Portezuelo Formation

__NOTOC__The Portezuelo Formation is a geologic formation outcropping in the Mendoza, Río Negro and Neuquén provinces of Argentina. It is the fourth-oldest formation in the Neuquén Group and the older of the two formations in the Río Neuquén Subgroup. Formerly that subgroup was treated as a formation, and the Portezuelo Formation was known as the Portezuelo Member. [Sánchez "et al." (2006)]

The type locality of the Portezuelo Formation is the mountain range known as Sierra del Portezuelo in Neuquén province [Wichmann (1929)] . This formation conformably overlies the Lisandro Formation of the Río Limay Subgroup. In the top layers it grades into the Plottier Formation, the younger formation within the Río Neuquén Subgroup.

Sandstones and siltstones, probably deposited under fluvial conditions, make up the Portezuelo Formation. There are also occasional cemented claystone deposits, as well as numerous paleosols (fossil soils). The formation varies between 95 and 130 meters thick throughout its range [Leanza "et al." (2004), Sánchez "et al." (2006)] .

Age

Era: Mesozoic
Period: Late Cretaceous
Faunal stage: late Turonian to early Coniacian
Absolute Age: ~91 to ~88 mya

Paleontology

Many dinosaur fossils have recently been described from this formation, as well as remains of several other types of animals:

* abundant and diverse turtles including "Portezueloemys" and a species of "Prochelidella"
* rare crocodilians
* titanosaurian sauropods including "Malarguesaurus"
* dromaeosaurid theropods ("Neuquenraptor", "Unenlagia")Agnolin "et al." (2006)]
* a carnosaurian theropod ("Megaraptor")
* an alvarezsaurid theropod ("Patagonykus")
* several other theropods, including a modern, possibly galliform bird
* ornithopods including "Macrogryphosaurus"

ee also

* List of fossil sites

Footnotes

References

* (2006): Neornithine bird coracoid from the Upper Cretaceous of Patagonia. "Ameghiniana" 43(1): 245-248. [http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142006000100019&lng=es&nrm=iso&tlng=en HTML fulltext]
* (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]
* (1929): Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén ["The dinosaur-bearing strata and their upper limit in estern Neuquén Territory"] . "Dirección General de Geología, Minería e Hidrogeología Publicación" 32: 1-9.