Lisandro Formation

Lisandro Formation Stratigraphic range: late Cenomanian – early Turonian
Type	Geological formation
Unit of	Neuquén Group
Underlies	Portezuelo Formation
Overlies	Huincul Formation
Location
Country	Argentina

The Lisandro Formation, alternatively known as the Cerro Lisandro Formation, is a geologic formation with outcrops in the Neuquén province of Argentina. It is the youngest formation within the Río Limay Subgroup, the lowest section of the Neuquén Group. Formerly that subgroup was treated as a formation, and the Lisandro Formation was known as the (Cerro) Lisandro Member.^[1]

The type locality of the Lisandro Formation is the hill known as Cerro Lisandro in Neuquén province^[2]. This formation conformably overlies the Huincul Formation, and it is in turn overlain by the Portezuelo Formation, which is a part of the Río Neuquén Subgroup.

The Lisandro Formation varies between 35 and 75 meters thick, the smallest of the three formations in its subgroup. It is made up of siltstones and claystones, red in color, which have been interpreted as a swampy environment. Usually, the red Lisando Formation rocks are easy to distinguish from the greenish or yellowish deposits of the Huincul Formation.^[3]

Age

Era: Mesozoic
Period: Late Cretaceous
Faunal stage: late Cenomanian – early Turonian
Absolute Age: ~94 to ~91 mya

Paleontology

Not many dinosaurs are represented in the Lisandro Formation; other types of animals are frequently found. Fossils documented from this formation are:

• freshwater bivalve molluscs
• fish
• turtles
• crocodilians
• an abelisauroid theropod
• at least one bird
• ornithopods (including Anabisetia)

The swampy terrain may have limited the numbers of larger dinosaurs such as sauropods and carcharodontosaurids, which are found in earlier formations in the region but have not yet been found in the Cerro Lisandro.

See also

• List of fossil sites

Footnotes

1. ^ Sánchez et al. (2006)
2. ^ Fossa Mancini et al. (1938)
3. ^ Leanza et al. (2004), Sánchez et al. (2006)

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 ["A YPF geologists' reunion and the problem of stratigraphy terminology"]. 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. doi:10.1016/j.cretres.2003.10.005 (HTML abstract)
• Sánchez, Maria Lidia; Heredia, Susana & Calvo, Jorge O. (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. PDF fulltext