Horseshoe Canyon Formation

Geological formation in Canada

The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta. It takes its name from Horseshoe Canyon, an area of badlands near Drumheller. The Horseshoe Canyon Formation is part of the Edmonton Group. In its type section (Red Deer River Valley at Drumheller), it is ~ thick, but further west the formation is older and thicker, exceeding near Calgary. It is of Late Cretaceous age, Campanian to early Maastrichtian stage (Edmontonian Land Mammal Age), and is composed of mudstone, sandstone, carbonaceous shales, and coal seams. A variety of depositional environments are represented in the succession, including floodplains, estuarine channels, and coal swamps, which have yielded a diversity of fossil material. Tidally influenced estuarine point bar deposits are easily recognizable as Inclined Heterolithic Stratification (IHS). Brackish water trace fossil assemblages occur within these bar deposits and demonstrate periodic incursion of marine waters into the estuaries. The Horseshoe Canyon Formation crops out extensively in the area around Drumheller, as well as farther north along the Red Deer River near Trochu and along the North Saskatchewan River in Edmonton. In more recent times, the Horseshoe Canyon Formation has become a major target for coalbed methane (CBM) production. Dinosaurs found in the Horseshoe Canyon Formation include Albertavenator, Albertosaurus, Anchiceratops, Anodontosaurus, Arrhinoceratops, Atrociraptor, Epichirostenotes, Edmontonia, Edmontosaurus, Hypacrosaurus, Ornithomimus, Pachyrhinosaurus, Parksosaurus, Saurolophus, and Struthiomimus. Other finds have included mammals such as Didelphodon coyi, non dinosaur reptiles, amphibians, fish, marine and terrestrial invertebrates and plant fossils. Reptiles such as turtles and crocodilians are rare in the Horseshoe Canyon Formation, and this was thought to reflect the relatively cool climate which prevailed at the time. A study by Quinney et al. (2013) however, showed that the decline in turtle diversity, which was previously attributed to climate, coincided instead with changes in soil drainage conditions, and was limited by aridity, landscape instability, and migratory barriers.

The Drumheller Coal Zone has been a primary coalbed methane target for industry. In the area between Bashaw and Rockyford, the Coal Zone lies at relatively shallow depths (about 300 metres) and is about 70 to 120 metres thick. It contains 10 to 20 metres of cumulative coal, in up to 20 or more individual thin seams interbedded with sandstone and shale, which combine to make an attractive multi completion CBM drilling target. In total, it is estimated there are 14 trillion cubic metres (500 tcf) of gas in place in all the coal in Alberta.

The timeline below follows work by David A. Eberth and Sandra L. Kamo published in 2019.

Ankylosaurs reported from the Horseshoe Canyon Formation Genus Species Stratigraphic position Material Notes ImagesAnodontosaurusEdmontoniaE. longicepsEuoplocephalusE. tutusWalter Coombs (1971) synonymised Anodontosaurus lambei with E. tutus. However, recent studies suggest that Anodontosaurus is distinct enough from Euoplocephalus to be placed in its own genus and species. Furthermore, all Horseshoe Canyon Formation ankylosaurine specimens were suggested to be reassigned to Anodontosaurus.

Hadrosaurs reported from the Horseshoe Canyon Formation Genus Species Location Stratigraphic position Material Notes ImagesEdmontosaurusE. regalisHorsethief; likely present in Drumheller. HypacrosaurusH. altispinusMorrin and Tolman. "[Five to ten] articulated skulls, some associated with postcrania, isolated skull elements, isolated postcranial elements, many individuals, embryo to adult."SaurolophusS. osborniUpper Morrin and Tolman. "Complete skull and skeleton, [two] complete skulls. "[Two] nearly complete skulls and [seven] partial skulls. A. brachyopsEotriceratopsE. xerinsularisMontanoceratopsA leptoceratopsid ceratopsian also known from the St. Mary River Formation. P. canadensisS. edmontonenseA. currieiA. borealisA. pennatusA. marshalliHorsethief, Morrin, and TolmanDaspletosaurusD. sp. Suggested from the skeleton of an immature tyrannosaurid (CMN 11315), thorough analysis of this specimen supports a referral to A. sarcophagus. An isolated maxilla and teeth from an Edmontosaurus bonebed were also mistakenly referred to Daspletosaurus, however all the tyrannosaurid material in the bonebed was confirmed to belong to A. sarcophagus.

Mammals reported from the Horseshoe Canyon Formation Genus Species Location Stratigraphic position Material Notes ImagesDidelphodonD. coyia stagodontid metatherian

Reptiles reported from the Horseshoe Canyon Formation Genus Species Location Stratigraphic position Material Notes ImagesStangerochampsaS. mccabei"a skull, partial lower jaws, and partial postcranial skeleton"An alligatoroidChampsosaurusC. albertensis"partial skeleton with partial skull"a choristodereLeurospondylusL. ultimus"a partial skeleton"a plesiosaur of uncertain classificationBasilemysB. morrinensis"nearly complete shell"a nanhsiungchelyid turtle

Fish reported from the Horseshoe Canyon Formation Genus Species Location Stratigraphic position Material Notes ImagesBoreiosturionB. labyrinthicusEdmonton. Partial skull. A sturgeon. HorseshoeichthysH. armaserratusAn ellimmichthyiform