| Sundance Formation | |
|---|---|
| Stratigraphic range: Bathonian - Oxfordian | |
| Type | Geological formation |
| Sub-units | Canyon 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 |
| Thickness | Up to 100 m |
| Lithology | |
| Primary | shale |
| Other | limestone, sandstone |
| Location | |
| Region | Western North America |
| Country | United States |
| Type section | |
| Named for | Sundance, Wyoming |
| Named by | Darton |
| Year defined | 1904 |
The Sundance Formation is a western North American sequence of Middle Jurassic to Upper Jurassic age1 Dating from the Bathonian to the Oxfordian, around 168-157 Ma, It is up to 100 metres thick2 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
Two unusual trackways from the formation are not easily identifiable to taxonomic group, though one could have been from an injured pterosaur.5
Paleobiota
Reptiles
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Trace fossils |
Pterosaur tracks | |
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Material now lost.7 |
Possibly a junior synonym of Pantosaurus striatus |
Fish
| Genus | Species | Member | Material | Notes |
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Teeth |
Belongs to a group of shark like cartilaginous fish called the Hybodontiformes. This might either be Hybodus or Asteracanthus.8 Found in association with Tatenectes. |
Invertebrates
| Genus | Species | Member | Material | Notes |
|---|---|---|---|---|
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References
References
- 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.
- 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.
- 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.
- BLM−Bureau of Land Management, Wyoming Office: "Red Gulch Dinosaur Tracksite" website, info, maps, photo gallery, accessed 8.21.2015
- Harris, Jerald D.; Lacovara, Kenneth J. (2004). "Enigmatic Fossil Footprints from the Sundance Formation (Upper Jurassic) of Bighorn Canyon National Recreation Area, Wyoming". Ichnos. 11 (1–2): 151–166. doi:10.1080/10420940490442304. ISSN 1042-0940.
- 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.
- 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
- Massare, Judy A.; Wahl, William R.; Ross, Mike; Connely, Melissa V. (January 2014). "Palaeoecology of the marine reptiles of the Redwater Shale Member of the Sundance Formation (Jurassic) of central Wyoming, USA". Geological Magazine. 151 (1): 167–182. doi:10.1017/S0016756813000472. ISSN 0016-7568 – via Geological Magazine.
44°15′24″N 105°40′57″W / 44.2568°N 105.6824°W / 44.2568; -105.6824