Ojo Alamo Formation

Ojo Alamo Formation
Stratigraphic range: Maastrichtian-Danian, 69–64 Ma
↓
Type Geological formation
Sub-units Naashoibito Member, Kimbeto Member
Underlies Nacimiento Formation
Overlies Kirtland Formation
Location
Region San Juan Basin, New Mexico
Country  USA

The Ojo Alamo Formation is a geologic formation spanning the Mesozoic/Cenozoic boundary. Dinosaur remains are among the fossils that have been recovered from the formation, though all dinosaur remains come from the lowest part of the formation, the Naashoibito member (sometimes considered part of the Kirtland Formation, which dates to the late Maastrichtian stage of the Cretaceous period.[1]

The Ojo Alamo formation is divided into two subunits separated by a large unconformity—a gap in the geologic record. The lower Naashoibito member (sometimes considered part of the Kirtland Formation) was deposited during the Maastrichtian age of the Cretaceous period, specifically between about 69-68 million years ago. It overlies the De-na-zin member of the Kirtland formation, though the two are separated by another large unconformity that spans 73-69 million years of geologic time.[2] All dinosaur fossils probably come from this unit.[3]

The upper unit of the Ojo Alamo Formation is the Kimbeto Member, which was deposited mainly during the earliest Cenozoic (Danian age of the Paleogene period), between 66 and 64 million years ago.[2] Some researchers have claimed to find isolated non-avian dinosaur remains in this younger unit. If this is the case, it would represent the only known instance of a non-avian dinosaur population persisting after the Cretaceous–Paleogene extinction event. However, most scientists consider these to have been stratigraphically misinterpreted or reworked from the older Naashoibito member.[3]

Alamo Wash Fauna

The following species are known to be present in the Naashoibito Member "Alamo Wash Fauna".[4]

See also

References

  1. ↑ Williamson, T.E. and Weil, A. (2008). "Metatherian mammals from the Naashoibito Member, Kirtland Formation, San Juan Basin, New Mexico and their biochronologic and paleobiogeographic significance. Journal of Vertebrate Paleontology, 28: 803-815.
  2. 1 2 Sullivan, R.M., and Lucas, S.G. 2006. "The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America." New Mexico Museum of Natural History and Science, Bulletin 35:7-29.
  3. 1 2 Sullivan, RM (2003). "No Paleocene dinosaurs in the San Juan Basin, New Mexico". Geological Society of America Abstracts with Programs 35 (5): 15. Retrieved 2007-07-02.
  4. ↑ Jasinski, S. E., Sullivan, R. M., & Lucas, S. G. (2011). Taxonomic composition of the Alamo Wash local fauna from the Upper Cretaceous Ojo Alamo Formation (Naashoibito Member) San Juan Basin, New Mexico. Bulletin, 53, 216-271.
  5. ↑ Robert M. Sullivan, Steven E. Jasinski and Mark P.A. Van Tomme (2011). "A new caenagnathid Ojoraptorsaurus boerei, n. gen., n. sp. (Dinosauria, Oviraptorosauria), from the Upper Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico" (PDF). Fossil Record 3. New Mexico Museum of Natural History and Science Bulletin 53: 418–428.
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