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Sundance_Formation Latitude and Longitude:
44°15′24″N 105°40′57″W / 44.2568°N 105.6824°W / 44.2568; -105.6824
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Sundance Formation
Stratigraphic range: Bathonian - Oxfordian 168–157  Ma
Type Geological formation
Sub-unitsCanyon Springs Sandstone Member, Hulett Sandstone Member, Lak Member, Pine Butte Member, Redwater Shale Member, Stockade Beaver (Shale) Member, Windy Hill Sandstone Member
Underlies Morrison Formation
Overlies Gypsum Springs Formation
ThicknessUp to 100 m
Lithology
Primary shale
Other limestone, sandstone
Location
RegionWestern North America
Country  United States
Type section
Named for Sundance, Wyoming
Named byDarton
Year defined1904

The Sundance Formation is a western North American sequence of Middle Jurassic to Upper Jurassic age [1] Dating from the Bathonian to the Oxfordian, around 168-157 Ma, It is up to 100 metres thick [2] and consists of marine shale, sandy shale, sandstone, and limestone deposited in the Sundance Sea, an inland sea that covered large parts of western North America during the Middle and early Late Jurassic.

Geology

The Sundance Formation underlies the western North American Morrison Formation, the most fertile source of dinosaur fossils in the Americas, and is separated by a disconformity from the underlying Middle Jurassic Gypsum Springs Formation.

Fossils

The Sundance Formation is known for fossils of an extinct species of marine cephalopod, the belemnite Pachyteuthis densus, as well as several extinct species of oyster, including Deltoideum, Liostrea, and Gryphaea nebrascensis. Other common invertebrates include crinoids, echinoids, gastropods, insects, ostracods, and foraminifera. [3]

Fossil dinosaur 'footprints' on an ancient ocean shoreline are preserved in the formation and protected at the Red Gulch Dinosaur Tracksite, located in the Bureau of Land Management Red Gulch/Alkali National Back Country Byway, near Shell in Big Horn County, Wyoming. [4]

Paleobiota

Vertebrates

Genus Species Member Material Notes

Pteraichnus [5]

  • P. stokesi
  • Alcova/Grey Reef Reservoir, Seminoe Reservoir and Bighorn Canyon National Recreation area. (Wyoming) [5]

Trace fossils

A Pteraichnid belonging to the Pterodactyloidea.

Tatenectes

  • T. laramiensis
  • Redwater Shale Member

A Cryptoclidid Plesiosaur.

Pantosaurus

  • P. striatus
  • Redwater Shale Member

A Cryptoclidid Plesiosaur.

Megalneusaurus

  • M. rex
  • Redwater Shale Member

A Thallasophonid Pliosaur.

Baptanodon

  • B. natans
  • Redwater Shale Member

An Ophthalmosaurid Ichthyosaur.

Plesiosaurus

  • "P." shirleyensis

Material now lost. [6]

Possibly a Plesiosaurid Plesiosaur.

Invertebrates

Genus Species Member Material Notes

Pachyteuthis

  • P. densus

A Belemnoid.

Fish

Genus Species Member Material Notes

Occithrissops

  • O. willsoni

An ichthyodectiform

References

  1. ^ Jennings, Debra S.; Stephen T. Hasiotis (2006). "Taphonomic analysis of a dinosaur feeding site using Geographic Information Systems (GIS), Morrison Formation, Southern Bighorn Basin, Wyoming, USA" (PDF). PALAIOS. 21 (5). SEPM Society for Sedimentary Geology: 480–492. doi: 10.2110/palo.2005.P05-062R. S2CID  55369947.
  2. ^ Syzdek, Joseph; Malone, David; Craddock, John (2019-08-01). "Detrital Zircon U-Pb Geochronology and Provenance of the Sundance Formation, Western Powder River Basin, Wyoming". The Mountain Geologist. 56 (3): 295–317. doi: 10.31582/rmag.mg.56.3.295. ISSN  0027-254X. S2CID  210290670.
  3. ^ Mcmullen, Sharon K.; Holland, Steven M.; O'keefe, F. Robin (June 2014). "The Occurrence of Vertebrate and Invertebrate Fossils in a Sequence Stratigraphic Context: The Jurassic Sundance Formation, Bighorn Basin, Wyoming, U.S.A." PALAIOS. 29 (6): 277–294. doi: 10.2110/pal.2013.132. ISSN  0883-1351. S2CID  126843460.
  4. ^ BLM−Bureau of Land Management, Wyoming Office: "Red Gulch Dinosaur Tracksite" website, info, maps, photo gallery, accessed 8.21.2015
  5. ^ a b Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. ISSN  1612-4138.
  6. ^ W. R. O'Keete, F. R. and Wahl Current taxonomic status of the plesiosaur Pantosaurus striatus from the Upper Jurassic Sundance Formation, Wyoming, article on pages 37-47 of the complete issue, 2003, Paludicola, 4 (2) : 27-68. Paperback – January 1, 2003

44°15′24″N 105°40′57″W / 44.2568°N 105.6824°W / 44.2568; -105.6824


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