Wapiti Formation | |
---|---|
Stratigraphic range: | |
Type | Geological formation |
Lithology | |
Primary | Sandstone, siltstone, mudstone |
Other | conglomerate, coal |
Location | |
Region | Alberta |
Country | Canada |
Type section | |
Named for | Lower part of Wapiti River |
Named by | G.M. Dawson, 1881. [1] |
The Wapiti Formation is a geological formation of the Western Canada Sedimentary Basin in northwestern Alberta, and northeastern British Columbia, Canada. Its deposition spanned the time interval from the lower Campanian through to the upper Maastrichtian, between approximately 80 and 68 Ma. [2] It was named by G.M. Dawson in 1881, [1] presumably for exposures along the lower part of the Wapiti River and downstream along the Smoky River in Alberta. [3]
Dinosaur remains are among the fossils that have been recovered from the Cretaceous portion of the formation. [4] The Wapiti Formation does not produce many fossils due to its limited surface exposure and accessibility, although two Pachyrhinosaurus bone beds have been productive. [5]
The Wapiti Formation consists of interbedded sandstones, siltstones, shales and mudstones, with thin conglomerates, coal seams and bentonite beds. The sandstones are typically thick, pale grey, crossbedded and bentonitic. The middle part contains less sandstones, more mudstones, and fewer and thinner coals. The upper part contains thicker lenticular sandstones and more coals. [3]
The Wapiti Formation was deposited in inland fluvial and floodplain environments, with local areas of lacustrine sediments. [6] The sandstones were deposited mainly in fluvial channel environments, with siltstones, carbonaceous shales and coals accumulating in overbank settings.
The Wapiti Formation rests conformably on the marine shales of the Smoky Group. It is more than 1,300 m (4,300 ft) thick in the foothills of the Canadian Rockies in the west, [6] and it thins eastward to its erosional edge. [7] It is correlative with the entire sequence of the Belly River Group, Bearpaw Formation, Edmonton Group and Scollard Formation in south-central Alberta. [6] In most areas it is unconformably overlain by glacial and post-glacial sediments of Quaternary age, or exposed at surface. In a few upland areas it is unconformably overlain by Paleogene gravel deposits. [3]
Color key
| Notes Uncertain or tentative taxa are in small text; |
Indeterminate ankylosaurids, albertosaurines, pachycephalosaurids, ornithomimids, and saurolophines are known from Alberta. [8] [9] Corythosaurus is also known from the formation. [10] A caenagnathid is in the process of being described.
Dinosaurs of the Wapiti Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Member | Material | Notes | Images |
cf. Albertosaurus [11] | Indeterminate |
| Teeth | |||
B. fredlundi |
|
| Three trackways and an isolated print. | Footprints of large tyrannosaurids. | ||
B. certekorum |
|
| ||||
Indeterminate |
|
| Teeth; probable troodontid footprints are also known [14] | |||
|
| |||||
Hadrosauridae nov. tax. [11] | sp. nov. |
| A new taxon of hadrosaurid. | |||
P. lakustai |
| |||||
R. gilmorei |
| |||||
S. sp. |
|
A bone bed is any geological stratum or deposit that contains bones of whatever kind. Inevitably, such deposits are sedimentary in nature. Not a formal term, it tends to be used more to describe especially dense collections such as Lagerstätte. It is also applied to brecciated and stalagmitic deposits on the floor of caves, which frequently contain osseous remains.
Pachyrhinosaurus is an extinct genus of centrosaurine ceratopsid dinosaur from the Late Cretaceous period of North America. The first examples were discovered by Charles M. Sternberg in Alberta, Canada, in 1946, and named in 1950. Over a dozen partial skulls and a large assortment of other fossils from various species have been found in Alberta and Alaska. A great number were not available for study until the 1980s, resulting in a relatively recent increase of interest in Pachyrhinosaurus.
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The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. It was laid down during the same time period as portions of the Two Medicine Formation of Montana and the Oldman Formation of Alberta. It is an historically important formation, explored by early American paleontologists such as Edward Drinker Cope, who named several dinosaurs from scrappy remains found here on his 1876 expedition. Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus.
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The Milk River Formation is a sandstone-dominated stratigraphic unit of the Western Canada Sedimentary Basin in southern Alberta, Canada. It was deposited in near-shore to coastal environments during Late Cretaceous time. Based on uranium-lead dating, palynology and stratigraphic relationships, deposition occurred between ~84.1 and 83.6 Ma.
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