Trincheras Formation

The Trincheras Formation (Spanish: Formación Trincheras, Kitr) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The formation consisting of a lower unit of calcareous shales and an upper sequence of shales dates to the Early Cretaceous period; Early Aptian epoch and has a maximum thickness of 1,260 metres (4,130 ft). The formation, deposited in a marine platform environment, part of a transgressive cycle, hosts ammonite, bryozoan, mollusc and echinoid fossils.

Trincheras Formation Stratigraphic range: Early Aptian ~120–115 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Villeta Group
Sub-units	Anapoima Mb., El Tigre Mb.
Underlies	Socotá Fm., El Peñón Fm.
Overlies	Murca Fm., La Naveta Fm., Útica Fm.
Thickness	up to 1,260 m (4,130 ft)
Lithology
Primary	Shale
Other	Sandstone, limestone
Location
Coordinates	4°30′13″N 74°36′22″W
Region	Altiplano Cundiboyacense Eastern Ranges, Andes
Country	Colombia
Type section
Named for	Quebrada Trincheras
Named by	Cáceres & Etayo
Location	Apulo
Year defined	1969
Coordinates	4°30′13″N 74°36′22″W
Region	Cundinamarca
Country	Colombia
Paleogeography of Northern South America 120 Ma, by Ron Blakey

Etymology

The formation was defined and named in 1969 by Cáceres and Etayo after Quebrada Trincheras, Apulo, Cundinamarca.[1]

Description

Lithologies

The Trincheras Formation has a maximum thickness of 1,260 metres (4,130 ft),[2] and is characterised by a sequence of claystones with intercalated limestones and sandstones. Fossils of the ammonites Heinzia sp., Pseudohaploceras sp., Heminautilus etheringtoni, Cheloniceras sp. and bryozoans, molluscs and echinoids have been found in the Trincheras Formation.[3]

Stratigraphy and depositional environment

The Trincheras Formation is the lowermost unit of the Villeta Group,[4] and conformably overlies the Murca, La Naveta and Útica Formations. The formation is overlain in a transitional pattern by the Socotá and El Peñón Formations.[2] The Trincheras Formation is subdivided into the El Tigre and Anapoima Members. The age has been estimated to be Early Aptian. Stratigraphically, the formation is time equivalent with the fossiliferous Paja Formation of Boyacá and the Las Juntas Formation.[5] The formation has been deposited in a marine well oxygenated platform environment.[3] In terms of sequence stratigraphy, this phase was transgressional.[5]

Outcrops

Type locality of the Trincheras Formation to the southwest of the Bogotá savanna

The Trincheras Formation is apart from its type locality in Apulo, found near La Mesa and Anapoima,[3] in the Villeta Anticlinal, the Murca-Guayabal-Nimaima Anticlinal and along the roads between Pacho and La Palma and Útica-La Peña.[2] The formation also crops out around San Joaquín east of La Mesa,[6] and on the right bank of the Bogotá River near Apulo.[7]

The reverse Bituima Fault thrusts the Trincheras Formation on top of the Güagüaquí Group,[6] while the Bogotá River Fault laterally displaces the formation near Anapoima.[7]

Regional correlations

Cretaceous stratigraphy of the central Colombian Eastern Ranges

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

See also

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

References

1. Acosta & Ulloa, 2002, p.39
2. Acosta & Ulloa, 2001, p.23
3. Acosta & Ulloa, 2002, p.40
4. Acosta & Ulloa, 2001, p.22
5. Villamil, 2012, p.168
6. Plancha 227, 1998
7. Plancha 246, 1998

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 2017-06-05.
• Acosta Garay, Jorge, and Carlos E. Ulloa Melo. 2001. Geología de la Plancha 208 Villeta - 1:100,000, 1-84. INGEOMINAS. Accessed 2017-06-05.
• 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.
• Acosta, Jorge E., and Carlos E. Ulloa. 1998. Plancha 246 - Fusagasugá - 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.