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).

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

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]}

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]

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]

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

• 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

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

• 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