Farellones Formation

Farellones Formation (Spanish: Formación Farellones) is a geological formation of Miocene age in the Andes of Central Chile up almost entirely of volcanic and volcaniclastic rocks. At some location reaches thicknesses in excess of 3,000 m.^[1] It overlies the Oligo–Miocene Abanico Formation across a diachronous unconformity.^[1] The best exposure of the formation is said to be at the ski resort of Farellones east of Santiago.^[2] From the latitude of Santiago to Rancagua the base of the formation becomes progressively younger and outcrops more scarce.^[1][2] In the mentioned latitudes the formation has been deformed by a diachronous tectonic inversion that produced reverse faults and destroyed the extensional sedimentary basin were the rocks deposited and contributed to the uplift of the Andes in the Late Miocene.^[1]

Rivano and co-workers define two sub-units of the formation: a lower member made up of rather fresh rhyolitic ignimbrite and tuff, and an upper member made up of lavas of basaltic and andesitic composition.^[3] The volcanic rocks of Farellones Formation have mostly a calc-alkaline character contrasting with the mostly tholeiitic Abanico Formation.^[1]

Jorge Muñoz Cristi was in 1957 the first to define the rocks of Farellones as distinct unit and not as a facies as previously thought. Carlos Klohn then established the Farellones unit as formation in 1960.^[3]

References

• "Edades K/ar de la formación Farellones en el cordón del Cerro La Parva, Cordillera de los Andes de Santiago, Chile" (in Spanish). 1986. 

Geology of Chile
Terranes	Arequipa-Antofalla Chilenia Chiloé Cuyania Fitz Roy Madre de Dios Mejillonia Patagonia
Sedimentary formations and groups	Cenozoic Abanico Formation Azapa Formation Caleta Herradura Formation Cola de Zorro Formation Coquimbo Formation Cura-Mallín Formation Estratos de Pupunahue Estratos de San Pedro Farellones Formation Lacui Formation La Portada Formation Lebu Group Malleco Formation Navidad Formation Oxaya Formation Ranquil Formation Santo Domingo Formation Traiguén Formation Trapa-Trapa Formation Tubul Formation Mesozoic La Negra Formation Pan de Azúcar Formation Quiriquina Formation Tobífera Formation Toqui Formation Vinita Formation Way Group Zapata Formation
Batholiths	Coastal Batholith of central Chile Elqui-Limarí Batholith North Patagonian Batholith Panguipulli Batholith South Patagonian Batholith Tierra del Fuego Batholith Vicuña Mackenna Batholith
Metamorphic complexes	Bahía Mansa Metamorphic Complex Belén Metamorphic Complex Chañaral Epimetamorphic Complex Choapa Metamorphic Complex Chonos Metamorphic Complex Cordillera Darwin Metamorphic Complex Eastern Andes Metamorphic Complex Puerto Edén Igneous and Metamorphic Complex Punta de Choros Metamorphic Complex Quebrada del Carrizo Metamorphic Complex Trafún Metamorphic Complex Tierra del Fuego Igneous and Metamorphic Complex
Faults	Atacama Fault Domeyko Fault Futrono Fault Gastre Fault Lanalhue Fault Liquiñe-Ofqui Fault Magallanes-Fagnano Fault Pichilemu Fault Reigolil-Pirihueico Fault San Ramón Fault Valeriano Fault