Lisandro Formation

The Lisandro Formation, alternatively known as the Cerro Lisandro Formation, is a Late Cretaceous (Late Cenomanian to Early Turonian) geologic formation with outcrops in the Neuquén, Río Negro and Mendoza Provinces 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]

Lisandro Formation
Stratigraphic range: Middle-Late Turonian ~93.4–90.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Neuquén Group  Río Limay Subgroup
Underlies	Río Neuquén Subgroup  Portezuelo Formation
Overlies	Huincul Formation
Thickness	35–75 m (115–246 ft)
Lithology
Primary	Siltstone, claystone
Other	Mudstone, sandstone
Location
Coordinates	34.1°S 68.9°W / -34.1; -68.9
Approximate paleocoordinates	40.1°S 64.8°W / -40.1; -64.8
Region	Mendoza, Río Negro & Neuquén Provinces
Country	Argentina
Extent	Neuquén Basin
Type section
Named for	Cerro Lisandro
Named by	Herrero Ducloux
Year defined	1938
Lisandro Formation (Argentina)

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 metres (115 and 246 ft) thick, the thinnest of the three formations in its subgroup. It is composed of siltstones and claystones, red in color, which have been interpreted as a swampy to fluvial environment. Usually, the red Lisando Formation rocks are easy to distinguish from the greenish or yellowish deposits of the Huincul Formation.^[1][3]

Fossil content

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 (Ceratodus and Chaoceratodus^[4])
• turtles
• a carcharodontosaurid theropod
• crocodilians
• an abelisauroid theropod
• "Bayosaurus pubica"
• at least one bird
• ornithopods (including Anabisetia)
• a peirosaurid Bayomesasuchus hernandezi
• a titanosaur sauropod Quetecsaurus rusconii^[5]

See also

• List of fossil sites
• Bajo Barreal Formation, contemporaneous formation of the Golfo San Jorge Basin
• Mata Amarilla Formation, contemporaneous formation of the Austral Basin
• List of dinosaur bearing rock formations