Hell Creek Formation
|Hell Creek Formation|
Stratigraphic range: Upper Cretaceous 66.8–66 mya
Exposure in the badlands near Fort Peck Reservoir
|Underlies||Fort Union Formation|
|Overlies||Fox Hills Formation|
|Region||Montana, North Dakota,|
South Dakota, Wyoming
|Named for||Hell Creek, Jordan, Montana|
It is a series of fresh and brackish-water clays, mudstones, and sandstones deposited during the end of the Cretaceous period and the beginning of the Palaeogene. It was laid down in river channels and deltas, and occasional peaty swamp deposits. along the low-lying eastern margin of the Western Interior Seaway.
The climate was mild, and the presence of crocodilians suggests a sub-tropical climate, with no prolonged annual cold. The famous iridium-enriched Cretaceous–Palaeogene boundary, which separates the Cretaceous from the Cenozoic, is a distinct thin bedding. It is above and occasionally within the formation, near its boundary with the overlying Fort Union Formation.
The world's largest collection of Hell Creek fossils is housed and exhibited at the Museum of the Rockies, in Bozeman, Montana. The specimens displayed are the result of the museum's Hell Creek Project. This is a joint effort between the museum, Montana State University, the University of California, Berkeley, the University of North Dakota and the University of North Carolina. The project began in 1998.
- Kielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi (2004). Mammals from the Age of Dinosaurs: origins, evolution, and structure. New York: Columbia University Press. pp. 98–99. ISBN 978-0-231-11918-4.
- Wilson, G. P. (2013). "Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: Dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling". Paleobiology. 39 (3): 429–469. doi:10.1666/12041.
- Archibald, J. D.; Zhang, Y.; Harper, T.; Cifelli, R. L. (2011). "Protungulatum: confirmed Cretaceous occurrence of an otherwise Paleocene Eutherian (Placental?) mammal". Journal of Mammalian Evolution. 18 (3): 153–161. doi:10.1007/s10914-011-9162-1.