The Trincheras Formation ( es, Formación Trincheras, Kitr) 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 expo ...

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 ...

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 Le ...

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 formation consisting of a lower unit of calcareous shales and an upper sequence of shales 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 Pr ...

period; Early Aptian epoch and has a maximum thickness of . The formation, deposited in a marine platform environment, part of a transgressive cycle, hosts

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 cuttle ...

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

n, mollusc and

echinoid Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

fossils.

Etymology

The formation was defined and named in 1969 by Cáceres and Etayo after Quebrada Trincheras,

Apulo Apulo (previously called ''Rafael Reyes Municipality'') is a Colombian town and municipality in the Cundinamarca Department. Municipalities of Cundinamarca Department {{Cundinamarca-geo-stub ...

, Cundinamarca.Acosta & Ulloa, 2002, p.39

Description

Lithologies

The Trincheras Formation has a maximum thickness of ,Acosta & Ulloa, 2001, p.23 and is characterised by a sequence of

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone, slate, and shale. Most of the particles of which the stone is composed are less than and are too sm ...

s with intercalated

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 wh ...

s and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s. Fossils of the

s '' Heinzia sp.'', '' Pseudohaploceras sp.'', '' Heminautilus etheringtoni'', '' Cheloniceras sp.'' and

ns, molluscs and

s have been found in the Trincheras Formation.Acosta & Ulloa, 2002, p.40

Stratigraphy and depositional environment

The Trincheras Formation is the lowermost unit 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 formatio ...

,Acosta & Ulloa, 2001, p.22 and conformably overlies the Murca, La Naveta and Útica Formations. The formation is overlain in a transitional pattern by the

Socotá Socotá is a town and municipality in the Valderrama Province, part of the Colombian department of Boyacá. The municipality is situated in the Eastern Ranges of the Colombian Andes. The urban centre is at an altitude of at a distance of fro ...

and El Peñón Formations. The Trincheras Formation is subdivided into the El Tigre and Anapoima Members. The age has been estimated to be Early Aptian. Stratigraphically, the formation is time equivalent with the fossiliferous

Paja Formation Paja may refer to: * Paja, Iran, a village in Sari County * Paja (given name), a Serbian masculine name * Paja (surname) * Paja Formation, geologic formation in Colombia * Paja Brava :''Paja Brava is also used in Spanish speaking countries to ref ...

of Boyacá and the

Las Juntas Formation The Las Juntas Formation or Las Juntas Sandstone ( es, (Formación) Areniscas de Las Juntas, Kiaj, Kialj, K1j) is a geological formation of the Altiplano Cundiboyacense and Tenza Valley, Eastern Ranges of the Colombian Andes. The Las Juntas Form ...

.Villamil, 2012, p.168 The formation has been deposited in a marine well oxygenated 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 terms of

sequence stratigraphy Sequence stratigraphy is a branch of geology, specifically a branch of stratigraphy, that attempts to discern and understand historic geology through time by subdividing and linking sedimentary deposits into unconformity bounded units on a variety ...

, this phase was transgressional.

Outcrops

The Trincheras Formation is apart from its

type locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

, found near La Mesa and Anapoima, in the

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 o ...

Anticlinal, the Murca- Guayabal- Nimaima Anticlinal and along the roads between

Pacho Pacho is a municipality and town of Colombia in the department of Cundinamarca. Pacho is part of the Rionegro Province and the urban centre is situated at a distance of from the capital Bogotá at an altitude of , while the altitude ranges from ...

and

La Palma La Palma (, ), also known as ''La isla bonita'' () and officially San Miguel de La Palma, is the most north-westerly island of the Canary Islands, Spain. La Palma has an area of making it the fifth largest of the eight main Canary Islands. The ...

and

Útica Utica is a town and municipality in the Cundinamarca Department, Colombia located some 127 kilometers from Bogotá. The village lies at an altitude of 506 meters above sea level and has an average daily temperature of 26 °C. Utica grew from ...

-La Peña. The formation also crops out around San Joaquín east of La Mesa,Plancha 227, 1998 and on the right bank of the

Bogotá River The Bogotá River is a major river of the Cundinamarca department of Colombia. A right tributary of the Magdalena River, the Bogotá River crosses the region from the northeast to the southwest and passing along the western limits of Bogotá. Th ...

near Apulo.Plancha 246, 1998 The reverse Bituima Fault thrusts the Trincheras Formation on top of the Güagüaquí Group, while the Bogotá River Fault laterally displaces the formation near Anapoima.

Regional correlations

References

Bibliography

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Maps

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External links

* {{cite LSA , last=Gómez , first=J. , last2=Montes , first2=N.E. , last3=Nivia , first3=Á. , last4=Diederix , first4=H. , year=2015 , title=Plancha 5-09 del Atlas Geológico de Colombia 2015 – escala 1:500,000 , url=https://www.researchgate.net/publication/309533589_Plancha_5-09_del_Atlas_Geologico_de_Colombia_2015 , publisher= Servicio Geológico Colombiano , pages=1 , accessdate=2017-03-16 Geologic formations of Colombia Cretaceous Colombia Lower Cretaceous Series of South America Aptian Stage Shale formations Open marine deposits Formations Geography of Cundinamarca Department