The La Frontera Formation (, K2F, Ksf) is a geological formation, part of the Villeta Group, of the Altiplano Cundiboyacense and neighbouring areas of the Eastern Ranges of the Colombian Andes. The sequence of limestones and lydites dates to the Late Cretaceous period; Turonian epoch and has a maximum thickness of .
Fossils of Yaguarasaurus columbianus were said to be found in this formation (listed as "La Frontera Member"), although the geological mapping of the area state the time-equivalent Hondita Formation as the stratigraphic unit present in the Quebradas El Ocal and Itaibe in Huila. The La Frontera Formation does not outcrop south of Cundinamarca. A high diversity of ammonites has been found in the La Frontera Formation.
Etymology The formation was first described by Hubach in 1931 and elevated to formation in 1969 by Cáceres and Etayo.Montoya & Reyes, 2005, p.24 The formation is named after the quarry La Frontera near Albán, Cundinamarca.Acosta & Ulloa, 2001, p.41
Description Lithologies The La Frontera Formation is characterised by a lower part consisting of limestones and an upper part comprising lydites.
Stratigraphy and depositional environment The La Frontera Formation overlies the Simijaca Formation and is overlain by the Conejo Formation, all units belong to the Villeta Group. The age has been estimated to be Turonian. Stratigraphically, the formation is time equivalent with the Chipaque, Hondita and La Luna Formations.Montoya & Reyes, 2005, p.26 The formation has been deposited in an open marine platform to submarine fan setting.García González et al., 2009, p.218 The deposition is represented by a maximum flooding surface.Villamil, 2012, p.164 The formation contains concretions and a high diversity of ammonites;Villamil, 2012, p.181 Wrightoceras munieri, Vascoceras cf. constrictum, Vascoceras cf. venezolanum, Kamerunoceras sp., Kamerunoceras cf. turoniense, Hoplitoides cf. lagiraldae, Codazziceras ospinae, Coilopoceras cf. newelli,Patarroyo, 2016, p.41 Hoplitoides wohltmanni, Neoptychites crassus, Hoplitoides ingens, Mammites sp., ?Fagesia sp., and Prionocycloceras sp.Blanco et al., 2004, p.26 Also the bivalves Anomia colombiana and Inoceramus sp. have been found in the La Frontera Formation.
Yaguarasaurus Fossils of Yaguarasaurus columbianus were described as coming from the "La Frontera Member", part of the "Villeta Formation", in the Quebrada El Ocal, southwest of Neiva, Huila,Yaguarasaurus columbianus at Fossilworks.org and in the Quebrada Itaibe southwest of Neiva,Páramo Fonseca, 2000, p.124 although in these areas the time-equivalent Hondita Formation is mapped.Plancha 344, 1999Plancha 345, 1999
Outcrops
The La Frontera Formation is apart from its type locality, found at surface in the north of the Bogotá savanna, in the Tabio anticlinal, along the road Ubaté-Carmen de Carupa, north and east of Chiquinquirá,Plancha 190, 2009 south of Cachipay,Plancha 227, 1998 to a thin band east of Viotá.Plancha 246, 1998
See also
Geology of the Eastern Hills Geology of the Ocetá Páramo Geology of the Altiplano Cundiboyacense
References
Bibliography
Maps La Frontera Fm. proper
Maps Yaguarasaurus locations
External links