The Bearpaw Formation, also called the Bearpaw Shale, is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

( Campanian) age. It outcrops in the U.S. state of

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

, as well as the

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

provinces of

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

and

Saskatchewan Saskatchewan ( ; ) is a Provinces and territories of Canada, province in Western Canada, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...

, and was named for the

Bear Paw Mountains The Bears Paw Mountains (Bear Paw Mountains, Bear's Paw Mountains or Bearpaw Mountains) are an insular-montane island range in the Central Montana Alkalic Province in north-central Montana, United States, located approximately 10 miles south of ...

in Montana. It includes a wide range of marine

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s, as well as the remains of a few

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s. It is known for its fossil

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

s, some of which are mined in Alberta to produce the

organic gemstone This is a list of gemstones, organized by species and type. Minerals There are over 300 types of minerals that have been used as gemstones. These include: A–B *Actinolite **Nephrite () * Adamite *Aegirine *Afghanite * Agrellite *Algodonite * ...

ammolite.

Lithology and depositional environment

The formation was deposited in the Bearpaw Sea, which was part of the Western Interior Seaway that advanced and then retreated across the region during Campanian time. It is composed primarily of dark grey

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

s, silty claystones and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

s, with subordinate silty

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s. It also includes bedded and nodular concretions (both

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...

and ironstone concretions) and thin beds of bentonite. As the seaway retreated toward the southwest, the marine sediments of the Bearpaw became covered by the deltaic and coastal plain sediments of the overlying formations.Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. .

Relationship to other units

The Bearpaw Formation conformably overlies the Dinosaur Park Formation of the Belly River Group in central Alberta, and the Judith River Formation in the plains to the east and Montana. It is overlain by the Horseshoe Canyon Formation in central Alberta; by the

Blood Reserve Formation The Blood Reserve Formation, also known as the Blood Reserve Sandstone, is a geologic formation of Late Cretaceous (Campanian) age in the Western Canada Sedimentary Basin. It is present in southwestern Alberta, Canada, and was named for Blood Ind ...

and the St. Mary River Formation in southern Alberta; by the

Eastend Formation The Eastend Formation is a stratigraphical unit of Maastrichtian age in the Western Canadian Sedimentary Basin. It takes its name from the town of Eastend, Saskatchewan, and was first described in outcrop around the settlement by L.S. Russell in ...

in southern Saskatchewan; and by the

Fox Hills Formation The Fox Hills Formation is a Cretaceous geologic Formation (geology), formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south. Fossil remains of dinosaurs, including tyrannos ...

in Montana. To the east, it merges into the

Pierre Shale The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico. The Pierre Shale was described by Meek and Hayden in 1862 in th ...

Fauna

Ammolite from Placenticeras fossil ammonite, Alberta

The Bearpaw Formation is famous for its well-preserved ammonite fossils. These include ''

Placenticeras meeki ''Placenticeras meeki'' is an ammonite species from the Late Cretaceous. These cephalopods were fast-moving nektonic carnivores. They mainly lived in the American Interior Basin (Western Interior Seaway). Description Shells of this species could ...

'', ''Placenticeras intercalare'', ''

Hoploscaphites ''Hoploscaphites'' is an extinct ammonite genus from the Upper Cretaceous and the Lower Paleocene, included in the family Scaphitidae. Morphology It is considered by some to be a subgenus of '' Scaphites''. Like ''Scaphites'' the shell of ''Hop ...

'', and '' Sphenodiscus'', the

baculite ''Baculites'' ("walking stick rock") is an extinct genus of cephalopods with a nearly straight shell, included in the heteromorph ammonites. The genus, which lived worldwide throughout most of the Late Cretaceous, and which briefly survived the ...

''Baculites compressus'' and the

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

'' Inoceramus'', some of which are mined south-central Alberta to produce the

ammolite. Other fossils found in this formation include many types of

shellfish Shellfish is a colloquial and fisheries term for exoskeleton-bearing aquatic invertebrates used as food, including various species of molluscs, crustaceans, and echinoderms. Although most kinds of shellfish are harvested from saltwater envir ...

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimo ...

s, rays, birds, and marine reptiles like

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Greek ' meaning 'lizard') comprise a group of extinct, large marine reptiles from the Late Cretaceous. Their first fossil remains were discovered in a limestone quarry at Maastricht on th ...

s such as ''

Prognathodon ''Prognathodon'' is an extinct genus of marine lizard belonging to the mosasaur family. It is classified as part of the Mosasaurinae subfamily, alongside genera like ''Mosasaurus'' and ''Clidastes''. ''Prognathodon'' has been recovered from depos ...

overtoni'' and '' Plioplatecarpus peckensis'',

plesiosaur The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...

s such as '' Dolichorhynchops herschelensis'', '' Albertonectes'' and ''

Nakonanectes ''Nakonanectes bradti'' is an elasmosaurid plesiosaur of the late Cretaceous found in 2010 the state of Montana in the United States. It is one of the most recently known elasmosaurids to have lived in North America. Unlike other elasmosaurids, ...

'', and

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, ...

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

remains have occasionally been discovered, presumably from carcasses that washed out to sea.Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. .Bearpaw fauna in Alberta
/ref>

Dinosaurs

Plesiosaurs

Mosasaurs

Turtles

References

{{Western Canadian Sedimentary Basin, Northeast_Plains=yes, Central_Plains=yes, Saskatchewan=yes Geologic formations of Canada Cretaceous Alberta Cretaceous Montana Cretaceous Saskatchewan Western Canadian Sedimentary Basin Campanian Stage Geologic formations of Alberta Geologic formations of Montana Upper Cretaceous Series of North America