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).[1] Marsupial fossils have been found in the formation.[2] The Friasian period in the South American Land Mammal Ages is named after the formation.[3]
| 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 (Chile) | |
Description
editRío Frías Formation was discovered by Santiago Roth in the summer of 1897–98. Roth was a Swiss immigrant who had been sent to survey the area by Francisco Moreno. Moreno was director of La Plata Museum and was involved in the Cordillera of the Andes Boundary Case between Chile and Argentina, thus there was both a political and scientific motivation behind the exploration of Patagonia. Santiago Roth called the upper course of Río Cisnes for Río Frías being unaware that it was the same river. Further he thought this unexplored area to be in Argentina and not in Chile. This led the formation to acquire its name.[1] Roth sent fossils he collected from the formation to Florentino Ameghino who was active at La Plata. It was with this fossils Ameghino established the Friasian period.[1] Later research on 40Ar/39Ar data revealed the base of the formation dating to 16.5 Ma, which means a slight overlap with the Santacrucian land mammal age (ending at 16.3 Ma).[4] The formation was deposited in a fluvial environment, characterized by an intermontane valley flanked by Cretaceous basement rocks.[5]
Fossil content
editThe following fossils have been found in the formation:
References
edit- ^ a b c Marshall & Salinas, 1990
- ^ Marshall, 1990
- ^ Paleo Database: Friasian
- ^ Bostelmann et al., 2012, p.44
- ^ Bellosi et al., 2014, p.40
- ^ Río Frías at Fossilworks.org
- ^ Alto Río Cisnes at Fossilworks.org
Bibliography
edit- Abello, María Alejandra; Rubilar Rogers, David (2012), "Revisión del género Abderites Ameghino, 1887 (Marsupialia, Paucituberculata)", Ameghiniana, 49 (2): 164–184, doi:10.5710/AMGH.v49i2(408), retrieved 2019-02-15
- Bellosi, Eduardo S. (2014), Ambientes asociados a la fauna Friasense (Mioceno Medio) en Alto río Cisnes (Aysén, Chile), XIV Reuñión Argentina de Sedimentología, pp. 40–41, retrieved 2018-09-10
- Bostelmann, J.E. (2012), The Alto Río Cisnes Fossil Fauna (Río Frías Formation, Early-Middle Miocene, Friasian SALMA): A keystone and paradigmatic vertebrate assemblage of the South American Fossil Record, III Simposio Paleontología en Chile, pp. 44–45, retrieved 2018-09-10
- Marshall, Larry G (1990), "Fossil Marsupialia from the type Friasian land mammal age (Miocene), Alto Río Cisnes, Aisén, Chile", Revista Geológica de Chile, 17: 19–55, retrieved 2017-10-21
- Marshall, Larry G.; Salinas, Patricia (1990), "Stratigraphy of the Río Frías Formation (Miocene) along the Alto Río Cisnes, Aisén, Chile", Revista Geológica de Chile, 17: 57–87, retrieved 2017-10-21