Pacho Formation

Pacho Formation
Stratigraphic range: Late Albian-Cenomanian
~102–97 Ma

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Pacho Formation; Stratigraphic range: Late Albian-Cenomanian; ~102–97 Ma PreЄ Є 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″N 74°03′20″W / 4.45194°N 74.05556°WCoordinates: 4°27′07″N 74°03′20″W / 4.45194°N 74.05556°W
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″N 74°03′20″W / 4.45194°N 74.05556°W
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

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]

Regional correlations

Cretaceous stratigraphy of the central Colombian Eastern Ranges
Age	VMM	Guaduas-Vélez		W Emerald Belt		Villeta anticlinal		Chiquinquirá- Arcabuco	Tunja- Duitama	Altiplano Cundiboyacense		El Cocuy
Maastrichtian	Umir Fm.	Córdoba Fm.		Seca Fm.		eroded		Guadalupe Gp.				Colón-Mito Juan Fm.
Maastrichtian				Umir Fm.
Campanian				Córdoba Fm.
Campanian				Oliní Gp.
Santonian	La Luna Fm.	Cimarrona Fm. - La Tabla Fm.										La Luna Fm.
Coniacian		Oliní Gp.				Villeta Gp	Conejo Fm.		Chipaque Fm.
Coniacian		Güagüaquí Gp	Loma Gorda Fm.	undefined			La Frontera Fm.
Turonian		Güagüaquí Gp	Hondita Fm.	La Frontera Fm.	Otanche Fm.		La Frontera Fm.
Cenomanian	Simití Fm.	hiatus		La Corona Gb.			Simijaca Fm.					Capacho Fm.
Cenomanian				Pacho Fm.			Hiló Fm. - Pacho Fm.	Churuvita Fm.	Une Fm.			Aguardiente Fm.
Albian				Hiló Fm.			Hiló Fm. - Pacho Fm.	Chiquinquirá Sst.	Tibasosa Fm.	Une Fm.		Aguardiente Fm.
Albian	Tablazo Fm.			Tablazo Fm.			Capotes Fm. - La Palma Fm. - Simití Fm.	Simití Fm.		Une Fm.		Tibú-Mercedes Fm.
Aptian	Tablazo Fm.			Capotes Fm.			Socotá Fm. - El Peñón Fm.	Paja Fm.		Fómeque Fm.		Tibú-Mercedes Fm.
	Paja Fm.			Paja Fm.	El Peñón Fm.		Trincheras Fm.					Río Negro Fm.
						La Naveta Fm.
Barremian
Hauterivian					Muzo Fm.					Cáqueza Gp	Las Juntas Fm.
Hauterivian	Rosablanca Fm.				Muzo Fm.			Ritoque Fm.			Las Juntas Fm.
Valanginian				Ritoque Fm.	Furatena Fm.	Útica Fm. - Murca Fm.		Rosablanca Fm.	Girón Fm.		Macanal Fm.
Valanginian				Rosablanca Fm.	Furatena Fm.			Rosablanca Fm.			Macanal Fm.
Berriasian	Cumbre Fm.			Cumbre Fm.				Los Medios Fm.			Guavio Fm.
Berriasian	Tambor Fm.			Arcabuco Fm.				Cumbre Fm.			Guavio Fm.
Sources

References

1 2 3 4 Acosta & Ulloa, 2002, p.45

Bibliography

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

Maps

Ulloa, Carlos, and Jorge Acosta. 1998. Plancha 208 - Villeta - 1:100,000, 1. INGEOMINAS. Accessed 2017-06-06.
Ulloa, Carlos E; Erasmo Rodríguez, and Jorge E. Acosta. 1998. Plancha 227 - La Mesa - 1:100,000, 1. INGEOMINAS. Accessed 2017-06-06.

External links

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

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[Acosta2002_p45-1] 1 2 3 4 Acosta & Ulloa, 2002, p.45