Río Frías Formation
| Río Frías Formation | |
|---|---|
| Stratigraphic range: Middle Miocene (Friasian) ~ | |
| Type | Geological formation |
| Overlies | Ñirehuao Formation |
| Lithology | |
| Primary | Tuff, tuffite, siltstone, unconsolidated sand, conglomerate |
| Location | |
| Coordinates | 44°36′S 71°12′W / 44.6°S 71.2°W |
| Approximate paleocoordinates | 45°12′S 66°18′W / 45.2°S 66.3°W |
| Region | Aysén Region |
| Country | Chile |
| Extent | Aysén Basin |
| Type section | |
| Named for | Río Frías |
| Named by | Santiago Roth |
| Year defined | 1898 |
Río Frías Formation (Spanish: Formación Río Frías) is a Middle Miocene geologic formation made up sedimentary rock located in Aysén Region, western Patagonia. The formation crops out along the upper course of Cisnes River (Spanish: Río Cisnes). Marsupial fossils have been found in the formation. The Friasian period in the South American Land Mammal Ages is named after the formation.