The Tunjuelo Formation, Río Tunjuelo or Río Tunjuelito Formation (, Q_1tu, Qpt, Qcc) 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

Bogotá savanna The Bogotá savanna is a savanna#Savanna ecoregions, 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 si ...

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. (Do not confuse with The Altiplano or the Altiplano Nariñense, both fur ...

Eastern Ranges The Eastern Ranges is an Australian rules football team that currently competes in the Talent League, the Victorian statewide under-18s competition. History Inaugural playing squad (1992) Honours *Premiers (2): 2002, 2013 *Runners-up (6): 199 ...

of the

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

. The formation consists mainly of conglomerates with intercalating

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s. The Tunjuelo Formation dates to the

Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...

period; covering the complete

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

epoch, and has a maximum thickness of . It is a formation of the

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

and fluvio-glacial sediments of Lake Humboldt.

Etymology

The formation was first defined and named by Helmens and Van der Hammen in 1995 after the

Tunjuelo River The Tunjuelo or Tunjuelito River is a river on the Bogotá savanna and a left tributary of the Bogotá River. The river, with a length of originates in the Sumapaz Páramo and flows northward through the Usme Synclinal to enter the Colombian capit ...

, also called Tunjuelito River, of southern

Bogotá Bogotá (, also , , ), officially Bogotá, Distrito Capital, abbreviated Bogotá, D.C., and formerly known as Santa Fe de Bogotá (; ) during the Spanish Imperial period and between 1991 and 2000, is the capital city, capital and largest city ...

.Montoya & Reyes, 2005, p.71

Description

Lithologies

The Tunjuelo Formation consists mainly of conglomerates with intercalating

s and

Stratigraphy and depositional environment

The Tunjuelo Formation conformably overlies the Marichuela Formation and in other parts the Subachoque Formation. The Tunjuelo Formation is overlain by the thin Chía Formation. The age has been estimated to be

based on

palynology Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in sediments, sedimentary rocks, and even some metasedimentary rocks. Palynomorphs are the mic ...

and

radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

, covering the Pleistocene from 2.6 to 0.01 Ma.Montoya & Reyes, 2005, p.72 The depositional environment has been interpreted as fluvio-glacial terraces.

Outcrops

The Tunjuelo Formation is found at its type locality in the

valley, in the synclinal of

Guasca Guasca is a Colombian town and municipality in the Guavio Province, part of the Cundinamarca Department located approximately 55 km from Bogotá passing through the town of La Calera, Cundinamarca or 65 km passing through Sopó. Guasca ...

, near

Cogua Cogua () is a municipality and town of Colombia in the department of Cundinamarca. It is situated on northern part of the Bogotá savanna with the urban centre at an altitude of at from the capital Bogotá. Cogua borders Tausa in the north, Ne ...

, Cundinamarca, and in the basins of the

rivers A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

San Cristóbal,

San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

, Arzobispo and Subachoque, and the creeks (''quebradas'') Las Delicias, La Vieja, Rosales and Chicó of the Colombian capital.Lobo Guerrero, 1992, p.6 In the Tunjuelo River valley, the formation is crossed by the northeast–southwest oriented Yerbabuena Fault.Geological Map Bogotá, 1997

References

Bibliography

* *

Maps

* *

External links

* {{citation , last1=Gómez , first1=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 , publisher=

Servicio Geológico Colombiano The Colombian Geological Survey (CGS) (; formerly known as INGEOMINAS) is a scientific Government agency, agency of the Colombian government in charge of contributing to the socioeconomic development of the nation through research in basic and ap ...

, pages=1 , accessdate=2017-03-16 Geologic formations of Colombia Pleistocene Colombia Conglomerate formations Fluvial deposits Glacial deposits Formations Geography of Cundinamarca Department Geography of Bogotá