Pacho Formation

Pacho Formation
Stratigraphic range: Late Albian-Cenomanian ~102–97  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Villeta Group
Underlies	Simijaca Formation
Overlies	Hiló Formation
Thickness	~1,050 m (3,440 ft)
Lithology
Primary	Siltstone
Other	Shale
Location
Coordinates	4°27′07″N74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
Region	Altiplano Cundiboyacense Eastern Ranges, Andes
Country	Colombia
Type section
Named for	Pacho
Named by	Ulloa
Location	Pacho
Year defined	1982
Coordinates	4°27′07″N74°03′20″W / 4.45194°N 74.05556°W / 4.45194; -74.05556
Region	Cundinamarca
Country	Colombia
Paleogeography of Northern South America 105 Ma, by Ron Blakey

The Pacho Formation (Spanish : Limolitas de Pacho, Kslp) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consisting of alternating siltstones and shales with siderite concretions dates to the Middle Cretaceous period; Late Albian to Cenomanian epochs and has an approximate thickness of 1,050 metres (3,440 ft).

Etymology

The formation was defined and named in 1982 by Ulloa after Pacho, Cundinamarca. ^[1]

Description

Lithologies

The Pacho Formation has an approximate thickness of 1,050 metres (3,440 ft), and is characterised by a sequence of alternating siltstones and shales with siderite concretions. ^[1]

Stratigraphy and depositional environment

The Pacho Formation, pertaining to the Villeta Group, partly overlies and is partly lateral equivalent with the Hiló Formation and is partly overlain by and partly time equivalent with the Simijaca Formation. The age has been estimated to be Late Albian to Cenomanian. Stratigraphically, the formation is time equivalent with the Une Formation. The formation has been deposited in an outer marine platform environment. ^[1]

Outcrops

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Type locality of the Pacho Formation to the northwest of the Bogotá savanna

The Pacho Formation is found around its type locality near Pacho. ^[1]

See also

• Colombia portal
• Geology portal

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

References

1. Acosta & Ulloa, 2002, p.45

Bibliography

• Acosta Garay, Jorge E.; Ulloa Melo, Carlos E. (2002), Mapa Geológico del Departamento de Cundinamarca - 1:250,000 - Memoria explicativa, INGEOMINAS, pp. 1–108, retrieved 2017-04-26
• Villamil, Tomas (2012), Chronology Relative Sea Level History and a New Sequence Stratigraphic Model for Basinal Cretaceous Facies of Colombia, Society for Sedimentary Geology (SEPM), pp. 161–216

Maps

• Ulloa, Carlos; Acosta, Jorge (1998), Plancha 208 - Villeta - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06
• Ulloa, Carlos E; Rodríguez, Erasmo; Acosta, Jorge E. (1998), Plancha 227 - La Mesa - 1:100,000, INGEOMINAS, p. 1, retrieved 2017-06-06

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