The sandstone and shale formation dates to the Middle Cretaceous period; Aptian to Albian epochs and has a maximum thickness of 411 metres (1,348 ft).

The formation was defined and named in 1967 by Corrigan after Cerro Caballos, to the west of Olaya Herrera, Tolima.

[1] The Caballos Formation has a maximum thickness of 411 metres (1,348 ft) in the Quebrada Bambucá and is characterized by a lower sequence of fine to coarse sandstones, of lithic arenite, quartz arenite and feldspar arenite composition, a middle section of fossiliferous black shales and siltstones, intercalated by micritic limestones and coals and very fine sandstones.

The formation has provided fossils of Heminautilus etheringtoni,[9] Araucarites sp., Brachyphyllum sp., Cladophlebis sp., and Weichselia sp.,[10] as well as many types of pollen.

[11] The Caballos Formation is apart from its type locality, found in Huila, Tolima and Putumayo Departments.