- Bajo de la Carpa Formation
__NOTOC__The Bajo de la Carpa Formation is a
geologic formation thatoutcrop s inPatagonia , in the provinces of Río Negro and Neuquén,Argentina . It is the first of two formations belonging to the Río Colorado Subgroup within theNeuquén Group . Formerly that subgroup was treated as a formation, and the Bajo de la Carpa Formation was known as the Bajo de la Carpa Member. [Sánchez "et al." (2006)]At its base, this formation conformably overlies the
Plottier Formation of the older Rio Neuquén Subgroup, and it is in turn overlain by theAnacleto Formation , the youngest and uppermost formation of theNeuquén Group . [Fossa Mancini "et al." (1938), Leanza "et al." (2004)]The Bajo de la Carpa Formation can reach 150
meter s thick in some locations, and consists mainly ofsandstone s of various colors, all offluvial origin, with thin layers ofmudstone andsiltstone in between. Geological features such asgeode s, chemical nodules, impressions of raindrops, andpaleosol s (fossil soils) are commonly found in this formation as well.Leanza "et al." (2004), Sánchez "et al." (2006)]Age
Era:
Mesozoic
Period: LateCretaceous Faunal stage :Santonian
Absolute Age: ~86 to ~83 myaPaleontology
Animal fossils are abundant within the Bajo de la Carpa Formation:* a snake-necked turtle, "
Lomalatachelys "
* diversecrocodylomorph s occupying a range ofecological niche s: "Comahuesuchus ", "Cynodontosuchus ", "Dinilysia ", "Lomasuchus ", "Neuquensuchus ", "Notosuchus ", "Peirosaurus "
*titanosauria nsauropod s including "Bonitasaura "
* theceratosauria ntheropod s "Velocisaurus "
* the bird-like theropod "Achillesaurus " and "Alvarezsaurus "
* theenantiornithine bird "Neuquenornis "
* the oldest known trueflightless bird "Patagopteryx "Small
nest s with eggs inside, found in this formation, probably belonged to "Neuquenornis" or a related taxon. Fossilwasp nests have also been found in these rocks.ee also
*
List of fossil sites Footnotes
References
* (1938): Una reunión de geólogos de YPF y el problema de la terminología estratigráfica ["A YPF geologists' reunion and the problem of stratigraphy terminology"] . "Boletín de Informaciones Petroleras" 15: 1-67.
* (2004): Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages. "Cretaceous Research" 25(1): 61-87. doi|10.1016/j.cretres.2003.10.005 (HTML abstract)
* (2006): Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén [Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquen Group), Confluencia, Neuquén] . "Revista de la Asociación Geológica Argentina" 61(1): 3-18. [http://www.scielo.org.ar/pdf/raga/v61n1/v61n1a01.pdf PDF fulltext]
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