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Cloverly Formation

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Cloverly Formation
Stratigraphic range: Maastrichtian
TypeGeological formation
UnderliesThermopolis Shale
OverliesMorrison Formation
Thickness150–400 ft (46–122 m)
Lithology
PrimaryMudstone
OtherConglomerate, sandstone
Location
Region Wyoming,  Montana,

 Colorado,

 Utah
Country USA
Type section
Named forCloverly post office, Wyoming
Named byNelson Horatio Darton, 1904[1]

The Cloverly Formation is a geological formation of Late Cretaceous age (Maastrichian stage)[2] that is present in parts of Montana, Wyoming, Colorado and Utah in the western United States. It was named for a post office on the eastern side of the Bighorn Basin in Wyoming by N.H. Darton in 1904.[1][3] The sedimentary rocks of formation were deposited in floodplain environments and contain vertebrate fossils, including a diverse assemblage of dinosaur remains. In 1973, the Cloverly Formation Site was designated as a National Natural Landmark by the National Park Service.[4]

Stratigraphy

The Cloverly Formation rests disconformably on the Morrison Formation and is conformably overlain by the Thermopolis Shale. It is subdivided into a variety of members, depending on the location.[3][5] In the Bighorn Basin along the Montana-Wyoming border, the Cloverly is divided into the following three members:

  • The 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.
  • The uppermost unit is the Himes Member, which contains some coarse-grained channel sandstone deposits, but consists primarily of brightly multicolored (variegated) mudstones.

Age

Radiometric dating by the fission track method has yielded dates of 115 ± 10 Ma (million years ago) for the lower part of the Little Sheep Member[2] and 108.5 ± 0.2 Ma near the top of that member,[6] confirming that the Cloverly Formation is of Aptian to Albian age.

Depositional environment

The sediments of the Cloverly Formation were deposited in alluvial and floodplain environments. The basal conglomerates probably represent braided river deposits, while the sandstones were deposited in fluvial channels. The mudstones that contain most of the fossils represent overbank, lacustrine, and pedogenic deposits.[3][5][7]

Vertebrate fauna

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 the lungfish Ceratodus.

Dinosaur eggs have been found in Montana.[8]

References for data: Ostrom 1970; Cifelli et al. 1998; Cifelli 1999; Nydam and Cifelli 2002. Possible goniopholidid remains are known from the formation.

Ornithischians

Ornithischians reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Aquilops[9]

A. americanus

  • Montana

A basal neoceratopsian.

Aquilops
Sauropelta
Tenontosaurus
Zephyrosaurus being attacked by Deinonychus

Sauropelta[10]

S. edwardsorum[10]

Known from "several articulated skeletons" and its armor plates are common fossils.[10] Only one partial skull is known."."[11]

Articulated skeletons are often encased in carbonate caliche deposits that require acid to be removed safely.[10]

Tenontosaurus[10]

T. tilleti[10]

Its remains are the most common of any dinosaur of the formation.[10]

Juvenile remains are sometimes found together, suggesting that young Tenontosaurus lived in sibling groups. Deinonychus teeth are sometimes associated with Tenontosaurus remains suggesting a predator–prey relationship between the two.[10]

Zephyrosaurus[10]

Z. schaffi[10]

Its remains are "very rare."[10]

Saurischians

Theropod eggshell fragments are known from the formation. Unidentifiable ornithomimmid remains are present and most commonly represented by toe bones.[10] Indeterminate allosauroid remains are known from the formation. Remains identified by John Ostrom as Ornithomimus are suspected by Jack Horner to be of a new ornithomimid genus.[10]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
Saurischians reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images
Acrocanthosaurus[13] A. atokensis[13] Cloverly VII[13]
Acrocanthosaurus
Deinonychus
Microvenator
Sauroposeidon

Deinonychus[10]

D. antirrhopus[10]

Its remains are "very rare."[10]

Tenontosaurus remains have been recovered in association with Deinonychus teeth on several occasions suggesting a predator–prey relationship between the two.[10]

Microvenator[10]

M. celer[10]

Its remains are "extremely rare."[10] Known only from a "[p]artial skeleton with partial skull."[14] The specimen lacks feet and is catalogued as AMNH 3041.[15]

The type specimen AMNH 3041[10] was recovered by Barnum Brown from Cloverly strata in Montana in 1933.

