Plottier Formation

The Plottier Formation is a geologic formation that outcrops in the Argentine Patagonian provinces of Río Negro and Neuquén. It is the younger of two formations belonging to the Río Neuquén Subgroup within the Neuquén Group of the Neuquén Basin, with the oldest rocks dating from the late Coniacian and its youngest maybe from the very start of the Santonian. Formerly, that subgroup was treated as a formation, and the Plottier Formation was known as the Plottier Member.

Description
A section near the Neuquén City airport, north of the town of Plottier, is the type locality of the Plottier Formation. At its base, this formation grades into the Portezuelo Formation, and it is in turn overlain conformably by the Bajo de la Carpa Formation, a unit of the Río Colorado Subgroup.

The Plottier Formation is the thinnest formation within the Neuquén Group, with a maximum thickness of only 25 m. It is differentiated from the underlying Portezuelo Formation primarily by its higher content of argillites (mud deposits) and was deposited under fluvial conditions. In 2006, a detailed lithostratigraphic and paleoecological study of a section of the Plottier Formation was published. This section contained alluvial deposits laid down by what was essentially a low-gradient wandering river throughout the millions of years, but often was of a single-channel type with little meandering.

Fossil content
Few animal fossils are known from this formation, including:
 * Titanosaurid sauropods (including "Antarctosaurus" giganteus, Petrobrasaurus puestohernandezi, Muyelensaurus pecheni and Notocolossus gonzalezparejasi )
 * A large basal coelurosaurian theropod
 * An azhdarchid pterosaur, Thanatosdrakon amaru
 * chelid turtles Linderochelys rinconensis and Rionegrochelys caldieroi
 * Abelisauridae
 * Unenlagiinae
 * Ornithopoda
 * Aeolosaurini
 * Saltasauridae
 * Mesoeucrocodylia
 * Crocodyliformes
 * Ichnofossils
 * Scoyenia sp.
 * Taenidium sp.
 * at least one mammal

There are also ichnofossils left on the river's mudflats, as well as fossil freshwater bivalves.