Bajo de la Carpa Formation

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The Bajo de la Carpa Formation is a geologic formation that outcrops in Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the first of two formations belonging to the Río Colorado Subgroup within the Neuquén Group.

At its base, this formation conformably overlies the Plottier Formation of the older Rio Neuquén Subgroup, and it is in turn overlain by the Anacleto Formation, the youngest and uppermost formation of the Neuquén Group (Fossa Mancini et al. 1938, Leanza et al. 2004).

Contents 1 Age 2 Composition 3 Paleontology 4 See also 5 References

[edit] Age

Era: Mesozoic
Period: Late Cretaceous
Faunal stage: Santonian
Absolute Age: ~86 to ~83 mya

[edit] Composition

The Bajo de la Carpa Formation can reach over 105 meters thick in some locations, and consists mainly of sandstones of various colors, all of fluvial origin, with thin layers of mudstone and siltstone in between. Geological features such as geodes, chemical nodules, impressions of raindrops, and paleosols (soil deposits) are commonly found in this formation as well.

[edit] Paleontology

Animal fossils are abundant within the Bajo de la Carpa Formation, especially those of crocodilians. A partial list includes:

• several turtles (including Lomalatachelys)
• primitive snakes (including Dinilysia)
• several crocodilians (including Comahuesuchus, Cynodontosuchus, Lomasuchus, Notosuchus, and Peirosaurus)
• an abelisauroid theropod (Velocisaurus)
• an alvarezsaurid theropod (Alvarezsaurus)
• birds, including Neuquenornis and the flightless Patagopteryx
• a larger theropod
• titanosaurian sauropods

Small nests with eggs inside, found in this formation, probably belonged to the bird Neuquenornis (Leanza et al. 2004).

[edit] See also

• List of fossil sites (with link directory)

[edit] References

• Fossa Mancini, E., Feruglio, E., Yussen de Campana, J.C.. 1938. Una reunión de geólogos de YPF y el problema de la terminología estratigráfica. Boletín de Informaciones Petroleras 15: 1-67.
• Leanza, H.A,, Apesteguia, S., Novas, F.E. & de la Fuente, M.S. 2004. Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages. Cretaceous Research. 25(1): 61-87.