| Redonda Formation | |
|---|---|
| Stratigraphic range: Norian ~221–206 Ma PreꞒ Ꞓ O S D C P T J K Pg N | |
| Type | Formation |
| Unit of | Chinle Group |
| Sub-units | Duke Ranch, Quay, Red Peak, San Jon Creek & Wallace Ranch members |
| Underlies | Entrada Formation |
| Overlies | Bull Canyon Formation |
| Thickness | 25–425 feet (7.6–129.5 m) |
| Lithology | |
| Primary | Shale |
| Other | Limestone, sandstone |
| Location | |
| Coordinates | 34°57′54″N 103°42′04″W / 34.965°N 103.701°W / 34.965; -103.701 |
| Approximate paleocoordinates | 9°54′N 43°12′W / 9.9°N 43.2°W / 9.9; -43.2 |
| Region | New Mexico |
| Country |  United States |
| Type section | |
| Named for | Redonda Mesa |
| Named by | Dobrovolny and Summerson |
| Year defined | 1946 |
  Redonda Formation (the United States)Show map of the United States Redonda Formation (New Mexico)Show map of New Mexico | |
The Redonda Formation is a geologic formation exposed in eastern New Mexico. It contains vertebrate fossils of the late Triassic Period. Fossil theropod tracks have been reported from the formation.
Description
The formation consists of interbedded fine-grained red-brown sandstone and mudstone. It conformably overlies the Bull Canyon Formation and underlies the Entrada Formation.
The formation is interpreted as having been deposited in a lake with an area of about 5,000 square kilometres (1,900 sq mi).
Fossils
The formation has few fossil plants, with only Neocalamites reported, but it contains abundant invertebrate fossils (conchostracans and ostracods) and a diverse assemblage of vertebrate fossils.
Vertebrate fauna
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Fish
| fish of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Skull fragments | A redfieldiid |
 | ||
| A lungfish | ||||
|
Coelacanthidae indet. |
Fragmentary material | Possibly assignable to Chinlea or Quayia | ||
| scales | A dapediid | |||
| Abundant, found in large deathbeds | A semionotid | |||
| Skull fragments | A redfieldiid | |||
Stereospondyls
| Stereospondyls of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Numerous specimens |
A metoposaurid, possibly juveniles of Koskinodon |
 | ||
Synapsids
| Synapsids of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| teeth | ||||
Archosauriforms
| Archosauriforms of the Redonda Formation | ||||
|---|---|---|---|---|
| Taxa | Presence | Notes | Images | |
| Osteoderms |
An aetosaur similar to Neoaetosauroides |
  | ||
| Numerous skulls and other skeletal remains | ||||
| Osteoderms and other fragments |
A typothoracisine aetosaur related to Typothorax | |||
| Snout bones and a scapulocoracoid |
A large, predatory basal crocodylomorph | |||
| Osteoderms | An unusual non-archosaurian archosauriform | |||
History of investigation
The unit was first named as the Redonda Member of the Chinle Formation by Dobrovolny and Summerson in 1947. Griggs and Read raised the unit to formation rank in 1959, and also assigned an age of late Triassic based on the presence of tracks of a bipedal dinosaur and of a phytosaur skull.
See also
References
- ^ Dobrovolny and Summerson 1947
- ^ Griggs and Read 1959
- ^ Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
- ^ Lucas and Hunt 1989
Bibliography
- Dobrovolny, Ernest; Summerson, C.H. (1947). "Geology of northwestern Quay County, New Mexico". U.S. Geological Survey Oila Nd Gas Investigations Map. OM-62. doi:10.3133/om62.
- Griggs, R.L.; Read, C.B. (1959). "Revisions in Stratigraphic Nomenclature in Tucumcari-Sabinoso Area, Northeastern New Mexico: GEOLOGICAL NOTES". AAPG Bulletin. 43 (8): 2003–2007. doi:10.1306/0BDA5E8E-16BD-11D7-8645000102C1865D.
- Lucas, S.G.; Hunt, A.P. (1989). "Revised Triassic stratigraphy in the Tucumcari basin, east-central New Mexico". In Lucas, S.G.; Hunt, A.P. (eds.). Dawn of the age of dinosaurs in the American southwest. New Mexico Museum of Natural History and Science. pp. 150–170. Retrieved 17 September 2020.
- Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.