Portezuelo Formation
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The Portezuelo Formation is a geologic formation outcropping in the 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.
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 Cerro 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.
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[edit] Age
Era: Mesozoic
Period: Late Cretaceous
Faunal stage: late Turonian to early Coniacian
Absolute Age: ~91 to ~88 mya
[edit] Composition
Sandstones and siltstones, probably deposited under fluvial conditions, make up the Portezuelo Formation. There are also occasional claystone deposits, as well as numerous paleosols (soil deposits). This formation varies between 95 and 130 meters thick throughout its range (Leanza et al 2004).
[edit] 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
- dromaeosaurid theropods (Unenlagia and Megaraptor, which are possibly the same animal)
- an alvarezsaurid theropod (Patagonykus)
- several other theropods
- ornithopods
[edit] References
- 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.
- Wichmann, R. 1929. Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén. Dirección General de Geología, Minería e Hidrogeología Publicación 32: 1-9.
