Murca Formation

Murca Formation Stratigraphic range: Late Valanginian ~135–133 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of
Underlies	La Naveta Fm., Trincheras Fm.,
Overlies	not observed
Thickness	up to 924 m (3,031 ft)
Lithology
Primary	Sandstone
Other	Claystone, siltstone
Location
Coordinates	5°15′27″N 74°21′12″W / 5.25750°N 74.35333°W / 5.25750; -74.35333Coordinates: 5°15′27″N 74°21′12″W / 5.25750°N 74.35333°W / 5.25750; -74.35333
Region	Altiplano Cundiboyacense Eastern Ranges, Andes
Country	Colombia
Type section
Named for
Named by	Moreno
Location	Pacho, El Peñón
Year defined	1990
Coordinates	5°15′27″N 74°21′12″W / 5.25750°N 74.35333°W / 5.25750; -74.35333
Region	Cundinamarca, Boyacá
Country	Colombia

The Murca Formation (Spanish: Formación Murca, Kim) is a geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The predominantly sandstone with claystones and siltstones formation dates to the Early Cretaceous period; Valanginian epoch and has a maximum thickness of 924 metres (3,031 ft).

Etymology[]

The formation was defined and named in 1990 by Moreno after the , Cundinamarca.^[1][2]

Description[]

Lithologies[]

The Murca Formation has a maximum thickness of 924 metres (3,031 ft), and is characterised by a sequence of coarse-grained, locally cross-bedded sandstones with intercalating siltstones and claystones. The basal part of the black and grey feldspar bearing sandstone beds contains large pyrite crystals. The matrix is formed by cements of calcite, iron oxide, sericite and chlorite.^[3]

Fossils of Berriasella colombiana and Pseudoosterella ubalaensis have been found in the Murca Formation.^{[4][5][6][7][8]}

Stratigraphy and depositional environment[]

The Murca Formation, belonging to the , underlies the Trincheras Formation, lowermost unit of the Villeta Group. The contact with the underlying unit has not been observed.^[3] The age has been estimated to be Valanginian. Stratigraphically, the formation is time equivalent with the , Rosablanca and . The formation has been deposited in a marine environment characterised by turbidites.^[4] A mid submarine fan and outer fan setting have been observed in the Murca Formation.^[9] A possible source for the sandstones were Precambrian sandstones, gneisses and granites, belonging to the Guiana Shield.^[3][10]

Outcrops[]

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

The Murca Formation is apart from its type locality, found near Nimaima and Guayabal in the western flank and Ubalá and Labranzagrande in the eastern flank of the Eastern Ranges.^[1][5][6][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							eroded		Guaduas
									Guadalupe
Campanian
					Oliní
Santonian			-
Coniacian			Oliní				Villeta	Conejo		Chipaque
				Loma Gorda	undefined			La Frontera
Turonian				Hondita	La Frontera
Cenomanian			hiatus					Simijaca
					Pacho Fm.			Hiló - Pacho		Une
Albian					Hiló						Une
								Capotes - -
Aptian					Capotes			Socotá - El Peñón	Paja		Fómeque
		Paja			Paja	El Peñón		Trincheras
							La Naveta
Barremian
Hauterivian												Las Juntas
		Rosablanca							Ritoque
Valanginian					Ritoque		- Murca		Rosablanca	hiatus		Macanal
					Rosablanca
Berriasian												Guavio
					Arcabuco
Sources

See also[]

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

References[]

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.
• Acosta Garay, Jorge E., and Carlos E. Ulloa Melo. 2001. Geología de la Plancha 208 Villeta - 1:100,000, 1-84. INGEOMINAS. Accessed 2017-03-16.
• Dorado Galindo, Jorge. 1990. Contribución al Conocimiento de la Estratigrafía de la Formación Brechas de Buenavista (Límite Jurásico-Cretácico). Región Noroeste de Villavicencio (Meta). 17. 7-38. Accessed 2017-03-31.
• Moreno M., Juan Manuel. 1990. Stratigraphy of the Lower Cretaceous Rosablanca and Cumbre Formations, Útica Sandstone and Murca Formation, West Flank, Eastern Cordillera, Colombia. 17. 65-86. Accessed 2017-03-31.
• Piraquive, Alejandro; Juan Sebastián Díaz; Tomas Cuéllar; Germán Pardo, and & Andreas Kammer. 2011. Reactivación Neógena de estructuras de rift del Cretácico Temprano asociadas con la Falla de Chámeza, Pajarito, Boyacá (Colombia): evidencias tectónicas y bioestratigráficas - Neogene reactivation of Early Cretaceous rift structures associated with the Chámeza Fault, Pajarito, Boyacá (Colombia): tectonic and biostratigraphic evidences. 36. 197-216. Accessed 2017-03-31.
• 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.

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.