Tunjuelo Formation

Tunjuelo Formation
Stratigraphic range: Pleistocene ~
Type	Geological formation
Underlies	Chía Fm., Sabana Fm.
Overlies	Marichuela Formation Subachoque Formation
Thickness	up to 150 metres (490 ft)
Lithology
Primary	Conglomerate
Other	Sandstone, shale
Location
Coordinates	4°28′04.0″N 74°08′11.9″W
Region	Bogotá savanna, Altiplano Cundiboyacense Eastern Ranges, Andes
Country	Colombia
Type section
Named for	Tunjuelo River
Named by	Helmens & Hammen
Location	Tunjuelo River valley
Year defined	1995
Coordinates	4°28′04.0″N 74°08′11.9″W
Region	Cundinamarca
Country	Colombia
Paleogeography of the Pleistocene by Ron Blakey

The Tunjuelo Formation, Río Tunjuelo or Río Tunjuelito Formation (Spanish: Formación Tunjuelo, Q_1tu, Qpt, Qcc) is a geological formation of the Bogotá savanna, Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consists mainly of conglomerates with intercalating shales and sandstones. The Tunjuelo Formation dates to the Quaternary period; covering the complete Pleistocene epoch, and has a maximum thickness of 150 metres (490 ft). It is a formation of the lacustrine 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, also called Tunjuelito River, of southern Bogotá.

Description

Lithologies

The Tunjuelo Formation consists mainly of conglomerates with intercalating shales and sandstones.

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 Pleistocene based on palynology and radiocarbon dating, covering the Pleistocene from 2.6 to 0.01 Ma. The depositional environment has been interpreted as fluvio-glacial terraces.

Outcrops

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Type locality of the Tunjuelo Formation to the south of the Bogotá savanna

The Tunjuelo Formation is found at its type locality in the Tunjuelo River valley, in the synclinal of Guasca, near Cogua, Cundinamarca, and in the basins of the rivers San Cristóbal, San Francisco, Arzobispo and Subachoque, and the creeks (quebradas) Las Delicias, La Vieja, Rosales and Chicó of the Colombian capital. In the Tunjuelo River valley, the formation is crossed by the northeast–southwest oriented Yerbabuena Fault.

See also

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

References

Bibliography

• Guerrero Uscátegui, Alberto Lobo (1992), Geología e Hidrogeología de Santafé de Bogotá y su Sabana, Sociedad Colombiana de Ingenieros, pp. 1–20
• Montoya Arenas, Diana María; Reyes Torres, Germán Alfonso (2005), Geología de la Sabana de Bogotá, INGEOMINAS, pp. 1–104

Maps

• Buitrago, José Alberto; Terraza M., Roberto; Etayo, Fernando (1998), Plancha 228 - Santafé de Bogotá Noreste - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Various, Authors (1997), Mapa geológico de Santa Fe de Bogotá – Geological Map Bogotá – 1:50,000 (PDF), INGEOMINAS, p. 1, retrieved 2017-03-16

External links

• Gómez, J.; Montes, N.E.; Nivia, Á.; Diederix, H. (2015), Plancha 5-09 del Atlas Geológico de Colombia 2015 – escala 1:500,000, Servicio Geológico Colombiano, p. 1, retrieved 2017-03-16