The La Frontera Formation ( es, Formación La Frontera, K₂F, Ksf) is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

, part of the Villeta Group, of the

Altiplano Cundiboyacense The Altiplano Cundiboyacense () is a high plateau located in the Eastern Cordillera of the Colombian Andes covering parts of the departments of Cundinamarca and Boyacá. The altiplano corresponds to the ancient territory of the Muisca. The Alt ...

and neighbouring areas of the

Eastern Ranges The Eastern Ranges is an Australian rules football team in the NAB League, the Victorian statewide under-18s competition. The club is a founding member of the competition (1992) and has produced several players for the Australian Football Leag ...

of the Colombian

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

. The sequence of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

s and lydites dates to the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', ...

period;

Turonian The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous Epoch, or a stage in the Upper Cretaceous Series. It spans the time between 93.9 ± 0.8 Ma and 89.8 ± 1 Ma (million years ago). The Turonian is preceded b ...

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 The Hondita Formation ( es, Formación Hondita, Ksh) is a fossiliferous geological formation of the Upper Magdalena Valley (VSM) and surrounding Central and Eastern Ranges of the Colombian Andes, extending from Cundinamarca in the north to Huila ...

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 San José de Albán is a town and municipality in the Nariño Department, Colombia. The town was established on 15 June 1573. As of 2018 it had a population of 8,197. Veredas The municipality contains the following ''veredas'': References ...

, Cundinamarca.Acosta & Ulloa, 2001, p.41

Description

Lithologies

The La Frontera Formation is characterised by a lower part consisting of

s 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 The Conejo Formation ( es, Formación Conejo, K2C, Kscn) is a fossiliferous geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The uppermost unit of the Villeta Group, a sequence of shales and sandstones d ...

, all units belong to the Villeta Group. The age has been estimated to be

. Stratigraphically, the formation is time equivalent with the

Chipaque Chipaque is a municipality and town in the Eastern Province of the department of Cundinamarca, Colombia. The municipality of is located at an altitude of in the Eastern Ranges of the Colombian Andes with its westernmost part situated in the E ...

, 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 In sequence stratigraphy, a maximum flooding surface is the surface that marks the transition from a Transgression (geology), transgression to a marine regression, regression. Maximum flooding surfaces are abbreviated by mfs, synonyms for them inclu ...

.Villamil, 2012, p.164 The formation contains

concretion A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...

s 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 Neiva () is the capital of the Department of Huila. It is located in the valley of the Magdalena River in south central Colombia with a population of about 357,392 inhabitants. It is one of the most important cities in southern Colombia, mainly ...

, 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

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 The Bogotá savanna is a montane savanna, located in the southwestern part of the Altiplano Cundiboyacense in the center of Colombia. The Bogotá savanna has an extent of and an average altitude of . The savanna is situated in the Eastern Ran ...

, 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

Regional correlations

References

Bibliography

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Maps La Frontera Fm. proper

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Maps ''Yaguarasaurus'' locations

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External links

* {{DEFAULTSORT:Frontera Formation, La Geologic formations of Colombia Cretaceous Colombia Upper Cretaceous Series of South America Turonian Stage Limestone formations Deep marine deposits Open marine deposits Fossiliferous stratigraphic units of South America Paleontology in Colombia Formations Geography of Cundinamarca Department Geography of Boyacá Department