Horseshoe Canyon Formation

Horseshoe Canyon Formation Stratigraphic range: Maastrichtian, 74–67 Ma PreЄ Є O S D C P T J K Pg N
Horseshoe Canyon Formation at Horsethief Canyon near Drumheller, AB. 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 meters (745 ft)
Lithology
Primary	sandstone
Other	shale, coal
Location
Coordinates
Region	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. 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. It is overlain by the Battle, Whitemud, and Scollard formations. 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. 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 Albertosaurus, Anchiceratops, Anodontosaurus, Arrhinoceratops, Atrociraptor, Epichirostenotes, Edmontonia, Edmontosaurus, Hypacrosaurus, Ornithomimus, Pachyrhinosaurus, Parksosaurus, Saurolophus, Stegoceras, Struthiomimus and Troodon. 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.

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 syntheses presented by Arbour et al. 2009, Cullen et al. 2013 Larson et al. 2010, Williamson & Carr 2002, Claessens & Loewen 2015, and Funston & Currie (2016).

Dinosaurs

Ankylosaurs

Ankylosaurids reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Anodontosaurus	A. lambei		Units 2-4			File:Edmontonia 6394.JPG Edmontonia
Edmontonia	E. longiceps		Unit 2
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. Furthermore, all Horseshoe Canyon Formation ankylosaurine specimens were suggested to be reassigned to Anodontosaurus.

Maniraptors

Maniraptors reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albertonykus	A. borealis		Upper unit 4	Limb bones, type specimen	An alvarezsaurid	Albertonykus File:Atrociraptor restoration.JPG Atrociraptor
Apatoraptor	A. pennatus		Unit 1	Partial skeleton and skull, type specimen	A caenagnathid.
Atrociraptor	A. marshalli		Upper unit 4	Partial skull, type specimen	A dromaeosaurid
Dromaeosaurus	Indeterminate			Teeth	A dromaeosaurid
Epichirostenotes	E. curriei		Unit 1	Partial skeleton, type specimen	A caenagnathid
Paronychodon	Indeterminate		Unit 2	Teeth	An indeterminate maniraptoran
Richardoestesia	R. gilmorei			Teeth	A dromaeosaurid
	R. isosceles			Teeth
Saurornitholestes	Indeterminate			Teeth	A dromaeosaurid
Troodon	Indeterminate			Teeth, braincase	A troodontid

Marginocephalians

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Marginocephalians reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Anchiceratops	A. ornatus		Units 1 & 2			File:Anchiceratops BW.jpg Anchiceratops File:Arrhinoceratops BW.jpg Arrhinoceratops File:Eotriceratops BW.jpg Eotriceratops Pachyrhinosaurus lakustai
Arrhinoceratops	A. brachyops		Units 1 & 2	"Complete skull."
Eotriceratops	E. xerinsularis		Unit 5
Montanoceratops	M. cerorhynchus			Isolated braincase AMNH 5244.	AMNH 5244 was probably left by an indeterminate leptoceratopsid.
Pachyrhinosaurus	P. canadensis		Upper unit 1		Ceratopsids
	P. lakustai		Lower unit 1
?Sphaerotholus	S. edmontonense		Unit 1		?Prenocephale.
"Almond Formation" ceratopsid	Unnamed		Upper Unit 1, Horseshoe Canyon Formation, 72.2-71Ma ago).		Misidentified as Anchiceratops, it is actually a new species, probably the same as a new Pentaceratops-like form from the Almond Formation of Wyoming

Ornithomimids

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Ornithomimids reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Dromiceiomimus	D. brevitertius			Type specimen	An ornithomimid	File:Dromiceiomimus BW.jpg Dromiceiomimus File:"Ornithomimus" sp. by Tom Parker.png Ornithomimus Struthiomimus
Ornithomimus	O. currelli				Junior synonym of O. edmontonicus
	O. edmontonicus		Units 1-4	Several specimens, type specimen	An ornithomimid
Struthiomimus	Unnamed			Unit 4	An ornithomimid

Ornithopods

Ornithopods reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Edmontosaurus	E. regalis		Units 1-2			Edmontosaurus Hypacrosaurus File:Parksosaurus Steveoc86.jpg Parksosaurus File:Saurolophus scalation.png Saurolophus
Hypacrosaurus	H. altispinus		Units 4-5	"[Five to ten] articulated skulls, some associated with postcrania, isolated skull elements, isolated postcranial elements, many individuals, embryo to adult."
Parksosaurus	P. warrenae		Unit 3
Saurolophus	S. osborni		Unit 4	"Complete skull and skeleton, [two] complete skulls."

Tyrannosaurs

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

Theropods reported from the Horseshoe Canyon Formation
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Albertosaurus	A. arctunguis				Junior synonym of A. sarcophagus	Albertosaurus
	A. sarcophagus		Units 2-5	Several skeletons and partial skeletons, type specimen	A tyrannosaurid
Daspletosaurus	D. sp.			Bonebed, Toothmarks on Saurolophus and Edmontosaurus	A tyrannosaurid. A specimen of Edmontosaurus regalis and Saurolophus osborni have toothmarks from a species of Daspletosaurus.

See also

• List of dinosaur-bearing rock formations

References

• 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.