Ornithomimus[16]

O. velox[16]

Later found to be indeterminate ornithomimid remains.[16]

Rugocaudia[17]

R. cooneyi[17]

class="wikitable" align="center" width="100%"
Sauropods of the Sânpetru Formation
Genus Species Location Stratigraphic position Abundance Notes Images

Magyarosaurus[18]

M. dacus[18]

Magyarosaurus scapula

M. hungaricus[18]

M. transsylvanicus[18] 

Journal of Vertebrate Paleontology 32(4):883–902.</ref>

|M. dacus |

|Cloverly VII[13] | | |}

Mammals

Mammals reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Corviconodon

C. montanensis

Gobiconodon

Gobiconodon

G. ostromi

Montanalestes

M. keeblerorum

Turtles

Turtles reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes

Glyptops[10]

G. pervicax[10]

Naomichelys[10]

N. speciosa[10]

Bony fish

Indeterminate amiiformes are known from the formation.

Osteichthyes reported from the Cloverly Formation
Genus Species State Stratigraphic position Material Notes Images

Ceratodus[10]

C. frazieri[10]

C. nirumbee[19]

Ceratodus

See also

Footnotes

  1. ^ a b Darton, N.H. 1904. Comparison of the stratigraphy of the Black Hills, Bighorn Mountains, and Rocky Mountain Front Range. Geological Society of America Bulletin, v. 15, p. 379-448.
  2. ^ a b Chen, Z.-Q. and Lubin, S. 1997. A fission track study of the terrigenous sedimentary sequences of the Morrison and Cloverly Formations in northeastern Bighorn Basin, Wyoming. The Mountain Geologist 34: 51-62.
  3. ^ a b c U.S. Geological Survey (1993). "Geologic Unit: Cloverly". Retrieved 2014-12-23.
  4. ^ "National Natural Landmarks - National Natural Landmarks (U.S. National Park Service)". www.nps.gov. Retrieved 2019-03-22. Year designated: 1973
  5. ^ a b Moberly, R.M., Jr., 1960, Morrison, Cloverly, and Sykes Mountain formations, northern Bighorn basin, Wyoming and Montana: Geological Society of America Bulletin, v. 71, no. 8, p. 1137-1176.
  6. ^ 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.
  7. ^ May, M.T. 1992. Intra- and extrabasinal tectonism, climate and intrinsic threshold cycles as possible controls on Early Cretaceous fluvial architecture, Wind River basin, Wyoming. In: Sundell, K.A., and Anderson, T.C., eds., Rediscover the Rockies: Wyoming Geological Association Field Conference Guidebook, 43rd Annual Field Conference, Casper, WY, September 12–19, 1992, no. 43, p. 61-74.
  8. ^ a b "3.11 Montana, United States; 1. Cloverly Formation," in Weishampel, et al. (2004). Page 556.
  9. ^ Andrew A. Farke, W. Desmond Maxwell, Richard L. Cifelli & Mathew J. Wedel (2014) A Ceratopsian Dinosaur from the Lower Cretaceous of Western North America, and the Biogeography of Neoceratopsia. PLoS ONE 9(12): e112055. doi:10.1371/journal.pone.0112055 http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0112055
  10. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag Horner. Pp. 93-100.
  11. ^ "Table 17.1," in Weishampel, et al. (2004). Page 365.
  12. ^ a b c d "3.12 Wyoming, United States; 2. Cloverly Formation," in Weishampel, et al. (2004). Page 556.
  13. ^ a b c d e f D'Emic, Michael D.; Melstrom, Keegan M.; Eddy, Drew R. (2012). "Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis". Palaeogeography, Palaeoclimatology, Palaeoecology. 333–334: 13–23. doi:10.1016/j.palaeo.2012.03.003.
  14. ^ "Table 8.1," in Weishampel, et al. (2004). Page 167.
  15. ^ "Table 5.1," in Varricchio (2001). Page 44.
  16. ^ a b c "3.11 Wyoming, United States; 1. Cloverly Formation" and "3.12 Montana, United States; 2. Cloverly Formation," in Weishampel, et al. (2004). Page 556.
  17. ^ a b c D. Cary Woodruff (2012). "A new titanosauriform from the Early Cretaceous Cloverly Formation of Montana". Cretaceous Research. 36: 58–66. doi:10.1016/j.cretres.2012.02.003.
  18. ^ a b c d Cite error: The named reference sanpetru was invoked but never defined (see the help page).
  19. ^ Frederickson J.A. and Cifelli R.L. (2016) New Cretaceous lungfishes (Dipnoi, Ceratodontidae) from western North America. Journal of Paleontology.

References

Wikimedia Commons has media related to Cloverly Formation.
  • 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 Cloverly 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.
  • Horner, John R. Dinosaurs Under the Big Sky (Cloverly Formation). Mountain Press Publishing Company. pp. 93–100. ISBN 0-87842-445-8.
  • 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
  • Varricchio, D. J. 2001. Late Cretaceous oviraptorosaur (Theropoda) dinosaurs from Montana. pp. 42–57 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Indianapolis, Indiana.
  • Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.
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