Cloverly Formation

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The Cloverly Formation are Lower Cretaceous strata located in Montana and Wyoming, in the western United States. The term now includes strata that had formerly been called the Dakota Formation in central and southern Wyoming. In the Bighorn Basin region along the Montana -Wyoming border, the Cloverly is divided into several members.

Brightly colored Himes Member of the Cloverly Formation near Shell, Wyoming. These Lower Cretaceous rocks have produced numerous dinosaurs.

• Pryor Conglomerate lies at the base and contains abundant black chert. It is named from thick beds exposed on the west side of the Pryor Mountains.
• The Little Sheep Member lies in the middle and is composed of pale-purple, gray to almost white, bentonitic mudstone. A radiometric date of 115 +/- 10 MA has been obtained from low in the member (Chen and Lubin 1997), and other near the top at 108.5 +/- 0.2 MA (Burton et al. 2006). These dates confirm that the Cloverly is Aptian-Albian in age.
• The uppermost member is the Himes Member contains some coarse grained channel deposits, but is primarily brightly, multicolored (variegated) mudstones.

Animals recovered include the dinosaurs Deinonychus, Microvenator Tenontosaurus, Zephyrosaurus and Sauropelta as well as fragmentary remains of Titanosaurs and Ornithomimids. As well, two genera of turtle Naomichelys and Glyptops and Ceratodus.

[edit] Fossil vertebrates

references for data: Ostrom 1970; Cifelli et al. 1998; Cifelli 1999; Nydam and Cifelli 2002.

[edit] References

• Burton, D., Greenhalgh, B.W., Britt, B.B., Kowallis, B.J., Elliott, W.S., and Barrick, R. 2006. New radiometric ages from the Cedar Mountain Formation, Utah and the Cloverly Formation, Wyoming: implications for contained dinosaur faunas. Geological Society of America Abstracts with Programs 38(7): 52.
• Chen, Z.-Q. and Lubin, S. 1997. A fission track study of the terrigenous sedimentary sequences of the Morrison and Cloverl Formations in northeastern Bighorn Basin, Wyoming. The Mountain Geologist 34:51-62.
• Cifelli, R.L. 1999. Tribosphenic mammal from the North American Early Cretaceous. Nature 401:363-366.
• Cifelli, R.L., Wible, J.R., and Jenkins, F.A. 1998. Triconodont mammals from the Cloverly Formation (Lower Cretaceous), Montana and Wyoming. Journal of Vertebrate PAleontology 18: 237-241.
• Nydam, R.L., and Cifelli, R.L. 2002. Lizards from the Lower Cretaceous (Aptian-Albian) Antlers and Cloverly Formations. Journal of Vertebrate Paleontology 22: 286-298.
• Ostrom, J. H. 1970. Stratigraphy and paleontology of the Cloverly Formation (Lower Cretaceous) of the Bighorn Basin area, Wyoming and Montana. Peabody Museum Bulletin 35:1-234