The El Peñón Formation ( es, Formación El Peñón, Kipe) 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 ...

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 Alti ...

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 Leagu ...

of the

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

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 formation consists of calcareous shales and siltstones and dates to the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

period; Late Aptian epoch and has a measured thickness at its type section of .

Ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

fossils have been found in the formation, deposited in a shallow marine platform environment.

Etymology

The formation was defined and named in 1982 by Ulloa after El Peñón, Cundinamarca.

Description

Lithologies

The El Peñón Formation has at is type section a thickness of , and is characterised by a sequence of calcareous

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

s and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

s. The middle part of the sequence contains

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

.Acosta & Ulloa, 2001, p.29 Fossils of the ammonites '' Cheloniceras sp.'' and '' Epicheloniceras sp. aff. carlosacostai'' have been found in the El Peñón Formation.Acosta & Ulloa, 2002, p.42

Stratigraphy and depositional environment

The El Peñón Formation, part of the

Villeta Group The Villeta Group ( es, Grupo Villeta) is a geological group of the Eastern Ranges of the Colombian Andes, to the west of the Altiplano Cundiboyacense. The group, a sequence of shales, limestones and sandstones, is subdivided into various formati ...

, conformably overlies the

Trincheras Formation The Trincheras Formation ( es, Formación Trincheras, Kitr) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consisting of a lower unit of calcareous shales and an upper sequence of sh ...

and is conformably overlain by the Capotes Formation.Acosta & Ulloa, 2001, p.30 The age has been estimated to be Late Aptian. Stratigraphically, the formation is time equivalent with the Tablazo Formation and a lateral facies equivalent of the Socotá Formation.Acosta & Ulloa, 2001, p.16 The formation has been deposited in a

shallow marine Shallow water marine environment refers to the area between the shore and deeper water, such as a reef wall or a shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below. The water in this ...

platform

environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

. In the Late Aptian, central Colombia was dominated by shallow marine carbonate platform environments.Villamil, 2012, p.164

Outcrops

The El Peñón Formation, restricted to Cundinamarca, is locally found around its type locality, between Bituima and Guayabal de Síquima,Plancha 227, 1998 and along the road from

Villeta Villeta is a city of Paraguay in the Central Department, on the banks of Paraguay River. It is an important industrial center and port. Toponymy The city was founded on March 5, 1714, by Juan Gregorio Bazán de Pedraza, with the original name ...

Sasaima Sasaima () is a municipality and town of Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific ...

.Acosta & Ulloa, 2001, p.27

Regional correlations

References

Bibliography

* * *

Maps

* *

External links

* {{DEFAULTSORT:El Penon Formation Geologic formations of Colombia Cretaceous Colombia Lower Cretaceous Series of South America Aptian Stage Shale formations Shallow marine deposits Formations Formations