Redonda Formation

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.

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).

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.

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.

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with theropod tracks

• 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.