Conejo Formation

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
Coordinates5°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
Coordinates5°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

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

Conejo Formation is located in the Altiplano Cundiboyacense
Conejo Formation
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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

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

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

References

  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

  • Acosta, Jorge E.; Ulloa, Carlos E. (2002), Mapa geológico del Departamento de Cundinamarca 1:250,000 - Memoria Explicativa, INGEOMINAS, pp. 1–108
  • Acosta Garay, Jorge; Ulloa Melo, Carlos E. (2001), Geología de la Plancha 208 Villeta - 1:100,000 (PDF), INGEOMINAS, pp. 1–84, retrieved 2017-03-16 Archived 2017-03-24 at the Wayback Machine
  • Luque, Javier; Hourdez, Stéphane; Vinn, Olev (2015), "A new fossil bristle worm (Annelida: Polychaeta: Aphroditiformia) from the late Cretaceous of tropical America", Journal of Paleontology, 89 (2): 257–261, Bibcode:2015JPal...89..257L, doi:10.1017/jpa.2014.22, retrieved 2017-04-04
  • Montoya Arenas, Diana María; Reyes Torres, Germán Alfonso (2005), Geología de la Sabana de Bogotá, INGEOMINAS, pp. 1–104
  • Tchegliakova, Nadejda; Pérez, Vladimir (1995), "Registro de la Zona bioestratigrafica Dicarinella concavata (Foraminiferida) en el Extremo noroccidental de Suramerica (Colombia)", Geología Colombiana, 19: 131–143, retrieved 2017-04-06
  • 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