Conejo Formation

Conejo Formation
Stratigraphic range: Turonian-Santonian
~90–83.6 Ma
Type Geological formation
Unit of Villeta Group
Underlies Guadalupe Group
Overlies La Frontera Formation
Thickness up to 1,022 m (3,353 ft)
Lithology
Primary Sandstone, shale
Other Limestone
Location
Coordinates 5°35′40.7″N 73°12′59.6″W / 5.594639°N 73.216556°W / 5.594639; -73.216556Coordinates: 5°35′40.7″N 73°12′59.6″W / 5.594639°N 73.216556°W / 5.594639; -73.216556
Region Altiplano Cundiboyacense
Eastern Ranges, Andes
Country  Colombia
Type section
Named for El Conejo Hill
Named by Renzoni
Location Toca, Boyacá
Year defined 1981
Coordinates 5°35′40.7″N 73°12′59.6″W / 5.594639°N 73.216556°W / 5.594639; -73.216556
Region Cundinamarca, Boyacá
Country  Colombia

Paleogeography of Northern South America
90 Ma, by Ron Blakey

The Conejo Formation (Spanish: Formación Conejo, K2C, Kscn) is a fossiliferous geological formation of the Altiplano Cundiboyacense, Eastern Ranges of the Colombian Andes. The uppermost unit of the Villeta Group, a sequence of shales and sandstones dates to the Late Cretaceous period; Turonian, Coniacian and Santonian epochs, and has a maximum thickness of 1,022 metres (3,353 ft).

Etymology

The formation was named in 1967 and published in 1981 by Renzoni, named after El Conejo Hill in Pontezuela, Toca, Boyacá, west of the Copa Reservoir.[1][2]

Description

Lithologies

The Conejo Formation is characterised by a sequence of calcareous sandstones, containing ammonites, shales and the uppermost part sandstone and limestone banks.[3] In the Conejo Formation, fossils of Protopholoe colombiana, Archaeglobigerina blowi, Dicarinella concavata, Dicarinella primitiva, Sigalitruncana sigali, Marginotruncana sp. ct. M. renzi, Marginotruncana angusticarenata, Marginotruncana sp. cf. M.sinuosa, Rosita tornicata, Heterohelix globulosa, Heterohelix reussi, Whiteinella inornata, Hedbergella sp., and the ammonites Gloriaceras correai, Protexamites cucaitaense and Codazziceras scheibei have been found.[4][5][6]

Stratigraphy and depositional environment

The Conejo Formation is the uppermost unit of the Villeta Group.[7] It overlies the La Frontera Formation and is overlain by the Guadalupe Group. The age has been estimated on the basis of ammonites to be ranging from Turonian to Santonian.[8] Stratigraphically, the lower part of the formation is time equivalent with the upper part of the Chipaque,[8] and Loma Gorda Formations.[7]

Outcrops

Type locality of the Conejo Formation on the Altiplano Cundiboyacense

The type locality of the Conejo Formation is located close to El Conejo Hill in Pontezuela, Toca, Boyacá.[2] Other outcrops of the Conejo Formation have been noted in Cucaita,[4][5] the urban areas of Boyacá and Ventaquemada, around the Puente de Boyacá, south of Pesca, west of Siachoque,[9] surrounding Chiquinquirá and Ubaté,[10] between Chivatá and Oicatá,[2] east of Paipa,[11] west of Tibacuy,[12] north and south of Albán, southeast of Cachipay, east of Anolaima, and San Antonio del Tequendama, Cundinamarca.[13]

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. ↑ Montoya & Reyes, 2005, p.29
  2. 1 2 3 Acosta & Ulloa, 2001, p.43
  3. ↑ Montoya & Reyes, 2005, p.30
  4. 1 2 Luque et al., 2015
  5. 1 2 Tchegliakova & Pérez, 1995
  6. ↑ Acosta & Ulloa, 2002, p.48
  7. 1 2 Acosta & Ulloa, 2002, p.22
  8. 1 2 Montoya & Reyes, 2005, p.34
  9. ↑ Plancha 191, 1998
  10. ↑ Plancha 190, 2009
  11. ↑ Planchas 171 & 191, 2005
  12. ↑ Plancha 246, 1998
  13. ↑ Plancha 227, 1998

Bibliography

Maps

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