Murca Formation

Murca Formation
Stratigraphic range: Late Valanginian
~135–133 Ma
↓
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 / 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 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 / 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 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

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
AgePaleomapVMMGuaduas-VélezW Emerald BeltVilleta anticlinalChiquinquirá-
Arcabuco		Tunja-
Duitama		Altiplano CundiboyacenseEl Cocuy
MaastrichtianUmir Fm.Córdoba Fm.Seca Fm.erodedGuadalupe Gp.Colón-Mito Juan Fm.
Umir Fm.
CampanianCórdoba Fm.
Oliní Gp.
SantonianLa Luna Fm.Cimarrona Fm. - La Tabla Fm.La Luna Fm.
ConiacianOliní Gp.Conejo Fm.Chipaque Fm.
Güagüaquí Gp
Loma Gorda Fm.undefinedLa Frontera Fm.
TuronianHondita Fm.La Frontera Fm.Otanche Fm.
CenomanianSimití Fm.hiatusLa Corona Gb.Simijaca Fm.Capacho Fm.
Pacho Fm.Hiló Fm. - Pacho Fm.Churuvita Fm.Une Fm.Aguardiente Fm.
AlbianHiló Fm.Chiquinquirá Sst.Tibasosa Fm.Une Fm.
Tablazo Fm.Tablazo Fm.Capotes Fm. - La Palma Fm. - Simití Fm.Simití Fm.Tibú-Mercedes Fm.
AptianCapotes Fm.Socotá Fm. - El Peñón Fm.Paja Fm.Fómeque Fm.
Paja Fm.Paja Fm.El Peñón Fm.Trincheras Fm.Río Negro Fm.
La Naveta Fm.
Barremian
HauterivianMuzo Fm.
Cáqueza Gp
Las Juntas Fm.
Rosablanca Fm.Ritoque Fm.
ValanginianRitoque Fm.Furatena Fm.Útica Fm. - Murca Fm.Rosablanca Fm.Girón Fm.Macanal Fm.
Rosablanca Fm.
BerriasianCumbre Fm.Cumbre Fm.Los Medios Fm.Guavio Fm.
Tambor Fm.Arcabuco Fm.Cumbre Fm.
Sources

See also

Geology of the Eastern Hills
Geology of the Ocetá Páramo
Geology of the Altiplano Cundiboyacense

References

  1. 1 2 Acosta & Ulloa, 2002, p.37
  2. ↑ Moreno, 1990, p.66
  3. 1 2 3 Moreno, 1990, p.72
  4. 1 2 Acosta & Ulloa, 2002, p.38
  5. 1 2 Dorado Galindo, 1990, p.23
  6. 1 2 Moreno, 1990, p.76
  7. 1 2 Piraquive et al., 2011, p.207
  8. ↑ Pseudoosterella ubalaensis
  9. ↑ Acosta & Ulloa, 2001, p.19
  10. ↑ Villamil, 2012, p.165

Bibliography

Maps

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