| Los Bastos Formation | |
|---|---|
| Stratigraphic range: Early-mid Coniacian ~ | |
| Type | Geological formation |
| Unit of | Neuquén Group Río Neuquén Subgroup |
| Underlies | Sierra Barrosa Formation |
| Overlies | Portezuelo Formation |
| Thickness | Up to 35 m (115 ft) |
| Lithology | |
| Primary | Mudstone |
| Other | Sandstone |
| Location | |
| Coordinates | 38°50′20″S 68°47′05″W / 38.83889°S 68.78472°W |
| Approximate paleocoordinates | 42°18′S 49°00′W / 42.3°S 49.0°W |
| Region | Mendoza Province Neuquén Province |
| Country | Argentina |
| Extent | Neuquén Basin |
| Type section | |
| Named for | Los Bastos Field |
| Named by | 2010 |
| Year defined | Garrido |
  Los Bastos Formation (Argentina) | |
Los Bastos Formation is a geologic formation of the Neuquén Basin in the northern Patagonian provinces of Mendoza and Neuquén. The formation dates to the Late Cretaceous, early to middle Coniacian, and belongs to the Río Neuquén Subgroup of the Neuquén Group. The formation overlies the Portezuelo Formation, in which it was formerly included and is overlain by the Sierra Barrosa Formation. Los Bastos Formation comprises mudstones and sandstones deposited in a fluvial environment. A meridiolestid mammal were recovered from the formation.