Chorrera Formation

Chorrera Formation
Chorrera Formation
Stratigraphic range: Pliocene; (Montehermosan-Chapadmalalan); ~5–3 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Underlies	Subachoque Formation
Overlies	Guadalupe Gp.
Thickness	up to 40 m (130 ft)
Lithology
Primary	Conglomerate
Location
Coordinates	4°55′30.0″N 74°06′22.6″W / 4.925000°N 74.106278°W
Region	Bogotá savanna, Altiplano Cundiboyacense; Eastern Ranges, Andes
Country	Colombia
Type section
Named for	La Chorrera waterfall
Named by	Helmens & Hammen
Location	Río Frío, Subachoque/Tabio
Year defined	1995
Coordinates	4°55′30.0″N 74°06′22.6″W / 4.925000°N 74.106278°W
Region	Cundinamarca
Country	Colombia

The Chorrera Formation (Spanish: Formación Chorrera, N_2ch) 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 Chorrera Formation dates to the Neogene period; Pliocene epoch (Montehermosan to Chapadmalalan in the SALMA classification), and has a maximum thickness of 40 metres (130 ft).

Etymology

The formation was defined by Helmens and Van der Hammen in 1995 after the La Chorrera waterfall in Subachoque.^[1]

Description

Lithologies

The Chorrera Formation consists of coarse to very coarse conglomerates.^[1]

Stratigraphy and depositional environment

The Chorrera Formation unconformably overlies the Late Cretaceous Guadalupe Group. The formation is overlain by the Pleistocene Subachoque Formation. The age of the Chorrera Formation has been estimated to be Late Pliocene based on its stratigraphical position. The depositional environment is characterised by alluvial fans formed during the main phase of tectonic uplift of the Eastern Ranges in the Late Pliocene.^[1] Dutch geologist Salomon Kroonenberg, who studied the Neogene uplift of the Eastern Andes in Colombia, defines the main stage of uplift between six and four million years ago. Other Dutch geologists Helmens, Van der Hammen and Hooghiemstra have pushed back this uplift phase to between 4.5 and 3 Ma.^[2] The facies origin of the Chorrera Formation is comparable to the Marichuela Formation, outcropping on the eastern edge of the Bogotá savanna, yet different in stratigraphic position.^[1] The deposition of sediments of the Chorrera Formation is time-equivalent with the explosive phase of the Paipa–Iza volcanic complex, active between 4.7 and 3.6 Ma,^[3] and the Miocene to Late Pliocene Tilatá Formation.

Outcrops

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Type locality of the Chorrera Formation on the northern Bogotá savanna

The Chorrera Formation is found at its type locality in the synclinal of the Río Frío, east of Subachoque, Cundinamarca.^[1]

References

^ ^a ^b ^c ^d ^e Montoya & Reyes, 2005, p.67
^ Molnar, 2004, p.75
^ Monsalve et al., 2011, p.120

Bibliography

Molnar, Peter (2004), "Late Cenozoic increase in accumulation rates of terrestrial sediment", Annual Review of Earth and Planetary Sciences, 32: 67–89, doi:10.1146/annurev.earth.32.091003.143456
Monsalve, Maria Luisa; Rojas, Nadia R.; Velandia P., Francisco A.; Pintor, Iraida; Martínez, Lina Fernanda (2011), "Caracterización geológica del cuerpo volcánico de Iza, Boyacá - Colombia" (PDF), Boletín de Geología, 33: 117–130, retrieved 2017-02-25
Montoya Arenas, Diana María; Reyes Torres, Germán Alfonso (2005), Geología de la Sabana de Bogotá, INGEOMINAS, pp. 1–104

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

[Ingeominas_p67-1] Montoya & Reyes, 2005, p.67

[Molnar_p75-2] Molnar, 2004, p.75

[Monsalve_p120-3] Monsalve et al., 2011, p.120

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