Frenchman Formation
Stratigraphic unit of Late Cretaceous age in the Western Canada Sedimentary Basin
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The Frenchman Formation is a stratigraphic unit of Late Cretaceous (late Maastrichtian) age in the Western Canada Sedimentary Basin. It is present in southern Saskatchewan and the Cypress Hills of southeastern Alberta. The formation was defined by G.M. Furnival in 1942[2] from observations of outcrops along the Frenchman River, between Ravenscrag and Highway 37. It contains the youngest of dinosaur genera, much like the Hell Creek Formation in the United States.
| Frenchman Formation | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Underlies | Ravenscrag Formation |
| Overlies | Battle Formation, Whitemud Formation, Eastend Formation, Bearpaw Formation |
| Thickness | up to 113 meters (371 ft)[1] |
| Lithology | |
| Primary | Sandstone |
| Other | Claystone, conglomerate |
| Location | |
| Coordinates | 49.49073°N 108.90467°W |
| Region | Western Canada Sedimentary Basin: Alberta Saskatchewan |
| Country | Canada |
| Type section | |
| Named for | Frenchman River |
| Named by | Furnival, 1942 |
Lithology
The Frenchman Formation consists of olive-green to brown, fine- to coarse-grained, cross-bedded sandstone with interbedded claystone bands and minor beds and lenses of intraformational clay-clast conglomerate.[1] A conglomerate layer with well-rounded quartzite pebbles is present above the basal unconformity in some areas.[3]
Thickness and distribution
The Frenchman Formation is present in southwestern Saskatchewan and the Cypress Hills area of southeastern Alberta. Its maximum reported thickness is about 113 m.[3]
Age
The Frenchman Formation is of latest Maastrichtian age, and the top of the formation coincides with the Cretaceous-Paleogene boundary, as evidenced by biostratigraphic changes and, in some areas, the presence of the terminal Cretaceous iridium anomaly.[4]
Relationship to other units
Although some early workers included the Frenchman Formation in the overlying Ravenscrag Formation, the two are separated by the Cretaceous-Paleogene boundary and are now treated separately. The contact is abrupt but conformable, and occurs at the base of the No. 1 or Ferris coal seam of the Ravenscrag Formation.[3]
The Frenchman is separated from the underlying formations by an erosional unconformity, and depending on the depth of the erosion, the Frenchman rests on the Whitemud Formation, the Battle Formation, the Eastend Formation, or the Bearpaw Formation.[3] It is equivalent in age to the lower part of the Scollard Formation, the lower part of the Willow Creek Formation, the lower part of the Coalspur Formation in Alberta, and the Hell Creek Formation in Montana and North Dakota.
Paleontology
Mammals and birds
J.E. Storer described fossil mammals from the Gryde locality in the Frenchman Formation, including Parectypodus and Alphadon.[5] A bone (the humeral end of the left coracoid) of a bird attributed to the genus Cimolopteryx has also been described from the Gryde locality.[6]
Dinosaurs
| Dinosaurs reported from the Frenchman Formation | |||||||
|---|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images | |
| Ankylosaurus | A. magniventris | An ankylosaurine ankylosaurid |  | ||||
| cf. Anzu[7] | cf. A. sp. | Two manual unguals | Claws from a large caenagnathid, tentatively referred to Anzu based on size | ||||
| ?Dromaeosaurus[8] | ?D. sp. | Scotty site | Three teeth | Some teeth are up to 3 cm in length. | |||
|
E. annectens |
"Complete skull, [three or four] partial skulls."[9] |
 | |||||
| E. saskatchewanensis |
Junior synonym of E. annectens[10] |
||||||
|
L. sp. |
A partial skeleton |
A caenagnathid theropod |
|||||
|
Ornithomimus sp. |
|||||||
| Sphaerotholus[13] | cf. S. buchholtzae | "nearly complete left postorbital" | The first pachycephalosaurid reported from the Frenchman Formation |  | |||
|
T. assiniboiensis |
Nearly complete skeleton |  | |||||
|
T. sp. |
Frill | A large chasmosaurine ceratopsian distinct from Triceratops. Fossils have also been unearthed in the Scollard Formation.[14][15] |  | ||||
|
T. prorsus |
Redpath, Saskatchewan | Nearly Complete Skull, one other partial skull | Being one of the most popular Dinosaurs, they are widely known. |  | |||
|
T. rex |
Nearly complete skeleton | "Scotty", possibly the largest T. rex ever discovered, is from the Frenchman Formation |  |
||||
Plants
Two megafloral assemblages were collected from Grasslands National Park and the Chambery Coulee site. The differences in floral composition as well as evidence of forest fires indicated these two localities represented an ecological succession in a fire-disturbed environment, with burned mature forests being colonised by pioneer shrubs and then a subsequent reestablishment of coniferous and hardwood forest. Leaf analysis estimated mean annual temperatures of 12–14 °C (54–57 °F) in a largely deciduous mixed forest of temperate climate.[16][17]
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Taxa | Species | Locality | Material | Notes | Images |
|---|---|---|---|---|---|
| Acer-like | Indeterminate | GNP[16] | |||
| Alnus | A. sp. | GNP[16] | |||
| Araucarites | A. sp. | Chambery Coulee[16] | Cone | ||
| Betula | B. sp. | GNP[16] | |||
| Cercidiphyllum | C. sp. | Chambery Coulee, GNP[16] | |||
| Cinnamomum-like | Indeterminate | Chambery Coulee, GNP[16] | Likely not Cinnamomum. | ||
| Ficus? | Indeterminate | Chambery Coulee, GNP[16] | Likely not in Moraceae. | ||
| Ginkgo | G. sp. | Chambery Coulee[16] | |||
| Juglans | J. sp. | Chambery Coulee[16] | Seeds | ||
| Macginitiea | M. sp. | Chambery Coulee, GNP[16] | |||
| Magnolia | M. sp. | Chambery Coulee, GNP[16] | |||
| Marmarthia | M. sp. | Chambery Coulee[16] | A Lauraceae, similar to Lindera.[18] | ||
| Menispermites | M. sp. | Chambery Coulee[16] | Belongs to Menispermaceae. | ||
| Metasequoia | M. sp. | Chambery Coulee[16] | |||
| Parataxodium? | Indeterminate | Chambery Coulee[16] | In need of revision.[19] | ||
| Platanus | P. sp. | Chambery Coulee, GNP[16] | |||
| Populus | P. sp. | Chambery Coulee, GNP[16] | |||
| Protophyllocladus | P. sp. | Chambery Coulee[16] | Belongs to Podocarpaceae, similar to Phyllocladus. | ||
| Pseudoctenis | P. sp. | Chambery Coulee[16] | |||
| Quercus | Q. sp. | Chambery Coulee[16] | |||
| Rhus | R. sp. | Chambery Coulee, GNP[16] | |||
| Sabalites | S. sp. | Chambery Coulee[16] | |||
| Salix | S. sp. | Chambery Coulee, GNP[16] | |||
| Sapindus | S. sp. | GNP[16] | |||
| Sassafras | S. sp. | GNP[16] | |||
| Sequoia | S. sp. | Chambery Coulee[16] | |||
| Taxodium? | T?. sp. | Chambery Coulee[16] | |||
| Zelkova | Z. sp. | Chambery Coulee[16] |
