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.

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.

Fossils of Berriasella colombiana and Pseudoosterella ubalaensis have been found in the Murca Formation.

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. 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. A mid submarine fan and outer fan setting have been observed in the Murca Formation. A possible source for the sandstones were Precambrian sandstones, gneisses and granites, belonging to the Guiana Shield.

Outcrops

Murca Formation is located in the Bogotá savanna
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.

See also

Geology of the Eastern Hills

Geology of the Ocetá Páramo

Geology of the Altiplano Cundiboyacense

Bibliography

  • Acosta Garay, Jorge E.; Ulloa Melo, Carlos E. (2002), , INGEOMINAS, pp. 1–108
  • Acosta Garay, Jorge E.; Ulloa Melo, Carlos E. (2001), (PDF), INGEOMINAS, pp. 1–84
  • Dorado Galindo, Jorge (1990), (PDF), Geología Colombiana, 17: 7–38
  • Moreno M., Juan Manuel (1990), , Geología Colombiana, 17: 65–86
  • Piraquive, Alejandro; Díaz, Juan Sebastián; Cuéllar, Tomas; Pardo, Germán; Kammer, & Andreas (2011), (PDF), Geología Colombiana, 36: 197–216
  • 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), , INGEOMINAS, p. 1

External links