The Caballos Formation (, KI) is a geological formation of the Upper Magdalena Valley (VSM), Caguán-Putumayo Basin, Central and Eastern Ranges of the Colombian Andes. The sandstone and shale formation dates to the Middle Cretaceous period; Aptian to Albian epochs and has a maximum thickness of .
Etymology The formation was defined and named in 1967 by Corrigan after Cerro Caballos, to the west of Olaya Herrera, Tolima.Velandia et al., 2001, p.53
Description Lithologies The Caballos Formation has a maximum thickness of 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 upper part of the formation contains conglomerates and glauconitic sandstones.
Stratigraphy and depositional environment The Caballos Formation in some parts concordantly overlies the Yaví Formation and in other parts rests unconformably on the Saldaña Formation and Ibagué Batholith.Velandia et al., 2001, p.34 The formation is overlain by the Hondita Formation. The age has been estimated to be Aptian to Albian. Stratigraphically, the formation is time equivalent with the Une, Aguardiente, Simijaca, El Peñón, Capotes, Tablazo, Tibú-Mercedes and Pacho Formations.Velandia et al., 2001, p.54 The formation has been deposited in a fluvial to estuarine and shallow marine environment.Villamil, 2012, p.166
The Caballos Formation is a source, reservoir and seal rock in the Upper Magdalena Valley,ANH, 2007, p.84García González et al., 2009, p.83 and a source and reservoir rock in the Caguán-Putumayo Basin.ANH, 2007, p.57García González et al., 2009, p.16 The Orito and Moqueta Fields of the latter basin produce from Caballos reservoirs.
Fossil content The formation has provided fossils of Heminautilus etheringtoni,Badouin et al., 2016, p.87 Araucarites sp., Brachyphyllum sp., Cladophlebis sp., and Weichselia sp.,Monje et al., 2016, p.38 as well as many types of pollen.Los Mangos at Fossilworks.org
Outcrops
The Caballos Formation is apart from its type locality, found in Huila, Tolima and Putumayo Departments.
Regional correlations
See also List of fossiliferous stratigraphic units in Colombia Geology of the Eastern Hills Geology of the Altiplano Cundiboyacense
Notes
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