The Tunjuelo Formation, Río Tunjuelo or Río Tunjuelito Formation ( es, Formación Tunjuelo, 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 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 Ra ...

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 consists mainly of

conglomerate Conglomerate or conglomeration may refer to: * Conglomerate (company) * Conglomerate (geology) * Conglomerate (mathematics) In popular culture: * The Conglomerate (American group), a production crew and musical group founded by Busta Rhymes ** C ...

s with intercalating

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, especia ...

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. The Tunjuelo Formation dates to the Quaternary period; covering the complete

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

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

lacustrine A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

and fluvio-glacial sediments of

Lake Humboldt Lake Humboldt or Humboldt Lake is an endorheic basin lake in northern Churchill County and southern Pershing County in the state of Nevada in the United States. The lake has the name of Alexander von Humboldt, a German natural scientist. ...

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 capi ...

, 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 period and between 1991 and 2000, is the capital city of Colombia, and one of the largest ...

.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 The Marichuela Formation ( es, Formación Marichuela, N1m) is a geological formation of the Bogotá savanna, Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consists of coarse to very coarse conglomerates. The Ma ...

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 dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposits ...

and

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

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

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. Guasc ...

, 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, ...

, Cundinamarca, and in the basins of the

rivers A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wat ...

San Cristóbal,

San Francisco San Francisco (; Spanish language, Spanish for "Francis of Assisi, Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the List of Ca ...

, Arzobispo and

Subachoque Subachoque is a municipality and town of Colombia in the Western Savanna Province, part of the department of Cundinamarca. The municipality is situated on the Bogotá savanna with the urban centre at an altitude of at a distance of from the c ...

, 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

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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 Pleistocene Colombia Conglomerate formations Fluvial deposits Glacial deposits Formations Geography of Cundinamarca Department Geography of Bogotá