Redonda Formation
{{Short description|Geologic formation exposed in eastern New Mexico}}
{{Infobox rockunit
| name = Redonda Formation
| image =
| caption =
| type = Formation
| age = Norian
~{{fossil range|221|206}}
| period = Norian
| prilithology = Shale
| otherlithology = Limestone, sandstone
| namedfor = Redonda Mesa
| namedby = Dobrovolny and Summerson
| year_ts = 1946
| region = New Mexico
| country = United States
| coordinates = {{coord|34.965|N|103.701|W|display=inline,title}}
| paleocoordinates = {{coord|9.9|N|43.2|W|display=inline}}
| unitof = Chinle Group
| subunits = Duke Ranch, Quay, Red Peak, San Jon Creek & Wallace Ranch members
| underlies = Entrada Formation
| overlies = Bull Canyon Formation
| thickness = {{convert|25-425|feet|meters}}
| extent =
| area =
| map = {{Location map+ | United States#New Mexico
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | United States#New Mexico
| lat_deg = 34.965
| lon_deg = -103.701
| mark = Pink ff0080 pog.svg
| marksize = 12
}}
}}
| map_caption =
}}
The Redonda Formation is a geologic formation exposed in eastern New Mexico.Dobrovolny and Summerson 1947 It contains vertebrate fossils of the late Triassic Period.Griggs and Read 1959 Fossil theropod tracks have been reported from the formation.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
Description
The formation consists of interbedded fine-grained red-brown sandstone and mudstone. It conformably overlies the Bull Canyon FormationLucas and Hunt 1989 and underlies the Entrada Formation.
The formation is interpreted as having been deposited in a lake with an area of about {{convert|5000|km2|sqmi}}.
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=
{{more citations needed section|date=September 2020}}
== Fish ==
| class="wikitable" align="center" width="100%" |
| colspan="5" align="center" |fish of the Redonda Formation |
|---|
| Taxa
! Presence ! Notes ! Images |
| Cionichthys
| Skull fragments | A redfieldiid | rowspan="99" | |
| Ceratodus
| | A lungfish |
| Coelacanthidae indet.
| Fragmentary material |
| Hemicalypterus
| scales | A dapediid |
| Semionotus
| Abundant, found in large deathbeds | A semionotid |
| Synornichthys
| Skull fragments | A redfieldiid |
== Stereospondyls ==
| class="wikitable" align="center" width="100%" |
| colspan="5" align="center" |Stereospondyls of the Redonda Formation |
|---|
| Taxa
! Presence ! Notes ! Images |
| Apachesaurus
| Numerous specimens | A metoposaurid, possibly juveniles of Koskinonodon | rowspan="99" | |
== Synapsids ==
| class="wikitable" align="center" width="100%" |
| colspan="5" align="center" |Synapsids of the Redonda Formation |
|---|
| Taxa
! Presence ! Notes ! Images |
| Redondagnathus
|teeth | | rowspan="99" | |
== Archosauriforms ==
| class="wikitable" align="center" width="100%" |
| colspan="5" align="center" |Archosauriforms of the Redonda Formation |
|---|
| Taxa
! Presence ! Notes ! Images |
| Apachesuchus
| Osteoderms | An aetosaur similar to Neoaetosauroides | rowspan="99" | |
| Redondasaurus
|Numerous skulls and other skeletal remains | |
| Redondasuchus
| Osteoderms and other fragments | A typothoracisine aetosaur related to Typothorax |
| Redondavenator
| Snout bones and a scapulocoracoid | A large, predatory basal crocodylomorph |
| Vancleavea
|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
{{Reflist}}
= Bibliography =
- {{cite journal |last1=Dobrovolny |first1=Ernest |last2=Summerson |first2=C.H. |title=Geology of northwestern Quay County, New Mexico |journal=U.S. Geological Survey Oila Nd Gas Investigations Map |date=1947 |volume=OM-62 |page=2 |doi=10.3133/om62|bibcode=1947usgs.rept....2D }}
- {{cite journal |last1=Griggs |first1=R.L. |last2=Read |first2=C.B. |title=Revisions in Stratigraphic Nomenclature in Tucumcari-Sabinoso Area, Northeastern New Mexico: GEOLOGICAL NOTES |journal=AAPG Bulletin |date=1959 |volume=43 |issue=8 |pages=2003–2007 |doi=10.1306/0BDA5E8E-16BD-11D7-8645000102C1865D}}
- {{cite encyclopedia |last1=Lucas |first1=S.G. |last2=Hunt |first2=A.P. |year=1989 |title=Revised Triassic stratigraphy in the Tucumcari basin, east-central New Mexico |editor1-last=Lucas |editor1-first=S.G. |editor2-last=Hunt |editor2-first=A.P. |encyclopedia=Dawn of the age of dinosaurs in the American southwest |publisher=New Mexico Museum of Natural History and Science |pages=150–170 |url=https://books.google.com/books?id=Ar1hCgAAQBAJ&dq=Revised+Triassic+stratigraphy+in+the+Tucumcari+basin%2C+east+central+New+Mexico&pg=PA150 |accessdate=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}}.
Category:Triassic formations of New Mexico
Category:Shale formations of the United States
Category:Siltstone formations of the United States