[1] The best exposure of the formation is said to be at the ski resort of Farellones east of Santiago.

[2] 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.

[3] 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.

[1] 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.