Sundance Formation

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.

Sundance Formation
Stratigraphic range: Bathonian - Oxfordian 168–157 Ma
TypeGeological 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
UnderliesMorrison Formation
OverliesGypsum Springs Formation
ThicknessUp to 100 m
Lithology
Primaryshale
Otherlimestone, sandstone
Location
RegionWestern North America
Country United States
Type section
Named forSundance, Wyoming
Named byDarton
Year defined1904

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.

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.[3]

Vertebrate paleofauna
Vertebrates of the Sundance Formation
Taxa Presence Description Images

Ichnogenus:

  1. P. stokesi[4]
  • Found in Wyoming at the Alcova/Grey Reef Reservoir, Seminoe Reservoir, and Bighorn Canyon National Recreation area.[4]
  1. Found in Wyoming, at the ichnospecies' type locality.[4]
  • Alcova/Grey Reef Reservoir and Seminoe Reservoir housed at University of Wyoming, Laramie.[4] Alcova/Grey Reef Reservoir specimens are also housed at Tate Museum, Casper College.[4]
  1. Specimens housed at University of Wyoming, Laramie.[4]
Tatenectes Redwater Shale Member Cryptoclidid Plesiosaur
Pantosaurus Redwater Shale Member Cryptoclidid Plesiosaur
Megalneusaurus Redwater Shale Member Pliosaur
Baptanodon Redwater Shale Member Ophthalmosaurid Ichthyosaur
"Plesiosaurus" shirleyensis Nomen dubium, material now lost.[5]

Invertebrate paleofauna

Belemnoids
Belemnoids of the Sundance Formation
Taxa Presence Description Images

Genus:

  • Pachyteuthis
  1. P. densus

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". PALAIOS. SEPM Society for Sedimentary Geology. 21 (5): 480–492. doi:10.2110/palo.2005.P05-062R.
  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.
  3. BLM−Bureau of Land Management, Wyoming Office: "Red Gulch Dinosaur Tracksite" website, info, maps, photo gallery, accessed 8.21.2015
  4. 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.
  5. 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


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