Las Juntas Formation

Las Juntas Formation
Stratigraphic range: Hauterivian
~132–130 Ma
↓
Type Geological formation
Unit of Cáqueza Group
Sub-units Arenisca de Almeida Mb.
Lutitas Intermedias Mb.
Arenisca de El Volador Mb.
Underlies Fómeque Fm., Apón Fm.
Overlies Macanal Formation
Thickness up to 910 m (2,990 ft)
Lithology
Primary Sandstone
Other Shale
Location
Coordinates 5°00′49″N 73°27′27″W / 5.01361°N 73.45750°W / 5.01361; -73.45750Coordinates: 5°00′49″N 73°27′27″W / 5.01361°N 73.45750°W / 5.01361; -73.45750
Region Altiplano Cundiboyacense & Tenza Valley
 Eastern Ranges
  Andes
Country  Colombia
Type section
Named for Cerro Las Juntas
Named by Rodríguez & Ulloa
Location Guateque
Year defined 1979
Coordinates 5°00′49″N 73°27′27″W / 5.01361°N 73.45750°W / 5.01361; -73.45750
Region Boyacá
Country  Colombia

The Las Juntas Formation or Las Juntas Sandstone (Spanish: (Formación) Areniscas de Las Juntas, Kiaj, Kialj, K1j) is a geological formation of the Altiplano Cundiboyacense and Tenza Valley, Eastern Ranges of the Colombian Andes. The Las Juntas Formation is found in the departments Cundinamarca, Boyacá and Casanare. The predominantly sandstone formation dates to the Early Cretaceous period; Hauterivian epoch, and has a maximum thickness of 910 metres (2,990 ft).

Etymology

The formation was defined and named in 1979 by Rodríguez and Ulloa after Cerro Las Juntas, Guateque, Tenza Valley, Boyacá.[1][2]

Description

Lithologies

The Las Juntas Formation has a maximum thickness of 910 metres (2,990 ft) and is characterised by a sequence of sandstones with interbedded shales.[1]

Stratigraphy and depositional environment

The Las Juntas Formation, the uppermost unit of the Cáqueza Group, overlies the Macanal Formation and is overlain by the Fómeque Formation and the Apón Formation in the Sierra Nevada del Cocuy.[3] The formation is subdivided into three members, from old to younger; Arenisca de El Volador, Lutitas Intermedias and Arenisca de Almeida. The age has been estimated to be Hauterivian. The formation has been deposited in a near shore deltaic environment,[1][2] with as provenance areas the Santander High and the Guiana Shield.[4] The formation represents a regressive sequence in the present-day Eastern Ranges, as the Rosablanca Formation in the Middle Magdalena Valley.[5]

Outcrops

Type locality of the Las Juntas Formation in the Tenza Valley east of the Altiplano Cundiboyacense

The Las Juntas Formation is apart from its type locality east of Guateque, found in Chingaza National Park,[1] in the El Cochal Synclinal east of the Ocetá Páramo,[6] between Lake Tota and Labranzagrande,[7] other parts of the Tenza Valley such as close to Macanal and Almeida.[8]

The Támara Fault thrusts the Las Juntas Formation southeastward on top of the Tertiary San Fernando and Diablo Formations,[9] and the Chámeza Fault thrusts the older Macanal Formation on top of the Las Juntas Formation around Chámeza, Casanare.[10]

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 3 4 Acosta & Ulloa, 2002, p.52
  2. 1 2 Rodríguez & Solano, 2000, p.47
  3. ↑ Villamil, 2012, p.168
  4. ↑ Villamil, 2012, p.165
  5. ↑ Villamil, 2012, p.166
  6. ↑ Plancha 172, 1998
  7. ↑ Plancha 192, 1998
  8. ↑ Plancha 210, 2010
  9. ↑ Plancha 193, 1992
  10. ↑ Plancha 211, 2009

Bibliography

Maps

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.