Conejo Formation

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).

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
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
RegionCundinamarca, Boyacá
Country Colombia

Paleogeography of Northern South America
90 Ma, by Ron Blakey

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
MaastrichtianUmirCórdobaSecaerodedGuaduasColón-Mito Juan
UmirGuadalupe
CampanianCórdoba
Oliní
SantonianLa LunaCimarrona - La TablaLa Luna
ConiacianOliníConejoChipaque
Güagüaquí
Loma GordaundefinedLa Frontera
TuronianHonditaLa FronteraOtanche
CenomanianSimitíhiatusLa CoronaSimijacaCapacho
Pacho Fm.Hiló - PachoChuruvitaUneAguardiente
AlbianHilóChiquinquiráTibasosaUne
TablazoTablazoCapotes - La Palma - SimitíSimitíTibú-Mercedes
AptianCapotesSocotá - El PeñónPajaFómeque
PajaPajaEl PeñónTrincherasRío Negro
La Naveta
Barremian
HauterivianMuzo
Cáqueza
Las Juntas
RosablancaRitoque
ValanginianRitoqueFuratenaÚtica - MurcaRosablancahiatusMacanal
Rosablanca
BerriasianCumbreCumbreLos MediosGuavio
TamborArcabucoCumbre
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. Acosta & Ulloa, 2001, p.43
  3. Montoya & Reyes, 2005, p.30
  4. Luque et al., 2015
  5. Tchegliakova & Pérez, 1995
  6. Acosta & Ulloa, 2002, p.48
  7. Acosta & Ulloa, 2002, p.22
  8. 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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