Nacientes del Biobío Formation
| Nacientes del Biobío Formation | |
|---|---|
| Stratigraphic range: Pliensbachian–Kimmeridgian | |
| Type | Geologic formation |
| Sub-units | Lonquimay Lolén-Pacunto Icalma |
| Underlies | Vizcacha-Cumilao Complex |
| Overlies | Unknown |
| Thickness | >2,450 m (8,040 ft) |
| Lithology | |
| Primary | Basaltic lava, sandstone, mudstone, limestone |
| Other | Tuff, volcaniclastic breccia, conglomerate |
| Location | |
| Coordinates | 38°54′S 71°18′W / 38.9°S 71.3°W |
| Region | Neuquén Province Araucanía Region |
| Country | Argentina Chile |
| Type section | |
| Named for | Bío Bío River |
| Named by | Suárez & Emparan |
| Year defined | 1997 |
Nacientes del Biobío Formation (Spanish: Formación Nacientes del Biobío) is a geological formation that crops out near the uppermost reaches of Bío Bío River, in south-central Chile, and nearby areas of Argentina. The formation is made up of basalt and pyroclastic rocks and marine sedimentary rocks, such as sandstone and mudstone. Some less abundant sedimentary lithologies are conglomerate, volcaniclastic sedimentary rock. The formation is intruded by Grupo Plutónico Galletué which is of Late Jurassic to Late Cretaceous age. Further north in Chile the formation is similar to Nacientes del Teno Formation while in Argentina it is similar to Los Molles Formation and Lotena Formation.