Bajo de la Carpa Formation

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 m 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.

Reptiles
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.

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.