Bajo de la Carpa Formation

Bajo de la Carpa Formation
Stratigraphic range: Mid-Late Santonian ~
Type	Geological formation
Unit of	Neuquén Group  Río Colorado Subgroup
Underlies	Anacleto Formation
Overlies	Río Neuquén Subgroup  Plottier Formation
Thickness	Up to 150 m (490 ft)
Lithology
Primary	Sandstone
Other	Mudstone, siltstone, paleosol
Location
Coordinates	38.8°S 68.8°W / -38.8; -68.8
Approximate paleocoordinates	43.4°S 49.8°W / -43.4; -49.8
Region	Neuquén & Río Negro Provinces
Country	Argentina
Extent	Neuquén Basin
Bajo de la Carpa Formation (Argentina)

The Bajo de la Carpa Formation is a geologic formation of the Neuquén Basin that crops out in northern Patagonia, in the provinces of Río Negro and Neuquén, Argentina. It is the oldest of two formations belonging to the Río Colorado Subgroup within the Neuquén 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.

At its base, this formation conformably overlies the Plottier Formation of the older Río Neuquén Subgroup, and it is in turn overlain by the Anacleto Formation, the youngest and uppermost formation of the Neuquén Group.

The Bajo de la Carpa Formation can reach 150 metres (490 ft) in thickness in some locations, and consists mainly of sandstones of various colors, all of fluvial origin, with thin layers of mudstone and siltstone in between. Geological features such as geodes, chemical nodules, impressions of raindrops, and paleosols (fossil soils) are commonly found in this formation as well.

Fossil content

Vertebrate fossils are abundant within the Bajo de la Carpa Formation:

• a snake-necked turtle, Lomalatachelys
• a lizard, Paleochelco
• the snake Dinilysia
• diverse crocodylomorphs occupying a range of ecological niches: Comahuesuchus, Cynodontosuchus, Lomasuchus, Gasparinisuchus, Neuquensuchus universitas, Notosuchus, Peirosaurus, Kinesuchus overoi, and Barrosasuchus neuquenianus
• titanosaurian sauropods including Bonitasaura, Inawentu, Overosaurus, Rinconsaurus, and Traukutitan
• the ceratosaurian theropods Llukalkan, Velocisaurus, and Viavenator exxoni
• the megaraptoran theropod Tratayenia rosalesi
• the bird-like theropods Achillesaurus and Alvarezsaurus
• the enantiornithine bird Neuquenornis
• the oldest known true flightless bird Patagopteryx
• the basal ornithopod Mahuidacursor
• an ankylosaur

Small nests with eggs inside, found in this formation, probably belonged to the bird Neuquenornis. Fossil wasp nests have also been found in these rocks.

See also

• List of fossil sites
• List of dinosaur bearing rock formations
• Mata Amarilla Formation, contemporaneous formation of the Austral Basin