceratopsid Coronosaurus C. brinkmani Upper A ceratopsid GremlinG. slobodorumLowerA right frontalA leptoceratopsid Wendiceratops W. pinhornensis Lower Partial skeleton and skull A centrosaurine ceratopsid Pachycephalosaurs Pachycephalosaurs of the Oldman Formation Genus Species Stratigraphic position Material Notes Images Brontotholus B. sp. Skull dome A pachycephalosaurid, also found in the Two Medicine Formation Foraminacephale F. brevis Also known from the Dinosaur Park Formation A pachycephalosaurid, once thought to be a species of Stegoceras Hanssuesia H. sternbergi Upper, also present in the Dinosaur Park Formation and Judith River Formation Skull dome A pachycephalosaurid, potentially synonymous with Stegoceras validum Hadrosaurs Hadrosaurs of the Oldman Formation Genus Species Stratigraphic position Material Notes Images Brachylophosaurus B. canadensis Upper Skull and partial skeleton A hadrosaurid Corythosaurus C. casuarius Upper A hadrosaurid, also found in the Dinosaur Park Formation Maiasaura M. peeblesorum Upper A hadrosaurid, also known from the Two Medicine Formation Parasaurolophus P. walkeri Upper A hadrosaurid, also found in the Dinosaur Park Formation Plesiolophus P. warnerensis Lower Partial skull A hadrosaurid
Other ornithischians Other Ornithischians of the Oldman Formation Genus Species Stratigraphic position Material Notes Images Albertadromeus A. syntarsus Upper A thescelosaurid Orodrominae indet. IndeterminateUpper An orodromine distinct from Albertadromeus. Closer to Oryctodromeus than to Albertadromeus, Orodromeus, and Zephyrosaurus. Scolosaurus S. cutleri Upper An ankylosaurid, may actually be from the Dinosaur Park Formation
See also List of fossil sites (with link directory) List of dinosaur-bearing rock formations
References
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