Redonda Formation
Redonda Formation | |
---|---|
Stratigraphic range: Norian ~ | |
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 |
Approximate paleocoordinates | 9°54′N 43°12′W / 9.9°N 43.2°W |
Region | New Mexico |
Country | United States |
Type section | |
Named for | Redonda Mesa |
Named by | Dobrovolny and Summerson |
Year defined | 1946 |
The Redonda Formation is a geologic formation exposed in eastern New Mexico.[1] It contains vertebrate fossils of the late Triassic Period.[2] Fossil theropod tracks have been reported from the formation.[3]
Description
[edit]The formation consists of interbedded fine-grained red-brown sandstone and mudstone. It conformably overlies the Bull Canyon Formation[4] and underlies the Entrada Formation.[2]
The formation is interpreted as having been deposited in a lake with an area of about 5,000 square kilometres (1,900 sq mi).[4]
Fossils
[edit]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.[4][3]
Vertebrate fauna
[edit]This section needs additional citations for verification. (September 2020) |
Fish
[edit]fish of the Redonda Formation | ||||
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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
[edit]Stereospondyls of the Redonda Formation | ||||
---|---|---|---|---|
Taxa | Presence | Notes | Images | |
Numerous specimens |
A metoposaurid, possibly juveniles of Koskinodon |
Synapsids
[edit]Synapsids of the Redonda Formation | ||||
---|---|---|---|---|
Taxa | Presence | Notes | Images | |
teeth |
Archosauriforms
[edit]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
[edit]The unit was first named as the Redonda Member of the Chinle Formation by Dobrovolny and Summerson in 1947.[1] 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.[2]
See also
[edit]References
[edit]Bibliography
[edit]- 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.