Horseshoe Canyon Formation

Horseshoe Canyon Formation Stratigraphic range: Maastrichtian ~74–67 Ma PreꞒ Ꞓ O S D C P T J K Pg N [1]
Horseshoe Canyon Formation at Horsethief Canyon, near Drumheller. The dark bands are coal seams.
Type	Geological formation
Unit of	Edmonton Group
Underlies	Whitemud Formation
Overlies	Bearpaw Formation
Thickness	227 m (745 ft)[2]
Lithology
Primary	Sandstone
Other	Shale, coal
Location
Coordinates	51°25′24″N 112°53′18″W / 51.42333°N 112.88833°W / 51.42333; -112.88833 (Horseshoe Canyon)Coordinates: 51°25′24″N 112°53′18″W / 51.42333°N 112.88833°W / 51.42333; -112.88833 (Horseshoe Canyon)
Region	Alberta Western Canadian Sedimentary Basin
Country	Canada
Type section
Named for	Horseshoe Canyon
Named by	E.J.W. Irish, 1970

The Horseshoe Canyon Formation is a stratigraphic unit of the Western Canada Sedimentary Basin in southwestern Alberta.^[3][4] It takes its name from Horseshoe Canyon, an area of badlands near Drumheller.

The Horseshoe Canyon Formation is part of the Edmonton Group and is up to 230 metres (750 ft) thick. 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.^[3] It is overlain by the Battle, Whitemud, and Scollard formations.^[4] The Drumheller Coal Zone, located in the lower part of the Horseshoe Canyon Formation, was mined for sub-bituminous coal in the Drumheller area from 1911 to 1979, and the Atlas Coal Mine in Drumheller has been preserved as a National Historic Site.^[5] In more recent times, the Horseshoe Canyon Formation has become a major target for coalbed methane (CBM) production.

Contact (red arrow) between the underlying marine shales of the Bearpaw Formation and the coastal Horseshoe Canyon Formation. Coal beds (black bands) are common in the Horseshoe Canyon Formation and were formed in coastal swamps.

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.^[6]

Oil/gas production[]

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.

Biostratigraphy[]

The timeline below follows work by David A. Eberth and Sandra L. Kamo published in 2019.^[7]

Dinosaurs[]

Ankylosaurs[]

Ankylosaurids reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Anodontosaurus[8][9]	A. lambei[8][9]		Horsethief, Morrin, and lowest Tolman	[Five] skulls, mandibles, cervical vertebra, caudal vertebrae, dorsal vertebrae, sacrocaudal vertebrae, sacrum, illium, ischium, partial pelvis, coossified ribs, femur, ?manual phalanx, [two] tail clubs, [two] tail club knobs, numerous cervical half-rings and osteoderms.
Edmontonia	E. longiceps		Upper Horsethief	A skull with right mandible, dorsal vertebrae, dorsal vertebrae, sacral vertebrae, and caudal vertebrae, cervical ribs, dorsal ribs, left humerus, radius, and ulna, right radius, right and left ilia, right and left ischia, both pubes (?), right femur, right tibia, right and left fibula and osteoderms.
Euoplocephalus	E. tutus				Walter 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.[8][10] Furthermore, all Horseshoe Canyon Formation ankylosaurine specimens were suggested to be reassigned to Anodontosaurus.[9]

Maniraptors[]

Maniraptors reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albertavenator[11]	A. curriei		Horsethief	Frontals, lower jaw, type specimen	A troodontid	Albertonykus Apatoraptor Atrociraptor
Albertonykus	A. borealis		Upper Tolman	Limb bones, type specimen	An alvarezsaurid
Apatoraptor [12]	A. pennatus [12]		Horsethief	Partial skeleton and skull, type specimen[12]	A caenagnathid.[12]
Atrociraptor	A. marshalli		Lower Horsethief	Partial skull, type specimen	A dromaeosaurid; teeth indicate it may have been present across all members.
Epichirostenotes	E. curriei[13]		Horsethief, Morrin, and Tolman	Partial skeleton, type specimen	A caenagnathid

Marginocephalians[]

Marginocephalians reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Anchiceratops	A. ornatus		Horsethief, Morrin, and Tolman; may have been present in Drumheller.			Anchiceratops Arrhinoceratops Eotriceratops Montanoceratops Pachyrhinosaurus lakustai Sphaerotholus
Arrhinoceratops	A. brachyops		Horsethief and Morrin; may have been present in Drumheller and Tolman.	"Complete skull."[14]
Eotriceratops	E. xerinsularis		Carbon
Montanoceratops	M. cerorhynchus		Upper Tolman	Isolated braincase AMNH 5244.
Pachyrhinosaurus	P. canadensis		Drumheller and Horsethief		Ceratopsid
Sphaerotholus	S. edmontonense		Tolman		May be a junior synonym of S. buchholtzae
"Almond Formation" ceratopsid	Unnamed				Misidentified as Anchiceratops, it is actually a new species, probably the same as a new Pentaceratops-like form from the Almond Formation of Wyoming[15]

Ornithomimids[]

Ornithomimids reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Ornithomimus	O. currelli				Junior synonym of O. edmontonicus	Ornithomimus Struthiomimus
	O. edmontonicus		Drumheller, Horsethief, Morrin, and Tolman	Several specimens, type specimen	An ornithomimid
Struthiomimus	S. altus		Drumheller, Horsethief, and Morrin		An ornithomimid

Hadrosaurs and thescelosaurs[]

Hadrosaurs and thescelosaurids reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Edmontosaurus	E. regalis		Horsethief; likely present in Drumheller.			Edmontosaurus Hypacrosaurus Parksosaurus Saurolophus
Hypacrosaurus	H. altispinus		Morrin and Tolman.	"[Five to ten] articulated skulls, some associated with postcrania, isolated skull elements, isolated postcranial elements, many individuals, embryo to adult."[16]
Parksosaurus	P. warreni		Tolman	Type specimen
Saurolophus	S. osborni		Upper Morrin and Tolman.	"Complete skull and skeleton, [two] complete skulls."[16]

Tyrannosaurs[]

Theropods reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albertosaurus	A. arctunguis				Junior synonym of A. sarcophagus	Albertosaurus Daspletosaurus
	A. sarcophagus		Horsethief, Morrin, and Tolman; likely present in Drumheller and Carbon.	Several skeletons and partial skeletons, type specimen	A tyrannosaurid which was the most common large carnivore in the area.[17][18]
Daspletosaurus	D. sp.				Suggested from the skeleton of an immature tyrannosaurid (CMN 11315), thorough analysis of this specimen supports a referral to A. sarcophagus.[19] 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.[20]

Other Animals[]

Mammals[]

Mammals reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Didelphodon[21]	D. coyi				a stagodontid metatherian	Didelphodon

Other Reptiles[]

Reptiles reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Stangerochampsa[22]	S. mccabei			"a skull, partial lower jaws, and partial postcranial skeleton"	An alligatoroid
Champsosaurus[23]	C. albertensis			"partial skeleton with partial skull"	a choristodere	Champsosaurus
Leurospondylus[24]	L. ultimus			"a partial skeleton"	a plesiosaur of uncertain classification
Basilemys[25]	B. morrinensis			"nearly complete shell"	a nanhsiungchelyid turtle

Fish[]

See also[]

• List of dinosaur-bearing rock formations

References[]

Bibliography[]

• Makovicky, P. J., 2001, A Montanoceratops cerorhynchus (Dinosauria: Ceratopsia) braincase from the Horseshoe Canyon Formation of Alberta: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, pp. 243–262.
• Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana.
• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.