| Judith River Formation | |
|---|---|
| Stratigraphic range: Campanian, | |
 Judith River Formation, Upper Missouri Breaks National Monument | |
| Type | Geological formation |
| Unit of | Judith River Group |
| Sub-units | Parkman Sandstone Member, McClelland Ferry Member, Coal Ridge Member, Woodhawk Member |
| Underlies | Bearpaw Formation |
| Overlies | Claggett Formation, Pakowki Formation |
| Thickness | max 360 meters (1,180 ft)[1] |
| Lithology | |
| Primary | Mudstone and sandstone |
| Location | |
| Region |  Montana |
| Country |  United States |
| Type section | |
| Named for | Judith River near the confluence with the Missouri River |
| Named by | F.V. Hayden, 1871;[2] F.B. Meek, 1876.[3] |
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,[4] 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[5] and the Oldman Formation of Alberta.[6] 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 (such as Monoclonius). Modern work has found nearly complete skeletons of the hadrosaurid Brachylophosaurus.
- ^ Lexicon of Canadian Geological Units. "Judith River Formation". Retrieved 2009-02-06.
- ^ Hayden, F.V., 1871. Geology of the Missouri Valley: Preliminary report (4th annual) of the Geol. Surv. of Wyoming and portions of contiguous territories.
- ^ Meek, Fielding Bradford, 1876. A report on the invertebrate Cretaceous and Tertiary fossils of the upper Missouri country, Hayden, F.V., Geologist in Charge; United States Geologic and Geographic Survey of the Territories, vol. 9, page 629
- ^ Ramezani, Jahandar; Beveridge, Tegan L.; Rogers, Raymond R.; Eberth, David A.; Roberts, Eric M. (2022-09-26). "Calibrating the zenith of dinosaur diversity in the Campanian of the Western Interior Basin by CA-ID-TIMS U–Pb geochronology". Scientific Reports. 12 (1): 16026. doi:10.1038/s41598-022-19896-w. ISSN 2045-2322. PMC 9512893. PMID 36163377.
- ^ Sullivan, R.M. and Lucas, S. G. (2006). "The Kirtlandian land-vertebrate "age"–faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." Pp. 7-29 in Lucas, S. G. and Sullivan, R.M. (eds.), Late Cretaceous vertebrates from the Western Interior. New Mexico Museum of Natural History and Science Bulletin 35.
- ^ Eberth, David A. (1997). "Judith River Wedge". In Currie, Philip J.; Padian Kevin (eds.). Encyclopedia of Dinosaurs. San Diego: Academic Press. pp. 379–380. ISBN 0-12-226810-5.