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Conejo Formation

Fossiliferous geological formation in the Eastern Ranges of the Colombian Andes
Conejo Formation
Stratigraphic range: Turonian-Santonian
~90–83.6 Ma
TypeGeological formation
Unit ofVilleta Group
UnderliesGuadalupe Group
OverliesLa Frontera Formation
Thicknessup to 1,022 m (3,353 ft)
Lithology
PrimarySandstone, shale
OtherLimestone
Location
Coordinates 5°35′40.7′′N 73°12′59.6′′W / 5.594639°N 73.216556°W / 5.594639; -73.216556
RegionAltiplano Cundiboyacense
Eastern Ranges, Andes
Country Colombia
Type section
Named forEl Conejo Hill
Named byRenzoni
LocationToca, Boyacá
Year defined1981
Coordinates 5°35′40.7′′N 73°12′59.6′′W / 5.594639°N 73.216556°W / 5.594639; -73.216556
RegionCundinamarca, 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

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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

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Lithologies

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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

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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

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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

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Cretaceous stratigraphy of the central Colombian Eastern Ranges
Age Paleomap VMM Guaduas-Vélez W Emerald Belt Villeta anticlinal Chiquinquirá-
Arcabuco
Tunja-
Duitama
Altiplano Cundiboyacense El Cocuy
Maastrichtian Umir Córdoba Seca eroded Guaduas Colón-Mito Juan
Umir Guadalupe
Campanian Córdoba
Oliní
Santonian La Luna Cimarrona - La Tabla La Luna
Coniacian Oliní Villeta Conejo Chipaque
Güagüaquí Loma Gorda undefined La Frontera
Turonian Hondita La Frontera Otanche
Cenomanian Simití hiatus La Corona Simijaca Capacho
Pacho Fm. Hiló - Pacho Churuvita Une Aguardiente
Albian Hiló Chiquinquirá Tibasosa Une
Tablazo Tablazo Capotes - La Palma - Simití Simití Tibú-Mercedes
Aptian Capotes Socotá - El Peñón Paja Fómeque
Paja Paja El Peñón Trincheras Río Negro
La Naveta
Barremian
Hauterivian Muzo Cáqueza Las Juntas
Rosablanca Ritoque
Valanginian Ritoque Furatena Útica - Murca Rosablanca hiatus Macanal
Rosablanca
Berriasian Cumbre Cumbre Los Medios Guavio
Tambor Arcabuco Cumbre
Sources


See also

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

References

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  1. ^ Montoya & Reyes, 2005, p.29
  2. ^ a b c Acosta & Ulloa, 2001, p.43
  3. ^ Montoya & Reyes, 2005, p.30
  4. ^ a b Luque et al., 2015
  5. ^ a b Tchegliakova & Pérez, 1995
  6. ^ Acosta & Ulloa, 2002, p.48
  7. ^ a b Acosta & Ulloa, 2002, p.22
  8. ^ a b 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

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Maps

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