Murca Formation

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	Cáqueza Group
Underlies	La Naveta Fm., Trincheras Fm., Útica 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
Region	Altiplano Cundiboyacense; Eastern Ranges, Andes
Country	Colombia
Type section
Named for	Murca River
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
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 subarkose 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 Murca River, 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 subarkose 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 Cáqueza Group, 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 Cumbre, Rosablanca and Útica Formations. 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

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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

References

^ ^a ^b Acosta & Ulloa, 2002, p.37
^ Moreno, 1990, p.66
^ ^a ^b ^c Moreno, 1990, p.72
^ ^a ^b Acosta & Ulloa, 2002, p.38
^ ^a ^b Dorado Galindo, 1990, p.23
^ ^a ^b Moreno, 1990, p.76
^ ^a ^b Piraquive et al., 2011, p.207
^ Pseudoosterella ubalaensis
^ Acosta & Ulloa, 2001, p.19
^ Villamil, 2012, p.165

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
Acosta Garay, Jorge E.; Ulloa Melo, Carlos E. (2001), Geología de la Plancha 208 Villeta - 1:100,000 (PDF), INGEOMINAS, pp. 1–84, retrieved 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)" (PDF), Geología Colombiana, 17: 7–38, retrieved 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", Geología Colombiana, 17: 65–86, retrieved 2017-03-31
Piraquive, Alejandro; Díaz, Juan Sebastián; Cuéllar, Tomas; Pardo, Germán; Kammer, & Andreas (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" (PDF), Geología Colombiana, 36: 197–216, retrieved 2017-03-31
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

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

[Acosta2002_p37-1] Acosta & Ulloa, 2002, p.37

[Moreno_p66-2] Moreno, 1990, p.66

[Moreno_p72-3] Moreno, 1990, p.72

[Acosta2002_p38-4] Acosta & Ulloa, 2002, p.38

[Dorado_p23-5] Dorado Galindo, 1990, p.23

[Moreno_p76-6] Moreno, 1990, p.76

[Piraquive_p207-7] Piraquive et al., 2011, p.207

[8] Pseudoosterella ubalaensis

[Acosta2001_p19-9] Acosta & Ulloa, 2001, p.19

[Villamil_p165-10] Villamil, 2012, p.165

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